r , \ / f—• S ■' <\ ■ . r ' 
~ r~ ' r * . e?"2- /**, i~, i *"• 'I rs r f\ i MAYO AERO MEDICAL UNIT 
STUDIES IN AVIATION MEDICINE 
Carried out with the assistance of the 
NATIONAL RESEARCH COUNCIL, DIVISION OF MEDICAL SCIENCES 
acting for the 
COMMITTEE ON MEDICAL RESEARCH 
of the 
OFFICE OF SCIENTIFIC RESEARCH AND DEVELOPMENT 
COMMITTEE ON AVIATION MEDICINE 
With the cooperation of the 
UNITED STATES ARM! AIR FORGES, MATERIEL COMMAND, WRIGHT FIELD, 
Responsible Investigators; Walter M. Boothby, E, J. Baldes and C, F« Cede 
aided by many associates. 
In Six Volumes 
These reports, originally in "restricted" classification, 
have been declassified and all are now "open*" 
VOLUME I; PRELIMINARY STUDIES 
Mayo Clinic and Mayo Foundation for 
Medical Education and Research, 
University of Minnesota 
Rochester, Minnesota 
19U0 - 19h5 COMMITTEE ON WAR MEDICINE, MAYO ASSOCIATES 
representing the 
MATO CLINIC AND MAYO FOUNDATION FOR MEDICAL EDUCATION AND RESEARCH 
Dr. D.C, Balfour, Dr* C.W, Mayo*, Dr. R.D, Mussey, Dr, A.R. Barnes and Mr. H.J, Harwick 
STAFF OF THE MAYO AERO MEDICAL UNIT • 
Responsible Investigators 
High Altitude Laboratory: Walter M, Boothby, Chairman. Member of the Subcommittee 
on Oxygen and Anoxia of the Committee on Aviation Medicine, National Research Council. 
Acceleration Laboratory*** E.J, Baldes, Vice Chairman* Member of the Subcommittee 
on Acceleration of the Committee on Aviation Medicine, National Research Council. 
C#F, Code, Secretary. Member of on Decompression Sickness 
of the Committee on Aviation Medicine, National Research Council. 
Investigators 
Staff of the Mayo Clinic and Mayo Foundation: (Full time) E.J. Baldes, J.B. Bateman, 
W#M. Boothby, A.H. Bulbulian, C.F, Code. H.F. Helraholz, Jr., E.H, Lambert, W.R. 
Lovelace, II and E.H. Wood. (Part time) J.D, Akerman,*** j, Berkson, H.B, Burchell, 
P.L* Cusick, H.E. Essex, G.A, Hallenbeck, W.W, Heyerdale, H.C, Hinshaw, J, Piccard,*** 
M, Power, C, Sheard, J.H. Tillisch, M.N. Walsh and M.M;D# Williams. 
Fellows of the Mayo Foundation: R. Bratt, B.P, Cunningham, W#H. Bearing, E.W, Erickson, 
N. Erickson, J.H. Flinn, J.K% Keeley, J, Pratt, F.J, Robinson, R.F, Rushmer, G.F* 
Schmidt, H.C, Shands, H.A, Smedal, A.R, Sweeney, A. Uihlein, R. Y/ilder, Jr., J. Wilson 
and K.G, Y/ilson, 
Officer assigned by the Air Transport Command of the Array Air Forces: K.R. Bailey, pilot 
Officers assigned by Air Surgeon1s Office: 0.0. Benson, Jr., J.W, Brown, J.H, Bundy, 
D, Coats, E. Eagle, M.F. Green, J.R. Halbouty, R.B, Harding, J.P, Marbarger, M.M, 
Guest, O.C. Olson, C.M. Osborne, H, Parrack, N. Rakieten, J.A, Resch, H.A, Robinson, 
H.E, Savely, C.B. Taylor, L, Toth and J.W, Wilson. 
Officers assigned by the Navy: W, Davidson and D.W* Cressley. 
Officers sent by other governments: J.R, Delucchi, Argentina, and R.T, Prieto, Mexico* 
i . J «• 
Other investigators: M, Burcham, C.J, Clark, M.A, Crispin, R.E . Jones, G. Knowlton, 
H, Lamport, C.A, Lindbergh, C.A, Maaske, G.L. Maison, Ai Reed and R.E, Sturm* 
Technicians 
High Altitude Laboratory: Henrietta Cranston, Lucille Cronin, Ruth Knutson, Eleanor 
Larson and Rita Schraelzer; Margaret Jackson (from Wright Field). 
Acceleration Laboratory: L. Coffey, R. Engstrom, H, Haglund and A. Porter; Ruth 
Bingham, Velma Chapman, Marjorie Clark, Wanda Hampel and Marguerite Koelsch. 
Secretaries 
Evelyn Cassidy, Esther Fyrand, Marian Jenkins and Ethel Leitzen. 
* Before going into military service. 
** The major reports of the Acceleration Laboratory will be published shortly in the 
monograph entitled "Tie Effects of Acceleration and Their Amelioration," edited 
by the Subcommittee on Acceleration of the Committee on Aviation Medicine of the 
l National Research Council. 
*** From the Department of Aeronautical Engineering, University of Minnesota. CONTENTS 
Physiological effects of reduced barometric pressure on man* 
By Wc Ra Lcvelace, March 21, 19uOa 
A laboratory aid* 
By variovs Array and Navy officers and Mayo Foundation Fellows assigned to 
the Mayo loro Medical Unit, August 19U2. 
Indoctrination program. Outlines and lectures for beginning and advanced Air 
Corps personnel. 
By R0 M, Halbouty and J. A, Resch, August 19U2, Physiologic Effects of Reduced Barometric 
Pressure on Man 
hy 
W, Randolph Levelaoo, II, M. D. 
Maye Clinic 
Mayo Foundation, University of Minnesota 
Mayo Aero Medical Unit 
Condensed from thesis presented March 21, 1940 in partial 
fulfillment of requirement for degree of Master of Science 
in Surgery, Mayo Foundation, University of Minnesota, 
Address given at George Washington University, 194C, 272 
Physiologic Effects cf Reduced Barometric 
Pressure cn Man 
oy 
W. Randolph Lovelace, II, M. D.* 
The Atmosphere 
Atmospheric air, dry, contains 20.S3 per cent of oxygen (Qg), approxi- 
mately 73 per cent cf nitrogen (N2)* 0.03 per cent of carbon dioxide (the 
percentage varies Between 0.025 and 0.035), end 1 per cent of the rare and 
inert gases, argon, helium, neon, zenon and krypton. The total amount of 
nitrogen and other inert gases is therefore 79.04 per cent- The cause of the 
uniform mixture of the air is the currents and whirls upward and downward 
produced hy the unequal warming of the earth’s surface. With increasing 
altitude the barometric pressure falls progressively, and the number cf gas 
molecules in every liter of air diminishes correspondingly but the quanti- 
tative relationship of the gases in the air mixture does net change, even 
at an altitude of 72,000 feet. 
As far as metabolism is concerned, nitrogen and the rare gases are 
absolutely inert and under ordinary atmospheric pressure are dissolved in the 
blood plasma according to their coefficient cf solubility at body temperature. 
The air has mass, and since it also has weight it is increasingly 
compressed as the earth’s surface is approached. Consequently, the density 
of the gaseous particles is increased as well as the air density and pressure. 
The atmospheric pressure is capable of counterbalancing a column cf 33 feet 
cf water or cf 750 mm. of mercury. Since there is an atmospheric pressure of 
nearly 15 pounds per square inch at sea, level, the body of an average adult 
is subject to an atmospheric pressure of approximately 30 tons at sea level. 
Although widely different conditions may be noted at any given time, 
the average decrease of temperature is about VJ T. for each 300 feet. The 
decrease cf temperature with altitude is known as the lapse rate. The normal 
temperature decrease with altitude continues to a level known as the 
propopause. Below this level lies the troposphere, with its turbulence and 
infinite variety of weather; above it lies the stratosphere, in which 
temperature variations are very small, and ideal flying wee,then prevails. 
The most common gas laws. Dalton’s law. In any mixture cf gases 
which do not unite chemically, each gas exerts the same pressure as if it 
were present alone in the volume occupied by all the components and the total 
pressure of the mixture is equal to the sum of the partial pressure of the 
gases. The partial pressure of any gas is proportional to its concentration. 
fflhen a gas is measured over water, it soon becomes saturated with 
* Author has just completed the Civilian Pilot Training Course sponsored by 
the Civil Aeronautics Administration. water vapor. Prom the above law* it is apparent that if the measurement 
is made under atmospheric pressure the "barometric pressure will he tne sum 
of the gas pressure and the water vapor pressure. To obtain the pressure 
of the gas in question it is necessary to subtract the water vapor pressure 
from the barometric pressure. 
Henry’s law. The amount of gas which can be dissolved in a given 
quantity of water varies directly with the pressure, the temperature being 
constant. 
Dalton’s law of solubility of mixed gases. If a mixture of several 
gases is kept over a liquid, each gas dissolves independently of any of the 
others and in proportion to its partial pressure. 
Boyle’s law. The volume of a given mass of gas kept at a constant 
temperature varies inversely as the pressure, that is, the concentration of 
a given quantity of a gas at a constant temperature is proportional to the 
corresponding pressure. .For example, a gram of gas occupies double its 
previous volume when the pressure decreases from 1 atmosphere to l/2 atmos- 
phere (18,000 feet). The calculation is readily made according to the 
formula P , P being pressure. 
760 
Charles’ law. The volume of a given mass of gas kept under a constant 
pressure varies directly as the absolute temperature, or, in other words, 
the concentration of a given quantity of gas under constant pressure is in- 
versely proportional to the corresponding absolute temperature. 
Graham’s law. At constant conditions of temperature and pressure 
the rate of diffusion is inversely proportional to the square root of the 
density of the gas. 
Partial Pressure. It was proved quite clearly by Paul Bert, in 1878, 
that diminution of barometric pressure, such as occurs at high altitudes, 
affects human beings only when the partial pressure of the oxygen in the 
inspired air is decreased with consequent subnormally low partial pressure 
of the oxygen supplied to the tissues by the blood. Ho also was well aware 
of the fact that the ill effects resulting from this diminution in pressure 
can be prevented by the inspiration of air sufficiontly rich in oxygen to 
maintain a normal partial pressure of oxygen. In order to secure adequate 
oxygenation of the blood, it is relatively unimportant whether the necessary 
partial pressure of oxygen is obtained by breathing air which contains only 
20,93 per cent of oxygen at normal atmospheric pressure, or, for example, by 
breathing pure oxygen at an altitude of 33,000 feet. 
The partial pressure of a gas in a mixture of gases having no 
action on one another is equal to that which the particular gas would exert 
did it alone take up the space occupied "by the mixture; in other words, in 
a mixture of gases at a certain pressure, the pressure is divided between the 
different gases in proportion to their relative volumes. At sea level the 274 
partial pressure of oxygen in dry air is 169.07 mm. of mercury (760 x 20.9o). 
As an airplane ascends, the "barometric pressure falls progressively, so tnat 
at any given altitude the partial pressure cf oxygen is correspondingly 
reduced. For example, at an altitude of about 18,000 feet the total atmos- 
pheric pressure is halved, and, consequently, the partial pressure of oxygen 
is only approximately 79.5 mm. of mercury (380 x 20.93) although the per- 
centile composition of the air is unchanged. The chemicophysical ability 
of the oxygen in the air to combine with hemoglobin is essentially dependent 
on its partial pressure. 
(The altitude pressure relationships are shown in table 1, p. 301.) 
Respiration 
Respiration consists in taking in of oxygen and throwing off the 
products of oxidation in the tissues, mainly carbon dioxide and water. The 
oxygen requirements and the amount cf carbon dioxide liberated are propor- 
tional to the degree of activity of the body; therefore, all other things 
being equal, the pulmonary ventilation is proportional to the metabolic rate. 
Thus the alveolar air is maintained at a fairly constant composition. For 
human respiration only the oxygen fraction cf the atmospheric air is important 
since nitrogen and rare gases are inert and are, therefore, inhaled and ex- 
haled in the same quantity. 
The process of respiration by which these two gases are carried 
through the body is in two parts. External respiration is concerned with the 
transport of oxygen from the air to the arterial blood and the elimination of 
carbon dioxide from the venous blood to the outer atmosphere; it keeps the 
alveoli of the lungs supplied with air of a comparative!y uniform compo- 
sition. Internal respiration transports oxygen between the alveoli and the 
tissue cells where metabolism actually takes place. It aids in the excre- 
tion of carbon dioxide from the tissues to the blood. The lungs, the bronchi, 
trachea and nasopharynx are primarily concerned with internal respiration. 
During inspiration, the thorax: is expanded and the lungs are filled 
by the raising of the ribs and by the descent of the diaphragm. In this man- 
ner, air is drawn in through the nose, then into the trachea, the bronchi, 
and finally into the alveoli. The tidal air, which is the amount of air 
breathed in or out of the lungs with every quiet respiration, averages about 
500 cc. The more the lungs are distended by deep inspiration, the more 
negative dees tho pressure in the pleural cavity become. Daring expiration 
the thorax collapses, owing to its weight and elasticity of the lungs. The 
more the lungs are stretched, the greater is their tendency to recoil. 
Supplemental air is the additional amount of air which can be ex- 
haled after a normal expiration by a maximal expiratory effort (1500 cc.). 
Complemental air is the amount cf air that; can be inhaled after a 
quiet inspiration by a maximal inspiratory effort (1500 cc.). 275 
Vital capacity is the sum of the preceding figures, and on the aver- 
age is about 3500 cc., that is, it is the maximal amount of air that can be 
inspired after a powerful expira-ticn. It is determined by having the subject 
make the deepest possible inspiration followed by the deepest possible expir- 
ation into a spirometer. The highest of two or three readings is taken as the 
vital capacity. The vital capacity varies with the sex, weight, age, chest 
expansion and the size of the individual and the use to which he has put his 
respiratory mechanism. It is related to the surface area; it amounts to 
2.5 liters per square meter for a male and 2.07 liters per square meter for 
a female. Athletes have a considerably higher vital capacity, and lower read- 
ings are obtained in the case cf old subjects. It is found that dyspnea 
develops as the depth of the breathing approaches the vital capacity. The 
vital capacity is diminished in manjr diseases, that is, in heart failure, 
various affections of the lung,like emphysema, pneumothorax and tuberculosis, 
and in exophthalmic goiter. In such diseases, patients tend to become 
breathless on exertion more readily than do normal persons. 
The residual air is the air -which remains in the lungs after a maxi- 
mal expiration. It can be expelled only by opening the thorax widely and 
allowing the lungs to collapse. 
Alveolar air. As the bronchioles branch and become smaller, their 
columnar ciliated epithelium becomes modified into a cubical epithelium. The 
terminal branches are called respiratory bronchioles because in places the 
normal bronchial wall is replaced by patches of thin flattened cells through 
which gaseous interchange can take place. Each respiratory bronchiole leads 
into an expansion, from the vestibule of which arise several passages, the 
atria. Each atrium leads into two or three air sacs (infundibula); the 
wall of the air sacs is studded with minute evaginations, the alveoli. The 
alveoli arc lined by large thin flattened cells, but in places clumps of 
cubical granular cells arc seen. External to the lining epithelium are 
yellow elastic fibers and numerous thin-walled blood vessels. The term 
"alveolar air" docs not refer to the air which is present in the anatomic 
alveoli, but is used to describe the air in the depths of the lung, which is 
more or less in contact with the respiratory epithelium and can thus effect 
gaseous interchange with the blood. Alveolar air is a physiologic and not an 
anatomic entity. It consists of the supplemental air and the residual air, 
and amounts to about 3000 cc. 
The dead space air is found in the air passages—nasopharynx, trachea, 
and bronchi. It amounts to 150 cc. It does not come into contact with the 
pulmonary epithelium and does not effect an interchange with the blood. 
Atmospheric air, irrespective of the barometric pressure, becomes 
so.turated with water vapor at 37° G. as it is inspired into the alveoli of 
the lungs. As barometric pressure is decreased, the alveolar pressure cf 
oxygen decreases at a greater proportional rate than docs the partial 
pressure of oxygen in the lungs because the aqueous vapor in the lungs remains 276 
nearly constant; this is only in part compensated for "by the fact that the 
alveolar carbon dioxide decreases with an increase in elevation. Thus, at 
18,000 feet, where the total atmospheric pressure is reduced by a half, the 
diluting effect of water vapor will be two times as great as at sea level 
(380 - 47 x 20.93). On the basis of repeated analyses of the alveolar air 
by the dew point method, Christie and Loomis have concluded that the aqueous 
vapor pressure in the lungs is 45 mm. of mercury instead of the commonly 
accepted pressure of 47 mm. They further discovered that the alveolar vapor 
pressure is lowered by as much as 9 mm, cf mercury by hyperventilation, which 
may be a compensatory factor as it permits a slight increase in alveolar oxy- 
gen pressure. 
Comparison of the gas pressures in alveolar air and blood (table 2, 
p. 304) reveals that the pressure differences are such as would enable gaseous 
interchange to take place by a simple process of diffusion, because cf the 
difference of gas pressure on the two sides of the pulmonary epithelium. The 
capillaries in the alveoli s,re so constituted that they furnish a maximum of 
surface and a minimum of resistance to diffusion of gases; this is essential 
since the gases of the blood and of the alveoli ifldst come into equilibrium 
in less than a second. The oxygen pressure in alveolar air averages 104 to 
106 mm. of mercury and in venous blood it averages 40 mm, of mercury, thus 
there is a difference of pressure cf more than 60 mm. of mercury on the two 
sides of the alveolar epithelium. The corresponding carbon dioxide pressures 
are 40 mm. and 45 mm. of mercury, that is, a difference of pressure of only 
6 mm. of mercury. However, the rate of diffusion of carbon dioxide is con- 
siderably higher than that for oxygen. 
During inspiration the capacity of the lungs is increased and the 
dead air space followed by the fresh air from the surrounding atmosphere 
enters the depths of the lungs. The fresh air alters the composition of the 
alveolar air so as to make up for the changes which have taken place between 
the alveolar air and the pulmonary blood. It is obvious that the oxygen 
content of the air in the alveoli is always lower than in the inspired air 
(table 2). Since the inspired air is always mixed with the air that has re- 
mained in the lungs during expiration and which has lost some cf its oxygen 
content and is rich in carbon dioxide and saturated with water vapor. 
During expiration the first portion cf the expired air has essentially 
the same composition as room air since it is expired from the "dead space" 
which includes the nasopharynx, trachea, bronchi and bronchioles up to the 
place where functioning epithelium is present. The last portion of the ex- 
pired air approaches in its composition the alveolar air. 
Oxygen passes through the living epithelium cf the alveoli into the 
serum and into the hemoglobin cf the erythrocytes. Carbon dioxide passes 
in the opposite direction, its removal from the hemoglobin being facilitated 
by the entrance of the oxygen. Thus, by simple diffusion through the walls 
cf the alveoli the two gases endeavor to reach a pressure equilibrium and 
pass from an area cf high pressure to an area cf lew pressure. The essential 277 
ccnd.ition for an adequate oxygen supply to the blood in the hangs is that 
the oxygen content and partial pressure of the oxygen in the lungs are higher 
than they are in the blood returned to the lungs. As pointed out by von 
Diringshofen, the blood actually loses some of its oxygen to the air in the 
lungs when a great reduction in the oxygen content of the inspired air occurs 
above 29,000 feet. 
The arterial blood transports oxygen from the lungs to the tissues, 
and the venous blood transports carbon dioxide from the tissues to the lungs. 
Oxygen is carried in the blood in two states: (l) a small amount in simple 
solution according to Henry1s law of solution of gases in liquids, and (2) 
a much larger amount in chemical combination with hemoglobin. The amount of 
oxygen which the blood will absorb from the air in the lungs and will carry 
to the tissues will depend in both instances on the partial pressure of oxy- 
gen in the lungs. Bohr, in 1905, showed that 100 cc. of blood at body 
temperature contains, in simple solution, approximately 2.2 cc. of oxygen 
(S.T.P.D.) when exposed to an atmosphere of pure oxygen. Under normal con- 
ditions, with a rather slow rate cf circulation, (table 2) the alveolar oxy- 
gen pressure averages approximately 14 per cent of an atmosphere, and in the 
arterial blood it averages approximately 13 per cent cf an atmosphere (about 
100 mm. of mercury); therefore, 100 cc. rf blood contains, in simple solution, 
about 0.3 cc. of oxygen. 
The hemoglobin capacity cf 100 cc, of blood, according to the studies 
cf Peters and Van Slyke, averages 20 cc. of oxygen, when completely saturated, 
but under ordinary respiratory and circulatory conditions it averages only 
95 to 96 per cent saturation, which, incidentally, leaves a per cent possi- 
bility for further oxygen take-up. Therefore, 100 cc. of arterial blood 
would contain approximately 19.2 cc. of oxygen combined with hemoglobin and 
0.3 cc. in solution, a total of about 19.5 cc. cf cxygen, if the subject is 
breathing air. The oxygen in simple solution is the immediate source from 
which the tissues obtain their supply. 
The pressure of oxygen In the arterial blood is 100 mm. of mercury, 
and it should he emphasized that this pressure applies only to oxygen in 
solution. The oxygen pressure in the tissue spaces (table 2) is only 20 to 
40 mm. of mercury so that as a result of this difference in partial pressure 
oxygen rapidly passes out of the plasma through the capillary wall and tissue 
fluid to reach the tissue cells. The partial pressure of oxygen in the blood 
falls tc about 40 mm. of mercury, and consequently the oxyhemoglobin in the 
erythrocytes is now exposed tc a pressure of 40 mm. of mercury in the surround- 
ing plasma and therefore it can no longer hold all of its oxygon as oxyhemo- 
globin, hence dissociation of hemoglobin occurs and oxygen is released and 
diffuses cut through the plasma into the tissue spaces. As a result of the 
preceding phenomenon, the venous hired leaves the tissues with an oxygen 
pressure cf 40 mm. ~f mercury and an oxygen content of 14,8 cc. per 100 cc. 
Carbon dioxide is at a higher partial pressure in tho tissue spaces 278 
(45-60 mra. of mercury) than it is in the arterial hlood (40 mn. of mercury); 
therefore, it diffuses out into the hlood and its partial pressure rises to 
46 mm. of mercury in the venous hlood. 
Bohr, Hasselhalch and Kroghvl (1904) made the important observation 
that the oxygen dissociation curve of hemoglobin is greatly influenced by 
the partial pressure of the carbon dioxide present. As the olood takes up 
carbon dioxide in its passage through the capillaries, oxygen is liberated 
from the oxyhemoglobin more readily than would otherwise be the case. 
When the mixed venous blood (oxygen pressure 40 mm. ox mercury, 
carbon dioxide pressure 45 mm. of mercury) reaches the lungs, the oxygen is 
replaced and the carbon dioxide is given off. 
Detailed reviews of the mechanism of oxygen and carbon dioxide trans- 
port are given by Haldane and Priestley, peters and Van Slyke, and Krogh^O) 
The method of Haldane and Priestley is used for the collection of 
samples of alveolar air. The procedure is simply to have the subject make a 
rapid, sharp and deep expiration through a, piece of rubber hose about 3 to 4 
feet long and 1 inch in diameter and provided with a well fitting mouthpiece 
and an automatic spring release type valve, which traps the air in the tube. 
By means of a very narrow bore rubber tubing connected to a small tube just 
distal to the metal valve, a sample of the last part of the expired air is 
then at once taken directly into a gas analysis apparatus, or else into an 
evacuated mercury sailing tube. When taking a sample of alveolar air, it is 
important that the rate and depth of breathing should be normal until the 
moment when the deep expiration is made. 
Haldane and Priestley have given a thorough description of the ef- 
fects on human beings of ascent to a high altitude. When the barometric 
pressure is rapidly reduced, the depth and frequency of breathing are in- 
creased at first, but after several minutes this increase diminishes markedly. 
As a direct result of the increased breathing, there is a fall in the alveolar 
pressure of carbon dioxide and more carbon dioxide than usual is washed out 
of the blood. This causes the respiratory quotient to be increased temporari- 
ly from the normal value of 0.8 to as much as 2.8 when the onset of anoxemia 
is sudden and marked. The elimination of carbon dioxide through the lungs 
decreases the stimulus to the respiratory center and causes the respiratory 
minute volume to fall. Then the extra elimination of carbon dioxide from the 
blood begins to lesson. . In the early stage of ascent, therefore, pulmonary 
ventilation is greater than normal and the alveolar pressure of carbon di- 
oxide is loss than normal and oxygen pressure is slightly increased. Later, 
the alveolar pressure of oxygen falls from the level at which it was 
maintained during the initial excess breathing, since the rate of absorption 
of oxygon remains undiminishod, while the pulmonary ventilation falls. The 
drop in the alveolar pressure of oxygen tends to increase the symptoms of 
anoxemia and thereby to increase the breathing, but finally a balance is 
reached, at least temporarily. If the anoxemia is produced gradually the 279 
initial marked increase of "breathing is unncticeable as tne extra canbcn 
dioxide is washed out gradually. 
Haldane and Priestley further found that the new lower level of alveo- 
lar pressure of carbon dioxide becomes the regulating level for the atmosphere 
breathed. A small increase above this level results in a great increase in 
breathing while a small diminution causes apnea. The primary and marked in- 
crease in breathing was attributable to the alveolar pressure of carbon di- 
oxide in the entire body being above the new level and the quieting down of 
breathing was a result of the gradual washing out of carbon dioxide until a 
now normal level was attained, which was itself determined by the secondary 
effects arising from the decreased pressure of the alveolar oxygon. Anoxemia 
tends to increase breathing but the increased breathing, by washing out carbon 
dioxide, quickly stops this increase, sc that after a time there is only a 
small increase. Since the alveolar air during normal breathing contains 
about a third less oxygen than docs the inspired air, it follows that when 
the partial pressure of oxygon in the inspired air is reduced a. third, the 
percentage of oizygcn in the alveolar air will be reduced to about half. Com- 
parison of this figure with the dissociation curve of oxyhemoglobin shows 
that this diminution corresponds to an arterial saturation of approximately 
90 per cent and that any further decrease will be followed by a rapid and 
dangerous fall in saturation. Haldane and his co-workers WGro rjnong the 
first to point out that the responsive breathing to a given reduction of 
pressure of oxygon in the inspired air varies considerably among different 
individuals. Those who respond by increased breathing arc, therefore, more 
protected against the onset of anoxemia because of the relatively higher per- 
centage of oxygen in their alveolar air, Christensen and Krogh, in com- 
paring a group of pilots who could tolerate very high altitudes with a. group 
of these who could net, found that .among the former there were greater 
pulmonany ventilation, a distinctly lower -partial pressure of carbon dioxide, 
and a. higher alveolar pressure of oxygen. The larger ventilation indicated 
that there was less difference between inspired and expired oxygen than 
there would be among average individuals. Haldane and Priestley further 
stated that if the carbon dioxide pressure in the respiratory center falls 
below a certain level, the center ceases to respond even to an excessive 
degree of oxygen want and is soon severely damaged. 
Symptoms and Effects cf Oxygon Want 
The symptoms of anoxemia are well known and have been determined from 
numerous studies made on expeditions to high altitudes, in the mountains,, in 
low pressure chambers, in low oxygen chambers, with rebreathing apparatuses, 
and also on ascents by balloon and airplane. In a comprehensive acid extensive 
report on the effects of deprivation of oxygon, Me Pari and listed the most' 
frequently encountered subjective symptoms as follows; headache, respiratory 
changes and difficulties, excessive sleepiness, vertigo or dizziness, diffi- 
culty in concentrating, sensory impairment, lassitude and indifference, and 
fatigue. He listed the following important variables which may affect the 
response of a pilot to the lowered axygen pressure at high altitudes! rate of 280 
ascent, height attained., length of exposure, amount of physical exertion, 
movement of the plane and the physical characteristics of the individual. 
Since anoxemia is of slow and insidious onset, the various senses 
and the intellect gradually become clouded without the individual perceiving 
the change. For this reason, it has been difficult in the past to convince 
pilots that they are inefficient at high altitudes. When such individuals go 
up without oxygen, remain at a considerable elevation for some time, and then 
begin to take oxygen for the first time, they are amazed at the sudden and 
dramatic increase in their powers of perception and sensation in general. 
Armstrong (l)has considered in detail the major problems resulting from 
anoxia in aviation, and also has considered the effect of repeated daily 
exposures to anoxemia. 
At different heights the "interval of reserve," that is, the time 
until the occurrence of symptoms after cutting off oxygon, shows a distinct 
individual variation. Ruff and Stmghold, 138) in Germany, found that this 
interval differs greatly in the case of different individuals and varies for 
the same person according to his physical condition. At 16,400 feet this 
interval of reserve varied from five minutes to more than one hour for dif- 
ferent individuals; at 19,600 feet it varied from a few minutes to half an 
hour, at 22,900 feet it varied from one minute to half an hour, and at 26,200 
feet it varied from ten seconds to fifteen minutes. 
The symptoms of anoxemia are often compared with those of alcoholic 
intoxication because of the close similarity of the two in many respects. 
The pilot and also the physician who is conducting tests in an airplane or 
in a low pressure chamber are almost always convinced that they are normal 
in every respect, even at extreme altitudes, and they seldom lack confidence 
or assurance. Some individuals become euphoric, others morose, and still 
others pugnacious and unwilling to listen to advice. The capacity for self- 
criticism is soon lost. Even a physiologist of Haldane's caliber insisted on 
keeping a pressure of 320 mm. of mercury in a lew pressure chamber experiment, 
although he had groat difficulty in making observations, was cyanotic, and 
could hardly calculate his pulse rate from observations made for twenty 
seconds. After an hour and a quarter at this pressure, he was still determ- 
ined (fixed idea) to remain in the chamber, but when he consented to an in- 
crease of pressure to 350 mm,, he began to regain his faculties. Even then, 
when ho attempted to look at his reflection in a mirror, some time elapsed 
before he realized that he was looking at the back, and not at the front, of 
the mirror. When he was questioned later ho had no recollection of his long 
stay at 320 mm. and was unreasonable, somewhat unsteady, and had a- headache 
for several hours. Haldane and Priestley also explained that at low pressures 
the diffusion of oxygen molecules within and into the pulmonary alveoli is 
more free than would be the case when breathing in the same percentage of 
oxygen at sea level. 
When the oxygen supply is inadequate the aviator concentrates ex- 
clusively on one particular aspect of his problem and forgets all other essentials of a normal procedure. At 300 miles or more per hour in an air- 
plane, fixed ideas may well eventuate in disaster. 
Many individuals can take a few drinks and seemingly can drive an 
automobile well. Somebody else, after the same number of drinks, will weave 
down the road at a high speed, insisting all the time that he can drive safe- 
ly and knows exactly what is going on. McFarland and Barach pointed out 
the relationship between alcoholic intoxication and anoxemia. In 80 per cent 
of twenty-three subjects who had ingested from 0.75 to 1.5 gm. of alconol 
per kilogram of body weight, inhalation of 50 per cent oxygen, mixed with 
2 to 5 per cent carbon dioxide, lowered the alcohol and lactic acid content 
of the venous blood. There also was a corresponding improvement in mental 
and motor behavior. Two subjects who complained of nausea, headache, in- 
ability to retain liquids, and general malaise on "the morning after" wore 
treated in the laboratory with inhalation of 100 per cent oxygen. Within 
45 minutes there was marked subjective improvement and the subjects wore 
able to take fluids and nourishment readily. 
(3) 
Barach's paper on the relationship between anoxemia and pilot error 
vividly called the attention of the medical profession and of individuals 
connected with commercial aviation to the dangers that could arise from oxy- 
gen want and the possibility cf accidents arising therefrom. Barach and his 
co-werkers carried cut a study on the effects cf deprivation of oxygen on 
the ability tc do multiplication and division n a slide rule during four 
hours at a simulated elevation of approximately 12,000 feet, in an oxygen 
chamber. They found that the number cf problems solved by three of four 
subjects was decreased. There was also a tendency toward boisterousness and 
excessive loquacity, Hie use of oxygen by aviators flying at, or above, 
12,000 feet was recommended. 
( TC ) 
Campbell and Boulton v w stated that when the oxygen pressure in the 
inspired air falls below 14 per cent the oxygen pressure in the tissues cf 
normal individuals begins to fall. Haldene and Priestley found that the 
barometric pressure must be reduced by about a third before there is any evi- 
dent effect, at the time, on the breathing and the carbon dioxide pressure 
cf most normal individuals, and that this effect differed according to the 
rapidity at which anoxemia was produced. The oxygen pressure in the inspired 
air at 10,700 feet (508.5 mm. of mercury) is approximately the equivalent 
of only 14 per cent oxygen at sea level and therefore it can be assumed that 
tissue anoxemia would begin at this point in the case of a perfectly normal 
individual with an efficient and adaptable cardio-respiratory system. This 
maybe designated as the critical level. In this connection, reference to 
experiments by Dill, Christenson and Edwards, showing the relation botwcon 
arterial saturation and the alveolar pressure of oxygen, reveals that the 
average alveolar pressure of oxygen at this altitude is about 60 mm., as 
was the case in experiments reported by Bcothby, Lovelace, and Benson. At an 
alveolar pressure of oxygen of 60 mm., the investigators named found that the 
hemoglobin of the arterial blood was, on the average, about 90 per cent 
saturated. They were also cf the opinion that at high altidues the partial 282 
pressure of oxygen in the arterial blood, measured "by referring its percentage 
saturation with oxygen to the dissociation curve of the same specimen of 
"blood, is approximately equal to that in the alveolar air. In addition, these 
investigators fully confirmed the fact that diffusion alone can account for 
the transfer of oxygen in the lungs, and that the oxygen saturation of ar- 
terial "blood does not necessarily increase during acclimatization. 
Campbell listed the following factors as "being in control of tissue 
oxygen tension: oxygen pressure in the inspired air, quantity of hemoglobin, 
circulation rate and vascular adjustment, and diffusion and secretion through 
the lung and through the capillary walls in the tissues and oxygen metabolism. 
It is well known that the body is unable to store oxygen to any appreciable 
extent. 
The effects of being just above the critical level at which tissue 
anoxemia occurs if individuals are normal is strikingly exemplified by the 
following experiments. These important experiments on the effect of repeated 
exposure to an altitude of 12,000 feet were carried out by Armstrong and Heim 
Before reporting the experiments themselves, it should be said that at an 
altitude of 12,000 feet the inspired air contains an equivalent oxygen per- 
centage of 13.31. Armstrong and Heim exposed normal, intelligent and co- 
operative subjects of an average age of twenty years to a simulated altitude 
of 12,000 feet above ground level for four hours daily, six days a week, for 
twenty-seven days. They condluded: 11 (l) Each exposure produced a concurrent 
mental and physical fatigue which persisted for approximately twenty-four 
hours and was manifested by difficulty in mental concentration, retention, 
and attention over periods of time in excess of a few minutes; by sleepiness 
and lassitude; by errors in construction, spelling and composition; and by 
lack of initiative. (2) repeated daily exposures produced a continuous 
mental and physical fatigue throughout each twenty-four hour period with mani- 
festations similar to those mentioned above. In addition, nervous irritability 
was increased." They recommended that flying personnel take oxygen at all 
times when flying at or abovo 12,000 feet. 
(32) 
Uihlein and I v conducted a series of tests, as yet unreported, on 
a Link trainer, which is a mechanical device for training pilots to fly by 
instruments and to use the radio ranges and other modern aids to air navi- 
gation and which resembles a small, hooded airplane with fuselage, wings, 
ailerons and the tail section. The controls and instruments in this device 
are essentially the same as those on a modern air-plane. We exposed experi- 
enced pilots to simulated altitudes of from 10,000 to 20,000 feet over periods 
from 30 minutes to 4 hours by having them wear a large gas mask which com- 
pletely covered the face but had glasses through which the pilot could see. 
The percentage of oxygen in the inspired air was carefully controlled by 
running in a mixture of nitrogen and oxygen from two separate tanks and 
repeatedly testing the percentage composition of the mixture by the Boothby 
modification of the Haldane apparatus, and thereby determining the simulated 
altitude. After 30 minutes to 1 hour on the Link trainer at simulated alti- 
tudes of 15,000 feet and higher, the majority of the pilots complained of 283 
fatigue and exhibited signs of tenseness, as shown by over-controlling the 
Link trainer, and there was definite slowing of the mental processes, as 
shown hy the increased time it took to solve the various orientation problems. 
Three of the ten pilots tested became lost, one at 16,000 feet after 40 min- 
utes, one after one hour and fifteen minutes at 15,300 feet, and one after 
one hour and forty-five minutes at 18,000 feet, and were unable to determine 
their position until they were given oxygen. Further tests are to be carried 
out on the Link trainer at various altitudes for more prolonged periods of 
time. Officials conducting investigations into the cause of airplane crashes 
should always give due consideration to the possible part that anoxemia may 
have had in causing the accident, and they should investigate the efficiency 
of the oxygen apparatus installed in the plane. 
Necessity for Oxygen at Various Altitudes 
At 28,800 feet the barometric pressure is 238.1 mm., of which approxi- 
mately 21 per cent, or 50 mm., represents the partial pressure of oxygen in 
the outside air, that is, the air to be inspired. In the lungs, however, the 
air will contain 47 mm. of water vapor and 40 mm. of carbon dioxide as a re- 
sult of absorption of 40 mm. of oxygen at H.Q,, of 1,0 for utilization by the 
cells in combustion and (assuming no acclimatization or temporary compensation 
by increased respiration) the partial pressure of oxygen in the lungs, 
therefore, would theoretically be zero, calculated according tc the formula 
which will be given. Of course, without previous acclimatization and training 
in how to breathe, the subject could live only a few minutes, even by excessive 
breathing. 
At 20,000 foot the barometric pressure is 349.1 mm., of which approxi- 
mately 21 per cent, or 73 mm., is the partial pressure of oxygen in the in- 
spired air. In the lungs, provided the body has no means of compensating 
temporarily by breathing more deeply, the partial pressure of oxygen would 
be only about 23 mm., calculated according to the formula which is given 
shortly. However, as shown by experiments in a low pressure chamber, the 
body can compensate for a brief period by excessive breathing, and the oxygen 
can be raised to approximately 36 mm. The time element comes in at this 
point because one cannot compensate by increased breathing to this degree for 
more than 15 to 30 minutes without development of fatigue and acapnia, with 
danger of cessation of respiration followed by death. Toward the end of the 
experiment the alveolar carbon dioxide is falling fast; this change indicates 
that the danger of acapnia is near. 
The theoretical partial pressure of oxygen in the alveoli of the 
lungs can he calculated by the formula: (Og) = |(B - Y.P.) X 02 “j - (CCs)a/E.$. 
inhere - pressure of oxygen in alveoli of lungs 
V.P. = vapor pressure saturation at body temperature (27° C.) = 47 mm. 
B. = barometric pressure 
02 « relative concentration of oxygen in air =0.21 per cent, or, more 
exactly, 6.2093 284 
(CO. ) = average pressure of carbon dioxide in alveoli of lungs = 40 nun. 
2 a 
R. Q. - respiratory quotient 
and where all pressure values are expiressed in millimeters of mercury. 
Examples Breathing air with R. Q,. of 1.0 at sea level 
(Oo) = f - 47) X 0.21 - 40/1.0 = 109 
p L 
It is important to note that the averages of the determination of tne 
alveolar oxygen at ascending altitudes made in the low pressure chamber cor- 
respond very closely to the theoretical curve up to about 12,000 feet. Above 
this elevation the partial pressure of oxygen in the alveoli becomes in- 
creasingly higher than the theoretical curve; the latter is based on the 
assumption that the body does net compensate. However, the fact that 
there is a corresponding decrease in the alveolar carbon dioxide pressure 
indicates that the body actually is able to compensate to a certain limited 
degree by hyperventilation, A similar tendency for the body to compensate 
is evident in the carbon dioxide curve in McFarland's data. 
The average alveolar oxygen pressure in the lungs can he increased 
definitely by slow deep breathing and the aviator's "ceiling" increased tempo- 
rarily by as much as 1000 or 2000 feet. It must be observed, however, that 
the alveolar oxygen increases and alveolar carbon dioxide decreases with 
deeper respiration. The decrease in carbon dioxide is dangerous because 
through its effect on the hydrogen-ion concentration of the blood it is a 
direct respiratory stimulant and is the chief factor in rendering breathing 
automatic. When the alveolar carbon dioxide is decreased, if the aviator is 
absorbed in fighting he may forget to breathe voluntarily and become uncon- 
scious from lack of oxygen before there is an automatic stimulation of respira- 
tion by rcaccuraulaticn of carbon dioxide. 
Oxygen consumption; rate of respiration, and rale of ventilation 
These are all essentially unaffected by changes in barometric pressure 
provided the development of anoxia is prevented by inhalation of oxygen. 
In this paper, several references have been made to the fact, well 
known to physiologists, that lack of oxygen is not a respiratory stimulant 
and that a subject will show no distress and slight increase in rate or depth 
of respiration from continuing to breathe decreasing concentrations of oxygen. 
This is very important to aviators because flyers may become unconscious at 
high altitudes without knowing that they are in danger. At the end of one 
experiment, with the subject breathing decreasing concentrations of oxygen, 
he was cyanotic owing to lack of oxygon and was already beginning to lose 
consciousness and would have done so completely in another few seconds if the 
experiment had not been terminated instantly. The great danger was the fact that he did not realize that he was in danger "because he experienced no dis- 
comfort or distress even toward the end of the experiment. This entire ex- 
periment was only about 27 minutes long, and the suoject of the experiment was 
above the simulated altitude of 15,000 feet only six minutes—a continuation 
of another minute and the subject might have collapsed and might not have re- 
covered. This is a dangerous type of experiment to conduct and should only 
be done by physicians thoroughly conversant with those dangers. 
Contrast the results of this experiment with these in cases in which 
the subject is breathing increasing concentrations of carbon dioxide with 
ample oxygen where the respirations are markedly increased with great respira- 
tory discomfort and distress as a result of increase in carbon dioxide from 
rebreathing oxygen without removal of the carbon dioxide by soda lime. Carbon 
dioxide, through the fact that it increases the hydrogen-ion concentration of 
the blood, is the chief regulator cf the respiratory mechanism as was shown 
by Haldane and Priestley. 
Carbon Monoxide 
The affinity of carbon monoxide for hemoglobin is approximately 300 
times as great as that cf oxygen. Carbon monoxide poisoning produces a more 
marked lowering of the oxygen pressure in the tissues than that produced by 
blooding, hemolysis, or inspiring air with half its normal percentage cf oxygen 
since the oxyhemoglobin still left gives up its oxygen less readily than normal 
oxyhemoglobin. Douglas, Haldane and Haldane (1912) shewed that the presence 
cf carbon monoxide hemoglobin causes the dissociation curve of the functioning 
hemoglobin which is still present to shift to the loft and the characteristic 
S shape disappears. As a consequence, hemoglobin has a stronger held on oxygen 
and will only release it to the tissues in appreciable amounts when the oxygen 
pressure is very low. Per adequate treatment, high concentrations of oxygen 
are indicated in order to displace the carbon monoxide from its union with the 
hemoglobin by mass action cf the excess oxygen. 
Cardiac Disease 
In a recent study on the effect of decreased barometric pressure on 
the electrocardiogram, Benson ' that when air is breathed by a normal 
subject, increased rate is seen in the electrocardiogram, beginning at about 
8,000 feet and increasing as the altitude is raised. The rate promptly returns 
to normal when oxygen is breathed up to and including 20,000 feet (Bar. 549); 
without oxygen, only a very slight and inconstant depression of the T wove and 
decrease in amplitude cf the QRS complex were observed in the case of healthy 
subjects. 
As a result of these observations and deductions from the literature 
on the subject, Benson felt that patients with cardiac disease and persons 
with silent and unknown coronary disease can fly in commercial aircraft pro- 
vided oxygen in adequate amounts is supplied by an efficient inhalation 286 
apparatus at altitudes in excess of 8,000 feet. Passengers wnc complain of 
respiratory distress or pain in the thorax while in flight should he immedi- 
ately supplied with oxygen as a precuaticnary measure. Patients with de- 
compensated cardiac disease should receive oxygen continuously. The fact 
that the action of the heart of a young healthy subject will quickly return 
to normal after oxygen has been administered at 20,000 feet does not neces- 
sarily apxdy to the pathologic heart. Anginal attacks nave been induced by 
lowering the oxygen tension of the inspired air, and Graybiel and his co- 
workers have called attention to the untoward effects of low oxygen tension 
in cases of cardiac disease, which may bo accentuated by the general physical 
unfitness so commonly associated with heart disease. Benson has reported the 
case in which a pilot had an initial and fatal attack of angina pectoris while 
flying at only 11,000 feet. 
G-raybiel and his co-workers made a study of the effects of experimental- 
ly induced asphyxiation on cardiac patients. These patients were subjected 
to an oxygen tension corresponding to an altitude of 14,500 feet for a short 
period. Although there were no subjective symptoms, three of the thirteen 
patients fainted, and four others exhibited signs of cardiac distress. The 
investigators concluded that many cardiac patients are in danger when the 
oxygen of the inspired air falls to 12 per cent or less. Levy, Barach and 
Brucnn, after observing the effects of the inspiration of air containing only 
12 per cent oxygen by patients with cardiac pain, concluded that persons 
known to have cardiac disease should rot bo allowed to go on flights at high 
altitudes unless proper provision had been made for supplying an adequate 
amount of oxygen at all times. 
White, on the basis of experiments on the effect cf anoxia in high 
altitude flight on the electrocardiogram, recommended 7,500 feet as a minimal 
level above which oxygen would bo required. 
It is agreed that patients with known cardiac disease are in definite 
danger from anoxemia, such as occurs in airplanes. It must be emphasized that 
there are many types of cardiac and respiratory lesions that may exist among, 
but that are unknown to, individuals who are intending to fly. It is accepted 
that many patients who have cardiac and respiratory diseases are on the verge 
of anoxemia at sea level, so that even a slight increa.se in elevation ?/ould 
rapidly bring them into a state of anoxemia. Fortunately, it is now unnecessary 
to subject passengers to these risks, since they can travel in perfect safety 
a.nd comfort by using an efficient inhalation apparatus for the administraction 
of oxygen. It is most important that passengers of this type use only a.n 
apparatus that is capable of maintaining them in the condition which exists 
at sea level, as far a,s oxygen is concerned- 
Effect of Sulfonamides on Pilots 
Pilots who are receiving sulfonamide compounds should be grounded until 
the course of therapy is completed and until they have returned to a normal 287 
condition. This is especially true in the case cf pilots with a definite 
history of severe sensitivity to sulfonamides. 
The reason for grounding pilots taking this group of drags is the 
toxic effects that may occur and require careful usage of the drugs and 
close daily observation cf the patients. Nausea and vomiting are the most 
constant symptoms of toxicity. Cyanosis and drug rashes are occasionally 
observed, as is drug fever. Cyanosis is believed partly due to the formation 
cf methemoglobin and this further reduces the oxygen-carrying power of the 
blood. Jaundice and toxic hepatitis rarely occur. The most important of the 
toxic manifestations, which are attributable to affection of the central 
nervous system of pilots arc headache, vertigo, malaise, mental depression 
and rarely a toxic psychosis. Any one of these manifestations would make 
it unsafe for the individual to pilot an aircraft. The mental reactions 
may occur early or late and generally disappear very quickly when the drug 
is discontinued. Ambulant patients should net even drive an automobile be- 
cause of the possible reduction in mental alertness. These mental symptoms 
are generally accentuated by altitude according to observations made on 
passengers on a large commercial airline. 
Equally important toxic effects are agranulocytosis or neutropenia 
and acute hemolytic anemia. Daily blood counts and hemoglobin determinations 
are an absolute requisite if these reactions are to be detected early. The 
danger of anemia, to pilots has been discussed elsewhere in this paper. No 
pilot should bo allowed to fly until all evidence of tcxic manifestations 
has subsided. 
In a recent discussion 'before the Aero-Medical Society in 1959, I 
described the case of a pilot who had to turn ever the controls of an airplane 
to the co-pilot at an elevation of 13,000 feet. His physician had ma,de a 
diagnosis of acute pharyngitis and laryngitis four days previously, and since 
then, the pilot had taken 160 grains (10.6 gm.) of sulfanilamide. The pharyn- 
gitis and laryngitis had cleared up, hut his "ceiling" had been reduced as 
the result of toxic manifestations and he found it impossible to pilot the 
flying boat at 13,000 foet. As a result of this observation a major airline 
made a ruling that no pilot shall fly while being treated with sulfanilamide 
or similarly acting drugs. Likewise, passengers who have been taking any of 
this group of drugs should bo given oxygen at relatively low altitudes. 
Aeroembolism 
Aerial warfare, with perfection of new types cf bombing, pursuit and 
interceptor airplanes, now may take place at altitudes of 30,000 to 40,000 
feet. The speed and rate of ascent of many of these aircraft expose their 
pilots to a new danger, in addition to the well-known danger of anoxia. 
Armstrong (1939) defined aeroembolism as a disease produced by a 
rapid decrease of barometric pressure below 1 atmosphere, such as may occur 
in .aircraft flights to high altitude, and which is marked by the formation cf nitrogen bubbles in the body tissues and fluids. 
Prevention of Aeroembolism 
On account of the serious discomfort lesulting from aeroemoolism, 
Soothby, Lovelace and Benson ( devoted their efforts to developing 
a practicable method of prevention by removal of the majority of the nitro- 
gen in the body by the inhalation of 100 per cent oxygen just before ascent. 
A preliminary report of our work was presented by me at the Annual Meeting 
of the American Association for the Advancement of Science in 1909. Up to 
the present time, in the low pressure chamber in Rochester, 102 ascents have 
been made to an altitude of 30,000 feet, eighty ascents to 35,000 feet, and 
thirty ascents to 40,000 feet. Although the simulated high altitudes as a 
rule were maintained for only a short time (ten to thirty minutes), in one 
instance two subjects remained at 35,000 feet for two hours and fifteen 
minutes. 
In some of these simulated ascents a certain train of symptoms were 
observed which were considered suggestive of aeroembolism. These symptoms 
were light-headedness, smarting and stinging of the conjunctiva, and 
formication and pains in extremities, around the joints or along the tendon 
sheaths or nerve trunks, none of our subjects has been paralyzed, become 
unconscious or experienced symptoms of such severity as to cause alarm; 
however, as soon as any of the symptoms appeared the simulated ascent was 
net only immediately stopped but the subjects usually descended about 5,000 
feet or until the symptoms disappeared. 
The next step in the investigation was to combine the inhalation of 
oxygen with exorcise. It was then found that symptoms no longer occurred, 
even if the period of decompression was reduced to thirty minutes, provided 
the exercise was the equivalent of walking at three miles per hour on a 
treadmill accompanied by considerable movement of the arms. The symptoms 
occurred occasionally when the decompression time was shortened cr the 
intensity of the exercise was decreased and the rapidity of ascent increased. 
The maximal rate cf simulated ascent was 4,700 feet per minute. 
Aural Distress. 
Among those accustomed to flying, it is well known that the most com- 
mon subjective complaint ox "both airplane pilots and. passengers is discomfort 
in the cars associated with ascent during flight. Lovelace, Mayo and Boothhy 
(193G) successfully used inhalation of 80 per cent helium and 20 per cent 
oxygen as an adjunct in the prevention or treatment cf aorc-otitis media. 
Inhalation cf this mixture through the B.L.3. inhalation apparatus, when 
descending from elevations cf 12,000 feet or with sufficient extra oxygen 
added at higher elevations, may he used to prevent aural distresses because 
the rate cf diffusion of helium is 2.7 times that of nitrogen; the helium 
will diffuse more rapidly through the eustachian tube than will air. More 
nearly similar pressures on both sides cf the tympanic membrane-can be maintained in this manner. As a result of tins suggestion the test pilots 
of a major airplane manufacturing company almost routinely inhale helium 
and oxygen during rapid descents. 
Types of Inahal&tion Apparatus 
Closed circuit system. She most economical principle ie admin- 
istration of oxygen is, of course, the closed circuit system. By such a sys- 
tem is meant a closed, circuitous pipe line, whose inside diameter is approxi- 
mately 1 inch, with an expansible chamber of bag of a capacity of net less 
than 5 liters for a single individual, although this ratio would not nave 
to be maintained for multiple units; a container for soda lime or similar 
substance for absorbing carbon dioxide; a circulating pump if the system is 
multiple, or a. properly placed inspiratory-expiratory valve when the system 
is constructed for use by only one individual, and an absolutely air-tight 
face mask. Large reducing valves arid automatic controls must be furnished 
to regulate the supply of oxygen. Both in the laboratory end in level fly- 
ing, this type of apparatus is particularly economical, as theoretically 
the total amount of oxygen needed should not exceed the amount of oxygen 
each individual actually burns, that is, approximately 0.25 liters at 
standard temperature and pressure dry (S.T.P.D.) per minute for a pilot who 
is relatively inactive and 0.7 liter (S.T.P.D.) per minute for an active mem- 
ber of the crew working or moving about in the plane. 
The practical objection to the closed circuit system is that air can 
easily leak into the system around the mask or at many other places, causing 
a dangerous accumulation of nitrogen. For this reason, the method is not 
used in commercial aviation. Furthermore, the economy in the use cf oxygen is 
not as great in aviation as one would at first suspect from theory, because 
of losses occurring during rapidly alternating ascent and descent. During 
descent the oxygen in the system will be compressed and the volume decreased, 
thus automatically activating the oxygen supply valves. On the following 
ascent, the oxygen would expand with the decrease in barometric pressure, 
and the oxygen would be lost through the escape or pressure safety valves. 
Rapid alternation of such procedure would be very wasteful of the oxygon 
reserves. 
Open circuit apparatus. The other type cf apparatus is known in the 
physiologic laboratories as an "open circuit apparatus," that is, the air 
is inspired with the addition of an appropriate amount of oxygen and then 
expired directly into the surrounding air with only a very small, incidental 
amount of rebreathing. In the open circu.it type of apparatus, no attempt 
is made to remove the carbon dioxide so that no more than a very small amount 
of the expired air with its enriched oxygon content can be used again. 
However, such a system, to bo economically of practice.! value in 
aviation or in clinical medicine for administration of oxygen, must contain 
a reservoir bag, in order to collect, save and have ready for use, on the 
next inspiration, the oxygen that ha.s been flowing from the tank during 290 
expiration. As the major part of the inspiratory phase of respiration is 
only from a third to a fifth of the respiratory cycle, it is obvious that 
unless such provision is made, only a third to a fifth cf the oxygen 
supplied can he utilized. This pcint is emphasized because many persons 
wonder about the necessity of a reservoir bag. Failure to use mere than 
a third to a fifth of the oxygen flow is one of many reasons why the old- 
fashioned '’pipestem11 method was sc inefficient and now is little used. 
However, to prevent the accumulation of an excessive and unbearable 
amount of carbon dioxide in such a reservoir bag, one must either use a 
small bag with a capacity somewhat less them the average amount of air ex- 
pired normally, or else prevent, by other rather complicated means, the ex- 
pired air from entering a larger bag. This reservoir bag is preferably placed 
close to the mask. However, it can be placed at the end of a long corrugated 
rubber tube (1 inch in diameter) provided that the capacity of the bag docs 
not exceed 450 to 600 cc.; provided that the intake of fresh oxygen is led 
directly into the bag, and provided that the automatic sponge rubber air 
regulator or expiratory valve is close to the monk. For most purposes, 
both in aviation and in therapy, it is preferable to have the bag attached 
directly to the mask. 
3.L.3. oxygon inhalation apparatus. The B.L.3. oxygon inhalation 
apparatus, which was developed by Boothby, (ll) Lovelace ( ' and Bulbulian 
in 1938, was modified by Boothby, Lovelace and TJihloin in 1940. At 
present, it consists of three separate parts: (l) the mask which is cf the 
nasal or oronasal type; (2) the regulating device, by means cf which the 
proper quantity of air is permitted tc enter the apparatus, so that any 
concentration cf oxygen desired can be obtained automatically without the 
wearer’s experiencing any significant resistance at any pha.se cf the respira- 
tory cycle, and (3) a. reservoir rebroathing bag, which conserves the oxygen 
(flowing from the reducing valve and flowmeter on the oxygen cylinder) 
without loss during the expiratory phase cf respiration, (normally about 
two-thirds to throe-fourths cf the respiratory cycle) and which at the same 
time automatically permits some rouse of the enriched oxygen mixture without 
undue or annoying accumulation of carbon dioxide. Those throe parts are 
constructed in relationship to each other for the greatest possible efficiency 
in the utilization of oxygen. 
A new principle in respiration apparatus is used in the present B.L.B. 
apparatus. Advantage has been taken of the fact that a porous sponge rubber 
disk will produce sufficient resistance tc the passage of air so that, during 
expiration, the light rubber reservoir rebreathing bag will fill completely 
before any appreciable amount of the inflowing oxygen and expired air will 
pass out of the apparatus through one of the sponge rubber disks. However, 
the resistance of the sponge rubber to passage of air is so slight that as 
soon as the reservoir bag is distended by the first part of the expired air, 
which is rich in oxygen and poor in carbon dioxide, the remainder of the 
expired air will pass out of the apparatus without any significant increase 
in resistance to normal expiration, and, conversely, on inspiration, the 291 
subject can barely detect an increased resistance to complete inspiration in 
those instances in which. the addition of a large proportion oi ai± is desired 
in order to obtain comparatively low concentrations of oxygen. In brief, 
the sponge rubber dish acts* with barely appreciable resistance, as b com- 
bined inspiratory-expiratory valve and nas an efficiency of approximately 
98 per cent. It is called an "automatic air regulator." The two sponge 
rubber disks are retained in a convenient position on the inhalation apparatus 
by means of proper sized receptacles molded directly in the rubber mask. 
When using the B.L.B. apparatus at xOw altitudes* mixtures of air 
and oxygen are used; at altitudes of more than 30,000 feet, practically pure 
oxygen is breathed. By a proper sotting of the oxygen flow the amount of 
additional air required at the lower altitudes is supplied automatically 
through the sponge rubber disk. 
The nasal typo of mask with the mouth free for talking or eating is 
preferable for use on commercial airlines, both for crew and passengers, 
as the elevations to which they ascend rarely exceed i5,000 feet. For mili- 
tary aviation, an oronasal type of mask is preferable in order to avoid the 
danger of unconsciousness resulting from mouth breathing at the higher alti- 
tudes. 
(13) 
The experimental data of Bocthby, Lovelace and Benson ' show that 
the amounts of oxygon recommended are sufficient to maintain an essentially 
normal concentration of alveolar oxygen (between 30 and 120 mm.) for all 
elevations up tc and including 35,000 feet, when the aviator is sitting and 
doing work comparable to operating a piano under normal air conditions. The 
experiments that show rather high results probably would be obtained in 
actual flight when the aircraft was being controlled by the automatic pilot 
and the lower results, when the pilot is actually flying the plane. Theoreti- 
cally, when inhaling pure oxygen the aviator should have a normal alveolar 
oxygen pressure at 33,000 foot; the data show, on the average, that this is 
true and even up to 35,000 feet in no single experiment was the alveolar oxy- 
gen pressure below what it would bo at 6,000 feet without inhalation of oxygen. 
Tiie data for 40,000 feet show that the alveolar oxygen pressure, in 
the few determine!ions that were made, corresponds to pressure that would be 
obtained by testing a pilot breathing air without an additional supply of oxy- 
gen at 11,000 feet. In fact, the data are even slightly above the line repre- 
senting the theoretical value for breathing pure oxygen. This is due to the 
fact that the compensatory increase in the rate and depth of respiration ele- 
vates slightly the average alveolar oxygon pressure. The entire scries of 
experiments give definite proof of the efficiency of the B.L.B. oxygen in- 
halation apparatus. 
In table 3 (p. 305) there are indicated under the heading "aviator, 
inactive, " the minimal rates of oxygen flow needed by an aviator at various 
altitudes using the B.L.B. oxygen apparatus while sitting and piloting his 292 
plane with a minimal amount of muscular exertion. Under these conditions* 
an aviator of average size would he consuming about 250 to 300 cc. (S.T.P.D.) 
of oxygen per minute* measured at standard temperature C.) and pressure 
(750 mm.) dry. Under the heading "aviator, active," is given the amount of 
oxygen needed for a pilot under conditions of rather difficult navigation 
or for a machine-gunner firing but not doing a great deal of lifting or 
moving about. These degrees of work would roughly correspond to an oxygen 
consumption of 400 to 500 cc. per minute (S.T.P.D.). Under the heading 
"aviator, very active," is given the amount of oxygen needed for a pilot or 
machine-gunner working rather strenuously. This is estimated to be between 
500 and 600 cc. per minute (S.T.P.D.). This degree of work would correspond 
to that of a man walking at a rate of approximately 2 miles per hour. Por 
each value as expressed at S.T.P.D. the value to which this amount of oxygon 
expands in the lungs of the aviator at each altitude is also given. 
Other types of inhalation apparatus. Administration of oxygon to 
aviators by the commonly used tube and pipestem method is inefficient and 
expensive. The primary drawback to taking oxygen through a tube is that a 
normal individual ordinarily exhales from half to two-thirds of the time, 
so that half to two-thirds of the oxygen which comes through the tube is lost. 
In addition, considerable training is required to get an individual to 
breathe in only through the tube. No matter how well trained he is, there 
is no way of controlling the amount of outside air breathed in during undue 
stress or excitement. Naturally, the higher the pilot goes, the greater 
will be the danger of brea.thing in atmospheric air and the more chance there 
will be for the development cf sudden, severe anoxemia; in fact, at high alti- 
tudes, if the tube should drop cut cf the pilot’s mouth he might become un- 
conscious in one minute. There is also a frequent complaint cf irritation cf 
the mucous membrane cf the meuth and threat and cf salivation. Moreover, it 
is difficult and dangerous to talk over the radio while using such equipment 
and the apparatus is in the way during acrobatic maneuvers. It is admitted 
that a. pilot, or, for that matter, a physician, is unable to recognize the 
onset of symptoms cf anoxemia, which can occur very easily when the oxygen 
is taken inefficiently by this method. 
Extensive research is now being carried cut on a demand type of 
apparatus in which the oxygen would be supplied only on inspiration. 
Emergency Parachute Escape 
=2 a.— 
Parachute jumps from 35,000 to 40,000 feet are made whenever abandon- 
ment of the ship is necessary to save life. After the necessity for bailing 
out arises, a minute probably elapses before the preparation to jump can bo 
completed. At an elevation of much more than 25,000 feet, cerebral anoxia 
would be present at the end of a. minute without oxygen, and unconsciousness 
would begin to come on. In a case in which a test pilot took off his oxygen 
mask at an altitude cf 35,000 feet in the low pressure chamber a.t the Mayo 
Clinic and then went through the motions of leaving a plane, unconsciousness 
and convulsions occurred in forty seconds. Even if the aviator descended as 293 
a free falling body until he reached 20,000 feet, he would in the second 
minute become unconscious and therefore be unable to pull his rip cord. 
On the other hand, if he pulled his rip cord within a few seconds after he 
left his plane, it would take five to ten minutes to descend to where he 
would have sufficient oxygen to live, and then he would have little chance 
of regaining consciousness. Therefore, a parachutist must be provided with 
special oxygen inhalation equipment for his descent. 
Boothby, Benson and Lovelace have devised such an apparatus, 
which consists of a small cylinder of oxygen with accessory apparatus and 
mouthpiece. The emergency cylinder contains 34 liters of oxygen, which is 
sufficient to last ten to fifteen minutes and to maintain consciouness. In 
fact, it is sufficient, if the aviator is properly trained in its use, to 
maintain consciousness down to 10,000 feet or 15,000 feet, at which height 
he will, of course, be safe. The emergency cylinder can be carried in a 
specially constructed and strongly reinforced pocket in his parachute harness. 
As the mask probably would be.blown away during the act of jumping out 
of the plane, it is necessary to supply a mouthpiece with automatic sponge 
rubber valve which the aviator places in his mouth and >grips with his teeth 
before jumping. This mouthpiece is held in place just below the chin by a 
rubber strap around the neck, so that the aviator can quickly place the 
mouthpiece in his mouth, grasp it firmly with his teeth, open the emergency 
cylinder valve, and jump. This procedure, about which it takes so long to 
tell, can be accomplished in a few seconds. Tests have been made with per- 
fect ease from a simulated 40,000 feet, in a low pressure chamber, with 
descent at the calculated rate of a parachutist. As yet, tests have not 
been made in an actual jump from a plane at a high elevation. 
Supercharged Cabin 
The best method on commercial airlines compensating for the decrease 
in the partial pressure of oxygen at altitude is by use of the supercharged 
cabin airplane. This procedure is possible and practical, since the per- 
centile composition of the air is essentially the same at very high alti- 
tudes as it is at sea level. By increasing the pressure of the air in the 
cabin of such an airplane, the partial pressure of oxygen is obviously 
raised to the desired level. By maintaining the pressure inside the cabin 
at or near ground level pressure, car and sinus pain, as well as gaseous dis- 
tress, is eliminated. 
Transportation of Patients by Airplane 
The airplane is continuing to be of more and more value not only for 
the conveyance of patients by air, but also for the transportation of doctors 
and medical supplies to the scene of disaster, particularly if there has been 
a major catastrophe, such as a tornado, flood, or earthquake. 
Simpson, in 1939, advocated the mere extensive use of airplane 294 
ambulances in the array and emphasized greater speed end comfort in flight. 
These two factors, in many instances, would mean the saving of lives, and 
in addition there would be a decided conservation of medical personnel, since 
the work of the mobile surgical unit in the field would be considerably 
diminished. He assumed 4,000 casualties a day in an infantry brigade in a 
beginning offensive; 150 killed, 450 ambulatory, 200 requiring transporta- 
tion in a sitting position, and 200 in a recumbent position. Of these 200, 
eighty were considered as "non-evacuable,,r but destined for a surgical hos- 
pital. If these eighty could be transported to a surgical hospital by 
litter and motor ambulance, they could then bo transported by airplane 
directly to a general hospital, which would shorten materially the time re- 
quired to bring casualties to their ultimate destination. When there is a 
landing field in the vicinity of a collecting station, these eighty patients 
could bo flown to a general hospital in less time than would be required to 
transport them to a surgical hospital by motor ambulance. Three large air- 
planes similar to those new in use on commercial airlines, with distinctive 
markings, could easily carry these patients at one trip or one such airplane 
could carry them in three trips. Approximately thirty minutes of flying 
time would bo required for a 100-mile flight of this nature. 
Lieutenant General Hippke, Surgeon General of the German Air Force, 
discussed (1940) airplane evacuation of the sick and wounded from Poland to 
hospitals in Germany, A total of 2500 patients wore evacuated in this manner, 
which, at this rate, would mean that 30,000 patients a year could be evacu- 
ated. Every airplane ambulance had an experienced medical officer aboard. 
Hippke advocated the use of commercial passenger planes on which the proper 
insignia could be painted and the necessary litter installations made. 
Of the 2500 patients transported by air from Poland to Germany, 
only four died either in the airplane cr immediately after landing. One 
patient had a gunshot wound of the lumbar vertebrae with retroperitoneal 
hemorrhage; two had pulmonary wounds and hemothorax, and the fourth had 
severe peritonitis. 
On the return trip, medical supplies and medical personnel for 
replacement purposes could be carried, which would decrease the amount of 
material that would ordinarily be carried by trucks and would relieve the 
roads of much traffic. During the Polish campaign, medicine, serums, medical 
and surgical equipment, special dressings and special diets for dysentery 
patients in field hospitals were all transported to the front by airplane 
ambulances. 
Airplane ambulances should bo well heated, comfortable, as quiet .as 
possible, have adjustable litters that could either bo placed in the shock 
cr head-up position, and carry suitable masks for the administration of oxygen. 
Simpson advocated the institution in flight cf such emergency treatment as 
applied ion or adjustment cf splints, administration cf stimulants and nar- 
cotics, the arrest cf hemorrhage, and the treatment of shock, including the 
intravenous admini strati on cf fluids. Light weight sponge rubber mattresses 295 
would be very comfortable for the patients. The litters should be so arranged 
that the patient could either be recumbent, in the shock position, or in the 
head-up position. 
heaven recommended (1335) the use of two types of airplane ambulances I 
a small or rescue type capable of landing and taking off in small emergency 
field, and a large or transport type of airplane for routine work. In addi- 
tion to the large transport type of airplane ambulance, Hippke (1940) also 
advocated small planes with a low landing speed in regions where the roads 
are blocked and the motor ambulance has difficulty in reaching the loading 
points or where suitable landing fields are not available. This sma.ll type 
of shuttle plane is independent of the roads and can land close to every 
dressing station. 
heaven also felt that the transportation of patients by airplane ambu- 
lances would relieve the hospital station and evacuation hospitals of a large 
percentage of their load. Other advantages would be the ability to reach 
isolated army stations with highly trained personnel or to transport some 
patients to larger hospitals where they could be treated by specialists, 
heaven also advocated the use of airplane ambulances during maneuvers and at 
air corps training schools. 
The disadvantages of airplane ambulances are: necessity for reasonably 
good lending fields and servicing facilities, adverse weather, the need for 
trained pilots, and the danger of attack by enemy aircraft. In many instances, 
the airplane ambulances could be flown and serviced from regular army air 
fields. Very bad weather would force cancellation of flights. Civilian 
pilots with adequate training could relieve the army pilots. Stewardesses 
from the commercial airlines could be quicly trained in the care of wounded 
in flight. All trips would bo behind the front linos and distinctive markings 
could bo employed on the wings and fuselage of the planes. Night flights 
could also be made. 
The advantages of transport of wounded by airplane are: unusual 
speed and comfort in transit instead of a rough and long ride in a motor 
ambulance; safety, conservation of medical personnel and field equipment, 
adequate treatment for the badly injured and seriously ill by shortening 
materially the period of time needed to bring them to their ultimate destina- 
tion, thereby improving his chance of recovery, especially if a major surgical 
procedure is necessary. Morale would be higher than the average if a soldier 
know such service was available. 
Schmidt pointed out that in contradistinction to all transportation 
on land, the airplane maintains its speed without appreciable interruptions 
from take-off to landing. Wounded German soldiers felt very grateful for 
their transportation to their home bases for treatment and they maintained a 
high morale. 
Air Commodore Glynn of the Royal Air Force considered (1940) the 296 
airplane ambulance as a very valuable addition to the existing mechanical 
means of transport, that is, motor ambulances, ambulance trains, ambulance 
barges and hospital ships. However, the airplane is considered the most 
efficient means of transporting casualties that exist since only aircraft 
can convey patients vast distances over rough terrain to large, well equipped 
hospitals in the shortest possible time with a minimum of discomfort. 
The advantages of judiciously employed airplane ambulances in Glynn's 
estimation are s.s follows; rapid evacuation of casualties from forward zone; 
quick transportation of seriously injured persons to a base hospital where 
specialists would be available; a more even distribution of patients to vari- 
ous base centers; decreased work of surgical teams in forward areas; decreased 
congestion on the lines of communication; maintenance of the morale of the 
patients since they would know that a completely equipped and adequately 
staffed hospital would be reached in a short time. 
Hippke (1940) felt that it is of decisive importance that seriously 
wounded patients reach the operating surgeon promptly, and on the basis of 
personal observation stated that it is clear that air transportation is far 
loss injurious to the patient than is ground evacuation, regardless of the 
time consumed in the movement. Other advantages stressed by Hippke are the 
actual speed and short duration of evacuation by air as well .as the opportuni- 
ty to haarc the patients constantly observed and cared for by trained personnel 
during flight. 
An example given by Tonnis as to the effective support ambulance air- 
planes can render was in the case of a patient who had an abdominal wound 
with prolapse of the small intestine, incurred near Warsaw. He arrived on 
the operating table of the surgical clinic of the University of Breslau 
two and a half hours after the wound was received. It was emphasized that 
this is a record to which the patient owed his uneventful recovery. Ocular 
injuries, wounds of joints, and gunshot fractures and wounds of the lung 
wore particularly benefited by airplane evacuation of patients to surgical 
clinics whore the best personnel and diagnostic therapeutic equipment were 
available. In previous campaigns it was observed that patients with gunshot 
wounds of the lungs and severe fractures of the extremities did not tolerate 
well transportation by land. 
The information required by the R.A.F. Headquarters, whose units will 
supply the aircraft, should include in Glynn's opinion the number of patients 
lying and sitting, to be evacuated, the site of the evacuating units, the 
desired time of arrival of the airplanes, and the destination. The medical 
authorities at the Base would be informed of the terminal airport, number of 
cases and condition of patients and expected time of arrival, to insure the 
availability of ambulances and hospital accommodation. 
Major F, Schmidt, commander of an ambulance -squadron in the German Air 
Force, advocated a strap to secure each litter in place to guard against 
sudden lurching of the plane caused by rough air, the smooth, rapid exchange of 297 
empty for loaded litters, the grouping of several planes into a medical squad- 
ron, well ventilated and heated cabins, and the use of small communications 
airplanes to restore broken contacts quickly, receive new orders, and select 
satisfactory landing fields near the wounded. 
Additional uses of aircraft listed by G-lynn include the mobile surgical 
teams in the Ro3ral Air Force which are maintained instantly available for dis- 
patch by air to any airport where the number end severity of the casualties 
demand their services. The personnel of these teams includes a surgeon, an 
anesthetist, a theater sister, and two operating room assistants. The equipment 
in portable packs is completely self-contained and includes operating lights 
and a portable operating table. Within a few minutes after the plane has land- 
ed, operations of any nature can be undertaken. The total weight of the equip- 
ment is about 1120 pounds, which is contained in a space of approximately 50 
cubic feet. Airplanes can also convey transfusion teams with apparatus and 
stored blood to any desired locality, as well as permit the teams to carry cut 
transfusions in flight. In the case of isolated posts with no adjacent land- 
ing fields, medical supplies can be dropped by parachute. 
It is new an accepted fact that the onset of anoxemia in a. normal in- 
dividual occurs at an altitude of 10,000 to 11,000 feet. It is seldom neces- 
sary to go higher in airplane ambulances. Since the amount of oxygen that is 
taken up by the hemoglobin and the plasma is directly dependent on the partial 
pressure of oxygen in the atmosphere and in the alveolar air, it is obvious 
that any clinical condition which causes anoxemia will be borne less well in 
high altitudes than at sea level. For example, at sea level the partial pres- 
sure of oxygen to which the alveoli of the lungs are exposed is calculated as 
follows: 760 mm. —47 mm. x 20.93 per cent = 149 mm.; whereas at 10,000 feet 
it would be 523 mm. —47 mm, x 20.93 per cent « 99.6 mm. instead of the normal 
sea level pressure of 149 mm. The percentile composition of the air is the 
same. Therefore, airplane ambulances should operate at as low an altitude as 
is safe and smooth not only to avoid anoxemia but also to prevent undue expan- 
sion of the gasses in the gastrointostinal tract. Anoxemia would na/turally occur 
at a much lower altitude in certain types of patients being transported by 
airplane ambulance, and for this reason it would be essential to have efficient 
oxygen masks available on the planes. 
Schnedorf, Munslow, Crawford, < nd McClure demonstrated experimentally 
that concussion of the brain, with or without fracture of the skull, caused 
a depression of the arterial oxygen from 5 to 44 per cent below normal in dogs 
and patients. Oxygen therapy restored the oxygen of the blood saturation to and 
above normal and decreased the marked elevations of body temperature to normal. 
They concluded that oxygen therapy is indicated for the combating of anoxmia 
which results from injury of the head and for the amelioration of reactions 
which follow injury of the brain and mild anoxia. As a result of the demonstra- 
tion of anoxia resulting from injury of the head at ground level, it would seem 
most advisable to administer oxygon to all patients with moderate to severe in- 
juries of the head, who are being transported in airplane ambulances, in order 
to reduce the morbidity and mortality of head injury with an associated cerebral 298 
injury. 
Walsh (43) reported the following observation in the case of a woman 
aged thirty-five years who had undergone right temporal craniotomy for focal 
encephalitis and had recovered satisfactorily. The center of the scalp over- 
lying the bony defect in the skull was, at times, depressed about 1.5 cm. 
below, and at other times it was elevated 0.5 cm, above the level cf the skull. 
During ascent in a low pressure chamber, this subject- inhaled a high concentra- 
tion of oxygen. At a simulated-altitude of 28,000 feet, corresponding to a 
barometric pressure-of 247 mm, or about a third-jof. an atmosphere, the scalp 
was elevated about 0,5 cm. above the level of the skull, from the-original level 
of 0,5 cm, below the level of the skull. On descent -to-ground level, the scalp 
returned to the original level. This observation was considered by Walsh to 
indicate a change in volume of the intracranial, contents#- the exact cause of 
which was not determined. However, if the cranium had boon intact, the 
spinal pressure,- according to Walsh and Boo they, (4*)- would have-shown" an in- 
crease of approximately 3 cm* of spinal fluid in a manometer arm attached to a 
■spinal-puncture needle on ascent to 28,000 feat* - -Walsh.and Boothby demonstrate 
air bubbles in a glass-manometer attached tc a spinal puncture needle introduce 
into-the -spinal canal of throe men; in cne case., -bubble formation was observed 
in the spinal fluid in-the ..ascending limb, cf the manometer at a height jf 
10,-QOO feot-r In the second and third cases the formation-was-seen at 12*000- 
feet. The became larger-and more .numerous up to 28,000 feet; after a 
few minutes’ at this altitude they decreased in size -and'number and- shortly 
disappeared. 
Armstrong-placed. animals -vrith-trephined-skulls, in~a’low-pressure 
-chamber-and observed the brain as the pressure was decreased. The brain began 
to expand, at-about 17,000 feet, and at 12,000, feet, or slightly above* definite 
■expansion, of the brain was observed. 
Major 'T/ Tonnis*- consulting ■ surgeon *_.Gf flee of irhev Surgeon - Gonerair ..Air 
■Pcrces"in Germany, found that all seriously wounded soldiers have suffered from 
more or less severe-hemorrhage so that on the second, or third days -the -concen- 
tration nf hemoglobin may range between 25 and 53 per cent. In such cases, an 
altitude of approximately 4,000 feet was not exceeded unless-oxygen was-avail- 
able. 'The-breathing capacity was found to be reduced in cases of gunshot wounds 
of the...lungs with hemothorax as well as in cases of gunshot■ wounds of the abdomen 
with a resultant elevated diaphragm resulting from .distention or accumulation cf 
fluid.-Such patients suffered from definite respiratory distress at altitudes 
as lew as 4,00.0. feet,- but this cculd. be relieved by the, adxainis.tration of oxygen* 
In considering the -transportation of .anemic, patients by,airplane,..it is 
important tc remember that the arterial blood as it leaves the lung is normally 
saturated with, oxygen, in cases, of anemia, but-since there is .a. ..sub normal .quantity 
of hemoglobin to unite with it, less oxygen can be carried. An anemic patient 
may not be cyanotic -oven if,.the .saturation of- arterial blood is as low as 60 
per cent* because- cyanosis is a direct result-of reduced hemoglobin* Oxygen, 
preferably in higincorrcrcrrt ration, should bo .administered even at relatively log 299 
altitudes in flight to patients with severe anemia as a prophylactic measure 
to forestall a failure in the normal compensatory mechanism. 
Oxygen deficiency can be controlled by the administration of oxygen 
by a suitable mask such as the B.L.B. inhalation apparatus. Hippke advised 
the routine administration of oxygen to all patients at an altitude of above 
11,500 feet. Oxygen deficiency certainly plays a role in cases of gunshot 
wounds of the lungs. 
The best preventive measure in cases of airsickness, according to 
Hippke» is the recumbent position (shock position). 
(31) 
Pneumothorax. Lovelace and Hinshaw have shown the hazards of 
aerial transportation to patients with pneumothorax. Boyle’s law states that 
the volume occupied by a given quantity of gas is inversely proportional to 
the absolute pressure exerted on it. It is obvious that this law would apply 
to the pneumothorax if the impounded air is enclosed in a pocket with adequate- 
ly flexible walls. A progressive decrease in atmospheric pressure produced 
by ascent will thus tend to increase pulmonary collapse in cases of thera- 
peutic, spontaneous cr traumatic pneumothorax. The volume occupied by a 
pneumothorax should be doubled by ascent from sea level to an altitude of 
slightly more than 15,000 feet (table 4, p. 306)Even an altitude cf only 
10,000 feet should cause considerable increase (1.5 times) in the volume of 
a pneumothorax. 
The hazards cf large and rapid increases in pulmonary collapse are 
well known. Pleural adhesions, if present, may be subjected to sufficient 
tension to produce rupture, and if tuberculous tissue is thus exposed, tuber- 
culous empyema could occur with disastrous results. Even in the absence of 
adhesions, a large pneumothorax can cause sufficient compression to embarrass 
respiration seriously. 
Demonstration of increased volume of a pneumothorax during simulated 
altitude ascent in a low pressure chamber was recently carried out by means 
of roentgenograms of the thorax taken at various altitudes up to 12,000 feet. 
This increased collapse was found to be very striking. 
The steadily increasing popularity of airplane transportation makes 
it urgent that physicians be warned of its special dangers to these patients. 
Those with pleural adhesions, those with a pneumothorax of large volume and 
these whose pneumothorax has recently been refilled are in greater danger. 
Willcox and Poster-Carter (1937) reported s. case in which spontaneous 
pneumothorax occurred, during flight, in a pilot who had an associated 
bullous emphysema as proved by roentgenograms and necropsy. 
Gas in gastro-intestinal tract. Just as in the case of expansion 
of the air in a pneumothorax, gas normally present in the gastro-intestinal 
tract will expand with altitude, according to the corresponding change in 300 
atmospheric pressure (table 4)-. Ordinarily* relief is obtained "by belcning 
and passing flatus. If patients who have penetrating wounds of the stomach 
or intestine are "being transported by airplane* the expansion of gas would 
he a serious problem, inasmuch as the gas would he forced out through the 
openings in the intestine and carry fecal material with it and materially 
increase the danger from peritonitis. The leakage of gas would prohahly not 
occur at very low altitudes, hut the only way to prevent it at high altitudes 
weald he hy the use of a pressure cahin type of airplane in which the pressure 
inside the cahin would he maintained at or near ground level. Armstrong has 
pointed out that patients with strangulated hernia cr intestinal obstruction 
should not he exposed to high altitude for this reason. 
Shock. Severe shock was considered hy Hippke to he on ohsolute 
contraindication to transport hy airplane ambulance. It is believed this 
contraindication refers to secondary or wound shock which is a condition of 
circulatory failure, caused hy diminished blood volume, with a consequent 
fall in cardiac output and blood flow through the tissues of the body. 
Contributory ■ factors to the development of such shock, aside from hemor- 
rhage, are fatigue, dehydration, exposure to cold, and pain. When a patient 
in shock would have to he transported by airplane ambulance because of ap- 
proaching enemy troops, it would he well to heed the advice of the Germans 
and administer 1,000 to 2,000 cc. of blood in order to restore a relatively 
normal blood volume, which will often prevent irreversible damage to blood 
■vessels and to the central nervous system. 
/ rj r \ 
As ‘brought out in the British ' ' ; report on shock, from a practical 
aspect and with wounds of war, the usual dehydration of a wounded man tends 
to inhibit compensatory blood dilution from hemorrhage, while the amount of 
tissue injury encourages loss of plasma. If signs of shock are present, 
particularly pallor and a pulse rate greater than 110, treatment should be 
instituted without delay, even though the systolic blood pressure is more 
than 100 mm, of mercury. As stressed in this report, if the blood pressure 
is more than 100 mm. of mercury, the condition is partially compensated, but 
the .arterial pressure is being maintained only by intense vasoconstriction 
and is likely to fall with the slightest intensification of shock, as, for 
example, as a result of anesthesia or a small loss of blood or plasma, or 
anoxemia. 
Procedures employed for the treatment of shock in the resuscitation 
wards in England include: complete rest in a quiet and comfortable shelter; 
warm clothes and external application of heat; morphine for the relief of 
pain; arrest of hemorrhage and loss of plasma by a properly applied 
tourniquet or pressure bandage; transfusion to restore blood volume; adminis- 
tration of fluids, and the administration cf oxygen in high concentration with 
the 3,L.B. inhalation apparatus cr other suitable equipment which tends to 
relievo tissue anoxia .and may bring about considerable improvement in case 
of shock. 
Infection. In the presence cf fulminating infection of any kind, 
even if the infection itself is uninfluenced, the circulatory collapse 301 
associated with peritonitis, septicemia, and similar conditions can he re- 
lieved partially, at least, hy the administration of high concentrations of 
oxygen. Oxygen is particularly indicated to prevent or decrease the 
additional anoxia and other secondary reactions which often accompany the 
administration of sulfanilamide or similar drugs. 
Hyperthyroidism. In cases of hyperthyroidism, anoxemia may develop 
easily and frequently may lead to serious consequence because of the rela- 
tively increased consumption of oxygen, as evidenced hy an elevated hasal 
metabolic rate. 
Table 1 
National Advisory Committee for Aeronautics 
Report No. 538 
Altitude-pressure tables cased cn the United States standard atmosphere (1935) 
A11 i tude -p r e s sur e-1 emp o rature t ah1e 
(To which is added the equivalent oxygen per cent)* 
Pressure 
Temp. 
Mean Temp. 
Equiv. oxygen 
Altitude, feet 
in. Hg 
mm. Eg 
* 
U . 
cC. 
per cent 
0 
29.921 
760.0 
15.0 
15.0 
20.93 
500 
29.38 
746.4 
14.0 
14.5 
20.56 
1,000 
28.35 
732.9 
13.0 
14.0 
20.18 
1,500 
28.33 
719.7 
12.0 
13.5 
19.82 
2,000 
27.82 
706.6 
11.0 
13.0 
19.46 
2, 500 
27.31 
693.8 
10.0 
12.5 
19.11 
3,000 
25.81 
631.1 
9.1 
12.0 
18.75 
3,500 
26.32 
668.5 
8.1 
11.5 
18.41 
4,000 
25.84 
656.3 
7.1 
11.0 
18.07 
4, 500 
25.36 
644.2 
6.1 
10.5 
17.74 
5,000 
24.89 
632.3 
5,1 
10.0 
17.41 
5,500 
24.43 
620.6 
4.1 
9.5 
17.09 
6,000 
23.98 
509.0 
3.1 
9.0 
15.77 
6, 500 
23.53 
597. G 
2.1 
8.5 
16.46 
7,000 
23.09 
586.4 
1.1 
8.0 
16.15 
7,500 
22.65 
575.3 
0.1 
7.5 
15.84 
8,000 
22.22 
564.4 
-0.8 
7.0 
15.54 
8,500 
21.80 
553.7 
-1.8 
6.5 
15.25 
9,000 
21.38 
543.2 
-2.8 
6.0 
14.96 
9,500 
20.98 
532.8 
-3.8 
5.5 
14.67 
10,000 
20.53 
522.6 
-4.8 
5.0 
14.39 
10,500 
20.18 
512.5 
-5.8 
4.5 
14.11 
11,000 
19.79 
502.6 
-6.8 
4.0 
13.84 
11,500 
19.40 
492.8 
-7.8 
3.5 
13.57 
12,000 
19.03 
483.3 
-8.8 
2.9 
13.31 
12,500 
18.65 
473.8 
-9.8 
2.4 
13.05 
13,000 
18.29 
464.5 
-10.8 
1.9 
12.79 302 
13,500 
17.93 
455.4 
-11.7 
1.4 
12.54 
14,000 
17.57 
445.4 
-12.7 
O.S 
12.2S 
14,500 
17.22 
437.5 
-13.7 
0.4 
12.05 
15,000 
16.38 
428.8 
-14.7 
-0.1 
11.81 
15,500 
16.54 
420.2 
-is;? 
-0.6 
11.57 
16,000 
16.21 
411.8 
-16.7 
-1.2 
11.34 
16,500 
15.89 
403.5 
-17.7 
-1,7 
11.11 
17,000 
15.56 
395.3 
-18.7 
-2.2 
10.89 
17,500 
15.25 
387.3 
-19.7 
-2.7 
10.67 
18,000 
14.94 
373.4 
-20.7 
-3.2 
10.45 
18,500 
14.63 
371.7 
-21.7 ' 
-3.7 
10.24 
19,000 
14.33 
364.0 
-22.6 
-4.3 
10.02 
19,500 
14.04 
355.5 
-23.6 
-4.8 
9.82 
20,000 
13.75 
349.1 
-24.5 
-5.3 
9.61 
20,500 
lo. 46 
341.9 
-5.3 
9.42 
21,000 
13.18 
334.7 
-26.6 
-6.3 
9..22 
21,500 
12.90 
327.7 
-2?. 6 
-6.9 
S.02 
22,000 
12.63 
320.8 
-28.6 
-7.4 
8 • 85 
22,500 
12.56 
314.1 
-29.5 
-7.9 
S.65 
23,000 
12.10 
307.4 
-30.5 
-8.4 
0.47 
23,500 
11.84 
300.9 
-31.5 
-9.0 
8.20 
24,000 
11.59 
234.4 
-32.5 
-9.5 
8.11 
24,500 
11.34 
288.1 
-35.5 
-10.0 
7.93 
25,000 
11.10 
281.9 
-34.5 
-1C.5 ' 
7.76 
35,500 
10.36 
275.8 
-35.5 
-11.1 
7.50 
26,000 
10. 52 
269.8 
-36.5 
-11.5 
7.43 
26,500 
10.39 
253.9 
-37.5 
-12.1 
7.27 
27,000 
10.16 
258.1 
-38.5 
-12.7 
7.11 
27,500 
3.94 
252.5 
-39.5 
-13.2 
6.95 
28,000 
S. 72 
246.9 
-40.5 
-13.7 
6.80 
28,500 
9.50 
241.4 
-41.5 
-14.3 
5.65 
29,000 
9.29 
236.0 
—42.5 
-14.3 
6.50 
29,500 
9.08 
230.7 
-43.4 
-15.3 
6.35 
30,000 
3.88 
225.6 
-44.4 
-15.3 
6.21 
30,500 
8,68 
220.5 
-45.4 
-15.4 
6.07 
31,000 
8.48 
215.5 
-45.4 
-16.9 
5.93 
31,500 
8.29 
210.5 
-47.4 
-17.5 
5.80 
32,000 
8.10 
205.8 
-43.4 
-18.0 
5.67 
32,500 
7.91 
201.0 
-49.4 
-18.5 
5.134 
33,000 
7.73 
196.4 
-50.4 
-19,1 
5.41 
33,500 
7.55 
191.8 
-51.4 
-19.6 
5.28 
34,000 
7.38 
187.4 
-52.4 
-20.2 
5.16 
34,500 
7.20 
183.0 
-53.4 
-20.7 
5.04 303 
35,000 
7.04 
178.7 
-54.3 
-21.3 
4.92 
35,332 
6.93 
175.9 
-55.0 
-21.6 
4.84 
35,500 
5.87 
174.5 
-55.0 
-21.8 
4.81 
35,000 
5.71 
170,4 
-55.0 
-22.3 
4.69 
36,500 
6.55 
166.4 
-55.0 
-22.8 
4.58 
37,000 
5.39 
162.4 
-55.0 
-23.3 
4.47 
37,500 
6.24 
158.6 
-55.0 
-23.8 
4.37 
38,000 
6.10 
154.9 
-55.0 
-24.3 
4.27 
38,500 
5.95 
151.2 
-55.0 
-24,8 
4.16 
39,000 
5.81 
147.6 
-55.0 
-25.2 
4.06 
59,500 
5.68 
144.1 
-55.0 
-25.6 
3.97 
40,000 
5.54 
140.7 
-55.0 
-26.0 
3,87 
40,500 
5.41 
137.4 
-55.0 
-25.4 
3.78 
41,000 
5.28 
134.2 
-56.0 
-26.8 
3.70 
41,500 
5.16 
131.0 
-55.0 
-27.2 
3.61 
,,42, COO 
5,04 
127.9 
-55.0 
-27.6 
3.52 
1T 43,000 
4.80 
122.0 
-55.0 
-28«5 
3.36 
43,500 
4.69 
119.1 
-55.0 
-28.6 
3.28 
44,000 
4.58 
116.3 
-55,0 
-29.0 
3.20 
44,500 
4,47 
113.5 
-53,0 
-29.3 
3.13 
45,000 
4.56 
110.8 
-55.0 
-29.5 
3.05 
45,500 
4.26 
108.2 
-53.0 
-29.9 
2.98 
50,000 
3.44 
87.3 
-56.0 
-32.4 
2.37 
60,000 
2.13 
54.2 
-55.0 
1.49 
70,000 
1.32 
rr ry r 
o3. o 
-55.0 
0.93 
* Example: Oxygen per cent - 20.93/760 x barometric pressure at that level. 
#42,500 4.92 124.9 -55.0 -20.0 3.44 304 
Table 2 
Normal gas pressures* 
Location 
0,, Pressure 
(i 
Pressure 
Per cent 
mm. cf 
Per cent 
mm. of 
atmosphere 
mercury 
atmosphere 
mercury 
Inspired air 
20.93 
15S 
0.03 
0.2 
Lun£ alveoli 
14.00 
106 
5.5 
40 
Arterial blood 
. 13.21 
IOC 
5.5 
40 
Venous blood 
5.50 
40 
6.2 
46 
Tissue spaces 
3—5.50 
20—40 
5.2—8.5 
46—60 
♦From Campbell, Argyll and Pulton, S. P.; Oxygen and 
carbon dioxide therapy. London, Oxford University 
Press, 1S34, 179 pp. 305 
Table 3 
Oaygen flow needed for B.L.3. oxygen inhalation apparatus. Rates cf oxygen 
flow needed “by aviators at various elevations with different degrees of 
activity when wearing the. B.L.B. inhalation apparatus are indicated. 
Actual elevation 
(thousand feet) 
Aviator, inactive 
Set 
oxygen flowmeter 
to correspond to 
actual elevation 
Liters per min. 
Aviator, active 
Set* 
oxygen flowmeter 
to correspond to 
5,000 feet above 
actual elevation 
Liters per min. 
Aviator, very activi 
Set* 
oxygen flowmeter 
to correspond to 
8,000 feet above 
actual elevation 
Liters per rain. 
S.T.P. 
D. In body 
S.T.P.D. In body 
S.T.P.; 
D. In body 
(C to) 
to 10 
0.5 
0.9 
0.8 
1,5 
1.0 
1.8 
11 
to 15 
0.7 
1.6 
1.2 
2.7 
1.4 
3.2 
16 
to 20 
1.0 
2.9 
1.6 
4.6 
1.8 
5.2 
21 
to 25 
1.3 
4.8 
2.0 
7.4 
2.2 
8.1 
26 
to 30 
1.7 
8.3 
2.4 
11.7 
2.6 
12.7 
27 
to 55 
2.1 
13.8 
2.7 
17.8 
2. S 
19.7 
35 
to 40 
2.4 
22.1 
Dangerous 
Dan 
gerous 
(l) "Inactive" - By this is meant that the pilot is sitting in 
his seat and flying the plane under ordinary atmospheric conditions corres- 
ponding approximately to an oxygen consumption of 250 to 300 cc. per minute 
S.T.P.D. 
(2) "Active" - By this is meant as strenuous an amount of work as a 
pilot handling the plane in emergencies or a machine gunner actively firing 
corresponding approximately to an oxygen consumption of 400 to 500 cc. per 
minute S.T.P.D. 
(3) "Very active" - By this is meant as strenuous an amount of work as 
can be performed in an airplane corresponding approximately to an oxygen con- 
sumption of 500 to 600 cc. per minute S.T.P.D., which is about the equivalent 
of walking at the rate of 2 miles per hour. 
*This setting refers be the Eeidbrink type of kinetic flowmeter that has boon 
calibrated according to the recommendations cf Boothby and Lovelace. At these 
settings the actual amount delivered corresponds tc the amount in the table. 306 
In the calibration of other types cf flowmeters, those rates of flew should 
he conveniently indicated. 
The columns under "liters per min.” headed "In "body" indicate the volume 
of the oxygen after it has expanded to the condition in the lungs at "body 
temperature (37° C.), saturated with moisture (47 mm.), and at the baromet- 
ric pressure corresponding to actual elevation. 
Table 4 
Comparative volumes cf gases (saturated at 3?'' C.*) 
inside the bod?/ at various altitudes 
Sarcmetric pressure 
Altitude 
Relative vcls 
mm., mercury 
feet 
of gas 
760 
0 
1,0 
523 
10,000 
1.5 
43 & 
15,000 
1.9 
349 
20,000 
2.4 
283 
25,000 
3.0 
226 
30,000 
4.0 
179 
35,000 
5.4 
141 
4-0,000 
7.6 
*Pres sure of aqueous vapor at 37r C. is 47 mm. cf 
mercury. Example cf calculation 760-47 _ 1.5 
523-47 307 
References 
1. Armstrong, H. G.; Principles and practice of aviation medicine. 
Baltimore, Williams & Wilkins Company, 1939, 496 pp. 
2. Armstrong, H. G. and Heim, J. W.: The effect of repeated daily exposures 
to anoxemia. J. Aviation Med. 9:92-96 (Jupe) 1938. 
3. Barach, A. L.: ’’Pilot error” and oxygen want; with a description of a 
new oxygen face tent. J.A.M.A. 108:1858-1872 (May 29) 1937. 
4. Barach, A. L., McFarland, R. A., and Seitz, C. P,: The effects of 
oxygen deprivation on complex mental functions. J. Aviation Med. 
8:137-207 (Bee.) 1937. 
5. Beaven, C. L. : The present need for airplane ambulances "by the 
United States. Mil. Surgeon. 77:138-146 (Sept.) 1935. 
6. Benson, 0. 0., Jr.: Coronary artery disease; report of fatal 
cardiac attack in a pilot while flying. J. Aviation Med. 8:81-84 
(June) 1937. 
7. Benscn, 0, 0., Jr.: The effect of decreased "barometric pressure on 
the electrocardiogram. J. Aviation Med. 11:67-74 (June) 1940. 
8. Bert, Paul: La pression barometrique; recbcrches de physiologic 
experimentale. Paris, G, Masson, 1873, 1163 pp. 
9. Bohr, Christian: Absorptions coefficienten des Blutes und des Elutplasma 
fur Gase. Skandinav. Arch. f. Physiol. 17:104-112, 1S05. 
10. Bohr, C., Hasselbalch, K. and 3£rogh, August: Ueber einon in biologischer 
Bcziehung wxchtigen Einfluss, den die Kohlensaurespannung des Blutes 
auf lessen Sauerstoffbindung ubt. Skandinav. Arch. f. Physiol. 
16:402-412, 1904. 
11. Bcothby, W. M.: Oxygen administration: the value of high concentration 
of oxygen for therapy. Proc. Staff Meet., Mayo Clin. 13:641-646 
(Oct. 12) 1938. 
12. Boothby, W. M., Benson, 0. 0. and Lovelace, W. R., II: Emergency oxygen 
unit for use in parachute escape or in case of failure of regular 
oxygen supply at high altitude. J. Aviation Med. 11:59-66 (June) 1940 
13. Boothby, W, M., Lovelace, W. R., II and Benson, 0. 0.: High altitude and 
its effect on the human body. J. Aeronaut. Sc. 7:461-469 
(Sept.); 1-7 (Oct.) 1940. MAYO AERO MEDICAL UNIT 
Walter M« Boothby, M. D», Chairman 
A LABORATORY AID 
Compiled for the most part by the various 
ARMY and NAVY OFFICERS and MAYO FOUNDATION FELLOWS 
* 
who have been assigned to the Unite 
SECOND EDITION - AUGUST 19h2 PREFACE TO FIRST EDITION 
The contents are not wholly the work of the authors as some parts are taken 
from various articles on the subjects* It is not meant to be put into circulation, 
but rather as an aid for local use to clarify subjects and methods used and taught 
in this laboratory© 
Most of the work was compiled from personal laboratory notes of the authors a 
It should enable future students to avoid voluminous note taking and thus devote 
more time to attentive absorption of knowledge with more time for practical work* 
For those students who will be stationed at aviation Medicine Laboratories 
in the future, it is our hope that these notes will prove to be of aid© 
Captain M* Robert Halbouty, M.C,, U, So Amy 
Cfptain Joseph A. Resch, M*C«, U* S. Array 
Lieutenant Robert F* Rushraer, M*C*, U.,S-Array 
January 19l*2 
PREFACE TO SECOND EDITION 
Since the first edition additional experimental methods and various new 
calculations are being utilized in the laboratory and these have been incorporated 
in the Manual* Practically none of the methods described are new although some 
of them have been modified specifically for high altitude problems* To conserve 
time in our war effort we have unceremoniously "lifted” charts and pictures from 
various sources* Unfortunately in several instances we find that we failed to give 
proper this omission will be corrected in our next edition* 
Mayo Aero Medical Unit 
September 19h2 RESPIRATION - DEFINITION OF TERMS 
1. Tidal Air is the volume of air breathed in or out of the lungs with every normal 
respiration. Since this volume is proportional to the activity, it varies greatly 
under normal non-basal conditions. However, unless specified to the contrary, a 
resting sitting condition is assumed. 
2. Complementary Air is the volume of air that can be inspired by maximum effort; the 
base line for this measurement is usually taken from the bottom of a normal resting 
expiration. 
3. Reserve Air (supplemental air) is the maximum volume of air that can be expired 
as measured from the base line of a normal resting expirationc 
Vital Capacity is determined by measuring the maximum quantity of air that can be 
expired after a maximal inspiration. 
5- Residual Air is the air which remains in the lungs following a maximal expiration^ 
It can only be expelled by opening the chest widely and allowing the lungs to collapse<, 
6. Functional Residual Air As measured by the method of Cournand'*' et alf, includes 
both the reserve air and true residual air; therefore to calculate the true residual 
air one must determine the reserve air and subtract this from the value obtained for 
the functional residual airs 
7. Total Lung Volume is the sum of the residual air and the vital capacity. 
8. Dead Space Air is that portion of the inspired air which fills the respiratory 
passageways but does not take part in the respiratory change. 
Alveolar Air is that portion of the inspired air which comes into gaseous and 
temperature equilibrium with the arterial blood of the alveolar walls; it contains 
therefore, U7 mm. of water vapor because it is completely saturated at the body 
temperature of 37° C. (see section on alveolar air for method of collection). 
10. Tracheal Air is an arbitrary term used to designate the inspired air just as it 
enters the lungs and before any gaseous exchange has taken place but after it has 
been warmed to 37° 0. (body temperature) and saturated with U7 mm. water vapor; 
aside from its added water vapor, the composition of the gases in the tracheal air 
is assumed for convenience of expression and calculation to be the same as in the 
air outside the body. 
11 r> Respiratory Quotient is the ratio of the volume of carbon dioxide evolved to the 
volume of oxygen absorbed and depends on the character of the food being metabolized* 
Both volumes to obtain the exact ratio must be corrected for any change in volume of 
the expired air from the volume of the inspired air, although when breathing normal 
air the correction for carbon dioxide is so small that it can be neglected. When 
the RoQ, is not corrected for change in volume, it is sometimes referred to as the 
uncorrected R.Q. 
1. Cournand, Baldwin, Darling and Richarez: J. Clin. Invest, 20:681 (19U1) 
Note embracing definitions 1 to 8 inclusive: The volume in most instances that is 
desired is the actual volume of the space occupied by the air. Therefore to determine 
this space by gasometric methods, one must express the gas volume at 37° C* and 
saturated with water vapor. While at sea level comparatively little error is 
produced by expressing this volume at the temperature and with the water vapor 
corresponding to the temperature of the measuring apparatus, yet at altitudes 
such a careless method results in large errors0 12, Alveolar Ratio is the quotient derived by dividing the percentage of carbon 
dioxide in the alveolar air by the difference between the percentage of oxygen in 
the inspired air (20.93 por cent when breathing normal air) and the percentage of 
oxygen in the alveolar air-, It is essentially the ’’uncorrected respiratory quotient-.” 
I 
13. Hyperventilation or Hyperpnoea is excessive breathing: respiration at a rate 
or depth or both which results in the washing out of carbon dioxide from the alveoDar 
air and the blood stream. Regardless of whether it occurs voluntarily or involuntar- 
ily from fright or hysteria, it results in profound physiological reactions and is 
used therefore in contrast to ”increased ventilation” which is due to the normal 
needs of the body such as in exercise, 
lit. Acapnia is the condition resulting from hyperventilation in which excessive 
amounts of1 carbon dioxide have been eliminated from the blood. 
Apnoea is the cessation of the respiratory movements and usually refers to that 
type caused by a reduction of the blood carbon dioxide to a concentration which no 
longer stimulates the respiratory center. 
l60 Dyspnoea is difficult breathing and may refer to either ’’obstructive dyspnoea1’ 
due to interference with the passage of air or to subjective dyspnoea in which one 
becomes conscious of definite discomfort in the effort to breathe, 
17» Periodic breathing is an alternation of respiratory movements with periods of 
apnoea.» It may follow or accompany hyperventilation. The term Cheyne-Stokes 
breathing is generally used with the same meaning as periodic breathing although 
the condition described by Drs. Cheyne and Stokes was limited to a clinical form 
of periodic breathing associated with pathological central nervous system changes. 
IS-, Anoxia is a term introduced by Peters and Van Slyke to describe a generalized 
oxygen deficiency throughout the tissues of the body and refers to a decrease in 
the partial pressure of oxygen in the tissues which may or may not be associated 
with a decrease in partial pressure or in the percentage saturation of the hemoglobin 
of the arterial blood. 
19 * Anoxemia is, strictly speaking, an oxygen lack in the blood and usually refers to 
incomplete saturation of the hemoglobin in the arterial blood. 
20o Cyanosis is a bluish color of the blood causing a corresponding change in the 
color of the skin, mucuous membranes or deeper organsj, It depends upon the absolute 
amount of reduced hemoglobin in the blood and if present is, in normal individuals 
an indication of both anoxia and anoxemia, but if absent does not necessarily mean 
that anoxia is present. THE MOST CONVENIENT BURET IS ONE HAVING A BULB CAPACITY 
OF 6 CC WITH THE GRADUATED STEM RUNNING FROM 6.0 to 10,1 CC 
Tap j*2 Main Buret Tap 
Tap )*1 Sampling Tap 
Tap |*3 Potash Tap 
► Tap 3*5 Control Tube Tap 
► Tap 3*4 Pyro Tap 
Sampling Set 
-Tabulated Buret 
Calibration 
HALDANE 
GAS ANALYSIS APPARATUS THE HALDaNE GAS ANALYSIS APPARATUS 
The analyses are done in a Haldane gas analysis apparatus, described very 
fully by Haldane in his book on Air Analysis. Briefly, a sample of air is taken 
into the buret and its volume measured; the air is passed back and forth into the 
tube containing potash solution to absorb the carbon dioxide and then a second 
reading of the volume contraction made. The contraction in volume of the sample, 
due to absorption of carbon dioxide present by the potash solution, divided by the 
original volume of the sample is the percentage of carbon dioxide present in the 
dry sample of air. In like manner the percentage of oxygen is determined by absorb- 
ing the oxygen in potassium pyrogallate solution and measuring the contraction in 
the volume of the air sample0 
The general arrangement of the apparatus is shown in the labeled illustration. 
It consists of a calibrated buret (a) of 10 cc9 volume, a control tube (B) of 
approximately the same volume as the buret, both surrounded by a water-bath (c) , and 
gvo absorption pipets of about 30 cc. capacity, the one containing potash (X) for 
carbon dioxide absorption and the other potassium pyrogallate (Z) for oxygen consump- 
tion* In addition, there are three three-way taps (l), (3), and (U) to connect 
the various parts of the apparatus, and there is also one diagonal tap (2) and one 
two-way tap (5). On all the taps a red spot or other mark is put on the handle to 
indicate the position of the arms. This mark if not on, can be improvised by 
putting a drop of colored sealing wax on the side where the 3rd hole is; that is, 
the bottom of the 11 T!l on 3-Way taps. All of the taps must be air-tight, fitting 
the bore perfectly, so that they turn without binding or making striations. Finally, 
there are the potash (P) and mercury (Q) reservoirs and beyond the pyro tube a seal 
tube (L) partly filled with dilute potash soluti on to prevent the pyro frcm coming 
in contact with the room air. The various parts of the Haldane are shipped dis- 
mounted and the buret has an extra tap fused in it to facilitate the calibration 
The standard sampling tubes for ground studies have a volume of UO to £0 cc„ 
with a two-way tap and small bored tip about U cm. long above the tap for the 
purpose of making connections with the collecting apparatus in sampling. Sufficient 
mercury is used in the sampling tube to completely fill it and the rubber tube 
leading to the mercury reservoir. In high altitude studies very large sampling 
tubes must be used of approximately 200 cc. capacity. A piece of rubber tubing 
about 1$ inches long connects the standard sampling tube to its mercury reservoir 
of about UO cc. capacity. The mercury reservoir of the high altitude sampling 
tube is about 200 cc. capacity. The standard sampling tubes are mounted in fours 
on a rack, and four samples of expired air are taken whenever possible; two are 
analyzed, and this leaves two extra samples in case of accident. The big tubes 
are mounted in pairs for high altitude analysis. The sampling tubes are filled 
to the tip with mercury. In sampling, connection is made to the petcock of the 
apparatus by means of rubber tubing. The tubing is tightly adjusted on to the 
sampling tube, the mercury reservoir lowered, and the tap on the sampling tube 
opened. The sample is collected, the tap is closed, and the mercury reservoir hung 
up to keep the sample under positive pressure. 
Calibration of the Haldane Buret: To obtain accuracy in gas analysis it is 
necessary to calibrate the buret carefully. A frequent source of error when the 
T type of buret tap is used is that the glass maker may not properly take into 
consideration the volume of the openings in the tap. Then too, there may be the 
assumption that the buret has an absolutely even bore or the calibration may be 
improperly carried out with the buret upside down, etc. 
A special calibration with fine point should be fused on the bottom of the 
buret. If this is impossible, the connection may be made with heavy rubber tubin^ 2 
around which adhesive tape is wound5 this is necessary, otherwise the bulging of 
the rubber connections ■when the buret is full of mercury will gradually decrease as 
the mercury is drawn out for weighing and thus cause an error in calculated volume* 
In calibration, the buret is filled with dry clean mercury ard the weights of the 
mercury corresponding to various volumetric readings on the buret are determined* 
Since the volume (V) of a liquid is equal to its weight (TIT) divided ty its density 
(D) the corresponding volumes of the various weights of mercury are determined in 
decimal parts of the volume corresponding to the lOcc. mark* The volume of the 
mercury thus calculated is compared with the corresponding volumetric readings on 
the buret and the correction determined. If the temperature is kept within plus 
or minus 0o5°C., then the calibration will have corrections for decimal parts of 
the total (10 ccs) and therefore it is not necessary to transform these into exact 
cubic centimeters. 
The buret is first thoroughly cleaned with warm cleaning solution, then rinsed 
with distilled water, and completely dried by sucking clean air through it. Bo 
not blow air through from an air pump as that will contain a very fine oil spray 
even if the pump is far away. The clean, dry buret is filled through the calibration 
tap with mercury and up through the buret tap and just over the curved right angle,-, 
A convenient way of doing this is by suction or by attaching rubber tubing v/ith a 
mercury reservoir to the lower end of the buret. It is important that no air bubbles 
are caught by the mercury. The calibration and the buret taps must never be left 
closed with the buret filled with mercury because the expansion of the mercury with 
the rise of room temperature will burst the buret. Instead, immediately out off 
the head of the mercury column by turning the tap and completely removing the tap 
from its bore being careful not to spill any mercury. Then the mercury is run 
slowly down, approximately to the reading 6.0 cm. and is collected in a dry and 
clean, weighed dish. After gently tapping the buret with a pencil, the accurate 
reading of the volume of mercury in the buret to 05001 cc. is recorded and the 
total weight to the nearest 0.001 gm. of mercury and dish found. Care should be 
taken that no particles of mercury cling to the inside of the buret and the mercury 
runs out. This usually means that the buret is greasy and should be recleaned. 
Touch the surface of the mercury in the dish to the mercury in the end of the cali- 
bration tap, so that a constant amount of mercury is left in the end of the buret 
after each portion of mercury is collected. The weighing should be done on a fine 
cnemical balance and recorded to the nearest 0.001 gm. 
To obtain correct readings the buret must be set up during the calibration 
so that it is perpendicular and the complete calibration carried out at one sitting 
without interruption. Before cutting off the head of the mercury wait until the 
mercury has had time to reach temperature equilibrium and be sure that the room 
temperature does not vary by more than 0o£°C, a thermometer should be hung near 
the buret and the temperature noted at each weighing and reading of the buret* 
Variations in the temperature affect the buret readings, a fluctuation of one 
degree causing a change in the volume 7 cc. of mercury of approximately 0C001 cc. 
The room in which the calibration is b eing carried out should, therefore, be kept 
at as constant a temperature as possible and drafts avoided. Likewise, care must 
be taken not to breathe on the buret or to touch it with the hands during the 
calibration. The buret should be gently tapped with a pencil before the reading 
is taken to obtain a true meniscus of the mercury. The reading lens should be 
held parallel with the buret v/ith the center of the lens opposite the mercury meni- 
scus e The eyes uugt be on the correct level before making a reading of the jnercurv 
monicus,.. To do this, thereflections on the mercury pi the twon0.0i cc. , 
markings on the buret just below the mercury meniscus are located and the eyes 
are on the correct level when these two lines and their reflections on the mercury 
exactly coincide. ■3 
The weights of successive portions of the mercury are found for various 
readings of the buret approximately at 6.0, 6*3, 6,7.0, 7*3., 7o£, 8„0, 9.0, 9c3j 
9*8, and 10cco The calibration is then repeated, without cleaning the buret, 
determining the weight of mercury at the reading, 6*0, 6S3 7*0, 7*£5 8.0, 
9o5> and 10* It is preferable to do the two calibrations at one sitting and the 
corrections should check within plus or minus 0o001 cc* 
Instead of using the absolute density of the mercury corresponding to the 
temperature recorded by the thermometer near the buret, we calculate the compara- 
tive density of the mercury from the experimental data* In calibrating buret 
number 29 at the reading 10o000 cc. the weight of the mercury was 135>oi70U gm«, its 
density is therefore 135*170U gm. « mu x ~ , 
TTrTTATx & - 13ol70lu The true volume of 6*000 cc* witn 
XUtUUU cc® 
mercury for this reading weighing 8l®llUU gra® is obtained by dividing by 13»5>l?Oi4. 
and equal to 6.001® That is, the buret at 6.001 ccc - 6.000 ccs s + 0.001 cc. 
’•Then the corrections for the various readings are determined as above they are 
plotted on graph paper and the plus or minus corrections for each 0*1 cc. reading 
of the buret are read off from the curve and listed for usec 
As noted before, the calibration tap should be fused to the buret and not 
attached by rubber tubing, because changes in level of the mercury from the top to 
the bottom of the buret will produce variations in pressure against the rubber tubingx 
and consequently the latter will not always have the same bore, and an appreciable 
error in the calibration results. 
Calibration Example 
Tamo, Reading 
wt. 
of 
Hgo 
Volume Hg in Stem 
27»1 6,000 
wt. 
Of 
container plus Hg 89*2266 
Wt, Hg in stem =6.,001=to001 
wt. 
Of 
container 
8,llU2 
Density Hg 13o5170q. 
Biaiuu 
Solutions for Haldane Gas Analysis: Potassium pyrogallate solution (Haldane): to 
c30 gms of stick potassium hydroxide (not purified by alcohol as vapor will always 
be present and cause errors) are added 300 cc. of distilled water. The specific 
gravity of the resulting solution should be exactly 1.55 (this can be determined by 
using a hydrometer or by finding the weight of 100 cc. of the solution, which should 
be 19$ gnu). If the specific gravity is too low, potassium hydroxide should be 
added until the desired concentration is obtained. To 100 cc. of this concentrated 
potash solution 10 gm. of Merck’s pyrogallic acid are added in a bottle with a 
greased glass stopper® Haldane emphasizes that the solution must be made exactly 
in the manner described otherwise unsatisfactory results are obtained. The resulting 
solution of potassium pyrogallate should have a brownish-green tint and should become 
a deep wine color immediately on exposure to air® The pyro should be at least a 
month old before using, although it improves with age. This again can sometimes 
be hastened by exposing the pyro for a few minutes to air and thus giving it a 
start. 
Potash solution for CO2 absorptions For the absorption of carbon dioxide we 
use a dilute solution of potassium hydroxide of specific gravity of about 1.09 - 
approximately a 10 per cent solution. 
After 50 standard Haldane analyses or 25 high oxygon concentration analyses 
in the Haldane apparatus solutions in the Haldane apparatus should be changed® Technique of Haldane Gas Analysis (standard); 
Setting levels: Pass sample already in apparatus back and forth several 
times alternately in both KOH tube and pyro tube to get rid of all CC2 and Og in 
apparatus* Turn control tap £ in position always keep pyro tap h Q set 
for pyro tube during analysis* Set pyro level by turning KOH tap 3 to pyro 
tube 0 Level exactly by raising or lowering the mercury bulb.- Turn KOH tap 3 0 
to potash tube and set potash levels of buret X and of control tube Y exactly by 
raising or lowering the mercury bulb for the KOH level and raising or lowering the 
KOH reservoir to set the control level. Close the control tap 5 CP * Whenever 
readings are to be made on the buret the pyro and the two potash levels must be 
very accurately set at the proper levels for X and I, Before starting the analysis 
the control tube tap 5> must be closed (J) and must never be opened during analysis 0 
If available a small steady stream of air must be constantly bubbled through 
the water bath. Otherwise a hand bulb like those used on blood pressure apparatus 
may be used and should be pressed before each readingo The water must be as high 
as possible in the water bath* Once the control tap is closed to room air it cannot 
be opened again -until the completion of the analysis* At the end of the analysis 
the control tap should be opened in order to reset all the levels at the existing 
atmospheric pressure and to compensate for marked temperature changes. In this 
case it is not necessary to recheck the machine« Sometimes a T type of tap is 
used for the buret and is all right if the buret is properly calibrated. Such a 
tap, however, cannot be used for high concentrations of oxygen. 
Transference of the sample to the buret: Turn sampling tap 1 (J) and turn 
buret tap 2 fip~{ to open the buret to room air only# Rinse the buret with room air 
by raising or lowering the mercury reservoir between 2 and 6 eras, four times. Hang 
the mercury reservoir on the ratchet so the mercury is half way in the bulb. The 
sample set is connected to the buret by means of a small sampling tubing and the 
sampling set tap opened to the buret. The index finger of the left hand is 
moistened with water and placed very tightly on top of the buret# The mercury 
reservoir is held in the right hand which is brought to a comfortable position on 
the top of the Haldane board. The air in the buret is then allowed to escape very 
gradually beneath the moistened index finger until the mercury has risen up to tap 
2 - not in it. Tap 1 is turned and the sample will run into the buret and the 
mercury should fall to about 2 or 3 cm. on the buret. With the moistened index 
finger held very tightly on the top of the buret, tap 1 is turned CB and the 
air allowed to escape until the mercury rises up to tap 2. At the end of the fifth 
rinsing the mercury reservoir is lowered until the mercury is about 9o$ eras# in 
the buret. Tap 1 is now to be left Q . Hang the mercury reservoir on the ratchet. 
Equalize the pressure in the sample set by leveling the mercury in the sample set 
tube. When these two levels are set bring the mercury in the buret down below 
9.5 cm. Check levels. Close the sample set tap, then open buret tap 2 to solutions 
r~ri~l # Pinch KOH tubing and the tubing connected to the mercury reservoir gently* 
Set KOH level X and Y very accurately. Take the volume reading. Check this reading 
after pinching the tubing and resetting the levels X and Y, 
Absorption of the CO2 and 02*. To absorb the CO2 shunt the sample of air 
back and forth in the KOH solution (by raising and lowering the mercury reservoir 
in the bulb between 2 and $ cm> ten times)# Hang mercury reservoir on ratchet. 
Set levels X and Y and read the buret. To get a check reading shunt the air 6 
times more in the KOH solution. The reading must check within .001. To absorb the oxygen turn tap 30* Shunt the air back and forth into 
the pyro solution times * Set approximate level in pyro tube, T1irn tap 3 0 « 
Shunt the air in the KOH 3 times to pick up the air contains 09 which is in the 
potash tube0 Set approxirx.te levels in potash tube. Turn tap'3 0 * Repeat this 
entire procedure two times, the second time set the pyro level accurately and turn 
tap 3 0 then set potash level before the first oxygen reading is taken. Check 
the oxygen reading twice by shunting the air 15> times in the pyro. The reading 
must check within 3001« 
Sample Calculations 
Buret Reading 
Corr. 
Corr. - Read 
Diff. 
% Calculation 
9.377 
+ 
o003 s 
9.380 
91,136 
i* 
cOO? = 
“9aii3 = 
0.237 
0,237 _ 
“ a> ou2 
V,UIi3 
+ 
.020 s 
7oU6U a 
1.679 
i7-9o $02 
Care of the Apparatus: Taps must.. be well greased and for this purpose 
lanolin may be used. When the sampling tubes become dirty they may be cleaned with 
concentrated nitric acid, rinsed with distilled water, and thoroughly dried. 
However, etching sometimes develops which cannot be removed. An excellent glass 
cleaning solution can be made up by using 2£ grams of (potassium bicromate), 
1$0 cc. of water, and 100 cc. of H2 (Sulphuric acid), Aad sulphuric acid to 
water and potassium bicromate very very slowly. This solution causes no etching* 
Cleaning once every six to twelve months is usually sufficient* Under no conditions 
should either alcohol or ether be used in cleaning any part of the apparatus as 
sapors from these may remain and interfere with accuracy of results. 
To Clean Haldane Apparatus 
If pyro or potash has been 11 sucked” over into the buret it must be cleaned 
at once so that the buret will not become etched and thus change its volume. To 
clean it use the following procedure: Open tap 1 <© and tap 2 to 0 Attach rubber 
tubing to top of buret and allow the free end of the tubing to lie in a beaker of 
distilled water. Lower mercury reservoir bulb; thus drawing water from the beaker 
into the buret. Do not let water get as far down as the mercury rubber tubing, 
Then by raising the mercury reservoir bulb, push the mercury up to the top of the 
buret, thus pushing out all excess water into the water beaker. After repeating 
this six or seven times, turn tap 2 dp, and potash tap 3 & and pyro tap U 63 . 
Attach rubber tubing with a glass funnel on open end of pyro tap, fill funnel with 
distilled water and let it run into buret to wash out connections, then turn tap 2 
fXm and repeat the first procedure until buret is clean. Test the mercury in the 
buret with litmus paper to be sure all acids or alkalies are out of buret. When a 
neutral reaction is obtained, the buret is clean. 
To clean potash pipettes turn potash and pyro taps & and control tap 
Take potash bulb from clamp and empty potash into sink. Clean potash bulb with 
dilute HCL, rinse thoroughly with distilled water and fill with new supply of 
potash. Clean pyro tube with distilled water by removing stopper from end of pyro 
tube and using rubber tubing with funnel. Remove all excess water from pyro tube 
before adding fresh pyro* •6- 
HIGH OXYGEN ANALYSIS 6.1 CC. SaMPLE 
The buret tap of a Haldane for use in analyzing high oxygen mixtures 
must always be of the three way double oblique type; a tap with a T type of 
bore must not be used. The bulb part of the buret should contain 6 cc« and 
the calibrated part of the buret U.l cc.; a total of 10.1 cc, For analyzing 
mixtures containing h0% or more oxygen check the residual nitrogen in the Haldane 
so that the amount in the buret for storage is between 6,0 and 6*1 cc. Gas 
mixtures below \\0% oxygen can with this type of buret be analyzed directly 
without storing nitrogen provided a 10a05 cc. sample is used; of course 
samples containing less oxygen can be easily analyzed. If practically 
pure oxygen from a tank is to be analyzed then the sample taken in should 
be approximately 9c5 cc0 
Transfer nitrogen into pyro tube by bringing mercury reservoir up so 
that the drop of water on top of the mercury is just in the bore of the 
buret tap which is then given a quarter turn to seal buret. Turn potash 
tap back to the potash tube. Open the buret tap to room air rinsing a few 
times then rinse five times with sample to be analyzed. Take about 7 cc, 
of sample in the buret, level bulb of sample tube carefully in the usual 
manner and close sampling tube tap. Close buret tap. Set the potash levels 
accurately and take sample volume reading (nitrogen is still stored in 
pyro tube)• Shunt sample back and forth several times in the potash tube and 
take reading of carbon dioxide absorption until they check. Turn potash 
tap so that the buret is connected with the pyro tube and draw port of the 
nitrogen into the buret; pass sample back and forth into the pyro tube being 
careful at first not to push too much into the pyro tube until part of the 
oxygen in the sample is absorbed. After absorption is practically complete 
wash potash and pyro tube two or three times in the usual manner until check 
readings are obtained. 
HIGH OXYGEN ANALYSIS 3*5 CC, SAMPLE 
Check Haldane so that the reading is between 6.0 and 6*1 cc« Transfer 
nitrogen into pyro tube by bringing mercury reservoir up so that the drop of 
water on top of the mercury is just in the bore of the buret tap. Open the 
buret tap to room air rinsing a few times then rinse five times with sample 
to be analyzed. Take 3.5 cc. of sample in the buret bulb* level bulb of 
sample tube carefully in the usual manner© Close sampling tube tap* Close- 
buret tap. Set pyro level by bringing mercury in bulb down slowly until 
the pyro is at the level mark; this must be done very carefully so none of 
the oxygen is absorbed during the process. When pyro level is set turn 
potash tap. Set potasl level© Take sample volume reading and then analyze 
sample in the usual manner. This method decreases the accuracy by about one 
half because of using a small sample. It also requires more practice to use 
correctly© It is a convenient and quick method and does not use up the pyro 
solution nearly as rapidly. 
Example of 
Calculation: 
Buret 
Corrected 
Reading 
Corrects 
Reading 
Diff « 
Percent 
N2 Stored 
6,068 4 
.016 
s 6-O84 
Sample N? 
9.602 + 
o002 
= 9.60U = 
3.520 = 
Sample 
COp 
9.123 + 
,ooU 
= 9.U27 = 
,177 = 
5 >03 % 
°2 
6.7UO * 
.016 
= 6.756 = 
2,671 = 
75.88 %  
Reading 
Buret 
Corr. 
Corrected 
Reading 
Nitrogen 
Biff, Sample 
Percent 
N2 Stored 
6.1E0 
.001 
- 6.181 
Sample 
7.009 
.002 
7.011 + 
6.181 
- 
13*192 
C\! 
o 
o 
6o692 
+ 
.003 
— 6.695 •)* 
6.181 
= 
12,876 - 
.316 7.03.1 3 
1.51 % 
°2 
6.698 
.003 
= 
6.701 = 
6,175 + 7.011 s 
88*08 % 
EXAMPLE - SHORT CUT WHEN 
NITROGEN DIFFERENCE 
IS TO B3 SUBTRACTED 
Reading 
Buret 
Corn. 
Corrected 
Reading 
Biff. 
Sample 
Percent 
Ng Stored 
6.180 
* 
.001 
= 6.181 
Sample 
7.009 
.002 
s 7.011 
co2 
6.692 
+ 
.003 
= 6.695 = 
.316 
* 
7.011 r 
u.51 % 
°2 
6.698 
•003 
n2 
= 6.701 = 
6.181 
- *006 
KW 
*r 
7.011 = 
88,08 % 
EXAMPLE - SHORT 
CUT WHEN 
NITROGEN DIFFERENCE IS TO B 3 ADDED 
N2 Stored 
Reading 
6.180 
4* 
Buret 
Corr. 
.001 
Corrected 
Reading 
r 6,181 
Biff. 
Sample 
Percent 
Sample 
7*009 
+ 
.002 
= 7.011 
C°2 
6.692 
•f 
.003 
= 6o695 * 
.316 
7.011 
lu5l % 
°2 
6.600 
+ 
.003 
. . N2 6.181 
= 6.603 = +k092 
S7Z73 
♦ 
7.011 = 
89.1+7 % 
CALCULATION OF HIGH OXYGEN ANALYSIS USING 1 CC. SAMPLE 
Example - adding volume of stored nitrogen to both sample & COp reading 8 
CALIBRATION OF GASOMETER 
The gasometer readings are made on a steel tape usually fixed on the counter- 
poise tube* The tape is graduated to 0*10 cm* and is read by means of stationary 
markers to 0*05 cm® It is, therefore, necessary to determine the factor of the 
gasometer in order to convert the linear rise of the bell into a unit of volume* 
This factor is derived in the following manner; the bell of the gasometer is a 
cylinder, and the circumference of it is determined by measurement at several points 
from top to bottom, either with the bell in position or removed entirely from the 
gasometer* On one gasometer the following measurements of the circumference were 
taken with the bell in position: 
Reading on tape 
Circumference of bell 
cm* 
cmQ 
97 • • . . 
87 . . ♦ . 
72 ... . 
59 ... . 
hS ... . 
33 ... . 
17 ... . 
9 . . . . 
Average 125«9 
Since the radius of a circle s circumference .. . .. . . , - 
then the radius to the outside of 
2 rr 
the wall of the bell equals 12$«,9 equals 20.,038 cm. The radius to the 
rx 3 0iui6 
inside of the bell is, therefore, equal to 20*038 cm* minus the thickness of the 
copper wall as determined by calipers* Thus the radius of the inside of the bell is: 
20*038 cm* - 0.0U6 cm. = 19.992 cm„ 
Since the area of a circle equals -77- then 3«lUl6 x cm* = 125?6 sq. cm. 
Therefore,the capacity of the bell corresponding to a rise of 1 cm* measured by 
the tape will be equal to 1 cm0 x sq. cm. = cc. or 1.2£6 liters, the 
factor of the gasometer. We read the centimeter scale to the nearest half-millimeter 
corresponding to a change in volume of 63 cc. 
DETERMINATION OF THE VOLUME OF A CLOSED CIRCUIT RESPIRATION APPARATUS 
Explanation*- In using any closed circuit type of apparatus such as the 
Boothby-Collins type for experimental work, in which it is necessary to know the 
total volume of gas in the entire apparatus, the volume of the apparatus when the 
spirometer bell is set at a definite low position must be determined* 
Equipment.- 1. Closed circuit type of respiratory apparatus* 
2* Supply of pure oxygen (strictly 99»7% pure) 
3. Haldane gas analysis apparatus. 
Principle*- The entire apparatus is repeatedly flushed out with air so that 
it contains nothing but atmospheric air, the oxygen content of which is 20*93$ if 
the apparatus has been efficiently washed out© This figure is checked by means of 
the Haldane gas analysis procedure. A known volume of oxygen is then introduced 
into the system and the gas again analyzed* The amount of oxygen in the resulting 
mixture can then be determined and the original volume of air can be calculated™ ■9 
Method*- Air is flushed in and out of the closed circuit apparatus repeatedly 
by manually elevating and depressing the spirometer bell. If the apparatus is 
equipped with a motor driven blower, it is kept operating to aid in the circulation 
of the air. If the machine has no intrinsic means for circulating the air, a 
hand pump must be installed in the circuit which is operated during the flushing 
and the nixing operations to be mentioned below e (If a hand pump is used, care 
must be taken to determine the added volume of the hand pump and consider it in 
the calculations*) Y/hen adequate flushing has been completed (5-10 minutes) the 
rubber tubes normally leading to the mask are attached to two ends of a "T" tube* 
The remaining orifice of the T tube is closed with a rubber stopper containing an 
outlet tube (for sampling) which is in turn closed off with a pinch clamps Thus 
the apparatus becomes a closed system containing nothing but atmospheric air* To 
thoroughly circulate the contents it is necessary to again operate either the motor 
driven blower or the hand pump for a period of 5 to 10 minutes. Four samples are 
withdrawn from the apparatus and analyzed to confirm the oxygen content cf the air 
within the apparatus, and the temperature is recorded* 
The pinch clamp on the sampling tube is released and air allowed to flow 
out until the spirometer is nearly empty at a point that can be reproduced at a 
later date if necessary* This point is established by allowing the revolving drum 
to make a complete revolution with the writing pen in contact with the paper. 
Pure oxygen (99°7%) from a tank is run into the spirometer until the added 
oxygen will, if possible, be nearly equal to the air in the apparatus in order to 
obtain a value of around $0% in the final oxygen analysis* If one is inexperienced 
in analysis of high oxygen values in the Haldane apparatus, it is best to regulate 
the volume of oxygen added so that the final analysis is within the range of the 
direct analysis on the Haldane* The value of oxygen added is recorded on the 
revolving drum and later measured. The gases within the apparatus are thoroughly 
mixed by means of the motor driven blower or the hand pump, as the case may be* 
The level of the pen on the revolving drum is allowed to reach an equilibrium with 
the oxygen supply completely turned off* Temperature changes should be kept as 
low as possible because the system acts as a delicate gas thermometer so that 
slight changes in the temperature of the enclosed gas results in considerable changes 
in the level of the spirometer bell. Four samples of gas are then removed from 
the apparatus and analyzed for oxygen content. 
CalculationsA formula is derived as follows: (per cent of O2 in atmospheric 
air x volume of air in the apparatus) plus (volume of O2 added) - equals - (per cent 
of Oo in the final mixture) x (volume of air in apparatus plus the volume of Op 
added). Thus: (0p$a x V&) * ~ (Va + Vq^) 
Where 0p$a - Per cent of Op in the original air in the apparatus 
Va - Volume of air in apparatus measured at existing barometric reading 
and saturated with water vapor at temperature of spirometer0 
V0p - Volume of Op added at existing barometer reading and saturated with 
water vapor at the temperature of the spirometer (for most purposes 
the Op is considered 100% pure and not 99*1% pure), 
Op/oM - Per cent of Op in the final mixture of air and Op 
This formula is solved for Va as follows: y _ VCp (l - Op$m) 
Op$m -Op$a 
Example: Where 0p$a = #2093, Vop = 12oil liters, and Op$m = t»U68? 
„ _ (1 - OcU687) 12,11 _ 0.5313 x 12.11 60U3U _ ,.. 
va - ~ T2595 " llters 
This volume now stands for the existing barometer and temperature readings, 
saturated with moisture at the temperature of the spirometer® B. C. CLOSED CIRCUIT APPARATUS 
WITH SUBJECT IN BODY FLETHYSMOGRAPH B, C. CLOSED CIRCUIT APPARATUS ARRANGED 
TO BE USED WITH BODY PLETHYSMOGRAPH  . CuRVgc; 7-31.-4Z } 
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PHYSICS OF GASES 
Boyle * s Lav/ 
Atmospheric pressure is measured by means of a barometer* This pressure at 
sea level and U3° latitude is normal and supports a column of mercury 760 ram* high 
If mercury is added to a J tube while it is on the same level in the closed arm 
and in the longer open arm, the air in the closed arm will be under atmospheric 
pressure, say 760 mm* After adding more mercury until its level in the open arm 
is ?60 mm* above that in the closed arm, the air enclosed in the shorter arm is 
under two atmospheres pressure* At the same ti me the volume of air is reduced 
to half its original volume* Boyle’s law states that the volume of a given mass 
of a gas kept at a constant temperature varies inversely as the pressure; that 
is, the concentration of a given quantitity of a gas at a constant temperature, 
is proportional to the corresponding pressure* 
Absolute Temperature 
In general it may be stated that the volume of a sample of gas at zero 
degrees increases 1/273 of its volume for each increase of 1 degree on the centi- 
grade scale and decreases in the same proportion when the temperature falls0 If 
the temperature were to fall to -273 degrees and the rate of contraction of a 
gas were to remain the same, then the volume of the gas would be zero at this 
temperature. Before -273 degrees is reached, all gases become liquids, to which 
the Charles1 law does not apply. The centigrade degree is arbitrarily chosen as 
l/lOO of the temperature interval between the temperature of melting ice under a 
pressure of 760 mm. and the temperature of aqueous vapor from water boiling under 
the same pressure. The zero point therefore on a centigrade thermometer corresponds 
to 273 degrees on the gas, or absolute scale. Hence, absolute zero is 273 degrees 
below zero centigrade. In making the correction of the volume of a gas we convert 
the temperature to the absolute scale by adding 273 degrees to the centigrade 
reading; for example, 20 degrees centigrade is 273 plus 20 or 293 degrees absolute® 
Charles’ Law 
The volume of a given mass of gas kept under a constant pressure varies 
directly as the absolute temperature. This statement is known also as the law 
tf Gay-Lussac. It may be expressed otherwise; namely, the concentration of a 
quantity of gas under constant pressure is inversely proportional to the corres- 
ponding absolute temperature. 
Correction of the Volume of a Gas to Standard Pressure and Temperature 
If 100 ml of a gas were measured under a pressure of 7U0 mm. and at a 
temperature of 27 degrees, what would be the volume of this quantity of gas at 
standard conditions (760 mm. and 0 degrees)? Will the volume of the gas increase 
or decrease as the pressure changes from the original value of 7h0 mm® to the new 
value of 760 mm.? Since the pressure upon the given mass of gas is increased, 
the gas must be compressed. It is evident that to obtain a smaller number of 
millimeters for the volume, 100 must be multiplied by a fraction having a value 
less than unity® We therefore change the volume in an inverse proportion to 
the pressures by making the smaller number the numerator and the larger the denom- 
inator, and multiply the fraction by 100: 
100 m. x 2|2 = 97.37 ml. The volume of the gas was measured at 27 decrees centigrade or 27 degrees plus 
273 degrees equals300 degrees absolute. Again the question arises as to whether 
the volume of the gas will decrease or increase changes from 300 
degrees absolute to 273 degrees absolute. The volume decreases, for according to 
Charles’ law the volume varies directly as the absolute temperature. Consequently: 
97°39 x IS = 08»61 
and by combining the two equations, we have 
100 x S * Wo 88'61 
It is customary to make the volume correction for both temperature and pressure 
in one operation* By orderly reasoning it will be easy to determine whether a 
change in temperature or pressure causes an increase or a decrease in the volume 
of a gas. Then the correction can be easily calculated after setting up the 
proper ratios. 
Dalton’s Law or Partial Pressure 
In any mixture of gases each gas exerts the same pressure as if it were 
present alone in the volume occupied by all the components, and the total 
pressure of the mixture is equal to the sum of the partial pressure of the gases. 
The partial pressure of any gas is proportional to its concentration* 
When a gas is measured over water, it soon becomes saturated with water 
vapor® The pressures of saturated water vapor for different temperatures may be 
looked up in tables. From Dalton’s law it is evident that if the measurement is 
made at atmospheric pressure, the sum of the gas pressure and the water vapor 
pressure is equal to the barometric pressure. Hence, when a gas is measured over 
water at a given temperature, its pressure is obtained by subtracting the pressure 
of saturated water vapor at that temperature from the barometer reading. Suppose 
for example, that 100 ml, of oxygen is jib asured over water at a temperature of 27 
degrees and a pressure of 7U0 ram. To obtain the correct volume of the gas under 
standard conditions we first look up the aqueous vapor pressure at 27 degrees. 
It is 26,mm. (2?mmo). Hence, 7h0 - 27 = 713 mm. which is the pressure of 
oxygen alone. The product given by 100 x x 273 represents the final 
?60 300 
volume in millimeters of the dry gas corrected to standard conditions. 
Problems Involving Gas Laws 
In aviation medicine it is frequently important to determine the volumetric 
changes that oxygen and other gases undergo during the flight of aircraft* These 
volumetric changes are easily computed if we correctly apply the Charles and Boyle 
laws to the problem to be solved. Sample Problems 
1. What is the volumetric change in a gas when one liter of oxygen in a tank 
reaches the lungs at 10,000 feet? 
In answering this problem we must remember that oxygen in a tank is measured 
as it flows out by a meter calibrated to give readings at S.T.P.D. (standard 
temperature, pressure, dry - 0 degrees C., 760 mm. Hg, dry) and that water vapor 
correction must be made only for the oxygen in the lungs, which is h7 mm* Hg because 
the lung temperature is jT3 C« Therefore, our formula begins as 
760 (standard pressure) - 
£23(10,000 ft. Bar. Press.)- hi (water vapor pressure at 37°C.) 
x 1 &iter) 
or 
By applying Boyle’s law we know that 760 is the numerator since lowered 
pressures increase the volume of gases (temperature remaining constant) and to 
obtain a larger number of liters of oxygen, 1 liter must be multiplied by a fraction 
having a value more than unity. We must also here consider temperature changes© 
Since the oxygen in the tank is measured as though it were at 0° C (273 absolute) 
and the lung temperature is 37° 0 (273 plus 37 absolute) and since by applying 
Charles’ law we know that the increase in temperature from tank to lungs will 
increase the volume of the gas, then our temperature correction becomes 
273 t 37 v , 
273 
and by combining the two, we have 
1 X x ~27'j ' 1 x x 1.135 = 1o813 liters of 02 in the lungs. 
2. One liter of gas in the human stomach at sea level changes to what volume 
during an ascent to 10,000 feet (523 ram. Hg)? 
The volume must increase as the pressure dec ases. Moreover, the gas is 
maintained under body conditions, so the water vapor correction must now be made 
in both the numerator and denominator of our formula. Thus we have 760_ - a7 x n 
523 - It? 
This is the completed formula because no temperature correction is needed, as the 
body temperature remains constant. Therefore, 
523 - iiV x = x 1 jb 1.50 liters 
3« One liter of oxygen in a dry toy balloon is taken from sea level to 10,000 feet 
in a low pressure chamber. What is the volume of the balloon at 10,000 feet 
altitude? This is relatively simple in that no water vapor or temperature 
correction is required^ 
Hence x 1 s 1«U5 liters 
523 
Of course, if the toy balloon were taken to 10,000 feet outside of a low 
pressure chamber (i.e. pilot balloon or sounding balloon) then corrections would 
have to be made for temperature also® 13 
TliE PRESSURE CHAMBER 
Before starting: Keep an accurate log of all chamber runs showing: 
A. Mission to be carried out. 
B* Names of all subjects and respective duties on mission, 
C. Time of reaching each 5*000 foot elevation* 
Do Note any symptoms of anoxia or aero-emphysema reported by subject and 
make inquiries at appropriate altitudesc 
E* Note time of starting and ending any experimental procedure and the 
elevation at which it is done* 
F* Note time and the number of the sample set and of the tube when used. 
G, Be sure observer is properly recording any data he is taking inside 
chamber* Crucial points should be correlated in time by outside observer. 
It will usually be impracticable to report over loud speaker but times 
should be recorded so that after descent to ground level the inside and 
outside data can be correlated immediately* 
Technic for running Pressure Chamber; 
li For chamber equipped for both positive (diving) and negative flying 
pressure be sure valves are properly turned for mission,, 
2. Turn on motor0 
3i Set manometer for existing barometer* 
U* Turn on loud speaker. 
5* Be sure the oxygen tanks of manifold contain sufficient pressure* 
6, Test oxygen regulator inside cnamber to see that oxygen will flow 
properly* 
7* Fit mask to subjects and be sure all subjects understand equipment and 
duties• 
8. Before closing door check for emergency mask, paper, pencils, stop clock, 
time piece, pliers, wrenches and any other apparatus needed for this 
particular flight* 
9m Close door. 
10* Close large valve in front of big door* 
11* Check oxygen flow with subjects inside chamber and at each level check 
flow again. 
12* When going up the door in front nay have to be tightened because of the 
negative pressure. Also on coming down the doors should be gradually 
loosened so they will open readily when at ground level, 
13. When you reach the ground open the door, (after first opening safety 
valve on door), turn off motor, oxygen flow and loud speaker* 
Ihm No one should go up in the chamber alone* It is better to have two 
persons in the chamber to check each other. When coining down from 
whatever altitude they have reached, the rate of descent depends on the 
subjects’ symptoms regarding the ears and sinuses0 INDIVIDUAL LOW PRESSURE CHAMBER GENERAL SET UP FOR TREADMILL EXPERIMENTS w 
Pi 
o 
& 
E-t 
N~ SLIMINATION 
El 
tn 
w 
« 
E-t 
<< APPARATUS TO FILL SMALL OXYGEN TANK 
FROM 
LARGE COMMERCIAL CYLINDER ONI FORM OF ©URGENCY BAIL OUT APPARATUS EFFECT ON CANDLE PLANE 
OF DECREASE IN BAROMETRIC PRESSURE 
1,000 feet 5,000 feet 10,000 feel 
15,000 feet 20,000 feet 25,000 feet 
(Still burning) 
Slide 1-16. Dr. Boothby (gg A TYPE OF SAFETY BELT TO PREVENT HEAD INJURY 
DESIGNED BY 
F.E. MCDONOUGH, M.D., and M.N. WALSH, M. D. 
H 
H 
65 
S=> 
*1 • 
<4 65 
o te 
H H 
8 a 
s a 
O 6h 
OS OT 
W M 
<aj W 
O 
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a 14 
EXAMPLE OF A CHAMBER RUN 
In chamber: Subject - Dr* M. R. Halbouty - Without oxygen* 
Observer - Lucille Cronin - B.L.B, Nasal Mask 
Date: December 22, 19Ul 
Barometer: 731 
10:22 Door and valve closed* 
10:25 5,000 feet 
10:27 10,000 feet 
10:30 15,000 feet 
10:31 18,000 feet 
10:31:20 Peg test - Dr, Halbouty 
10:33 Code test - Dr* Halbouty 
10:35 Code test - Dr. Halbouty 
10:U5 Peg test - Dr* Halbouty 
5.5, *55 10;U7 Alveolar sample taken - Dr* Halbouty - 9o85$-33 mm. Hg CO2 
10oUl$-35 mm, Hg O2 
10:56 Code test - Dr. Halbouty 
10:58 Code test - Dr. Halbouty 
11:02 Peg test - Dr, Halbouty 
5.5. #55 11:OU Alveolar sample taken - Dr. Halbouty - 9*30$-31 mm. Hg CO2 
mm, Hg 02 
ll;0ij.!l0 Started down 
11:OU:30 15,000 feet 
11:05:15 10,000 feet 
11:06:30 5,000 feet 
11:09 Ground 
* Sample set 
GAS BUBBLE FORMATION AT HIGH ALTITUDES 
In order that one may better understand the formation of gas bubbles in the 
body at high altitudes, a simple experiment has been devised to demonstrate it® 
Instructors in aviation medicine will find the demonstration to be of value for 
teaching purposes, especially as regards aeroembolism and aeroemphysema, which are 
found when rapid ascents are made to high altitudes without proper preliminary 
decompression or denitrogenization* 
The apparatus needed includes the following: a mercury manometer, rubber 
and glass tubing, a gallon bottle with a one-hole perforated stopper and a suction 
apparatus capable of creating a negative pressure (the low pressure chamber may be 
used for this purpose: or if necessary an ordinary hand suction pump may be used); 
should a mercury manometer not be available an altimeter may be placed in a small 
bell jar low pressure chamber to indicate altitudes simulated* Of course the bell 
jar chamber is to be connected to the rest of the apparatus in place of the manometer 
The apparatus is connected as shown in the labeled diagram* The gallon jar 
should be filled with tepid water* 
Turning on the suction apparatus causes the mercury in the manometer to 
rise due to the negative pressure* Controlling the amount of negative pressure 
also controls the level of the mercury column so that any reasonable altitude can 
be simulated - depending on the amount of negative pressure produced® Of course. 15 
if the negative pressure source is the low pressure chamber, then altitudes may 
be simulated in the water-bottle manometer corresponding to those reached by the 
low pressure chamber. In fact the bottle or even an open beaker of water can be 
taken up in the chamber with each class of students* 
The bubbles often begin forming at altitudes of 12-15,000 feet* At first 
these bubbles are microscopic in size, but wi th the reaching of higher altitudes 
larger bubbles are formed by fusion and by expansion of the smaller bubblesj a 
variation in the Refraction of light through the water will be noted if sudden 
changes in pressure are produced« This may be better illustrated if a light source 
is placed behind the bottle. AERO—EMPHYSEMA 
BUBBLE FORMATION 
-TO VACUUM 
MERCURY 
ALTIMETER 
BOTTLE CONTAINING WATER WITH 
TUBE INTRODUCED FROM SIDE TO 
REPRESENT NEEDLE IN SPINAL 
CANAL >16 
THE PRINCIPLES AND CONSTRUCTION OF FLOWMETERS 
Principle: There are two main types of flowmeters: (l) Kinetic or float type of 
flowmeter and (2) Static or pressure type. 
The first, the float type depends upon the pressure of a flowing column of 
gas elevating a ball or plunger in a tube with gradually increasing bore, In this 
type the pressure of the flowing gas overcomes'the gravitational force of the ball 
or plunger, The tube must be maintained at a standard inclined position so that 
the weight of the indicator supported by the pressure of the gas is always comparable 
The tube is so constructed that the internal diameter at its base is slightly larger 
than the base of the plunger or the diameter of the ball indicator. The bore of the 
tube is such that the internal diameter of the tube increases gradually from its 
base to the upper end, the increase in size or pitch of the walls of the tube may be 
uniform throughout or it may be divided into sections with different pitch in each 
section, so that as the flow becomes larger the scale can be contracted0 When gas 
flows into the bottom of the tube, the base of the plunger (for example) is elevated 
in the venturi tube by the pressure of gas beneath it. The higher the plunger is 
elevated the greater is the space between the base of the plunger and the inside 
wall of the tube so that the gas can more easily flow past. When oxygen is being 
supplied by a reducing valve so that a steady flow of oxygen is being introduced 
into the venturi tube, the plunger will be elevated to a definite point where it 
will remain because an equilibrium is reached such that the space about the periphery 
of the plunger- is just large enough to allow sufficient gas to flew on through the 
tube to maintain a pressure under the plunger exactly equal to the weight of the 
plunger. When the plunger has been elevated to a definite height by a definite 
flow of gas, this flow of gas can be calibrated on a scale parallel to the tube by 
comparing the oxygen delivery with a previously calibrated master flowmeter, prefer 
ably in a bell jar or low pressure chamber at each altitude. This master flowmeter 
must be previously calibrated by weight for the required mass of gas desired and 
must be done either in a large chamber or in a bell jar evacuated to the desired 
altitude pressure. 
The great advantage of a kinetic type of flowmeter is that it does not 
indicate flow unless flow is occurring. 
The second type of flowmeter is the static type and does not truly indicate 
flow but merely the pressure in a pipe back of a given sized orifice which if 
patent will give a known rate of flo?;, a pressure gauge can thus be readily cali- 
brated to indicate flow. The usual type of pressure gauge is used which is based 
on the principle of a Bordin tube which is curved and tends to straighten out in 
proportion to increase in pressure of gas or fluid inside tube; by means of gears 
small movements of the tube can bo transferred to an indicator needle and the rate 
of flow for a given pressure am be calibrated on a dial. 
As in the kinetic type the static type must also be calibrated to give the 
desired flow at that altitude. The dangerous fact in regard to a static or pressure 
type of flowmeter like this just described is that it may indicate a 11 flow” where 
no flow is occurring even if it accurately . records the pressure in the pipe back 
of the nport hole0,f FLOW METERS 
BOTH TYPES MUST BE CALIBRATED FOR DELIVERING 
AT EACH ELEVATION 
STATIC 
OR 
PRESSURE TYPE 
FLOW METER 
KINETIC 
OR 
FLOAT TYPE 
FLOW METER 
FRONT VIEW 
-TAPERED TUBE 
rLOAT 
TUBE CONTAINING FLOAT IS CONE 
SHAPED SO THAT THE HIGHER IT IS 
RAISED BY THE FLOW OF OXYGEN 
THE GREATER THE AMOUNT OF FLOW 
AROUND THE SIDE OF THE FLOAT 
BACK. INSIDE VIEW 
SHOWING CURVED METAL TUBE 
OF THE BORDEN TYPE WHICH 
TENDS TO STRAIGHTEN OUT 
AS THE PRESSURE INSIDE TUBE INCREASES BELL JAR LOW PRESSURE CHAMBER FOR TESTING SMALL INSTRUMENTS AT HIGH ALTITUDE OXYGEN DEMAND SYSTEM 
APPARATUS FOR MEASURING AMOUNT OF OXYGEN 
USED BY SUBJECT 
THE SMALL TANK IS FILLED TO A GIVEN PRESSURE FROM BIG TANK. 
THE AMOUNT OF OXYGEN USED IS DETERMINED BY TAKING THE TIME NEEDED FOR 
THE PRESSURE TO DECREASE IN MULTIPLES OF 100 lbs. 
-STANDARD REDUCING VALVE 
HIGH PRESSURE GAGE FOR 
DETERMINING FALL IN PRESSURE 
STANDARD 
DEMAND 
VALVE 
LARGE TANK VALVE FOR FILLING 
SMALL TANK 
SAMLL TANK DELIVERING 
3.80 L STPD PER 100 
lbs PRESSURE 
BUBULIAN 
DEMAND TYPE MASK WITH 
RESERVOIR REBREATHING 
BAG TO ALLOW USE OF 
CONSTANT FLOW AS WELL 
AS THE DEMAND PRINCIPLES. 17 
quantitative OXYGEN DETERMINATIONS 
The quantitative determination of oxygen used may be desired at times« Need 
for this is found in determining active and inactive flows through various apparatus. 
Oxygen regulators can thus be checked for the flow the regulator allows at various 
altitudes and under various amounts of exercise, A wet test flowmeter can thus be 
checked as can oxygen consumption of individuals under various conditions. 
There are various methods for these determinations. Several will be considered 
here# Probably the simplest of these is by using only a tank of oxygen, rubber 
tubing and an oxygen mask. 
As an example, let’s create a problem: YJe wish to determine the amount of 
oxygen used by an individual active for 3 minutes at an altitude of 15,000 feeto 
Our ’’active1’ individual does about 1200 foot-pounds of work per minute - 1260 foot 
pounds to be exact. We use a 12 pound weight and raise it 3«5 feet for 30 times 
in one minute (12 x 3*5 x 30 = 1260 foot pounds). It must be realized that this 
calculated amount of work is only theoretically present, however, biologically 
more than this amount of work is done because the theoretic calculation only 
considers lifting, wereas biologically the individual is also doing work when he 
lowers the weight since he is acting against the force of gravity here, too. 
Equipment needed: 
1. Two 100$ oxygen tanks - preferably 100 gallon size0 
A® Tank #1 - To be weighed. 
B„ Tank #2 - Not to be weighed. 
2. Rubber tubing connections* 
3. Oxygen mask. 
h» Accurate balance - reading accurately to 10 mgra. with kgm, weight. 
5. Low pressure chamber. 
6, Stop watch. 
7* 12 pound weight for weight-lifting exercise. 
8. Metronome for timing exercise. 
9* Reducing valve and an aviation flowmeter mounted on the base only of a 
bell jar chamber (the glass cover is not heeded here). The set up is as 
drawn in the illustration on ’’Checking Aviation Flow Meter Using a Master 
Flow Meter” except that the glass jar and mercury manometer are not needed, 
and only one flowmeter is needed* 
Procedure: 
1. Weigh the oxygen tank #1 and record weight. 
2. Connect the apparatus as described* 
3. Place the apparatus in the chamber with the subject* 
iu Ascend to 15,000 feet using the oxygen system and mask of the chamber. 
5. Attach O2 tank #2 to bell jar base, taking care to check the washer at this 
connection. 
6. Turn on flow of Op tank #2. 
7. Set flowmeter at the altitude to be checked (15,000 feet active.) 
8. Shut off tank # 2 and remove it* 
9o Connect tank # 1 to bell jar base* 
10. Remove the regular chamber mask from the subject, place the experimental mask 
on him, turn on the oxygen flow of the 100 gallon tank while being careful to 
start the stop watch simultaneously with the oxygen flow. As soon as the oxyge’ 
flow is started the subject begins his exercise by raising and lowering the 12 
pound weight 3*£ feet for 30 times per minute* 11. At the end of 3 minutes shut off the small #1 tank’s flow the instant flowmeter 
level drops, have the subject stop work, and reconnect him to the oxygen flow 
system of the chamber, 
12# Descend to ground level. 
13# Weigh tank #1 again and record# 
lli# Sample calculation: 
Wt. of ©2 tank before test ® 6080.891 gms, (See section on ’’Selection of a Master 
Wt. of ©2 tank after test ■ 6073*891 gms# Aviation Flow Meter Using Determina- 
Tank Weight Loss *= 7.000 gras. tion of Flow Rate by Weighing” for 
weighing procedure.) 
Mol# Wt. cf 02 32 
22X 22TH * lftk29 gms. « Wt. of one liter of dry 02, 
Therefore * U.899 liters ©2 used in 3 minutes 
and Titers e 533 liters 0? used in 1 minute# 
3 min. 
We must realize that this method even though relatively simple has its 
limitations* It is dangerous to use this method at higher altitudes such as 
35.000 to U0,000 feet, for at these altitudes one may lose consciousness in 
about 35 seconds or lass* Such a situation may be met if there is any delay in 
changing over from the oxygen supply system of the chamber to that of the small 
tank or vice versa* It is probably best to reserve this method for determining 
quantitative oxygen flow to altitudes below 20,000 feet unless a two-way valve 
is used so that one may readily switch from one oxygen system to the other by 
merely turning a tap* 
In connecting up an oxygen regulator to the above system and setting the 
regulator for a certain altitude and physical exercise (i#e# 15,000 feet active) 
we may also determine if the regulator is supplying the correct amount of 
oxygen for that altitude and resting or exercise state, (See section of nA 
Master Aviation Flow Meter Using Determination of Flow Rate by Weighing”.) 
We can attach a wet test flowmeter to the above apparatus, record the 
number of liters of Og the wet test flow meter dial shows as having flawed 
through for a given period of time and compare this recording with the flow 
calculated by weighing the oxygen tank as outlined above. Thus we can check 
the accuracy of the wet tost flow meter. 
This leads us to our second method of determining the quantitative flow of 
oxygen* Assuming our wet test meter is accurate, connect it to an oxygen 
tank with flowmeter so that all oxygen going to the mask has to first flow 
through the wet test meter. By merely noting the reading on the wet test meter 
dial at the beginning and end of each test we can learn the ambient amount of 
oxygen which has been used. However this reading must be corrected to S.T.PJ5# 
to give us the reading commonly used. Assume that the test is conducted at 
10.000 feet altitude Yvith a barometric pressure of 523 mm * Hg and the temperature 
reading of the wet test meter is 25 degrees C. (temperature must be taken in this 
method)# By looking at the tables of water vapor we note that the water vapor 
for 25 degrees C# is 23o8 (or 2iu0), If 6 liters of oxygen flow is recorded 
in 10 minutes, then 6,0 liters * e60 liters/min. measured at ambient temperature 
and pressure flowed through the me bar t. Ccrrecting to S.T.P.D, (760 mra. Hg 0° C., Dry) then 
.60 x -■2-3-ygp--- * 2P2g » .60 x .657 x ,916 ' .36 liters 02/min. at S.T.P.D, 
With this method there is no need to weigh the oxygen tank, and it is relatively 
safe in that there is no need to change oxygen masks as one merely continues to use 
the chamber oxygen system the whole time he is in the chamber. This method is 
commonly used to check the flow of regulators connected to this system* 
There is still another method of determining the amount of osygen used* We have 
used it mostly in testing regulators. It is excellent for testing regulators and 
masks used with either the demand system or constant flow system. 
The equipment is shown in illustration QD02* 
Equipment needed: 
1* Paper and pencil. 
2* An oxygen tank - standard size is satisfactory,, 
3* A small accessory oxygen tank for measuring. (The volume for a drop of 
100# pressure has been predetermined by methods previously mentioned*) 
U« A pressure gauge for the accessory oxygen tank* 
Low pressure chamber, 
6* Oxygen mask and tubing. 
7. Stop watch or electric stop clock preferably calibrated for tenths and 
hundredths of a minute, 
8. Weight for lifting exercises (preferably 12#). 
9* Oxygen regulator, 
10. Metronome for timing exercise* 
Assume that our problem is to determine amount of oxygen used per minute with 
a regulator and mask designed for a demand system at an altitude of 20,000 feet 
while actively exercising. 
Procedure: 
1* Draw an outline form on paper as follows: 
Altitude 
Starting pressure End pressure 
Pounds used 
Time in 
in tank 
in Tank 
min. 
2* Connect the apparatus in the chamber as noted in illustration QD02* The valve 
on the large tank is slowly opened so that oxygen flows into the small accessory 
tank and fills it* This is done slowly to prevent generation of too much heato 
Now shut off the large tank* The pressure gauge now records the pounds of oxygen 
pressure in the accessory tank and its connections. Connect the oxygen mask to 
the accessory tank flow and fit the mask to the subject* He receives his oxygen 
from the accessory tank* 
3* Ascend to 20,000 feet* Record the altitude* 
h* Refill the accessory tank to say 1500 pounds* Exercise and the stop clock 
are to be started the instant the pressure gauge needle records IhOO pounds and 
are to be continued and then stopped the instant the pressure gauge registers 
1100 pounds* Record* The metronome should be set to enable the subject to lift 
the weight 30 times in one minute* 20 
£, Out recording sheet should show; 
Altitude Starting pressure 
in tank 
End pressure 
in tank 
Pounds used 
Time in 
min* 
20,000 ft* 1U00# 
1X00# 
300# 
1.35 
60 Then by calculation: 
300 pounds of oxygen were used in 1*35 min® 
Since there are 3.7 liters of Op per 100 lbs., of O3 at S.T.P.D.; then there are 
o037 liters of Op per 1 pound of Op at SoT,P«Da 
Therefore; ■ 222,22 pounds of 02 used/min0 at S.T.P.D. 
and 222*22 x .037 *= 8,22 liters O2 used/min. at S.T.PoD. 
7, By repeating the process the amount of oxygen used at other altitudes for 
rest or exercise may be determined. The following is taken from such 
determinations: 
Altitude 
Work 
Starting pressure 
in tank 
End pressure 
in tank 
Pounds used 
Time in 
min. 
5,000 ft. 
33135? 
700# 
600# 
"unir- 
15,000 ft. 
lUoc# 
100c# 
1*00# 
1.38 
20,000 ft. 
U*OC# 
HOC# 
30c# 
1.35 
30,000 ft. 
11*00# 
120c# 
200# 
1.1*3 
U0,000 ft. 
11*00# 
1300# 
100# 
1.22 
Rest 5,000 ft. 
11*00# 
900# 
500# 
2.89 
15,000 ft. 
11*00# 
1100# 
300# 
2.80 
20,000 ft. 
il*oo# 
1200# 
20c# 
2.63 
30,000 ft. 
11*00# 
130c# 
100# 
2.22 
ho,000 ft. 
11*00# 
130c# 
100# 
3.91* 
It will be found that the pressure gauge needle moves much faster at low altitudes 
than at high altitudes* As an example, we found that at rest one subject used £00 
pounds of oxygen in 2.89 minutes at £,000 feet, whereas he used only 100 pounds of 
oxygen in 3*9U minutes while at rest at U0,000 feet* This is because the lowered 
barometric pressure of high altitudes causes the oxygen to expand in the body where 
it is no longer under S.T.P.D. This may be noted in studying the tables entitled 
’•’Oxygen Flow Needed for BLB Oxygen Inhalation Apparatus.” Hence, the pounds of 
pressure used should be greater at lower altitudes* In order for an individual to 
use £00 pounds of oxygen resting at U0,000 feet he would have to wait about 20 
minutes* As a guide the above table may be used* Let’s also note and remember that 
more pounds of oxygen are used in exercise than in resting since the metabolic rate> 
circulation rate, etc* are increased in the former. 
The amount of oxygen used can similarly be determined if set up for any type of 
air-oxygen demand * If this air-oxygen demand system is run under similar conditions, 
both for air-oxygen or straight oxygen, the amount of air added under various condi- 
tions can be calculated* CALIBRATION OF A MASTER AVIATION FLOY/ METER USING DETERMINATION OF FLOY/ RATE 
BY WEIGHING 
A* Equipment* 
1* Accurate balance - reading accurately to 10 mgm® with 5 kgm, weight, 
2, ©2 ank ■" to be weighed ~/ / 100 gal© each, or midget emergency 
3. 02 tank if2 - not to be weighed -/ ' & 3 & tanks, 
ho Negative pressure supply - preferable low pressure chamber, 
5>c Mercury manometer, 
6, Stop watch or electric stop clock preferably calibrated for tenths and 
hundredths of a minute, 
7, Bell jar pressure chamber® 
8, Reducing valve for flow meter (to be fitted inside bell jar), 
9e Flow meter to be calibrated (aviation) equipped with mm, graph paper, 
B, Apparatus Arrangement, 
1, As in accompanying illustration, 
C, Procedure, 
1, Weigh tank #1 - and record, 
2, Hun low pressure chamber to highest altitude and keep it there throughout 
work, 
3, Connect bell jar pressure chamber to low pressure chamber as illustrated, 
he Connect flow meter to be calibrated to belljar chamber. 
Attach O2 tank #2 to bell jar chamber. Be certain washer is tight at this 
connection and change it several times during work, 
6, Turn on flow of O2 tank #2, 
7, Reduce pressure in bell jar chamber until desired altitude is attained on 
mercury manometer, i.e*, 1*0,000 ft, active (or inactive, if calibrating inactive*' 
8, Set flow meter at the altitude to be checked (same as in #7), i,e,, U0,000 ft® 
active), 
9, Shut off tank #2, and remove it, 
10, Connect tank #1 to bell jar chamber, 
11. Turn on O2 tank #1 flow and immediately start stop clock as flow meter levels 
jump, 
12® Let O2 flow through for at least 9 minutes, 
13, Shut off O2 tank #1, and immediately watch flow meter levels because tubing 
of apparatus will contain much oxygen. They will slowly rise and then 
suddenly drop to zero. Stop the clock at the fraction of a second after they 
start their final drop, 
1U, Disconnect tank #1 and weigh it to get weight change® 
15• Calculate amount of used per minute at S,T,PcD. which is 760 mm, 0° C, dry. 
16, Sample calculation: 
iiO.OOO feet (active) altitude test conducted at 
Weight before test of Tank #1: 
(On loft pan of balance 
Weight after tost 
of Tank #1 
Pendulum 
\ 
Swings 
Pendulum 
Swings 
Left 
Right 
Left 
Right 
-6.2 
+2.9 
-11«2 
+ *9 
-6*2 
+2.8 
-11*2 
+ .9 
-572 
+2.9 
-11 ©2 
+ *9 
-3.3 „ 
2 
-l©6f? x 
-6.2 
+2,9 
-3.3 
-1,65 
.066# • —e 
,109 gras. 
-11.2 
+ c9 
-10 o 3 
- -5.15 
-5 elf? x .066# *= 
-«3U0 gms. 
* This is the sensitivity of the balance used; * 1 div® *= ,066 grans*  
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ftfP-M,—HSLiK = Wta of one liter of the dry gas if the gas is as nearly a 
perfect gas as is oxygen* 
Mol a Wt, of C>2 op 
22711 ~ *= 1«U29 s wto of one liter of dry O2 (this figure can be 
229U found in physical tables)* 
ltO<231 = 28053 
l7u29 (which is time of O2 flow) « iio?U liters of O2 flow per minute 
through aviation flow metera 
17e A flow of UcTU liters per minute is found to be sufficient for 1*0,000 feet 
active if we consult the charts and tables indicating the required flow of 
oxygen at various altitudes and under rest or activity* 
18« In a similar manner the flow meter is checked for each of the other altitudes 
marked on its face, both rest and active* 
19o If the flow calculated is too high or too low by more than 5> or 10$ then one 
should change the flow accordingly and by use of the graph paper on the flow 
meter determine the correct level, erase the old marking and paint in the new 
calibrated marking* 
20* Once a flow meter is found to be absolutely accurate then it may be used as a 
master flow meter and other aviation flow meters may be checked against it by 
setting both flow meters in the low pressure bell jar chamber and connecting 
them in series0 Then by setting the master flow meter at the desired levels 
merely note whether the other flow meter levels correspond with those of the 
master flow meter within allowable limits of 5> to 10$, See the accompanying 
labeled diagram* 23 
DETERMINATION OF OXYGEN FLOW THROUGH AN aVIaTION FLOW METER USING A V/ET TEST METER 
This method is relatively simple in that no weighing is necessary. The prime 
requisite is to have a standard wet or dry test meter which is accurate3 preferably 
with a 10 liter dial, as a smaller one, such as a 3 liter meter dial, would revolve 
too fast at altitudes above 30*000 feet. If an issue test meter is not available, 
then one can perhaps be borrowed from a local gas company. The gas company meters 
are usually calibrated in cubic feet. One cubic foot is equal to 28.32 liters. 
The technique of testing the accuracy of flow of an aviation flow meter is 
relatively simple and may at times be valuable. New aviation flow meters should be 
frequently checked, especially if they are for use at high altitudes or in low 
pressure charabers3 After one is convinced by repeated rechecks that an aviation 
flow meter is, and remains, accurate then it is only necessary to be rechecked 
again about every 6 months. Knowledge of the technique will undoubtedly be of value 
at Air Corp stations. First, for accuracy and second, for the psychological effect 
on the pilot it is well to check his regulator and flow meter before a high altitude 
flight over 30,000 feet if it is a new regulator or one that he suspects is inac- 
curate , 
The equipment used for the test is as follows: 
1, Portable oxygen tankj 100 gallon tank sufficient* 
2, Accurate wet test flow meter* 
3, Stop watch* 
U. aviation flow meter which is to be calibrated* Flow meter should be fitted 
with graph paper, ice, 10 mm* to 1 cm. 
Technique for calibration of aviation flow meter: 
I, The oxygen tank, aviation flow meter, and wet test flow meter are connected. 
II, Check the wet test flow meter and all connections. 
Ill, Ascend in the low pressure chamber to the altitude desired, i.e,, 10,000 ft. 
IV, Turn the oxygen tank flow on. 
V, Set the aviation flow meter at 10,000 feet inactive. 
VI. Read the temperature of the wet test flow meter and record, 
VII. With the stop watch get the time it takes for 2 complete revolutions of the 
large dial needle. Six liters is therefore the arbitrary amount for the 
small 3 L. meter. One may choose to let any number of liters flow through, 
however, the time should be at least 2 minutes for the flow* 
VIII, Assume that 6 liters is allowed to flow through and the time for it is 10 
minutes. Assume the barometric pressure at 10,000 feet altitude is 523 mm. 
Hg and the wet test meter temperature is 25 degrees e The water vapor for 
25 degrees temperature is 23»8 (Look up in tables of water vapor). 
IX. Calculation: 
- .60 liters/min. measured at ambient temperature and pressure 
m:mo flowing through the aviation flow meter and wet 
test meterc 
Correcting to 3.T.P.D,: (760 mm. 0° C. dry) 
.6 x 
523 - 23*8 
760 
x 
273 
273 + 25 
s ,6 x *657 x ,916 • *36 liters O2 S.T.P.D. 
X. Since an inactive man at 10,000 feet requires .50 liters of oxygen per minute 
- taken from the tables of oxygen requirements using the oxygen apparatus - 
then the aviation flow meter may bo considered as giving slightly less than 
the required flow at 10,000 feet altitude0 
XI* The from the aviation flow meter at other altitudes are calculated In i 
similar manner* 24 
TKE WET TEST FLOW METER 
I. Preparing wet test flow meter for use; 
A© Level the meter by adjusting the leveling screws at the base until 
the bubble in the spirit level is exactly in the center. 
B© Fill the meter with water one or two degrees above room temperature 
until the water level is slightly above the tip of the pointer in the 
gauge glass, 
Co Make sure all connections are tight© 
D, Pass the gas to be measured through the meter until the water is saturated* 
The approximate volumes necessary at room temperatures under various 
conditions ere as follows: 2 to 3 cubic feet for routine test using the 
same gas 5 
E, Disconnect the tubing leading to the meter so that both inlet and outlet 
are under atmospheric pressure© Draw off water through the small pet 
cock at the base of the water line gauge until the center of the concave 
meniscus in the gauge glass coincides exactly with the tip of the 
pointer-. 
F© Reconnect the tubing and test again for tightness before proceeding 
with test* 
II. Operation and care of wet test flow meter; 
A© The wet test meter is built for operation at a few inches of water column 
pressureo Excessive pressures will cause the shaft stuffing box to leak 
and distort the case, producing a bind in the meter which will affect 
the accuracy© Differential pressures much in excess of .3 inch water 
column will blow the seal in the meter, causing gas to by-pass the measur- 
ing compartments© 
B, The water used in the meter, particularly for brass meters, should not 
be corrosive or contain solids in concentrations high enough to crystallize 
on the bearings or to alter the density of the water appreciably© 
C© Piping connections must not strain or distort the meter case because the 
bearings will be thrown out of alignment© Care must be taken to preserve 
the original position of the spirit level, as well© 
D, Periodically the meter should be flushed free of sediment, which if 
allowed to accumulate will reduce the size of the measuring compartments 
and unbalance the drum© Accumulation of oil on the surface of the water 
may produce an opposite tendency by creating a false water line within 
the measuring compartment when the meter s in operation* WIT T1ST MITER 
THREE SIZES: 1, 3 and 10 LITERS CAPACITY PER REVOLUTION Tilt: CONSTRUCTION OF REDUCING VALVES 
Fundamental requirements 
1, The pressure of the gas in the cylinder must be reduced to a low delivery pressure# 
'2m The delivery pressure must be maintained at a fairly constant value independent 
of all disturbing influences# 
3. Means must be provided to adjust th6 delivery pressure to any desired level* 
U. Maintenance must be reduced to a minimum# 
5* The regulator must be safe under all conditions of normal use and as fool-proof 
as possible* 
In considering the principle of the reducing valve, a clearer conception 
can be obtained by utilizing a more or less homely simile* The water backed up 
behind a dam is under pressure varying with the depth of the water* The pressure 
under 33*899 feet of water is equal to one atmosphere (llu? pounds per square inch)* 
From this it can be calculated that at a depth of 10 feet the pressure is U*3 
pounds per square inch and at 100 feet U3 pounds per square inch* SINGLE STAGE REDUCING VALVE 
ADJUSTING SPRING —" 
Diaphragm 
Lou Pressure CHflriBf r — 
Marginal .Spring 
Nozzle. 
‘Valve Stem 
Compensating Spring 
Inverse Trre 
He I 
Typical Welding Regulator* 
Direct Type 
FI® Z 
Fig. 3 -RED BORDERED SiGNAu BUTTON 
— signal retainer 
—first stage control SPRING 
f— HIGH PRESSURE DIAPHRAGM PLATE 
HIGH pressure diaphragm 
HIGH PRESSURE SEAT RETAINER 
HIGH PRESSURE SEAT 
1 high PRESSURE NOZZLE 
-MARGINAL SPRING 
L 3 S' ~T -ND ~0_DER 
L p ASS v 
BOOV 
—ADJUSTING SPRING 
-spring Button 
j-SPRiNQ CASE 
, ADjuST.NG 
SCREW 
SLIP RING 
GUIDE TMiMBLE 
RETAINING SCREW 
L lever 
bearing platf 
COMPENSATING SPRING 
-—Sl p Ring 
-BACK CAP 25 
A pipe is laid at the 100 foot level into the bottom of another.pool, as 
shown in the diagram, and an outlet from the smaller pool made at the level of the 
pipe (P), A float is arranged 10 feet above the bottom of the smaller pool so 
constructed that should the water in the smaller pool rise above 10 feet, a valve 
closes the pipe leading from the dam. Under these conditions the pressure of the 
water at the inlet of the Pipe is U3 pounds per square inch*, The pressure of the 
water at the bottom of the second pool is maintained at pounds per square inch 
and the pressure of the water in the outlet from the smaller pool is maintained 
at this same level. This is the fundamental mechanism of the reducing valve. Regu- 
lation of the level of the float changes the delivery pressure and the flow through 
the outlet of the smaller pool just as regulating the adjustment screw *'f a 
reducing valve changes the delivery pressure and flow of gas through its outlet tube. 
Typical construction of reducing valves is shown in the diagram. The gas 
enters from the cylinder at the point labeled n inlet0JI It passes through a valve 
which throttles the flow of th > gas. The diaphragm is a pressure-responsive 
element which opens the valve slightly in case the pressure falls off, thus 
permitting an increased flow of gas, reestablishing the pressure. This mechanism 
works in reverse in case the delivery pressure of the gas increases. The pressure 
therefore remains quite uniform at any specific setting of the adjustment screw,. 
This adjustment screw increases or decreases the tension on a spring which is trans- 
mitted to the diaphragm. If the adjustment spring is under considerable compression, 
it will exert a relatively heavy thrust against the diaphragm which results in a 
relatively high delivery pressure. If the tension on the spring is reduced, the 
delivery pressure is reduced,, When the deliveiy pressure is increased the actual 
flow of the gas is increased and vice versa. 
The amount of flow of oxygen out of a definite-sized orifice produced by a 
constant setting of the adjustment screw on a reducing valve results in a marked 
decrease in the rate of flow as the barometric pressure decreases. For example, 
if one type of reducing valve is set to deliver 3«»6 liters per minute at ground 
level, the actual delivery at 35*000 feet at the same setting of the adjustment 
screw is only 2,06 liters per minute. This is dependent upon the following two 
facts. On the outside of the reducing valve, the diaphragm is exposed directly to 
the atmospheric pressure through holes deliberately made in the case of the instru- 
ment because, as a rule, under ordinary conditi at ground level, change in 
barometric pressure is negligible. However, in aviation these changes are no 
longer negligible but become very important because a decrease to one half of the 
barometric pressure (under standard conditions) on the outside of the diaphragm 
reduces the pressure from lUo? pounds per square inch to 7.35 pounds per square inch 
and similarly for any other change in altitude* Therefore, if no change is made 
in the adjustment screw which works through the adjustment spring on the outside 
of the diaphragm, the total pressure on this diaphragm will be decreased, thus 
reducing the amount of oxygen flow. In one type of two-stage reducing valve this 
results in a decrease of delivery of oxygen from 3©7 liters per minute S.T.P.D, to 
2.1 liters per minute in going from sea level to 35*000 feet altitude. 
This is of extreme importance because if the flow of oxygen is set for 
35,000 feet while a pilot is at ground level and the rducing valve has no automatic 
compensator, the pilot will get a progressively decreasing flow of oxygen. Conversely, 
if the reducing valve is set accurately when the pi}ot is at 35,000 feet and he 
descends, there is serious o:xygen waste so that his supply of oxygen would last 
only 2/3 the length of time the supply would last if adequately compensated for 
altitude. To prevent the flow of gas when the apparatus is not in use, most types of 
reducing valves have a spring which completely closes the valve when the tension 
of the compression spring is completely removed. 
With regard to structure there are three types of reducing valves, (l) inverse 
(or indirect) (2) direct pressure regulators and (3) compound or two state reducing 
valves in which two regulators are connected in series. 
(l) An indirect pressure regulator is one in which the thrust of the high 
pressure gas is in such a direction as to tend to close the valve seat against the 
nozzle. (2) A direct pressure regulator is one in which the thrust of the high 
pressure gas is in such a direction as to tend to force the seat away from the 
nozzle. (3) The compound or two-stage regulator may be any combination of the 
above, usually built into a compact unit. 
Most pressure regulators (reducing valves) are important because, as the 
pressure of the tank decreases, the delivery pressure (and flow of the gas) also 
decreases perceptibly. In glancing at fig* (U) it will be noted that the pressure 
of the ga.s from the tank on the valve seat (in the direct type of reducing valve) 
plus the pressure of the adjustment spring on the diaphragm must balance the 
pressure of the gas on the diaphragm plus the tension on the compensating spring* 
Inijh| inverse or indirect type, as the pressure in the tank decreases the delivery 
To minimize this effect, the area of the diaphragm is large and the 
diameter of the inlet nozzle, very small. As the pressure in the tank diminishes, 
it arrives at a point at which the inlet nozzle cannot discharge enough gas to keep 
up the delivery pressure* This is the regulation end-point for any particular 
rate of flow* In using the excessively small inlet nozzle, this end point is 
reached at a higher pressure than is the case with a larger nozzle. The small 
nozzle, however, will handle a greater load at higher pressures so the size of 
the nozzle varies with the use to which the regulator is put. 
At relatively low levels of cylinder pressure, at points above the regulation 
end point, the regulating characteristics of any particular reducing valve may 
markedly change* The effect on the direct type of reducing valve is to markedly 
reduce the delivery pressure and the flow of the gas. The direct type of regulator 
in general is more satisfactory if the cylinder pressures are of adequate magnitude* 
In low pressure units the indirect type of valve is superior. 
Other disturbing influences are (l) seat recovery and (2) pre-cooling. When 
the reducing valve is not in use, the valve seat is tightly pressed against the 
nozzle, leaving an impression on the rubber or fiber valve seat. If the plastic 
properties of the material from which the valve seat is made are such that the 
material tends to continue to change its shape long after the pressure has been 
removed, the delivery pressure is reduced, rapidly at first and then more gradually* 
At low rates of flow, the seat recovery is greater than the magnitude of the seat 
displacement so that the regulator must be constantly watched for a period of an 
hour or more. This has been cut down markedly by the use of non-hygroscopic seat 
materials with very rapid recovery values. 
When the pressure is rapidly released from a volume of gas, there is consider*- 
able refrigeration effect. This may lead to, first, condensation of the small 
amount of moisture in the gas and later to freezing of the moisture in and about 
the nozzle. This will also cause marked changes in flow. A satisfactory solution 
is the two stage reducing valve. In cold weather the first stage of pressure re- 
duction may develop some pressure fluctuations but these will rarely be transmitted 
through the second stage into the delivery hose. When two stage regulators are not available, the following precautions must 
be taken: 
1, Do not take oxygen cylinders from a warm room and attempt to use them 
outdoors in cold weather because until thoroughly chilled, the gases may 
contain traces of moisture which may block the nozzles of the reducing valve, 
2c Operate the regulators at somewhat increased flow over the normal in cold 
weather. 
One other danger involved in the use of reducing valves is what is known as 
seat ignition. When the compressed ouygen in the cylinder is first turned on, it 
rushes through the nozzle and strikes the valve seat which is made of some organic 
material (usually hard rubber). This rapidly compresses the air in the valve 
chamber and may produce temperatures up to 1700° F, If the valve seat is irregular 
from use or has inflammable foreign particles on the surface, the presence of such 
high temperatures in an atmosphere of pure oxygen may cause explosive oxidation of 
the valve seat • This nay indeed be quite dangerous in spite of the presence of 
safety valves in the apparatus. 
Compound regulators are combinations of the direct and indirect type of 
reducing valves. As indicated above, it is most advantageous to use the direct 
type of regulator for the first stage in which the pressure may be reduced from 
pounds to level of 60-80 pounds per square inch. This level of the first 
stage reduction is maintained as a constant and the adjustment for varying rates 
of flow is made on the second stage reducing valve which usually contains an 
indirect type of valve. 
GENERAL RULES FOR HANDLING iiND USING OXYGEN EQUIPMENT 
A« Oxygen Cylinders: 
1» Never place an oxygen cylinder so that it can be knocked down or fall over. 
Reasons: (a) If there is a crack in the cylinder wall from previous accidents or 
from inferior metal in the tank, and the pressure of oxygen in the 
tank high, the cylinder may explode, 
(b) If the valve on the top of the tank is knocked off, the pressure 
of the oxygen in rushing out may propell the tank about the room 
like a rocket® 
2, Do not store cylinders near inflammable material, especially oil, grease, 
or any substances likely to cause or accelerate fire* 
Reason: Leak of oxygen may raise the oxygen content of the air in the room so 
that any chance spark from static electricity or short in electrical 
apparatus may produce a fire or explosion* 
3* Oily or greasy substances must never be used in or about cylinder valves, 
couplings, gauges, hose and connections, especially where high pressure 
oxygen is to be used. Do not handle oxygen cylinders with greasy hands or 
gloves 6 
Reason: Small droplets of film of oil or grease in contact with oxygen in a 
high pressure syston forms a detoning mixture which may explode with violencec 
U. Store cylinders in cool dry places* 
Reason: Most tanks are equipped with safety devices to allow oxygen to escape if 
the pressure in the tank becomes too great® The effect of heat is to 
increase the pressure in the tank so that oxygen is forced out into the 
room air* 
5* Do not expose cylinders to water, snow or rain* 
Reason: Threads on the valve caps might rust and make it difficult to remove the 
caps. The use of grease to prevent rust is, of course, prohibitedo 
(See rule 3). 6, Iron Cap over cylinder valve must be kept in place at all times -when not in 
use. 
Reason: This protects the cylinder valve from damage in case it is accidentally 
dropped (See Rule l). 
7* Never use cylinders without a suitable reducing valve or regulator* 
Reason: The flow of oxygen cannot be controlled by means of the cylinder valve 
alone* This may result in great waste of oxygen as well as pouring 
oxygen into the room air, predisposing any combustible material around 
the room to rapidly spreading fire® 
8* After removing the iron valve cap from the cylinder, carefully crack the 
cylinder valve for an instant to blow out any dust or particles from the oxygen 
outlet* 
Reason: Particles of dust are large enough to partially or completely clog 
reducing valves, 
9® After adjusting a reducing valve on the oxygen outlet of the cylinder, be 
sure the adjustment screw on the reducing valve has been released. 
Reason: This prevents a sudden flow of oxygen under high pressure through the 
reducing valve* (See valve seat ignition*) 
10® Never permit oxygen to enter the regulator suddenly* Open cylinder slowly® 
Reason; (See valve seat ignition,) 
11* Avoid using wrenches to tighten cylinder valves® 
Reason: Cylinder valves are closed by means of a needle valve* Too severe 
tightening of the valve may impair the fit of valve and result in leaks 
in the future, 
12. Always open the cylinder valve slowly and continue gradually to completely 
open it when the cylinder is in use* Leakage about the valve stem occurs if 
the valve is only half open* 
13* Never use a lifting magnet or a rope or chain sling in moving tanks. 
Reason: These devices are not secure against dropping the tanks, 
llu Do not store full and empty or partially empty tanks together. Before removing 
a reducing valve from a tank, record in a prominent place the pressure of the 
oxygen in the tank* 
Reason; These precautions protect the flight crews from finding themselves 
without oxygen at a time when oxygen supply may be vital* 
15>. If a cylinder is found to be out of order or is suspected of having a crack, 
mark the cylinder defective and be sure it is returned to the air corps supply® 
16C When a cylinder is empty, be sure cylinder valve is closed securely. 
Reason: Daily changes in temperature may expand and contract the gas in the tank 
drawing moisture and room air into the tank® This is known as "breath- 
ing” and predisposes to rusting of the needle valve in the cylinder 
and may result in freezing if the tank is exposed to low temperatures® 
In addition to this, moisture in the oxygen supply, especially if it is 
used in oxygen equipment at high altitudes predisposes to freezing of 
the reducing valves* 
17o Before removing reducing valve from the cylinder, always close the cylinder 
valve securely. 
Reason: (see Rules 7 and 1?) 
18* In filling a small tank with oxygen from a large tank, open the cylinder 
valve slowly and allow the pressure in the small tank to increase gradually* 
Reason; Sudden opening of the valve of the large tank, compresses the gas 
present in the small tank rapidly enough to generate a great deal of heat 
19. If high pressure oxygen tanks are arranged in series, do not allow the pressure 
of one tank to fall below the others. 
Reason; The effect is the same as in Rule 18e Seat ignition* The valve seats in cylinder valves and reducing valves are frequently 
made of organic material such as rubber or fiber• If oxygen at full cylinder pressure 
is suddenly admitted into a valve, considerable heat may be developed at the valve 
seat as a result of the heat of compression imparted to the gas which was originally 
in the regulator inlet passages (as in Rule l8)a Since the valve seat is in an 
atmosphere of 100$ oxygen (strictly 99*7%) it requires only a particle of inflam- 
mable material on the valve seat to cause an explosive combustion of the valve seat* 
This is the basis for the repeated rules regarding the careful opening of high 
pressure oxygen cylinders* 
CLOSED CIRCUIT OXYGEN THERAPY APPARATUS - HIGO No* 130 
General Description 
The apparatus is of the closed circuit type and is designed for the economical 
therapeutic administrations of high concentrations of oxygen up to 100$, Shell 
natron interposed in the circuit absorbs the carbon dioxide and moisture exhaled by 
the patient. All sizes of medical and commercial oxygen tanks having standard 
valve threads may be used, as adapters for each type are included in the equipment. 
Assembly 
The apparatus as shipped is completely assembled except for a few rubber parts. 
The method of attaching these is explained. Reference to the accompanying cuts 
will prove helpful* 
Loosen the clamps holding the cover of the carrying case to its base. Turn 
the cover up-side-down. Place the base containing the apparatus on top of the 
cover and snap the clamps to place, to elevate the apparatus to convenient working 
height* 
Connect one of the 50” corrugated tubings 1125” to the outlet of inspiratory 
valve ”1”, Connect the other like tubing 1125” to the inlet of expiratory valve 
”2M, Connect the two free ends of these tubings to metal Y connector n3”, Attach 
one end of either the 8” corrugated tubing MU” or 10” corrugated tubing f,5” to 
the base end of Y connector ”3” and the other end of this tubing to the connector 
on the mask. 
Attach reservoir rebreathing bag ”6” by means of its metal ’’L1' connection ”7” 
to the lower side opening of inspiratory valve nl"« (This opening has a rubber 
connector.) 
By means of its union nuts connect tubing ’'ll” tightly to the corresponding 
threads of oxygen control valve ”12” and reducing valve ”13”, 
The union nut of the reducing valve fits the threads of standard large size 
medical oxygen tank valves. Yoke adapter ”10” for small standard medical oxygen tank 
valves and an adapter having union nut ”lU” for large standard commercial oxygen 
tank valves are supplied. 
To attach a container of shell natron ”16” first remove (pry out) the metal 
sealing cap from the opening on each side of the container using the screw-driver 
provided for the purpose. Then position the container in its holder so that gasketed 
metal Y connection ”1?” extends into the opening of the container on one side, push 
gasketed metal L connector ”18” against the opposite side of the container and 
tighten to place moderately with thumb screw of bracket ”19”* 30 
The apparatus is now ready for use when its reducing valve is attached to a 
tank. 
Description 
The supply of oxygen to the patient is delivered by reducing valve "13u having 
3000 lb* gauge to indicate tank pressures, through tubing "11" to flowmeter nl5tf, 
Valve "12" controls the rate of delivery as indicated in liters per minute by the 
flow meter. Additional emergency volumes of oxygen from valve ”19" may be introduced 
instantly by finger pressure on the valve at "20", Valve ”19” when subjected to 
approximately 2 cm, HgO negative (inspirational) pressure, also automatically 
supplies oxygen to the closed breathing circuit* The valve is connected by 811 
corrugated tubing "2U" to Y connector "17”, 
Two types of masks are provided. Each mask has straps for attaching to head 
harness "23" to hold the mask in place on the patient's face. 
Harness ,,23,, should be placed on the patients head with the elastic strap 
forward and on top. The leather straps are adjustable* 
Strap "26" goes around the neck to support the mask tubings and thus relieve 
strain on the mask* 
Expirations pass through the closed circuit in one direction guided by the 
expiratory and inspiratory valves. Expirations first pass through expiratory valve 
"2" and by means of 10" corrugated tubing "21" enter and pass through shell natron 
container "16" for CO2 and moisture absorption and are conducted therefrom by 8" 
corrugated tubing "22" to bag "6" and inspiratoiy valve "1" and thence again to 
the mask for inhalation. 
Valves "1" and "2" may be readily lifted from their grooved suspensions and 
taken apart (without tools) for ready cleaning. 
Whistle "8" v/arns when the oxygen supply is exhausted or not turned on. 
Valve "9) opens automatically to release excessive pressure in the breathing 
circuit• 
Adapters "10" and "lU" and reducing valve "13" when not in use should always 
be screwed onto the studs attached to the inside of the carrying case. 
Wrenches for the union nut of reducing valve, adapters and small tank valves 
are supplied. The screw driver supplied is for uncapping the shell natron container* 
There is a stout handle on the apparatus for lifting. 
Operation 
Grasp corrugated tubings "25" near the mask and hold them closed tight with 
the left hand. Open oxygen control valve "12" to about 15 liters flow per minute, 
When the reservoir-rebreathing bag becomes completely distended, loosen grip on 
tubings and press the bag to empty it. Repeat this three times, then when the 
bag is again full apply the mask to the patient's face, reduce the oxygen flow rate 
to 1 liter per minute and adjust the neck and head harness straps in a manner to 
retain the mask comfortably in air-tight position® Ask the patient to indicate 
when he thinks the mask is so adjusted. 
With the mask applied the patient is in communication with the closed circuit 
of the apparatus and is constantly consuming oxygen at the rate of 300 to i±00 ccfi 
per minute. Therefore when the oxygen flow is set at 1 liter per minute the supply OXYGEN THERAPY CLOSED CIRCUIT TYPE FOR FIELD SERVICE 0XYG1SN THERAPY CLOSED CIRCUIT TYPE FOR FIELD SERVICE 31 
is more than twice the patient’s requirements and should as a rule be sufficient 
to keep the reservoir bag from collapsing on inspiration even if the mask is not ad- 
justed in absolutely air-tight manner - which it should be* If the bag collapses 
on inspiration there is leakage around the rim of the mask* 
If the bag distends unduly, reduce the rate of oxygen flow to that which just 
keeps the bag normally distended on expiration and not collapsed on inspiration 
In other words there should always be some oxygen-air in the bag* With a cooperative 
patient and no leaks at the mask about UOO cc» per minute of oxygen will accomplish 
this a With a non-cooperative patient and mask leakage the oxygen flow rate may 
have to be more than 1 liter per minute* 
The mask should occasionally be removed from the patient’s face, the perspira- 
tion should be wiped out with a moist cloth and the patient’s face should be dried 
and -when possible dusted with talcum powder* 
The 8” corrugated tubing ”Un provides for less rebreathing and less stimulation 
by CC>2 than does 10" tubing ”5”, 
A container of fresh shell natron lasts from six to eight hours, depending 
on the patient. When symptoms indicate, replenish the supply* 
Shell Natron 
Shell natron absorbs CO2 and moisture in the average case to an extent 
sufficient to maintain the carbon dioxide content within the closed circuit of the 
apparatus normal for six hours (5 hours for large individual) and relative humidity 
below 30% with the oxygen being delivered at the rate of 1 liter per minute* During 
the following hour the COp content may rise to as much as per cent and relative 
humidity to 80 per cent, both within tolerable limits« With some patients these 
latter conditions may not prevail until during the next hour* 
Using 1 liter of oxygen per minute about one-half the total expired air leaves 
the apparatus carrying CO2 and moisture with it* If less oxygen is used the period 
of usefulness of the shell natron is shortened* 
When COp water are absorked heat is generated. Most of this however is 
dissipated by the long respiratory tubings and essentially room temperature and low 
humidity prevail at the mask. 
Shell natron is caustic, will burn the skin and is injurious to fabrics. 
Therefore care must be exercised in its handling* During use the water collected 
in the container dissolves the shell natron, forming a strong alkaline liquid* In 
removing and replacing a container of this chemical DO NOT SPILL* 32 
Determination of Pressure Changes in Masks 
Purpose: The oxygen demand : regulator, the air oxygen demand regulator and 
the constant flow types of oxygen equipment depend upon small degrees of 
pressure differential for their operation. The negative pressure developed 
during inspiration opens the oxygen valve of both the oxygen demand and 
air-oxygen demand types. At low rates of oxygen flow in the constant 
flow type when the bag becomes emptied, air passes into the mask through 
the sponge rubber discs as long as the negative pressure continues. In 
the same way it is important to know how much pressure is produced during 
expiration due to the difficulty with which air passes to the outside. 
Breathing in the presence of either a high or a low pressure in the mask 
for any period of time is extremely tiring*. 
Apparatus: The principle of the Borden tube is utilized in the mechanism 
used here. It consists of a glass tube with very thin walls in the shape 
of a horse shoe. As the pressure changes, the tube tends to straighten 
out. This is recorded by means of a concave mirror which is turned by 
the movement of the tube. The deviations of the mirror are recorded and 
magnified by a beam of light which is reflected back to a scale. (See figure) 
The numbers on the scale are so arranged that if the deviation of the beam 
of light are noted and this figure is divided by two, the result is the 
change in pressure in terms of cm. of water. SENSITIVE PRESSURE RECORDER 
THIN GLASS SPOON BORDEN PRINCIPLE 
MODIFIED BY BALDES 
THIN SPOON SHAPED 
GLASS BULB 
RUBBER TUBE LEADING 
TO PLACE WHERE AIR 
-PRESSURE IS TO BE 
MEASURED 
CONCAVE MIRROR SUPPORTED 
BY WIRE ACTIVATED BY GLASS 
TUBE PROJECTING FROM GLASS 
BULB 
SLIT LAMP 
SMALL TRANSFORMER 
METAL BOX CONTAINING 
GLASS SPOON 
-CENTIMETER SCALE 
GENERAL SET-UP WITH CENTIMETER SCALE 
ARRANGED SO THAT PHOTOGRAPHIC BOX CAN BE SUBSTITUTED CHIN TYPE CONSTANT FLOW MASK 33 
Alveolar Air Samples 
Alveolar air, according to the Haldane School, consists of the specific gas 
mixture in the lungs which has reached an essential equilibrium with the gas tensions 
of the capillary blood in the alveolar walls. In this sense it is not limited to 
the portion of air which fills the alveoli, bu t includes all of the lung air which 
freely participates in the gaseous exchange and it comprises, therefore, a physio- 
logical rather than an anatomical entity. 
It is important to know how closely the tensions of the gases in the alveolar 
air approximate the gas tensions of capillaiy (arterial) blood since alveolar air 
samples may be easily obtained while arterial blood sampling is difficult;, Carbon 
dioxide presents no problem as the tensions of this gas in the alveolar air and 
the arterial blood are nearly identical. During either rest or v/ork the pressure 
gradient does not exceed approximately 1 mm* of mercury. The oxygen pressure 
gradient between the alveolar air and the arterial blood also tends to be maintained 
at a minimal value until the blood is more than 92 per cent saturated. 
Since the blood at high altitudes does not ordinarily reach a saturation of 
92 per cent, the oxygen tension in alveolar air and in the artery are very closely 
approximated. At low altitudes, on the other hand, as the oxygen saturation of 
the arterial blood approaches completion, above 92 to 93 per cent, retardation in 
the chemical and physical processes within the capillaries may prevent a complete 
equalization between the oxygen tensions on the two sides of the capillary wall. 
In addition, technical difficulties in the exact determination of the alveolar Pm 
and the estimation of the arterial Pno from the percentage saturation of the 
globin in the upper part of the saturation curve nay possibly make an apparent 
increase in the gradient. 
With these facts in mind, the arterial gas tension can be closely approximated 
if the alveolar gas tensions are known, so long as the pulmonary epithelium is 
normal in character. This relationship between the gas pressures of the alveolar 
air and the arterial blood greatly facilitates respiratory research as applied to 
the problems of aviation, since arterial punctures are technically difficult to 
perform and are frequently so painful that it is difficult to obtain a sufficient 
number of voluntary subjects. 
In collecting the alveolar air samples not only at ground level but especially 
in high altitude research, the technic used must be capable of uniformity in both 
individual and group sampling. The technic also must be relatively simple and 
foolproof so that a short training of the subjects is all that is required. The 
Haldane-Priestley method of obtaining alveolar air sample is used in this laboratory. 
However, the collecting tube is modified as illustrated, and instead of using the 
tongue to close the proximal end, a special valve has been designed. This valve is 
so constructed that it instantaneously and automatically snaps shut to trap the 
alveolar air sample on removing the pressure of the thumb and while open there is 
a perfectly straight, unobstructed Haldane alveolar air tube which, when making 
a complete rapid expiration, reduces turbulence in the air stream to a minimum. 
Haldane and Priestley usually obtained maximal expirations into the collecting 
tube after (l) a normal inspiration and (2) a normal expiration and both samples 
were analyzed and the mean used. However, under many conditions it is only possible 
to obtain one sample; therefore our averages are based on collections made following 
only a normal inspiration (see illustration). 
Dill, D, B. and Hall, F. G.: Gas exchange in the lungs at high altitudes, 
Journal Aeronautical Sciences, 9*.220, (191*2)• 34 
The following is a more detailed description of the method used in this 
laboratory* The glass sampling sets have been described in the section on the 
’’Haldane Gas Analysis Apparatus,” The large glass cylinders (175 cc*) must be 
used for alveolar air samples at high altitudes while the standard size (U5 cc0) 
is adequate for samples obtained at sea level or low altitudes. Each sampling set 
and each tube in the set is numbered* The lowest numbers should be used first 
and complete records kept* 
Before taking a sample the mercury level in the glass sampling tube must be 
checked. The mercury should completely fill the cylinder and the glass tube exten- 
sion above the stopcock. The short length of small-bore (l to 1,5 mm*) rubber 
tubing attached to the side of the collecting tube is then connected to the glass 
tube extension of the glass sampling cylinder. Just before the alveolar air sample 
is obtained, the mercury reservoir on the sampling set should be lowered, vdth the 
upper stopcock closed. Above 25,000 feet this produces a vacuum within the glass 
cylinder of the sampling set, and facilitates a rapid transfer of the alveolar air 
sample to the glass sampling cylinder. To obtain an instantaneous or so-called 
evacuated sample at ground level, the level of the mercury in the reservoir would 
have to be lowered to nearly 3 feet below the sampling set and the stopcock (if 
present) at the bottom of the sampling tube closed. 
To collect an alveolar air sample, the subject at the top of a normal inspira- 
tion makes a rapid maximal expiration into the mouthpiece of the modified Haldane 
alveolar air collecting tube while holding the perpendicular cylindrical valve 
open with the thumb. As soon as the maximal expiration is completed, the subject 
immediately releases the valve; this action closes the orifice to the mouthpiece. 
The subject’s mouth is removed from the metal mouthpiece only after the valve has 
snapped back into the shut-off position. When the valve is closed, the assistant 
immediately opens the stopcock (vertical position) of the glass sampling cylinder, 
the mercury reservoir having previously been lowered to the base of the sampling 
set. The vacuum produced in the glass sampling cylinder by lowering the mercury 
permits the last part of the alveolar air which was expired into the collecting 
tube to pass into the glass sampling cylinder. The assistant then closes the 
stopcock at the top of the galss cylinder and brings the mercury reservoir to its 
normal position at the top of the sampling set. The alveolar air sample is thus 
safely collected in the glass sampling cylinder and it is maintained at a positive 
pressure by the position of the mercury reservoir so that if leaks occur around 
the stopcock the sample will be lost instead of diluted by room aire After a 
little experience the whole procedure can be carried out in from five to ten seconds-, 
The subject should be required to give consistent alveolar carbon dioxide determina- 
tions before using him for investigation of a problem; as a rule we require here 
a preliminary series of eight consistently normal alveolar carbon dioxide and 
oxygen determinations. 
If any type of mask is used, a carefully arranged routine should be worked 
out so that just before obtaining the alveolar air sample, the straps holding the 
mask in place should be unfastened by the assistant with the subject holding the 
mask in place with his left hand; he should have the alveolar air tube in his 
right hand with the thumb holding the spring valve open. He then at the end of a 
normal inspiration removes his mask with his left hand and instantly puts the 
alveolar air tube in his mouth, gives the quick maximal expiration, closes the 
valve by removing his thumb, lowers the alveolar air tube and with his right hand 
puts his mask on his face and breathes normally; the assistant fastens the mask 
straps. At high altitudes, 35,000 to U2,000 feet, only those thoroughly trained in 35 
the routine both as subject and assistant should carry out this procedure, since 
with trained personnel there is no danger. The need for precision and economy in 
motion in these procedures at high altitudes can be more fully appreciated when it 
is realized that the subject has approximately only 35 seconds of consciousness when 
breathing the ambient air at 35*000 feet and above* 
Normal alveolar air at sea level has the following composition: carbon 
dioxide varies between Iu7 and 6,1 per cent (usually about 5*6 per cent) or from 
3h to U3 mm, Hg pressure; oxygen per cent varies from about 13 to 15 per cent 
(usually liu6 per cent) or from 93 to 107 mm. Hg pressure (usually about 10U ram*). 
However in aviation, values between 80 and 120 mn. can be considered normal* The 
balance is nitrogen and water vapor* In the Haldane analysis the cancelling out of 
the water vapor results in a determination which is based on dry air. 
To calculate the tension or pressure of the gases in the alveolar air from 
the percentage composition, we first determine the barometric pressure which is the 
total pressure exerted by all the gases including water vapor in the alveolar air* 
The barometric pressure will average 760 ram, Hg at sea level* Since alveolar air 
is saturated with water vapor at body temperature, 37° C., the partial pressure of 
the water vapor will always be hi mn,, therefore this value must be subtracted 
from the total pressure. Thus, ?60 - Ul * 713 mm. Hg will be the total pressure of 
the dry gases, carbon dioxide, oxygen and nitrogen and the partial pressure of 
each will be (B - hi) multiplied by the fraction representing the percentage found 
by analysis, thus: 
the C09 pressure is x 713 c hO m, Hg 
c 100 
the 02 pressure is x 713 = 100 rnm. Hg and 
the N2 pressure is x 713 * £73 nun,, Hg (N2 includes the rare inert gases)» DETACHABLE 
METAL MOUTHPIECE 
THE MODIFIED HALDANE ALVEOLAR AIR SAMPLING TUBE 
METAL SLIDE VALVE WHICH WHEN PUSHED DOWN MAKES A 
PERFECTLY STRAIGHT TUBE WITHOUT CONSTRICTION 
OR AIR POCKETS FROM MOUTH TO END OF BIG RUBBER TUBE 
I 
METAL SPRING INSIDE DESCENDING ARM. THIS SPRING ON 
REMOVAL OF THUMB FROM TOP OF METAL SLIDE VALVE FORCES 
VALVE BACK INTO POSITION THUS AUTOMATICALLY TRAPPING 
THE ALVEOLAR AIR SAMPLE 
RUBBER TUBING FOR GLASS SAMPLING TUBS 
18" LENGTH 
1#5 MM BORE 
RUBBER TUBING 
40" LONG AND * 
1" DIAMETER RBSBXvA 
4 /HR 
y ASSUMPTION - RBSP/RATORY <P«->o7:- /.o 
cc/z ABSORPTION WITH SODA LIME 
/VITAL CAPACITY' <40,000 REET 
v.C.COMPLEMENTAL + RESERVE AIR 
COMPLEMENT* L 
AIR / 
SEPT ISAS 
MAJ, HA.ROBINSON, NJC 
RU, ROBINSON, M.D. 
COM PL EM EN ML 
A JR 
ASSUMPTION - RESR QUOTIENT - J.O 
COz ABSORPTION WITH SODA LIME 
vital CAPACITY - c-round LEVEL 
V.C.* COMPLEMENTAL -t- RESERVE AIR 
VITAL CAPACITY 
METHOD OF MEASUREMENT 
I 
RESERVE 
AIR 
MAYO AERO MEDICAL UNIT 
A PPENCHX Fj O. IL 
COMPLEMENTAL 
ATP 
ASSUMPTION - RESP QUOTIENT - J.O 
NO SODA L/MB EOR COz ABSORPTION 
VITAL CAPACITY 
HORIZONTAL BASE L/NB 
RESERVE 
AIR 
XTK~ Z b MAYO AERO MEDICAL UNIT 
INDOCTRINATION PROGRAM 
OUTLINES aND LECTURES FOR BEGINNING AND ADVANCED 
alR CORPS PERSONNEL 
First Edition prepared by 
Captain M. Robert Halbouty 
Medical Corps, U. S# Any 
and 
Captain Joseph A© Resch 
Medical Corps, U» S9 Any 
While assigned to 
MAYO AERO MEDICAL UNIT 
Walter k. Boothby, M* D,, Chairman 
First Edition - January 19U2 
Second Edition - August 19h2 LECTURE OUTLINE FOR INSTRUCTORS 
OF BEGINNING AVIATION CiiDETS 
Concerning 
FLIGHT PROPHYLAXIS 
Equipment: I, Proper charts showing barometric changes with altitude, the anatomy 
of the ear, physiology of a blackout, etc. 2, Blackboard, 3# Various 
types of oxygen equipment, i.e,, masks, tanks, regulators, etc, U, 
Motion pictures. 
Time: Approximately one hour, 
I* Introduction, 
A, Relation of aviation medicine to flying, 
B, Responsibilities of flying officers, 
1, To selves, 
2, To crew, 
3, To passengers, i,e., wounded, 
II. The Atmosphere, 
A, Definition, 
B, Atmospheric pressure, 
1, Definition. 
2. High altitude; thin air; decreased atmospheric pressure, 
C, Composition of atmosphere, 
1, By volume. 
a. Nitrogen 7&%; roughly U/5* 
b. Oxygen 21%; roughly l/5, 
c. Rare gases 1 
2, Partial pressure, 
a. Definition, 
b. Variability with altitude. 
c. Effect on available amount of oxygen, 
D, Flight Surgeon’s division of the atmosphere, 
1, Upper limit of unimpaired performance; 10-11,000 feet, 
a. Individual variability, 
b. "Physiological zone” of the atmosphere, 
2, Critical limit; 20,000 feet, 
III, Effects of Lack of Oxygen, 
A, Organs effected, 
1, Brain and nervous system; very susceptible, 
2, Heart. 
3, Muscles, etc. 
B, Amount and extent of body changes, 
1, Dependent on following factors: (Assuming a healthy man), 
a. Altitude attained, 
b: Duration of lack of oxygen, 
c. Flight frequency, 
C, Individual factors varying reactions to a lack of oxygen, 
1, Natural ability, 
2, Physical activity, 
3, General physical condition. 2 
D, Subjective symptoms, 
1, Unawareness of the progressive effects of decreasing oxygen 
pressure (increased altitude), 
2, Pulse rate increase; compensatory, 
3, Surprisingly little increase in depth or rate of respiration. 
U. Euphoria, 
5, Poor judgement with mental and physical response. 
6, Dizziness, 
7, Unconsciousness. 
8, Accessory symptoms, 
a. Pain in ears, sinuses, etc. 
To be discussed later, 
9, Headache and fatigue on recovery, 
IV, Use of Oxygen During Flight, 
A. Advantages, 
1, Prevention of oxygen lack; prophylactic - even at low altitudes0 
B. Precautions, 
1, Complete equipment check before flight, 
2, Avoid flames, 
3, Avoid oils or grease on any metal oxygen connection, 
C. Equipment, 
1, Oxygon tanks; demonstration, 
2, Regulators; demonstration. 
3® Tubing; demonstration, 
iu masks; demonstration. 
a. Proper fit. 
b. Explanation of mask principle, 
D. When to use in flight (A,R.) 
1* 10-12,000 feet; 6 hours or more, 
2. 12-15,000 feet; 2 hours or more. 
3, 15,000 feet and higher; always, 
U. All night flying, 
5. Lower altitudes if low individual altitude tolerance present. 
E. Misconceptions concerning oxygen, 
1, Effect on teeth and fillings. 
2, Effect on lungs, 
3, Inflamability; (one drop of oil makes high pressure oxygen an 
explosive.) 
V, Relation of Physical Condition to Oxygen Requirements, 
A. Lack of sleep and exercise. 
B. Improper diet, 
C. Drugs and alcohol, 
1® Sedatives. 
2. Headache powders, 
3. Sulfonamids, 
U, Excessive tobacco, 
5, Alcohol, 3 
VI, Barometric Pressure Changes in the Ear# 
A* Ear anatomy; brief, 
B, Ascent, 
1, Effect on tympanic membrane* 
a, Eustachian tube opened, 
b, Eustachian tube closed* 
C« Descent, 
1, Effect on tympanic membrane, 
a, Eustachian tube opened. 
b, Eustachian tube closed, 
D, Symptoms of ’’ear block,” 
1, Fullness in middle ear; ”stuffy,” 
2, Varying degrees of hearing loss, 
3* Head noises, 
U, Pain, 
Vertigo, 
6, Rupture, 
E, Prophylaxis, 
1, Yawning, singing, shouting, 
2, Swallowing; mints or chewing gum, 
VII, Barometric Pressure Changes and the Sinuses, 
A, Brief anatomy, 
B, Ascent, 
1, Sinuses openD 
2, Sinuses obstructed, 
a. Symptoms, 
C, Descent, 
1, Sinuses open, 
2, Sinuses obstructed, 
a. Symptoms0 
D, Treatment, 
1* Benzedrine inhaler, (Caution:) 
2, Correction of cause of obstruction* 
VIII. Barometric Pressure Changes and Intestinal Gases, 
A, Physiology of expansion of gases, 
1, Toy balloon illustration, 
2, Volume increased nearly times at 35>,000 feet, 
B, Symptoms, 
1* Distention, discomfort, cramps, 
2, Dyspnea, cardiac embarrassment, 
C, Treatment. 
1, Abdominal massage with belching and passing of flatus. 
2, Powdered charcoal tablets orally, 
D, Prophylactic diet, 
1, Avoid beans, cabbage, peas, beer, carbonated drinks, 
2, Avoid constipation. li- 
IX* to be avoided* 
Ae Definition. 
Be Symptoms. 
1* Dizziness* 
2* Rapid pulse* 
3* Perspiration* 
U« Claniiness. 
5>* Visual disturbances* 
6. Judgment errors. 
7. muscular spasms. 
8. Unconsciousness* 
C. Causes* 
1. Anxiety. 
2. Fear 
3* Panic. 
D. Treatment. 
1* Holding breath* 
E. Demonstration using six class members. LECTURE FOR BEGINNING AVIATION CADETS 
Material Required: 1* Proper charts showing barometric changes with altitude, the 
ear anatomy, physiology of a blackout, etc* 
2# Blackboard* 
3* Various types of oxygen equipment* 
iu iloving pictures* 
Time Required: Approximately one hour# 
I. Introduction 
A. Relation of aviation medicine to flying* 
Without aviation medicine and flight surgeons aviation would probably not have 
progressed to its present advanced stage# Probably no other occupation requires 
as great a degree of coordination between mind and body as does aviation* In 
addition to carrying on their duties of selecting favorable men for pilots and 
maintaining the health and value of the older pilots, the flight surgeons and 
civilian physicisns have done commendable work in attempting to make the human 
machine as fit as the mechanical machine by continuous experimentation and research# 
The Collier Trophy which, aa you know, is awarded to those individuals or 
organizations who have contributed most to the progress of aviation was given, in 
ipltl, to three physicians* Two of these were civilians and one was an arty 
flight surgeon* 
B, Responsibilities of flying officers* 
Perhaps the greatest reason for this lecture is to make you fully realize some 
of the dangers of flying and to inform you as to the protective measures you 
should use to combat these dangers - in short, flight "prophylaxis.” The pilots 
and crews of combat planes are highly trained individuals# It is your responsi- 
bility to take proper care of all the men who are dependent upon you, not only 
the crew but also in many instances the sick and wounded passengers. You must 
understand the dangers involved in high altitude flying and all the methods used 
for maintenance of the safety and efficiency of the human machine in the air* 
You must understand not only the mechanical phases of flying but also be able 
to thoroughly instruct and supervise your crew and to transport vdth safety 
any casualties, or wounded passengers assigned to you for evacuation* Problems 
that may confront you later may be as follows: How high should I fly with a 
passenger ill with pneumonia? How rapidly may I descend with a passenger 
having severe injuries with shock? What stops must I and ray crew take in order 
to avoid a lack of oxygen at high altitudes? 
II* The Atmosphere# 
A. Definition* 
The atmosphere may be defined as the layer of air surrounding the earth* This 
layer of air is approximately sixty-two miles thick (327,360 feet)# 2 
B, Atmospheric pressure. 
This layer of air (the atmosphere) has mass and weight, and its weight or 
pressure exerted on the earth’s surface at sea level is known as the ’’atmospheric 
pressure” at sea level* The air layers nearest the earth’s surface are pressed 
on by the air layers above so that the air at lower altitudes is more dense and 
under greater pressure than those at higher altitudes. Thus, the higher the 
altitude, the ’’thinner” the air and the lower the barometric pressure. To 
illustrate this, if we have a pile of duck feathers uniformly mixed with chicken 
feathers, the feathers at the bottom of the pile are more compressed than those 
at the top, and a cubic foot of feather mixture from the base of the pile will 
contain more feathers than a cubic foot taken from the top. However, the 
percentage of each kind of feathers will be the same. The barometric (or 
atmospheric) pressure at sea level under standard condition is ?60 ram. Hg - that 
is, it is equal to the pressure a column of mercury 760 ram. high would exert0 
This figure (?60 mm. Hg) may also be expressed as 29*9 inches of mercury. 
C. Composition of atmosphere. 
1. By volume. 
By volume, the atmosphere is composed of ?8 per cent nitrogen, 21 per 
cent oxygen (more accurately 20.93 per cent), a small amount of carbon 
dioxide (CO2 = and traces of rare gases make up the balance of about 
1 per cent. Roughly, therefore, the air is composed of U/5 nitrogen and l/5 
oxygen. 
2. Partial pressure. 
According to Dalton’s law, the partial pressure of a specific gas in 
mixture of gases is the pressure exerted by the specific gas only - that is, 
the pressure that the specific gas would exert if it alone occupied the 
space of the whole gaseous mixture* Since oxygen composes 21 per cent of 
the atmospheric air, then at sea level the partial pressure of oxygen is 
21 per cent of 760, or 159 mm. Hg. Partial pressures are important, 
especially that of oxygen, for it is the partial pressure that forces oxygen 
through the walls lining the air sacs of the lungs into the blood and from 
there it is transported to the tissues. Since the barometric pressure decreases 
with increase in altitude, the partial pressure of oxygen also decreases so 
that at higher altitudes less oxygen is driven into the blood from the lungs. 
D, Flight Surgeon’s division of the atmosphere. 
For beginners in flying it is probably only necessary to divide the 
atmosphere in a rough manner, using the flight surgeon’s division; that is, 
first, the upper limit of unimpaired performance, which is at an altitude 
of 10,000 to 11,000 feet, and, second, the critical limit which is at 18,000 
to 20,000 feet. Ten to eleven thousand feet is set as a limit because most 
individuals can fly at these altitudes for several hours without undue fatigue 
or effect on the body. However, some individuals have less resistance even for 
a small lack of oxygen. They may experience symptoms of lack of oxygen after 
several hours of flying at only 8,000 feet during a period of days. At the 
critical limit of 18,000 to 20,000 feet danger of unconsciousness and death is 
even present without additional oxygen. Any flight for any length of time at 
15,000 feet or more must be made with the help of additional oxygen. Without additional oxygen, an average individual can carry on efficiently 
during the following lengths of time at tha following altitudes: 
35.000 feet - about 35 seconds 
25.000 feet - about £ minutes 
20.000 feet - 10 to 15 minutes 
18.000 feet - U5 to 75 minutes 
15.000 feet - 5 to 6 hours 
10.000 feet - all day, but symptoms of chronic oxygen lack 
will be present if repeated daily. 
A very important figure to remember is 35 seconds at 35,000 feet before the 
subject becomes completely unconscious if making an attempt to get out of an 
airplane; he would last a few seconds longer if he sat quietly and held his 
breath. Breathing air after the oxygen has been out off or stopped washes out 
the enriched mixture so that with exercise and breathing the aviator will last 
only about seven or eight breaths at 35*000 feet and a shorter time if at a 
higher elevation* Should he sit quietly and hold his breath, he would last a 
few seconds longer. 
Ill, Effects of Lack of Oxygen 
Increase of altitude (decrease in atmospheric pressure) will result in the 
following effects on the human body: 
lo altitude sickness due to lack of oxygen (anoxia) 
2. effects due to decreased pressure such as the expansion of gases in the 
abdomen and in the middle ear, and also aero-emphysema and aeroembolism 
3, effect of cold 
U. airsickness, which is due to the motion of the ship and is similar to 
seasickness. 
In considering the effects of lack of oxygen special stress is to be put 
on some of the organs affected. The brain and nervous system are very suscep- 
tible to even small amounts of oxygen lack* The heart, muscles, and other 
parts of the body are also affected. The amount and extent of body changes are 
dependent on the following factors, assuming that we have a healthy man: 
1« Altitude attained, since the higher the altitude, the less is the 
availability of oxygen to the body, 
2» The duration of the lack of oxygen, since the longer the duration the 
more changes there are, 
3, The frequency of flighte Repeated trips on successive days to altitudes 
producing only very slight lack of oxygen will, if frequently repeated, (as 
daily for a month) cause definite symptoms of impaired mental and physical 
functions « 
There are several individual factors which affect responses to a lack of 
oxygen. These are natural ability, physical activity and general physical 
condition. Some individuals have a natural ability to show little change to 
moderate amounts of oxygen lack - that is, they have a high resistance to lack 
of oxygen; their symptom threshold is high. This was important in the previous war when ability to go to 20,000 feet made you superior in fighting an enemy 
that could only go to 18,000 feet. Today this difference is because 
with proper equipment you can go to 33*000 feet and be normal'had can reach 
Ij.2,000 feet as safely as you could formerly reach 20,000 feet, as far as oxygen 
is concerned. Increased physical activity stimulates body metabolism and oxida- 
tion so that more oxygen is needed by the body, and if the additional supply of 
oxygen is not received, then symptoms of oxygen lack set in earlier and are more 
severe than if . the body were at rest. An individual in good general 
physical condition almost invariably reacts less to the same amount of oxygen 
lack than does one in poor physical condition, assuming everything else to be 
equal. 
There is surprisingly little awareness of the progressive effects of 
decreasing oxygen pressure. There is usually a compensatory increase in the 
pulse rate, but only a little increase in depth or rate of respiration. 
Euphoria (a false sense of well-being) and poor judgment with poor mental and 
physical response are usually followed by dizziness and unconsciousness with 
possible disastrous results. Should consciousness be regained, headache and 
marked fatigue will be noted. Accessory symptoms, as earache, will be discussed 
later. 
IV, Use of Oxygen During Flight, 
A. Advantageso 
The one big advantage in using additional oxygen during flight is that 
by so doing one prevents an oxygen lack, a simple, but important fact. Benefits 
of oxygen administration may be summed up in the one word - "prophylactic.11 It 
is prophylactic against symptoms of oxygen lack even at low altitudes. 
B. Precautions. 
Before attempting to use oxygen we should become familiar with a few of the 
precautions we should use. First, and perhaps of most importance, is a 
habitual complete check of oxygen equipment before each flight. Either you or 
someone you are certain is a responsible individual should make the check. 
Avoid flames 1 Oxygen makes things more inflammable. Last, but not least, avoid 
using oils or grease on any metal oxygen connections. Oils and high pressure 
oxygen can result in an explosionl Warn your mechanics. 
C. Equipment. 
Here you see some of the various oxygen tanks used by the Array, (Short 
discussion of the characteristics of the various tanks, i.e., low pressure, 
high pressure, etc. and discuss tank poundage and refilling and necessity for 
using dry oxygen.) 
Here, gentlemen, we have some of the various types of oxygen regulators 
in use. These (deomonstrate) are the hand controlled type and should be set at 
about the altitude at which one is flying if sitting quietly and 5*000 feet 
higher if exercising. Some How meters are correctly marked on one side for 
"resting" flow and on the other side for use if the aviator is "active"; that 
is, using his muscles by working. These (demonstrate) are the demand types 5 
which supply oxygen according to the demands of the body* They are automatic and 
will supply more oxygen at higher altitudes or while the individual is active 
instead of resting* There are two types of demand regulators* One type mixes the 
necessary amounts of air and oxygen, and is best suited to altitudes under 30*000 
feet, The other type supplies only oxygen with no added air and therefore is 
wasteful of oxygen at altitudes below 30,000 feet* These vail how be passed around 
for your inspection* Please handle them with care* 
The tubing before you is used in connecting the oxygen apparatus. (Short talk 
and demonstrationo) 
One of the most important parts of our oxygen equipment is the oxygen mask, based 
on two different principles, (l) the constant flow principle with reservoir 
rebreathing bag and (2) the demand principle* Recently these two principles have 
been combined so as to obtain the advantages of both vdthout the disadvantages of 
either* (The various types will be demonstrated by the lecturer and much emphasis 
placed on the aviator’s understanding his equipment and the necessity of taking 
proper care of itc) 
Army regulations regarding use of oxygen in flight are as follows; When 
lc An altitude of 10,000 to 12,000 feet is contemplated for six hours or more, 
2* An altitude of 12,000 to 15,000 feet is contemplated for two hours or more* 
3„ An altitude of 15,000 feet or higher is contemplated for any length of time0 
In addition, all night flying is to be done with oxygen, since even small amounts 
of oxygen lack may interfere with night vision* Any individual with low altitude 
tolerance should not hesitate to use oxygen at lower altitudes than those specified 
above• 
Before leaving oxygen I wish to correct some misconceptions concerning oxygen© 
Oxygen as used today has absolutely no deleterious effect on the teeth or fillings 
and none on the lungs even if used repeatedly for hours. As a matter of fact, 
oxygen is used in the treatment of pneumonia, heart disease, and many other medical 
conditions* And let's not forget that oxygen is inflammable, and that high pressure 
oxygen, in contact with oils or grease will explode* There is no such thing as 
"medical oxygen,” For hospital use the outside of the tanks are more often repainted 
and the valves more frequently changed. In aviation, however, for high altitude 
flying or in planes relatively unheated, dry oxygen must be used, otherwise the water 
the oxygen contains may freeze on the needle point of the reducing valve. If this 
freezes the aviator will be suddenly deprived of his oxygen supply© 
Vc Relation of Physical Condition to Oxygen Requirements. 
There is a definite relation between one’s physical condition and the harmful 
effects of oxygen lack; his "ceiling” is lowered© Lack of sleep makes us more 
susceptible to the effects of oxygen lack, especially if continued over a period of 
weeks or monthso Your grammar school teacher’s advice about getting eight or ten 
hours of sleep nightly still holds good. As stated already, one’s general physical 
condition is one of the factors determining reaction to a lack of oxygen* The worse the physical condition, the worse the reaction* A balance between sufficient 
sleep and proper exercise will tend to prevent fatigue. Fatigue is associated 
with inefficiency, weakness, weariness, and lack of perseverance. Fatigue is 
aggravated by anoxia. 
Improper diet is also detrimental. Try to eat a well-balanced diet always. 
Don't overstuff yourselves at mealtime, and don’t attempt to lose weight by 
dieting without first consulting your flight surgeon. Digestive disturbances, 
irritability, constipation, early fatigue, inefficiency, etc. may result from 
improper diet. The diet supplied you while you are cadets is well balanced. 
Drugs are often taken indiscriminately by flying personnel - a dangerous 
practice. Always consult your flight surgeon before taking any kind of drug: 
sedatives such as seconal, phenobarbital, amytal, nembutal, etc. may result in 
tragedy, especially if one attempts to fly while still under the prolonged effects 
of these drugs. The nervous system and entire body are affected by sedatives. 
Under no conditions should flying personnel take "on their oWn" any of the 
sulfonaraid group of drugs. Among these drugs which are used by physicians to 
combat infections of various t:/pes are sulfapyridine, sulfanilamide, and sulfa- 
thiazole. Their effects on the blood, heart, nervous system, etc., are so 
pronounced that they are extremely dangerous for self-administration. The effects 
are so dangerous, that Army regulations permit Army physicians to prescribe these 
drugs only to hospitalized cases - those that can be observed at least daily and 
who can have blood counts daily if needed. 
Even headache powders such as Bromo- Seltzer, "B-C", and other patented 
preparations may cause a severe agranulocytosis in the blood which seriously 
affects your susceptibility to anoxia, to say the least. In short, consult your 
flight surgeon before taking any drugI 
Alcohol has often been used to pickle and preserve dead things, and many now 
"preserved things" were pickled just before deadl Avoid alcohol if you expect 
to get near any kind of machine - especially an airplane. With a little sub- 
stitution the highway signs may well be used in flying: "If you fly, don't 
drink," Even reporting to the flying line with a slight trace of alcohol on the 
breath is a serious offense. We are all familiar with the dangers of alcohol, 
and it will perhaps suffice if you are reminded of the marked impairment in 
judgment resulting from alcohol. If you've imbibed a little too much the night 
before, report to your flight surgeon, and he will in peace time relieve you from 
flying that day* Think a hundred times before endangering your life, and the lives 
of others and expensive government property. 
VIv Barometric Pressure Changes and the Ear. 
As mentioned previously, ascent to high altitudes (decreasing barometric 
pressure) affects the ears, sinuses and intestines. We shall first consider the 
ear. If you will notice the chart of the ear’s anatomy, you will see the external 
auditory canal, the ear drum or tympanic membrane, and the eustachian tube. 
(Instructor uses pointer on anatomical chart.) The external auditory canal is what 
the physician peeks into with an otoscope to get a good view of the ear drum 
(tympanic membrane)c The tympanic membrane may bo compared to a sheet of thin 
rubber in its ability to "pooch out" (bulge) and "pooch in" (retract), especially if that sheet of rubber is thought of as covering one end of a tube. By blowing 
into the open end of the tube, the rubber sheet will bulge outward, and if we 
suck in on the open end, we create a.negative pressure and cause the rubber 
sheet to retract; and the rubber sheet will burst. Similarly, the tympanic 
membrane will bulge out if the atmospheric pressure in the middle ear is greater 
than that in the external auditory canal and outside atmosphere; and if the pres- 
sure in the middle ear is less than that in the atmosphere, then there is a 
retraction of the tympanic membrane. 
The principal action of the eustachian tube is to drain and ventilate or 
equilibrate the middle ear. We are primarily interested in its equilibrating 
or ventilating action. The eustachian tube is opened by its dilator muscles 
in the nasopharynx; opening, it equalizes any pressure differential existing 
between the middle ear and the atmosphere. The dilator muscles act to open 
the eustachian tube during swallowing, yawning and the other physiologic acts. 
If we begin at sea level and ascend without ventilating the middle ear by 
opening the eustachian tube, there is pain with a bulging outwards of the ear 
drum with the degree of bulging dependent on the altitude attained. As we 
ascend, the pressure in the non-ventilated middle ear remains the same as it 
was at sea level, while the atmospheric pressure decreaseso Hence the greater 
pressure in the middle ear pushes the tympanic membrane outward toward the lesser 
pressure of the atmosphere• If sufficient altitude is reached, the bulging may 
be great enough to burst the tympanic membrane. Similarly, if we assume the 
middle ear and atmospheric pressure have been equalized at high altitude and then 
begin to descend without ventilating the middle ear, we have a reversal of the 
process, i.e., the tympanic membrane is pushed inward. The pain and other symp- 
toms are more prominent on descent than on ascent. If there is no middle ear 
ventilation during descent, then its pressure remains stationary with develop- 
ment of a relative negative pressure, while the atmospheric pressure progressively 
becomes greater and forces the tympanic membrane in toward the middle ear result- 
ing in a retracted ear drum. 
In this instance, there is a negative pressure within the middle ear while 
that of the atmosphere is a positive pressure. A negative pressure of 80 to 
90 mm. of mercury or more makes it impossible for the eustachian muscles to 
overcome this negative pressure which holds the eustachian tube tightly collapsed. 
It then becomes necessary to decrease the middle ear pressure to about 70 mm. 
of mercury of negative pressure or less before the eustachian tube can again 
be voluntarily opened. This necessitates ascending again to an altitude where 
the middle ear and atmospheric pressure are more nearly equalized. "Aero- 
otitis media" or "aviation ear" is a term employed in referring to the results 
due to the lack of ventilation of the middle ear during changes of atmospheric 
pressure resulting in injury to the tympanic membrane. The two principal causes 
of improper middle ear ventilation are: first, a failure to open the eustachian 
tube voluntarily when necessary; second, inability to open it which is much 
more prevalent than is generally recognized. Frequent causes of inability to 
open the eustachian tube are: ignorance of the physiologic mechanisms, obstruc- 
tions of the nose, sinusitis, tonsillitis, tumors or growths of the nose, 
mouth, etc. On the other hand, experience and training greatly increase one!s 
ability to open the eustachian tube. Every flight surgeon has had innumerable 
experiences with the cadet who thought he should certainly not be grounded 
because he had a sore throat. The flight surgeon realizes only too well the 
dangers of a sore throat* The inflammation of the throat often involves the 
opening of the eustachian tube and causes a partial or complete closure of the tube so that proper ventilation of the middle ear is not possible and woe 
betides the flier who flies with a sore throat and then after landing "blows 
his ears out" by closing the nose and mouth# Usually this forces germs from 
the infected throat into the eustachian tube and middle ear leading to serious 
complications # 
Let us briefly consider the symptoms of aero-otitis media which may be 
brought on by ascent or descent with improper ventilation of the ears# One 
of the earliest symptoms is a feeling of fullness in the middle ear* In chronic 
cases due to repeated mild injury to the ears, there is a "full and stuffy" 
feeling in the ears and difficulty in "clearing" them# Varying degrees of 
loss of hearing may occur and be accompanied by head noises# In more severe 
cases the noises may be hissing, roaring, or crackling in character# Actual 
pain and dizziness may occur and become unbearable, with rupture of an ear drum. 
The subject feels "as though hit along the side of the head with a plank" and 
there is a sharp piercing pain on the affected side with marked dizziness and 
nausea# Collapse or shock may follow# 
Again, the simplest maneuver to open the eustachian tube is to swallow# 
Yawning, singing, shouting, etc., may also accomplish it# The sucking of candied 
mints while flying causes frequent swallowing and is probably better than 
chewing gum, as the latter soon loses its flavor# The average person swallows 
involuntarily about once very 60-?£ seconds so that rates of climb of 5>00 feet 
per minute or more result in progressively greater degrees of discomfort if no 
effort is made to ventilate the middle ear# Sleeping and unconscious individuals 
present a serious problem* Coramerical air lines have an allowable rate of ascent 
and descent of 200 to 300 feet per minute# However, military flying requires 
more rapid rates of ascent and descent with, of course, greater care regarding 
the ears# 
VII, Barometric Pressure Changes and the Sinuses, 
The nasal accessory sinuses are also affected by barometric changes# These 
are located in the hollowed out spaces of the face bones# Two of these sinuses 
are located here (demonstrate) in the cheek bone, two are located here in the 
forehead, and two of them arc located in the bones just back of the root of the 
nose# Ordinarily air passes in and out of those sinuses through small openings 
in the nose# During ascent and descent to and from high altitudes, the air in 
these sinuses changes pressure with the atmospheric pressure, as does the air 
in the middle cars, and similarly, should there be an obstruction to the sinuses, 
the air cannot escape readily and ill effects are produced. For instance, in 
ascent the expanded air in the sinuses cannot escape, and by building up 
pressure within the sinuses it causes pain. The reverse of this is true during 
descent when a vacuum is created in the sinuses and air from the atmosphere 
pannot enter the sinuses. Pain is produced,.here also and nay be accompanied by 
headache, eyeache, dizziness, and nausea. Pilots with sinus infection, obstructed 
sinus opening, or head colds, should not fly until the condition has been corrected 
To do so may aggravate the condition and perhaps cause serious complications^ 
A benzedrine inhaler sniffed just before flying may help at times but warning 
is given that the inhaler should be used not more often than once every hour 
and should only be used after consulting your flight surgeon# 9 
VIII, Barometric Pressure Changes and Intestinal Gases. 
Expansion of abdominal gases may cause marked discomfort in high altitude 
flying. Gases expand with decrease in atmospheric pressure. For example, a 
toy balloon v/hen taken from sea level to 35,000 feet will increase its volume 
more than five times. Similarly, the intestinal gases will do likewise, often 
leading to narked abdominal distension and discomfort. When abdominal cramps 
are marked, difficulty in breathing and interference with the heart's action 
may result. Anyone contemplating a high altitude flight should avoid gas forming 
foods and drinks such as beans, cabbage, peas, beer and carbonated drinks a Avoid 
constipation. Once distension and discomfort are experienced, relief may be 
obtained by either descending to lower altitudes or by massaging the abdomen with 
the hand followed by belching and the passage of flatus. 
XX. Hyperventilation. 
There is one more important thing to consider, and that is hyperventilation, 
"Hyper" meaning very much or too much, and "ventilation," meaning just that. In 
hyperventilation there is more breathing, or ventilation, than is necessary for 
the requirements of the body at that time. The symptoms of hyperventilation 
may be serious, and are; dizziness, a rapid pulse, marked perspiration, claminess 
of the skin, visual disturbances, errors in judgment, muscular spasms and uncon- 
sciousness. Hyperventilation usually occurs insidiously, coming on without the 
victim being aware of it unless he is familiar with the signs and symptoms. 
Anxiety as during combat, fear, panic or hysteria often cause hyperventilation, 
thus adding to the seriousness of the situation. The treatment, fortunately, is 
quite simple, just hold the breath for about one minute in order to build up the 
carbon dioxide content of the blood which was diminished by hyperventilating. 
We shall now have six members of the class hyperventilate under my direction for 
2-| minutes and at the conclusion I shall have them describe to the class the 
symptoms they have experienced. SUGGESTIVE OUTLINE FOR LOW PRESSURE CHAMBER 
"RUN" FOR BEGINNING AVIaTION CADETS, 
Operating personnels Two trained medical officers, one trained chamber operator, one 
trained mechanic. 
Time required; Approximately one hour. 
1. Inquire as to whether any students have colds, ear or sinus symptoms. Leave these 
students out of chamber ascent. 
2, Explain that high altitudes will be simulated by exhaustion of air pressure in 
chamber. 
3* Demonstrate oxygen supply system. 
U. Explain that tests for mental and physical changes will be made in the chamber. 
5. Close chamber door after all students are seated. Take slightly filled toy balloon 
along to demonstrate expansion of gases. 
6. Medical officer and alternate one-half of students put on oxygen masks. Medical 
officer has microphone connected to public speaker system and also to operator 
outside of chamber by earphones. 
7. Ascent made to feet. Altitude announced. Notify students that a descent 1500 
feet in one minute is to be made and students are to swallow and care for ears 
and sinuses. 
8. Descend to 3000 feet. Then descend to ground level and remove from chamber those 
students with marked ear or sinus symptoms, and send them to E.N.T. department for 
examination. 
9. Ascend to 5000 feet. Give written test. Be certain that alternate students only 
are using oxygen with mask. 
10. Ascend to 18,000 feet at a rate of U,000 to 5,000 feet per minute. Carefully note 
reactions of students while ascending for fear, uneasiness, calmness, hyperventila- 
tion, etc. Give proper assurance and instruction. 
11. At 18,000 feet give written test to students, after ten minutes. 
12. Have students not taking oxygen compare with the students next to them who are 
using oxygon the color of their fingernails, earlobes, and skin. Have students 
write down any sensations noted, especially as to clearness of vision, clearness 
of mind, rapid pulse rate, respiratory changes, irritability, etc. 
13. Have all students put on masks with oxygen. Check each mask and oxygen supply. 
After 5 minutes have students again write down sensations. Call their attention 
to changes now noted with the use of oxygen in those who were not using oxygen 
previously. 
lU. Announce ascent to 30,000 feet to be made. Assure students of safety. Answer 
questions. Ask students to record sensations while ascending, and to note lessened 
effect on ears and sinuses than when ascending from ground to 12,000 feet. Have 
them note balloon expansion. 
15. Signal ascent to 30,000 feet. 
16. Remain at 30,000 feet 10 to 15 minutes. Have students record sensations. Give 
written test* Comment on comfort as compared with 18,000 feet. Comment on 
intestinal gas expansion. Exhibit balloon, 
17. If any student has marked symptoms from intestinal gases, descend to 25,000 feet for 
3 to 5 minutes, then return to 30,000 feet. Review symptoms of anoxia, 
18. Announce descent to be made at 3000 feet per minute to 10,000 feet, then at 2000 feet 
to ground level. Warn about ears and sinusesc Level off if marked complaints given. 
19. Signal descent. 
20. Remove oxyren masks at 10,000 feet altitude, 
21. Answer student questions. 
22. Record findings and impression of each student. LECTURE AND DEMONSTRATION OUTLINE FOR 
INSTRUCTORS OF AIR FORCE AND MEDICAL OFFICERS 
Concerning 
FLIGHT PROPHYLAXIS 
Equipment: 1* Proper charts showing barometric changes with altitude, the anatomy of 
the ear, physiology of a blackout, etc® 
2. Various types of oxygen equipment, i,e., masks, tanks, etc* 
3. Blackboard, 
U. Motion pictures0 
Time: Approximately two hours. 
I, Introduction. 
Ac Relation of aviation medicine to flying* 
B. Responsibilities of flying officers. 
1* To selves* 
2* To crew. 
a. Informed constantly concerning 
(1) Course, 
(2) Altitude. 
(3) Maneuvers, etc. 
b. Trained to care properly for selves. 
3* To passengers, i.e., wounded. 
II. The Atmosphere* 
A. Definition. 
B* Atmospheric pressure. 
1. Definition. 
. 2. High altitude; thin air; decreased atmospheric pressure. 
3. Molecular action. 
h. Torricelli’s experiment. 
Measuring of atmospheric pressure. 
C. Composition of atmosphere* 
1* Volume. 
a. Nitrogen - 78$; roughly U/5. 
b. Oxygen - 21$; roughly l/£. 
c. Rare gases - 1$. 
2. Partial pressure, 
a* Definition* 
be Variability with altitude, 
c. Effect on available amount of oxygen. 
(1) Supply to lungs, 
(2) Supply to blood and tissues* 
d* Relation to manifold pressure. 
D. Vertical section of the atmosphere. 
1* Division by layers, 
a. Troposphere, 
(1) Definition. 
(2) Characteristics. 
(a) Contains 3/U of atmosphere by weight, 
(b) Contains hydrometeors. 
1. Clouds. 
2, Rain, 
3® Snow, 2 
b, Stratosphere* 
(1) Definition. 
(2) Characteristics. 
(a) Relatively constant temperature, 55° C, 
(b) Hydrometeors absent, 
c* Tropopause. 
(l) Definition* 
d* The term ”substratosphere” is a convenient term to indicate flights 
between 35,000 and U2,000 feet* 
2o Flight surgeon’s division* 
aG Upper limit of unimpaired performance; 10-11,000 feet* 
(1) Individual variability* 
(2) "Physiological zone of the atmosphere.” 
b* Critical limit; 20,000 feet. 
(l) Unconsciousness and death; 23,000 to 28,000 feet. 
III. Tactical Considerations in Altitudes. 
A, World War IT 
lo Combat altitude often 15,000 to 18,000 feet. 
B, World War II. 
1* Combat altitude often 20,000 to 30,000 feet; becoming 30,000 to U0.000 
feet* 
C* Advantages of high altitudes. 
1* Interception less probable for bombers, 
2* Greater operating freedom. 
3. Detection probability less. 
U. Progressively less danger from anti-aircraft. 
D. Mechanical problems. 
1„ Supercharging; crank case; magnetos; ignition systems, etc, 
2. Intorcooling* 
3. Lubrication, 
U. Pressure cabins and suits. 
5* Heating. 
IV, Effects of Lack of Oxygen* 
A. Organs affected, 
1. Brain and nervous system - very susceptible, 
2. Heart* 
3* Muscles. 
U« Rest of body* 
B. Amount and extent of body changes, 
1, Dependent on following factors: (assuming a healthy man). 
a. Altitude attained. 
b. Duration of exposure to lack of oxygen. 
c. Frequency of flight. 
2. Individual factors varying reactions to lack of oxygen, 
aa Natural ability. 
bo Physical activity, 
c. General physical condition. 
C. Subjective symptoms. 
1, 10,000 - 12,000 feet up 
a. Unawareness of the progressive effects of decreasing oxygen pressure 
(increased altitude). 
b. Pulse rate increase; compensatory* 
c. Surprisingly little increase in depth or rate of respiration. d. Euphoria, 
e* Poor judgment with poor mental and physical response. 
f. Dizziness. 
g. Unconsciousness. 
h. Headache and fatigue on recovery, 
i. Accessory symptoms, i.e., ear pain, sinus pain, etc. discussed later. 
V. Use of Oxygen During Flight. 
A. Advantages. 
1. Prevention of symptoms of oxygen lack - prophylactic, 
B. Precautions, 
1© Complete equipment check before flight* 
2. Avoid flames, 
3. Avoid oils or grease on any metal oxygen connections. 
U. Seal tank threads with lead oxide and glycerine« 
5. Must be 99% pure. 
60 Store cylinders in cool, dry place. 
C. Equipment. 
1. Oxygen tanks. 
a• High pressure. 
(1) Advantages. 
(2) Disadvantages. 
b0 Low pressure. 
(1) Advantages. 
(2) Disadvantages, 
2. Regulators. 
a. Manual type, 
b. Demand type. 
3. Tubing connections. 
It. Masks, 
a. lypes. 
b. Precautions. 
(1) Fit. 
(2) Understanding principle of mask. 
5, When to use masks in flight, 
ac 10-12,000 feet; 6 hours or more contemplated, 
b« 12-15,000 feet; 2 hours or more contemplated. 
c. 15,000 feet or more always. 
d* At lower altitudes if individual low altitude tolerance present. 
Do Emergency parachute jumps from high altitudes, use of oxygen, 
1. 35,000 feet. 
au In region where human life non-existent without 
b* At least 8-15 minutes from safety in open parachute, 
c. Unconsciousness in 35 seconds. 
do Danger of delayed open 'chute jump with no oxygen. 
e. Danger of delayed jump with no oxygen. 
f<» Emergency midget tank. 
(1) 10-15 minute supply. 
(2) Carried in pants leg (reinforced). 
(3) Tubing under clothes. 
(It) Special mask; mouth bite. 
(5) Adjust before attempting to leave seat; first maneuver. 4 
E. Misconceptions concerning oxygen, 
1. Effect on teeth and fillings, 
2. Effect on lungs, 
3. Inflammability, One drop of Oil makes high pressure oxygen explosive. 
VI. Relation of Physical Condition to Oxygen Requirements. 
A, Lack of sleep and exercise, 
B, Improper diet. 
C, Drugs and alcohol, 
I® Sedatives, 
2, Headache powders, 
3, Sulphonamids. 
U. Excessive tobacco. 
5. Alcohol. 
VII, Aero-emphysema or Aeroembolism, 
A. Definition. 
B0 Mechanism of: 
1, Atmospheric pressure change. 
2, Role of nitrogen. 
3, HSoda pop:i illustrations, 
U, Physiological changes - similarity to diver’s bends. 
C, Symptoms. 
1* Factors in production, 
a. Rate of ascent, 
b. Altitude attained, 
c. Time remaining at altitude. 
d. Individual susceptibility, 
2, Symptoms experienced (subjective), 
a. Eyelid scratching and smarting, 
bo Skin crawling, 
c. Joint and extremity pain, 
d. Dizziness. 
ee Deafness, 
fo Paralysis, 
3, Prophylactic measures: preliminary decompression (denitrogenization; 
with special equipment. 
ac 100$ Op; 2j - 3 n.p.h. exercise rate, 
b„ Treadmill, bicycle, standing walk, etc* 
VUI, Effects of Heat and Cold. 
Au fcffect of cold on body - mechanism for maintaining body temperature. 
1, Normal body temperature, 
2. Metabolic rate. 
a0 Definition* 
bo Factors affecting metabolic rate. 
B. Atmosphere. 
C, Effects of freezing on the body, 
1. Often no subjective symptoms. 
2. Early stages, 
3. Later stages, 
D, Protection against cold. 
1, Cold cream, vaseline, bland ointments on exposed parts, 
2, Clothing. 
a. Not too bulky. b. Two thin garments better than one thick garment* 
c. Not too tightj snug at wrists, collar, ankles* 
d* Electrically heated* 
(l) Disadvantages. 
(a) Heat source may fail* 
(b) Not practical if ship abandoned. 
(c) Requires much electrical energy. 
3* Heated cabins* 
an Heat collection around exhaust to cabin. 
(l) Carbon monoxide leakage, 
b. Steam circulation. 
(l) Satisfactory. 
IX* Effects of Speed and Centrifugal Force. 
A, Speed. 
1. Straight-away flying. 
a. Only danger in exposing parts of body to terrific air pressure* 
B, Centrifugal force and speed. 
1* In banks and turns. 
a. Blackout, 
(1) Definition. 
(2) Physiology. 
(a) Direction of blood flow. 
(b) Effect on visual fields. 
(c) Maximum blackout point. 
l/ Role of "pull out" angle in 
2/ Role of speed in 
(d) Importance in combat. 
l/ Temporary loss of plane control. 
2/ Enemy in darkened area of visual field. 
3/ Probable effect of repeated blackouts. 
(e) Prophylaxis. 
1/ Abdominal belt. 
2/ Crouch position. 
3/ Prone position. 
h/ Tightening of collar. 
5/ Shouting. 
(f) Blood pressure in black out <> 
1/ Susceptibility of hypertensive and hypotensive individuals 
b. Redoutsc 
(1) Definition. 
(2) Physiology of: 
(a) Direction of blood flow. 
(b) Effect on visual field. 
(c) Maximum redout point* 
1. Radius of circle. 
2. Speed. 
(d) Effect of repeated redouts, 
1. Minute hemorrhages. 
2. Apoplexy, 
(3) Blood pressure in: 
(a) Susceptibility of hypertensive and hypotensive individuals. X* Barometric Pressure Changes and the Ear. 
A* Ear anatomy. 
1, Tympanic membrane (ear drum) _ 
2. Eustachian tube ) Emphasized. 
B. Ascento 
1» Effect on tympanic membrane• 
a# Eustachian os opened; mechanism# 
b# Eustachian os closed; mechanism and symptoms# 
C, Descent- 
1# Effect on tympanic membrane. 
a. Eustachian os opened; mechanism# 
bo Eustachian os closed; mechanism and symptoms. 
(1) Negative pressure over 80 ram. Hg. 
(2) Very high negative pressure; rupture. 
D# Aero-otitis media (’’ear block’1, "aviation ear"). 
lo Definition# 
2. Causes of improper middle ear ventilation# 
a# Failure to open eustachian tube# 
(1) Ignorance# ) 
(2) Carelessness) Inexperience. 
b# Anatomical causes# 
(1) Upper respiratory infections# 
(2) Nasal obstructions. 
(3) Sinusitis. 
(U) Tonsillitis. 
(5) Nose and mouth tumors, 
c© Inability to open eustachian tube. 
(1) Sedatives. 
(2) Anesthetics. 
(3) Unconsciousness. 
(U) Shock. 
3. Symptoms. 
a. Fullness in middle ear; "stuffy". 
b. Varying degrees of hearing less# 
c. Head noises; hissing, roaring, etc# 
d. Pain# 
e. Vertigo. 
f# Rupture; collapse; or shock, 
h. Prophylaxis. 
a. Education, 
b. Correction of anatomical deformities, etc. 
5# Swallowing. 
a> Average rate - once per 60-75 seconds# 
b* 500 feet or more ascent per minute may cause discomfort. 
c5 Commercial rates 200-300 feet per minute# 
d. Rapid descent and ascent in military work. 
6. Other dangers, 
a# Sore throat; "blowing ears out"; middle ear infection# 
XI. Barometric Pressure Changes and the Sinuses. 
A, Brief Anatomy# 
B. Ascent. 
1# Sinuses open0 
2# Sinuses obstructed# 
a# Symptomso 7 
C, Descent, 
1, Sinuses open, 
2, Sinuses obstructed, 
a. Symptoms, 
D, Treatment, 
1, Benzedrine inhaler (cautiocf), 
2, Correction of cause of obstruction, 
XII, Barometric Pressure Changes and Intestinal Gases, 
A, Physiology of expansion of gases, 
1, Toy balloon illustration, 
2. Volume increased h times at 35,000 feet, 
B, Symptoms, 
1. Distention, discomfort, cramps, 
2, Dyspnea, cardiac embarrassment, 
C, Treatment, 
1, Abdominal massage with belching and passing of flatus. 
2, Powdered charcoal tablets orally, 
D, Prophylactic diet. 
1, Avoid beans, cabbage, peas, beer and carbonated drinks. 
2, Avoid constipation, 
XIII, Hyperventilation. 
A, Definition, 
B, Physiology, 
1, Decreased blood C02# 
2, Alkalemia, 
C, Symptoms, 
If Vertigo, 
2* Rapid pulse, 
3, Perspiration, 
U, Coldness; clamminess, 
5, Visual disturbance. 
6, Judgment errors, 
7, Carpo-pedal spasm, 
D, When found. 
1, Anxiety, i.e,, combat. 
2, Fear, 
3, Panic, 
£, Treatment, 
1, Holding breath about one minute 
F, Demonstratione LECTURE FOR AIR FORCE aND MEDICAL OFFICERS 
Material Required: 1* Proper charts showing barometric changes with altitude, the 
anatony of the ear, physiology of a blackout, etc* 
2* Blackboard. 
3. Various types of oxygen equipment* 
h• Moving pictures* 
Time Required: Approximately two hours* 
I. Introduction. 
A. Relation of aviation medicine to flying* 
Without aviation medicine and flight surgeons aviation would probably not have 
progressed to its present advanced stage. Probably no other occupation requires 
as great a degree of coordination between mind and body as does aviation. In 
addition to carrying on their duties of selecting favorable men for pilots and 
maintaining the health and value of the older pilots, the flight surgeons and civ- 
ilian physicians have done commendable work in attempting to make the human machine 
as fit as the mechanical machine by continuous experimentation and research. 
The Oollier Trophy which, as you know, is awarded to those individuals or 
organizations who have contributed most to the progress of aviation, was given in 
19l|0 to three physicians. Two of these were civilians and one was an Army flight 
surgeon. 
B. Responsibilities of flying officers. 
Perhaps the greatest reason for this lecture is to make you fully realize some 
of the dangers of flying and to inform you as to the protective measures you should 
use to combat these dangers - in short, flight '’prophylaxis The pilot and crew 
of combat planes are highly trained individuals. It is your responsibility to take 
proper care of all the men who are dependent upon you, not only the crew but also 
in many instances the sick and wounded passengers. You must understand the dac;;err 
involved in high altitude flying and all the methods used for the safety and 
efficiency of the human machine in the air. You must understand not only the 
mechanical phases of flying, but also be able to thoroughly instruct and supervise 
your crew and to transport with safety any casualties or wounded passengers assigned 
to you for evacuation. Problems that may confront you later may be as follows: 
How high should I fly with a passenger ill with pneumonia? How rapidly may I 
descend with a passenger having severe injuries with shock? What steps must I 
and my rew take in order to avoid a lack of oxygen at high altitudes? 
The pilot should at all times, if possible, keep his crew members informed of 
any anticipated changes in altitude, course, or maneuvers so that the crew 
members may properly care for themselves during these changes. The pilot should 
assure himself that the crew members are familiar with the procedure necessary to 
take care of themselves in preventing ear and sinus symptoms, blackouts, aero- 
embolism, etc. If necessary, he should instruct them concerning these necessary 
procedures. 2 
II* The Atmosphere. 
A. Definition# 
The atmosphere may be defined as the layer of air surrounding the earth. 
This layer of air is approximately sixty-two miles thick (327,360 feet). 
B, Atmospheric Pressure. 
This layer of air (the atmosphere) has mass and weight, and its weight or 
pressure exerted on the earth’s surface at sea level is known as the ’’atmospheric 
pressure” at sea level. The air layers nearest the earth's surface are pressed 
on by the air layers above so that the air at lower altitudes is more dense 
and under greater pressure than those at higher altitudes. Thus, the higher- 
the altitude, the ’’thinner” the air and the lower the barometric pressure. As 
an example, if we have a pile of duck feathers uniformly mixed with chicken 
feathers, the feathers at the bottom of the pile are more compressed than those 
at the top, and a cubic foot of feather mixture from the base of the pile will 
contain more feathers than a cubic foot taken from the top. However, the 
percentage of each kind of feathers will be the same© The barometric (or 
atmospheric) pressure at sea level under standard conditions is 760 mm, Hg - 
that is, it is equal to the pressure a column of mercury 760 mm, high would 
exert. This figure (760 mm, Hg) may also be expressed as 29®9 inches of mercury© 
Toricelli’s experiment, as your probably remember, illustrates the measurement 
of atmospheric pressure and the fact that this pressure is equal to the weight 
of the column of air which lies above the surface involved, Toricelli used a 
glass tube more than 30 inches long, closed at one end, and filled with mercury - 
This he inverted over an open vessel containing mercury* The mercury in the tube 
descended, leaving a vacuum above it. The vertical, . 
height or'the column of mercury measured the atmospheric pressurej 760 mm, or 
29•9 inches at sea level. 
C. Composition of atmosphere. 
1. Volume. 
By volume the atmosphere is composed of ?8 per cent nitrogen, 21 per ce:.t 
oxygen (more accurately, 20.93%), a small amount of carbon dioxide (0.03%; 
and traces of rare gases (about 1%)$ that is roughly h/5 nitrogen and l/5 
oxygen. 
2* Partial pressure. 
According to Dalton's law, the partial pressure of a specific gas in a 
mixture of gases is the pressure exerted by the specific gas only - that is, 
the pressure that the specific gas would exert if it alone occupied the 
space of the whole gaseous mixture. Since oxygen composes 21% of the atmos- 
pheric air, then at sea level the partial pressure of oxygen is 21% of ?60 
rnnu, or 159 mm. Hg. Partial pressures are important, especially that of 
oxygen for it is the partial pressure that forces oxygen through the walls 
lining the air sacs of the lungs into the blood and from there it is trans- 
ported to the tissues. Since the barometric pressure decreases with increase 
in altitude, the partial pressure of oxygen also decreases so that at higher 
altitudes less oxygen is driven into the blood from the lungs. D, Vertical section of the atmosphere, 
1, Division by layers. 
We divide the atmosphere into layers. These are: the troposphere, strato- 
sphere, and the tropopause. They are shown on this chart, (Demonstrate.) 
The troposphere extends from sea level to about 33>000 to 3^>000 feet 
altitude. It contains three-fourths of the atmosphere by weight and 
various hydrometeors as olouds, rain and snow. 
The stratosphere extends about 37>500 feet to hundreds of miles of 
altitude. Here the temperatures are much more constant than in the troposphere 
being from 62 to 71 degrees below zero (Fahrenheit). Hydrometeors are absent 
here. 
The tropopause varies from about 33>000 to 1*0,000 feet and is the area 
between the upper limit of the troposphere and the lower limit of the strato- 
sphere . 
2. Flight Surgeon’s division. 
From the flight surgeon's point of view it is probably only necessary to 
divide the atmosphere in a rough manner; that is, first, the upper limit of 
unimpaired performance, which is at an altitude of 10,000 to 11,000 feet, and, 
second, the critical limit, which is at 18,000 to 20,000 feet. Ten to eleven 
thousand feet is set as a limit because most individuals can fly at those 
altitudes for an hour or more without severe effect on the body. However, 
some individuals have a less resistance even to a small lack of oxygen. 
They may experience symptoms of lack of oxygen after several hours of flying 
at only 8,000 feet over a period of days. At the critical limit of 18,000 
to 20,000 feet danger of unconsciousness and even death is present. On any 
flight for ary length of time at l£,000 feet or more oxygen must be used. 
XII, Tactical Considerations in Altitudes, 
Let us briefly consider military tactics and altitudes. In World War I 
combat often took place at altitudes of 15,000 to 18,000 feet. In World War I 
combat altitudes are often from 20,000 to 30,000 feet and are rapidly progres- 
sing toward 1*0,000 feet. In the future, perhaps it will be over 1*0,000 feet 
with the use of pressure suits or pressurized cabins. 
The advantages of high altitude are: 
1. Interception is less probable for bombers. 
2. There is greater operating freedom, 
3o There is less probability of detection, 
I*. There is progressively less danger from anti-aircraft. 
High altitude flying has, on the other hand, created many mechanical problems 
such as supercharging, intercooling, lubrication, pressure cabins and suits, 
and heating. Progress has been made in meeting these problems. IV, Effects of Lack of Oxygen, 
Without oxygen, an averate individual can carry on efficiently for only 
the following lengths of time at the following altitudes: 
35.000 feet - about 35 seconds 
25.000 feet - about 5 minutes 
20.000 feet - about 10 to 15 minutes 
18.000 feet - about U5 to 75 minutes 
15.000 feet - about 5 to 6 hours 
10.000 feet - all day, but symptoms of chronic oxygen lack 
will be present if repeated daily. 
A very important figure to remember is 35 seconds at 35,000 feet before 
the subject becomes completely unconscious; this is equivalent to about seven 
breaths• 
Increase in altitude (decrease in atmospheric pressure) will result in the 
following effects on the human body. 
1* Altitude sickness due to lack of oxygen (anoxia), 
2, The effects due to decreased pressure such as expansion of gases in the 
abdomen and in the middle ear, and als? aero-emphysema and aeroembolism, 
3, The effects of cold, 
U. Airsickness, which is due to the motion of the ship and is similar to 
seasickness. 
In considering the full effects of lack of oxygen special stress is to be 
put on some of the organs affected. The brain and nervous system are very 
susceptible to even small amounts of oxygen lack. The heart, muscles and 
other parts of the body are also affected. The amount and extent of body 
changes are dependent on the following factors, assuming that we have a 
healthy mans 
1* Altitude attained, since the higher the altitude the less the availabiji' 
of oxygen to the body, 
2• The duration of the lack of oxygen, since the longer the duration the 
more changes there are. 
3* The frequency of flight. Repeated trips on successive days to altitudes 
producing only very slight lack of oxygen will, if frequently repeated 
(as daily for a month), cause definite symptoms of impaired mental and 
physical functions. 
There are several individual factors which affect responses to a lack of 
oxygen. These are natural ability, physical activity and general physical 
condition. Some individuals have a natural ability to show little change to 
moderate amounts of oxygen lack - that is, they have a high resistance to lack 
of oxygen; their symptom threshold is high. This was important in the previous 
war when ability to go to 20,000 feet made you superior in fighting an enemy 
that could only go to 18,000 feet. Today this difference is insignificant 
because with proper oxygen equipment you can go to 33,000 feet and be normal 
and can reach U2,000 feet as safely as you could formerly reach 20,000 feet, 
as far as oxygen is concerned. Increased physical activity stimulates body 
metabolism and oxidation so that more oxygen is needed by the body, and if the 5 
additional supply of oxygen is not received, then symptoms of oxygen lack set 
in earlier and are more severe than if the body were at An individual in 
good general physical condition almost invariably reacts less to the same 
amount of oxygen lack than does one in poor physical condition, assuming 
everything else to be equal. 
There is surprisingly little awareness of the progressive effects of 
decreasing oxygen pressure* There is usually a compensatory increase in the 
pulse rate, but only a little increase in depth or rate of respiration, Euphoria 
(a false sense of well-being) and poor judgment with poor mental and physical 
response are usually followed by dizziness and unconsciousness with possible 
disastrous results* Should consciousness be regained, headache and marked 
fatigue will be noted. Accessory symptoms, as earache, will be discussed later0 
The symptoms of anoxia are very similar to those of alcoholic intoxication. 
V, Use of Oxygen During Flight, 
A. Advantages. 
The one big advantage in using additional oxygen is that by so doing one 
prevents an oxygen lack, a simple but important fact. Benefits of oxygen 
administration may be summed up in one word - "prophylaxis," 
B. Precautions. 
Before attempting to use oxygen we should become familiar with a few pre- 
cautions we should use* First, and perhaps of most importance, is a habitual 
complete check of oxygen equipment before flights. Either you or someone 
you are certain is a responsible individual should make the check. Avoid 
flames I Oxygen makes things more inflammable. Avoid using oils or greases 
on ary metal oxygen connections. Oils and high pressure oxygen can result in 
a tremendous explosionl Warn your mechanics. Cylinders should be stored in a 
cool, dry place and not handled too roughly. Tank threads should be sealed wit: 
a lead oxide and glycerine preparation instead of greases. 
C, Equipment, 
1, Oxygen tanks. 
You see here some of the various oxygen tanks used by the Array, (Demonstv' 
tion and short discussion of the characteristics of the various tanks, ice0; 
low pressure, high pressure, etc,, and discuss tank "poundage," refilling, 
and the necessity for using dry oxygen) 
2, Regulators. 
Here we have some of the various types of oxygen regulators in use. There 
(demonstrate) are the hand controlled type and should be set at the altitude 
at which one is flying if sitting quietly, and £000 to 8000 feet higher if 
exercising. Some flow meters are correctly marked on one side for "resting" 
flow and on the other side for use if the aviator is "active"; that is, 
using his muscles by working* These (demonstrate) are the demand types which 
supply oxygen according to the demands of the body, They are automatic and 
will supply more oxygen at higher levels or while the individual is active 
instead of resting. There are two types of demand regulators. One type 
mixes the necessary amounts of air and oxygen, and is best suited to altitudes 
under 30,000 feet. The other type supplies only oxygen with no added air, 
and is therefore wasteful of oxygen at altitudes below 30,000 feet. These 
will now be passed around for your inspection® Please handle them with care. 3. Tubing connections. 
The tubing before you is used in connecting the oxygen apparatus* (Short 
talk and demonstration.) 
Masks 
One of the most important parts of our oxygen equipment is the oxygen 
mask. Here are some of the various types of masks in use. (Demonstrate.) 
This is the latest type issue. An excellent mask is the type A-8-A here 
shown* (Demonstrate.) It is of utmost importance that you use a proper 
fitting mask, and you should fully understand the principle or mechanism 
of operation of the mask you use. 
(The latest masks and accessory equipment should be demonstrated very 
carefully and especial .attention payed to the respective merits and demerits 
of the "constant flow system,” the "demand system" and finally the "combined 
constant flow and demand systems" which has all the advantages of both 
systems with practically none of the disadvantages*) 
5» When to use masks in flight. 
Array regulations regarding use of oxygen in flight are as follows: 
Oxygen is to be used in flights when 
1. An altitude of 10,000 to 12,000 feet is contemplated for six hours 
or more. 
2. An altitude of 12,000 to 15,000 fe et is contemplated for two hours 
or more* 
3* An altitude of l£,000 feet or higher is contemplated for any length 
of time. 
In addition, all night flying is to be done with oxygen, since even 
small amounts of oxygen lack may interfere with night vision* Any individual, 
with low altitude tolerance should not hesitate to use oxygen at lower 
altitudes than those specified above* 
D. Emergency parachute jumps from high altitudes. 
What would you do if an emergency arose at 35*000 feet and a ’’bail out” war 
necessary? There you are in a region where unconsciousness sets in after 35 
to hS seconds without an extra oxygen supply; you are a number of minutes from 
a safe altitude at which the pressure of oxygen in the atmosphere would be 
sufficient to maintain consciousness* The aviator does not have time to get 
out of his plane unless the first thing he does after his oxygen supply has 
been shot away or damaged is to shift to the emergency midget oxygen tank* 
This is a small tank carrying fifteen minute’s oxygen supply (demonstrate)* 
E« Misconceptions concerning; oxygeru 
Before leaving the subject of oxygen I wish to correct some misconceptions 
concerning oxygen* Oxygen as used today has absolutely no deleterious effect 
on the teeth or fillings and none on the lungs even if used repeatedly for 
hours. As a matter of fact, oxygen is used in the treatment of pneumonia, 
heart disease* and many other medical conditions* And let’s not forget that 
high pressure oxygen in contact with oils or grease will explode. There is 
no such thing as "medical oxygen" since this is the same as what we use except 
for the tank label and valve connections. In aviation for high altitude flying 
relatively unheated dry oxygen must be used. Any water in it would freeze on 
the needle point of the reducing valve. Th is would cut off the oxygen flow 
to the aviator. 7 
VI. Relation of Physical Condition to Oxygen Requirements. 
A, Lack of sleep and exercise. 
There is a definite relation between one’s physical condition and the 
harmful effect of oxygen lack; the ceiling is lowered if one's physical 
condition is poor. Lack of sleep makes us more susceptible to the effects 
of oxygen lack, especially if continued over a period of weeks or months. 
Your gramraer school teacher’s advice about getting eight or ten hours sleep 
nightly still holds good. As stated already, one’s general physical condition 
is one of the factors determining reaction to a lack of oxygen. The worse the 
physical condition, the worse the reaction; hence, be certain you receive 
your rightful share of exercise and recreation* A balance between sufficient 
sleep and proper exercise will tend to prevent fatigue* Fatigue is aggravated 
by anoxia. 
B. Improper diet. 
Improper diet is also detrimental. Try to eat a well-balanced diet. 
Don’t overstuff yourselves at mealtime, and don’t attempt to lose weight by 
dieting without first consulting your flight surgeon. Digestive disturbances, 
irritability, constiptation, early fatigue, inefficiency, etc., may result 
from improper diet. The diet supplied you while you were cadets was well 
balanced. 
C. Drugs and alcohol. 
Drugs are often taken indiscriminately by flying personnel - a dangerous 
practice0 Always consult your flight surgeon before taking any kind of drugI 
Taking sedatives such as seconal, phenobarbital, araytal, nembutal, etc.,may 
lead to tragedy, especially if one attempts to fly while still under the 
prolonged effects of these drugs* The nervous system and entire body are 
affected by sedatives* 
Under no condition should flying personnel take any of the sulfonamid group 
of drugs which are used by physicians to control infections of various types. 
Among these drugs are sulfaphyridine, sulfanilamide, and sulfathiaaole. 
Their effects on the blood, heart, nervous system, etc© are so pronounced that 
they are extremely dangerous for self-administration* The effects are so 
dangerous that Army regulations permit Army physicians to prescribe these 
drugs only to hospitalized patients, those who can be observed throughout the 
day and who can have blood counts daily if needed. 
Even headache powders such as bromc-seltzer, ”B-C” and other patent 
preparations may cause agranulocytosis in the blood which would seriously 
affect your susceptibility to anoxia, to say the least. In short, consult 
your flight surgeon before taking any drug? 
Alcohol has often used to pickle and preserve dead things and many 
now ’’preserved things” were pickled just before deathI Avoid alcohol if you 
expect to get near any kind of a machine - especially an airplane. With a 
little substitution the highway signs may well be used ih flying: ”If you 
drink, don’t flyc If you fly, don’t drink„” Even reporting to the flying 
line with a slight trace of alcohol on the breath is a serious offense. We 
are all familiar with the dangers of alcohol, and it will perhaps suffice if 8 
you are reminded of the marked impairment in judgment resulting from alcohol. 
If you’ve imbibed a little too much the night before, report to your flight 
surgeon and he will relieve you from flying for that day. Think a hundred 
times before endangering your life, the lives of others, and expensive govern- 
ment property* 
VIII© Aero-emphysema or Aeroembolism. 
A. Definition* 
Aero-emphysema is a term used to designate the presence of air bubbles of 
very small, usually microscopic, size. in the tissue cells or in the inter- 
cellular fluids of the body* 
An ’’embolus” (plural, ’’emboli”) is a foreign body which may be in any part 
of the blood stream, and it may consist of gases, pieces of tissue, bacteria, 
etc. The terra, ’’aeroembolism”, was first used by Major Armstrong of the U.S, 
Army Medical Research Laboratory at Wright Field to describe the presence of 
air bubbles in the blood. These bubbles are composed largely of nitrogen 
and in part of oxygen, carbon dioxide and water vapor; each being present in 
proportion to the partial pressures of those gases© 
B, Mechanism of: 
1. Atmospheric pressure change. 
Gases are present in the body in proportion to their pressure in the 
alveoli of the lungs, and at sea level the composition of alveolar air is 
as follows: Nitrogen, about 79$; oxygen, about l£.£$; and carbon dioxide, 
about £©£$© The alveolar carbon dioxide pressure, because it is formed in 
the body and acts as the regulator of respiration, remains relatively 
constant at approximately 1*0 mm. Hg. regardless of the altitude. The 
partial pressure of oxygen decreases with altitude unless artificially 
maintained at the normal level of 100 ram. by the administration of additional 
oxygen© Nitrogen makes up the balance of the percentage and partial pressure 
of gases in the lungs. 
2. Role of nitrogen. 
At sea level, the partial pressure of alveolar nitrogen is 79 per cent 
of the barometric pressure less water vapor. That is, 0.79 x (760 - U7)* 
or 0.79 x 713* which is £63 mm. Hg« As the total barometric pressure is 
decreased by altitude, the partial pressure of nitrogen like that of oxygen 
is decreased proportionately. Also if 100$ oxygen is inhaled, the amount 
of nitrogen in the lungs rapidly decreases; this will permit the gradual 
elimination of nitrogen from the body as fast as the blood can pick it up 
from the tissues and carry it to the lungs for elimination because gases, 
like water, ’’run down hill” from a higher to a lower pressure. 
The procedure of nitrogen elimination from the body can therefore be 
hastened before ascending to high altitudes by the breathing of pure oxygen, 
and elimination is even more rapid if oxygen inhalation is accompanied by 
exercise © Since nitrogen is the principle factor in the formation of 
bubbles, we decrease this factor by getting rid of much of the nitrogen 
gas dissolved in the body. If from one-half to two-thirds of the nitrogen 
can be eliminated, the danger of aero-emphysema or aeroembolism is much 
decreased} 9 
3, ’’Soda pop” illustrations. 
The principle underlying bubble formation is easily understood if we 
recall that ’’soda pop” is bottled under increased pressure, and when 
the bottle cap is removed gas bubbles are liberated because the contents 
of the bottle are then exposed to a lower atmospheric pressure than the 
pressure at which the bottle was capped. Similarly, the gases in our 
body are liberated if the atmospheric pressure is decreased. When the 
air in the environment is decreased the whole body comes into a new gaseous 
equilibrium. According to Dalton’s law, gases are soluble in fluids accord- 
ing to their partial pressures. The tissues which contain a large propor- 
tion of fat will contain more nitrogen in solution than the blood because 
fat dissolves more nitrogen than water or blood; therefore, fatty tissues 
will give up their dissolved nitrogen much more slowly than non-fatty 
tissues. In this connection it is necessary to remember that nerve and 
brain tissue contain a high proportion of fatty material. 
iu Physiological changes (similar to ’’divert bends”)• 
Aero-emphysema with aeroembolism is similar to "caisson’s disease” or 
the ’’bends” which develops is caisson workers and in divers during ascent 
from deep diving. However, the danger for divers is greater than in 
aviation because the actual mass of gas, or in other words, the actual 
number of molecules of gas in the bodies of these caisson workers is 
greater and they often endure a greater percentage change in atmospheric 
pressure. However, even with the same percentage change, that is, reducing 
the diver’s atmospheric pressure from five atmospheres to one atmosphere 
and reducing the flyer’s atmospheric pressure from one atmosphere to one- 
fifth atmosphere (ground level to 35,000 feet) the symptoms produced in 
the case of the diver will be more serious for reasons explained by Piccard, 
In summarizing, aero-emphysema with aeroembolism is due to the fact 
that atmospheric gases, largely nitrogen, are dissolved in the body at 
ground level pressure and exist in a supersaturated state at the decreased 
pressures of high altitudes; thus forming bubbles just as a bottle of ’’soda 
pop” does when the cap is removed. 
C, Symptoms. 
1# Factors in production. 
The danger of bubble formation under 30,000 feet altitude is comparatively 
slight, even though bubblesmicroscopic in size may actually begin to form 
as low as 12,000 feet. Rapidity of ascent, altitude reached, length of 
time of exposure to that altitude, and individual susceptibility are the 
determing factors in the nitrogen bubble production and associated symptomse 
Modern day airplanes and modern warfare enable and require rapid climbs to 
very high altitudes, about 6 to 8 mileso It is here that the greatest 
danger of aeroembolism exists, especially if prolonged flights are made 
at these altitudes. 
2, Symptoms experienced (subjective - roughly in order of occurence). 
All or part of the following symptoms may be noted roughly in the order 
mentioned: smarting and scratchy sensation of the eyelids; a crawling 
sensation over the skin; pains in the hands, feet, legs and arms, especially 
around the joints or along the nerve trunk; giddiness, dizziness, or 
deafness (from bubbles in the inner ear); paralysis, usually in the legs 
which may appear suddenly and vary from weakness to complete loss of motion. 
In extreme cases, unconsciousness may set in with spontaneous defecation 
and urination, A pilot might occasionally regain consciousness by the time 
he had fallen to 8,000 to 12,000 feet. 3. Prophylactic measures: preliminary decompression (denitrogenization) 
with special equipment. 
Adequate protection may be had by "preliminary decompression" or 
"denitrogenization." This is accomplished by having the pilot and crew 
breathe pure oxygen while exercising, with vigorous movements of the legs 
to simulate a walk of two and one-half to three miles per hour together 
with a comparable movement of the arms. Massage of the abdomen helps 
to clear out the intestinal gases and t h ere should be no hesitation about 
passing gas both "up and down." A treadmill, stationary bicycle, or 
"standing running" exercise may be used to increase the circulation of 
the bloodo In addition, the mask and bag set up for this purpose must 
be properly constructed so that nothing but oxygen and a small amount of 
the carbon dioxide that will accumulate in a U or £ liter reservoir rebreath- 
ing bag is breathed (no air should leak in). The carbon dioxide also 
increases the circulation rate in non-exercising parts of the body like 
the spinal cord and brain. However, care should be taken not to rebreathe 
enough so that the accumulation of carbon dioxide makes the subject 
uncomfortable. The amount of carbon dioxide is regulated by changing the 
oxygen flow and also by emptying the reservoir bag more frequently * 
The breathing of oxygen combined with exercise enables the body to rid 
itself of one-half to two-thirds of the total gaseous nitrogen in the bodyc 
Following the exercise the aviator should si4- down and rest until he 
has regained his breath. The oxygen is breathed also while going to the 
plane and during flight. This procedure when properly carried out will 
protect against a clamb of a mile a minute to altitudes corresponding to 
U0,000 or even feet. 
Not only low pressure chamber experiments but also experience in actual 
flights show that without preliminary denitrogenization very few symptoms 
occur under 30,000 feet regardless of the rate of climb except in very 
susceptible individuals. However, above this altitude even rates of 
climb of 2,000 feet per minute or less may produce symptoms which increase 
in intensity after remaining more than 10 to 15 minutes above 30,000 or 
35,000 feet. 
From fifteen to twenty per cent of any advanced training group will 
have bends at 35,000 feet sufficient to force them to a lower altitude 
withih three hours. Rapid treatment may be had by rapid descent to 
lower altitudes. Descent should be started immediately once severe symptoms 
are noted, but mild symptoms should cause no great concern if the aviator 
is at least partially denitrogenized. Severe symptoms usually disappear 
with descent of 5,000 to 10,000 feet, and after a few moments there, one 
may climb again but should be extremely cautious, especially if not 
decompressed. 
VIII. Effects of Heat and Cold. 
A, Effect of cold on body - mechanism for maintaining body temperature. 
Before considering temperature changes in the atmosphere let us first 
consider the temperature and temperature regulating mechanism of our own 
bodies. Our normal body temperature is 37 degrees C, or 98.6 F, This may 
vary by +1,5 degrees F, and still be considered normal. 11 
The metabolic rate is the rate of heat production in the body® It is 
dependent on numerous factors which we will not take up in detail. The 
metabolic rate is determined in the laboratory by measuring the amount of 
oxygen used by the body within a given time, i.e., rate of oxygen consumption. 
Work or exercise raises it, as does shivering which is a strenuous form of 
exercise. Shivering may raise the metabolic rate to four or five times what 
it is at rest and thus compensate for loss of heat. The ingestion of food 
requires energy for digestion and assimilation, and this raises the metabolic 
rate. We are all familiar with the fact that food or drink much warmer or 
colder than the body temperature will change the body temperature. The 
thing to keep uppermost in our minds, however, is that increased metabolism 
requires an increase of oxygen supply. Thus, in freezing weather our bodies 
strive to furnish us sufficient heat by increasing our metabolic rate. This 
calls for a greater supply of oxygen since metabolism is primarily a process 
of combustion or oxidation, that is, food is burned up in the body as coal 
is in the furnace. In addition, during cold weather, the heat regulating 
center tends to prevent loss of body heat by decreasing the amount of perspira- 
tion and by decreasing the amount of blood flowing to the skin. 
Since the modern military pilot experiences rapid and great changes of 
altitude, he also experiences rapid and great changes of temperature. He 
should be fully aware of these changes and the danger involved, and most 
important, know how to protect himself against these temperature changes. 
Fortunately, most of our present day airmen are young, and young men possess 
rapid and more adequate responses to cold than do older men who are more 
sensitive to temperature. 
B. Atmosphere. 
In the atmosphere there is a gradual and fairly regular temperature drop 
(in summer) from an average temperature of l£° C. at sea level to about -5>0° G0 
at 11 kilometers after which it remains essentially constant. In winter the 
decrease in temperature reaches -5>£° C. at 10 kilometers (Figp-17 and 18, 
"Physics of the Air," by W* J, Humphreys). 
C. Effects of freezing on the body. 
Mild chilling, Mgoose pimples,” and shivering may follow in the named order 
in the early stages of freezing. Unless adequate protection against cold is 
available these symptoms become progressively more severe and finally stiffness 
of the extremities with numbness, poor coordination, poor judgment and a 
tendency to sleep occurs. In the later stages of freezing, as is well known, 
the unfortunate victim may experience no subjective symptoms and be totally 
unaware of his extreme danger; he becomes drowsy and wants to drop off to 
sleep - and may never awaken. 
D. Protection against cold. 
For preventing frost bite, cold cream, vaseline or other bland ointments 
smeared on the hands and face are excellent. Care should be taken when 
applying such greases to the hands that not enough is used to make the joystick, 
throttle, etc. so slippery that proper control of them would be difficult. 
The principle means of combating cold temperatues is by means of proper 
clothing and by heated cabins. In combat it is essential that every plane 
crew member be as comfortable as possible - at least to such an extent that he is not hindered in carrying out his duties efficiently. This not only 
means that each must be comfortably warm, but he must also not be handicapped 
by clothes that are too bulky. Two thin garments afford better protection 
against cold than does one thick garment, ever chough the total thickness of 
the two is less than that of the one thick garment. This is because of the 
insulating layer of air between the two garments which serves to prevent excess 
loss of heat from the body surface as well as serving to insulate against the 
outside cold. Garments should not fit too tightly; however, they should be 
snug at the wrists, collar and ankles to prevent outside air from blowing in. 
The fur-lined clothing which is now used is rather bulky. Electrically 
heated clothing now in use is far less bulky and permits each individual to 
adjust the heat as he desires. The disadvantages of this latter type are that 
the source of heat may fail, it won't be available if the ship is forcibly 
abandoned, and it requires a very large amount of electrical energy. Electric- 
ally heated clothing is only efficient when well insulated on the outside by 
properly constructed clothing. Progress is now being made in incorporating the 
best features of both types of clothing for the future. 
Two principal methods have been used to heat the cabins of planes. The 
first is not desirable, is dangerous, and practically obsolete now. This is 
the collection of heated air from around the exhaust and conducting it to the 
cabin. This is a very dangerous method as a small leakage of carbon monoxide 
could result in disaster to the plane’s occupants in a very short time. The 
second type is more satisfactory, and utilizes the exhaust to heat a small 
tank of hot water which in turn gives off steam for circulation within the 
plane. This is by far the safer and more desirable method. 
DC. Effects of Speed and Centrifugal Force. 
A. Speed. 
A speed in excess of U25> miles per hour has been attained. In straight-away 
flying probably speed in flight has no other effect than that of a terrific 
blast of air. While traveling at such a tremendous rate of speed the flyer 
does not dare expose parts of his body to such terrific pressure. If he held 
out an arm it would probably be broken, or if he stood up in his cockput his 
head would probably be snapped backward with such force that his neck would 
be broken. 
B. Centrifugal force and speed. 
The real danger in tremendous speed, however, is during banks and turns, 
and is due to centrifugal force, as the flier makes a bank and turns abruptly 
from his original line of flight the "pull” of centrifugal force acts in the 
direction of the radius of the turn, that is, away from his head and toward 
his feet. The result is that the blood is literally thrown away from his 
brain, causing cerebral anemia or a faint. The underlying principle of the 
blackout (on inside loop) is that 1 pint of blood instead of weighing 1 pound 
as is normal under the influence of normal gravity (l g), weighs five, six or 
seven times as much when the force of gravity becomes equivalent to five, six 
or seven g. The heart cannot pump this heavy blood up into the head* As a matter of fact, 
it "falls" down into the lower belly and legs* Note that the direction of 
blood flow is toward the pilot’s head until he starts to pull out of his dive* 
At this latter period he meets centrifugal force which reverses the direction 
of the blood flow* Very shortly afterward he begins to go into a blackout, 
with progressive decrease in the blood supply and therefore, of the oxygen 
supply to the brain* Note that the blackout, which is experienced 
is a darkening of the fields of vision* The complete blackout occurs not as 
soon as the individual begins to come out of the dive but at a later 
period© As the plane levels out, normal vision is restored* The more 
rapid and sharp "pull outs" cause more rapid and more complete blackouts* This 
phenomenon is often noticed by pilots flying in races, and also in pulling out 
of fast dives abruptly. The tendency toward fainting or "passings out" on turns 
and pulling out of dives apparently varies greatly with individuals* Some 
state emphatically that they have never experienced such a sensation, possibly 
because the aviator failed to appreciate that he had for a few seconds become 
unconscious* It seems to vary at times in one individual, and possibly depends 
to some extent upon his general physical condition* One pilot described the 
sensation that he experienced in pulling out of a dive as follows; "Suddenly 
spots appeared before ray eyes and then everything went black for an instant, 
probably one or two seconds, judging from the altitude I had gained. 
There is also a condition we call a "redout" which is just the opposite to 
a blackout. Redouts are experienced in outside loops where centrifugal force 
acts to throw the blood flow toward the head* This increases the blood volume 
and pressure in the heat to such an extent that the small blood vessels of the 
eyes are overfilled with red blood and may even rupture* The individual in 
which this occurs looks through this, blood and receives the same visual effect 
as looking through a red film - in this instance a film of blood* Individuals 
with high blood pressure may have redouts of such severity that they may be 
accompanied by rupture of blood vessels of the brain - similar to an apoplectic 
stroke, and very dangerous. 
Another method of preventing blackouts, is, by crouching forward in the 
cockpit* When a pilot is sitting in an erect position, the distance from his 
heart to hie brain is greater than when he is crouching* The completely prone 
or supine position is the best position for prevention of blackout since the 
heart and head are at the same level;; however, such positions are not practical* 
The crouch position is practical and may prevent some blackouts or at least 
diminish the severity of blackouts* 
An abdominal pressure belt and later "suits" have been used for prevention 
of blackouts, but these contrivances have not yet been found entirely satisfac- 
tory* The pressure belt or suit is sometimes automatically inflated as one 
"pulls out" and by exerting pressure against the blood vessels of the legs and 
abdomen it acts to lessen their capacity to collect blood from the head. X, Barometric Pressure Changes and the Ear. 
A* Ear anatomy. 
As mentioned previously, ascent to high altitudes (decreasing barometric 
pressure) affects the ears, sinuses and intestines* We shall first consider 
the ear* If you will notice the chart of the of the ear, you will see 
the external auditory canal, the tympanic membrane or ear drum, and the eusta- 
chian tube«, (Instructor uses pointer on anatomical chart*) The external 
auditory canal is what the physician peeks into with an otoscope to get a good 
view of the ear drum (tympanic membrane). The ear drum may be compared to a 
sheet of thin rubber in its ability to "pooch out" (bulge) and "pooch in" 
(retract), especially if that sheet rubber is thought of as covering one end 
of a tube. By blowing into the open end of the tube, the rubber sheet will 
bulge outward, and if we suck in on the open end, we create a negative 
pressure and cause the rubber sheet to retract. The ear drum will bulge out if 
the gas pressure in the middle ear is greater than that outside; on the other 
hand the pressure in the middle ear is less than that in the atmosphere and the 
ear drum bulges inward (retraction). 
The principle action of the eustachian tube is to drain and ventilate or 
equalize the air pressure of the middle ear and the atmospheric pressure. 
The eustachian tube is opened by its dilate r muscles in the nasopharynx; 
opening, it equalizes any pressure differential existing between the middle 
ear and the atmosphere. The dilator muscles act to open the eustachian tube 
during swallowing, yawning, and other physiologic acts. 
B, Ascent 
If we begin at sea level and ascend without ventilating the middle ear by 
opening the eustachian tube, there is pain with bulging outwards of the ear 
drum, the degree of bulging depending on the altitude attained. As we ascend, 
the pressure in the non-ventilated middle ear remains the same as it was at 
sea level, while the atmospheric pressure decreases. Hence the greater pressure 
in the middle ear pushes the tympanic membrane outward toward the lesser pres- 
sure of the atmosphere. If sufficient altitude is reached, the bulging may 
be great enough to burst the tympanic membrane. Similarly, if we assume the 
middle ear and atmospheric pressure have been equalized at a high altitude 
and then begin to descend without ventilating the middle ear, we have a 
reversal of the process, i,e,, the tympanic membrane is pushed inward. 
C, Descent, 
The pain and other symptoms are more prominent on descent than on ascent. 
If there is ventilation of the middle ear during descent, then its pressure 
remains stationary with development of a relative negative pressure, while 
the atmospheric pressure progressively becomes greater and forces the tympanic 
membrane in toward the middle ear, resulting in a retracted ear drum. 
In this instance, the pressure within the middle ear is less than that of 
the atmosphere. Such a negative pressure of 80 to 90 mns of mercury within . 
the middle ear makes it impossible for the eustachian muscles to overcome the 
negative pressure which holds the eustachian tube tightly collapsed® It 
then becomes necessary to decrease the middle ear pressure to about 70 mme of 
mercury of negative pressure or less before the eustachian tubes can again 15 
be voluntarily opened# This necessitates ascending again to an altitude where 
the middle ear and atmospheric pressure are more nearly equalized. 
De Aero-Otitis Media (nEar BlocknAviation Earn). 
1. Definition© 
"Aero-otitis media" or "aviation ear" is a term coined to refer to the 
results due to the lack of ventilation of the middle ear during changes of 
atmospheric pressure to the extent that the tympanic membrane and cavity 
are injured. 
2. Cause of improper middle ear ventilation. 
The two principal causes of improper middle ear ventilation are; first, 
a failure to open the eustachian tube voluntarily when necessary; second, 
the inability to open it and this is much more prevalent than is generally 
recognized. Frequent causes of inability to open the eustachian tube are: 
ignorance of the physiologic mechanisms, obstructions of the nose, sinusitis, 
tonsillitis, tumors or growths of the nose, mouth, etc# On the other hand, 
experience and training greatly increase one’s ability to open the eustachian 
tube. Every flight surgeon has had innumerable experiences with the cadet 
who thought he should certainly not be grounded because he had a sore throat. 
The flight surgeon realized only too well the danger of a sore throat. The 
inflammation of the throat often involves the opening of the eustachian 
tube and causes a partial or complete closure of the tube so that proper 
ventilation of the middle ear is not possible and woe betides the flier who 
flies with a sore throat and then after landing "blows his ears out" by 
closing the nose and mouth, for this usually forces germs from the infected 
throat into the eustachian tube and middle ear with serious complications 
resulting. 
3 . Symptoms. 
Let us briefly consider the symptoms of aero-otitis media which may be 
brought on by ascent or descent with improper ear ventilation. One of the 
earliest symptoms is a feeling of fullness in the middle ear. In chronic 
cases due to repeated mild injury to the ears there is a "full,, and stuffy" 
feeling in the ears and difficulty in "clearing" them. Varying degrees 
of loss of hearing may occur. With rupture of an ear drum pain may become 
unbearable# The subject feels "as though hit along the side of the head 
with a plank" and there is a sharp pierc ing pain on the affected side 
with marked dizziness and nausea. Collapse or shock may follow. 
k* Prophylaxis . 
Again, the simplest maneuver to open the eustachian tube is to swallow# 
Yawning, singing, shouting, etc. may also accomplish it. The sucking of 
candied mints while flying causes frequent swallowing and is probably 
better than chewing gum, as the latter soon loses its flavor# The average 
person swallows involuntarily about once every 60-?£ seconds so that rates 
of climb of 500 feet per minute or more result in progressively greater 
degrees of discomfort if no effort is made to ventilate the middle ear# 
Sleeping and unconscious individuals present a serious problem. Commercial 
airlines have an allowable rate of ascent and descent of 200 to 300 feet per 
minute; however, military flying requ ires more rapid rates of ascent and 
descent with, of course, greater care regarding the ears# Diagrammatic sketch of the external, middle 
and Internal ear and the eustachlan tube. SAG IT A I* SECTION 
TO SHOW 
ORIFICE Of EUSTACHIAN TUBE 
Sphenoidal sinus 
Orifice of 
Eustachian tube AND THEIR CONNECTION TO THE NASAL CAVITY 16 
XI* Barometric Pressure Changes and the Sinuses. 
A. Brief anatomy. 
The nasal accessory sinuses are also affected by barometric changes* These 
are located in the hollowed out spaces of the face bones. Two of these sinuses 
are located here in the cheek, two are located here in the forehead, and two 
of them are located in the bones just back of the root of the nose. Ordinarily 
air passes in and out of these sinuses through small openings in the nose. 
B0 Ascent. 
During ascent and descent to and from high altitudes, the air in these 
sinuses changes pressure with the atmospheric pressure, as does the air in 
the middle ears, and similarly, should there be an obstruction to the sinuses, 
the air cannot escape readily and ill effects are produced. For instance, in 
ascent the expanded air in the sinuses cannot escape, and by building up 
pressure within the sinuses it causes pain. 
C. Descent. 
The reverse of this is true during descent when a vacuum is created in the 
sinuses and air from the atmosphere cannot enter the sinuses. Pain is 
produced here also and may be accompanied by headache, eyeache, dizziness, 
and nausea0 Pilots with sinus infection, obstruction of the sinus openings, 
or head colds should not fly until the condition has been corrected. To 
fly may aggravate the condition and perhaps cause serious complications. 
D. Treatment. 
A benzedrine inhaler sniffed just before flying may help at times but 
warning is given that the inhaler should be used no more often that once every 
hour and should only be used after consulting your flight surgeon. 
XII. Barometric Pressure Changes and Intestinal Gases. 
Expansion of abdominal gases may cause marked discomfort in high altitude 
flying unless properly combatted* Gases expand with decrease in atmospheric 
pressure. As an example, a toy balloon when taken from sea level to 35>,000 
feet will increase its volume more than four times. Similarly, the intestinal 
gases will do likewise with production of marked abdominal distension and 
discomfort. In severe cases marked abdominal cramps, difficulty in breathing 
and interference with the heart’s action may result. 
Anyone comtemplating a high altitude flight should avoid gas forming foods 
and drinks such as beans, cabbage, peas, beer and carbonated drinks. Avoid 
constipation. The taking of charcoal by mouth helps absorb some of these 
gases. Once distension and discomfort are experienced, relief may be obtained 
by either descending to lower altitudes or by massaging the abdomen with the 
hand followed by belching and the passage of flatus. 17 
XIII, Hyperventilation. 
A, Definition, 
There is one more important thing to consider and that is hyperventilation, 
"Hyper,” meaning very much or too much, and "ventilation” meaning just that. 
In hyperventilation there is more breathing, or ventilation, than the body 
requires# 
B, Symptoms<> 
The symptoms of hyperventilation may be serious, and are: dizziness, a 
rapid pulse, marked perspiration, clamminess, visual disturbances, errors of 
judgment, muscular spasms and unconsciousness. Hyperventilation usually 
occurs insiduously, coming on without the victim being aware of it unless he 
is familiar with the signs and symptoms, Anxiety such as occurs during combat, 
fear, panic or hysteria often lead to hyperventilation, 
C, Treatment, 
The treatment of hyperventilation, fortunately, is quite simple, just 
hold the breath for about one minute in order to build up the carbon dioxide 
content of the blood which was diminished by hyperventilating. 
D, Demonstration^ 
We shall now have six members of the class hyperventilate under ray 
direction for minutes and at the conclusion I shall have them describe 
to the class the symptoms they have experienced, (Demonstration by instructor 
and six students,) SUGGESTIVE 
OUTLINE FOR LOW PRESSURE CHAMBER “RUN" 
FOR AIR FORCE AND MEDICaL OFFICERS, 
Operating Personnel; Two medical officers, one trained chamber operator, one 
mechanic. 
Time Required; 
Approximately l| hours. 
1, Review again the physiology and symptoms of aeroembolism and effects of denitro- 
genization preliminary to rapid high altitude ascents, 
2, Inquire as to whether any students have colds, ear or sinus trouble. Leave these 
affected students out of chamber ascent, 
3, ibcplain that group preliminary denitrogenization will be followed by chamber 
3. ascent to 1*0,000 feet, 
U, Demonstrate exercise. Explain and demonstrate that rate of 3 miles per hour for 
30 minutes will be used, and while exercising the student must keep arms in 
motion using weights. He must deflate rebreather bag every $ minutes with hands 
to prevent uncomfortable CO2 accumulation, 
5# Demonstrate oxygen supply system for denitrogenization and in chamber, 
6, Fit denitrogenization masks to students and start exercisec 
7* Check students for correct decompression procedure with assistants. Be certain 
each has lU to 20 liters oxygen flow per minute depending on size, 
8, Allow students to rest in chairs for $ to 10 minutes after exercise, continuing 
oxygen inhalation, 
9, Transfer students to chamber in pairs. Have each take large breath of oxygen, 
disconnect him from oxygen tank, shut off tank, then seat student in chamber 
and connect chamber oxygen supply, 
10„ Close chai-ibcr door after all students are seated. Check oxygen flow and mask 
of each student© 
11, Medical officer has microphone connected to public speaker system and also 
connected by earphones to operator outside of chamber© 
12, Ascent made to £000 feet. Altitude announced. Warn students that a descent of 
feet in one minute is to be made and students are to swallow and care for 
ears and sinuses© 
13» Descend to 3000 feet at rate of 1$00 feet per minute. Level off if any student 
has marked symptoms, then descend to sea level and remove these complaining 
students from chamber and send them to E. E, Nc T, Department for examination, 
lU, Announce ascent to be made to 30,000 feet at 3000 feet per minute for first 
10,000 feet and 6000 feet per minute for last 20,000 feet. Ask students not 
to hesitate in informing you of any difficulty they may seem to be having, i,e,, 
sinus or ear trouble, abdominal cramps, soreness in joints, crawling sensation 
of skin, etc. Level off or drop $000 to 10,000 feet for 10 minutes; if definite 
symptoms noted then, proceed with care. Observer constantly watches for hyper- 
ventilation 
1$, Signal ascent. Constantly observe students, check their equipment and review 
orally to them the symptoms of aeroembolism, and remind them again of intestinal 
gas expansion© Have students with mild abdominal discomfort massage abdomen, 
belch and pass flatus, 
16. Stop at 30,000 feet for $ to 10 minutes. Have students note their own and 
neighbor's fingernail color, and skin color. Have them note clearness of vision 
and mind, pulse rates, etc. Ask them to note same at higher altitudes, 
17, Announce ascent to be made to i|0,000 feet. Check all equipment, 
IS© Signal ascent, Ascend to i;0,000 feet. Remain there $ minutes. Keep emergency 
oxygen supply masks handy© Closely observe all students. Return to 30,000 feet 
for $ minutes, then return to U0,000 feet for as long as time permits, (Altera- 
tion of altitude is beneficial physically and psychologically). 19« Have three students lift 10 pound weight from lap vertically above head (U feet) 
about 1$ times in 30 seconds. Have other students note any cyanosis or other 
symptoms that may result. This amount of work is equivalent to 1200 feet 
pounds per minute. 
20. Announce descent. 
21* Signal descent. Should any student develop dangerous symptoms at high atltitudes, 
use air lock, if available. 
22. Descend at U,000 to $,000 feet per minute to 10 or 12,000 feet. Remove oxygen 
masks then descend at 1000 or 2000 feet per minute to ground level. Avoid 
sudden pressure drops near ground level. 
23. Answer students1 questions. Impress students with value and safety of prelira- 
inary decompression. 
2lu Record findings and impressions of each student. RECOMMENDATIONS CONCERNING OPERATION OF 
THE LOW PRESSURE CHAMBER AND LABORATORY 
I, That two trained flight surgeons supervise the low pressure chamber and 
laboratory. 
II. That each medical officer ascend in chamber above 30,000 feet no more often 
than every other day; lower ascents could be made daily. 
Ill* That the duties of the medical officers be to: 
A. Supervise laboratory. 
B. Supervise low pressure chamber. 
C. Be available near chamber at all times while his fellow medical officer 
is in the chamber, and to help prepare and observe students for and 
during a "run.” 
D# Keep a complete log of each run: names of students, instructors, times 
of reaching each 5000 foot altitude and any severe or serious reactions 
of students. 
E. Make recommendations and reports on students regularly. 
IV, That two trained operators, preferably of one of the grades of sergeant, be 
used to control the chamber. Their duties would be to: 
A. Control chamber ascents and descents in the chamber on direction of the 
medical officers. 
B. Clean oxygen masks after each run. 
C. Be responsible for oxygen tanks and oxygen supply in tanks at all times. 
D. Supervise department sanitation. 
E. Care for equipment and run projector for ary films shown. 
F. Care for log books and other laboratory data. 
G. Care for all material to be distributed to students, as printed tests, 
pencils, etc. 
V. That a trained mechanic, preferably of one of the grades of sergeant, be 
available at all times. His duties would be to: 
A. Care for and maintain pumps and chamber. 
B. Routinely check and care for all equipment, especially oxygen connections0 
G. Assist chamber operator and medical officers when necessary. 
VI. That the medical officers be permitted to do research work, especially "clinical-' 
if they show ability, interest and desire and that under those conditions the 
seventh recommendation be followed. 
VII. That two trained laboratory technicians be made available. They should be 
familiar with: 
A. Haldane gas analyses (alveolar and mask air analyses). 
B. Slyke analyses (blood gas analyses). 
' C.Blood counts. 
D.Typewriting ability. 
VIII. That moving picture films be used to supplement lectures and demonstrations. 
(Dr. W. M. Boothby of the Mayo Clinic has some excellent ones for teaching 
purposes and is producing more.) 
IX. That chamber communication available be of the following types: 
A . One permitting the medical officer in the chamber to address students by 
loudspeaker and yet have connection with the outside operator by means of 
earphones on the medical officer. At times the operator; may wish to 
convey a warning or personal message regarding students to the medical 
officer inside the chamber. 
B. One permitting the medical officer on the outside to lecture by loudspeaker 
system to the students on the inside of the chamber. This is important 
at U0,000 feet when the medical officer on the inside should do as little 
talking as possible. 
X. That "standing running" exercises be used in producing preliminaiy decompress:on 
if treadmills or bicycles are not available. This would require no installat:.on 
or expense. (Attention is called to the proper procedure for preliminary 
denitrogenization as presented in the "Outline for Pressure Chamber nun' 
for Air Force Medical Officers.")