Preliminary Account of Ex- 
periments in regard to the 
Circulatory and Respiratory 
,Changes observed in Ani- 
mals placed in the Pneu- 
matic Cabinet. 
H. N. MARTIN, P. R. S., 
BY 
PROFESSOR IN THE JOHNS HOPKINS UNIVERSITY, 
AND 
FRANK DONALDSON, Jr., M. D., 
SOME TIME GRADUATE SCHOLAR IN THE SAME. 
JElie ‘Neto York fHetucal 
REPRINTED FROM 
for May 15, 1886. Reprinted from the New York Medical Journal. 
for May 15, 1886. 
PRELIMINARY ACCOUNT OF EXPERIMENTS 
IN REGARD TO THE CIRCULATORY AND RESPIRATORY 
CHANGES 
OBSERVED IN ANIMALS PLACED IN 
THE PNEUMATIC CABINET * 
11. N. MARTIN, F. R. S., 
PROFESSOR IN THE JOHNS HOPKINS UNIVERSITY, 
and FRANK DONALDSON, Jr., M. D., 
The great objection to the use of the pneumatic cabinet 
has been, beyond doubt, that we had no knowledge of the 
physiological effect of rarefied and compressed air applied 
under these conditions on the respiration and circulation ; 
and, indeed, I found myself so timid and embarrassed in its 
every-day use that I determined to submit no person fur- 
ther to treatment by pneumatic differentiation until I had 
got at its physiology. I was, therefore, very glad to take 
advantage of Professor Martin’s suggestion that we should 
conduct a series of experiments upon animals placed in the 
pneumatic cabinet. The results of these experiments are 
given very briefly below. A more detailed account of them, 
with illustrations showing the changes in blood-pressure, 
pulse, and respiration actually observed, will appear here- 
SOME TIME GRADUATE SCHOLAR IN THE SAME. 
* Read before the American Climatological Association, May 10, 
1886. EXPERIMENTS IN THE PNEUMATIC CABINET. 
after. Our experiments have been made on rabbits, and 
have so far had reference only to changes in arterial press- 
ure, in pulse-rate, in respiratory rhythm, and in the extent 
of respiratory movements when the air within the cabinet is 
rarefied or condensed. 
The rabbits were chloralized, and a glass tube was 
placed in the trachea. From the glass tube a rubber tube 
led to a T-piece. From one limb of the T-piece a tube led 
to a Marey’s tambour, which recorded on the kymograph 
paper the rate and extent of the breathing movements. To 
the other limb a tube was attached through which the ani- 
mal inspired and expired. In some cases this tube opened 
outside the cabinet and the animal took air into its lungs 
under the normal atmospheric pressure. In other cases the 
breathing-tube opened inside the cabinet, and the animal 
breathed rarefied or condensed air, as the case might be. 
A cannula placed in the femoral artery recorded on the 
kymograph paper the arterial pressure and pulse-rate. An- 
other manometer, placed in communication with the interior 
of the cabinet, recorded the variations of atmospheric press- 
ure within it. A fourth pen was connected with the clock, 
and recorded seconds of time on the paper. We are ena- 
bled to state our results as follows: 
I.—When the animal is breathing air from outside the 
cabinet, rarefaction of air within the cabinet causes a marked 
fall of general arterial pressure, but has no influence on the 
pulse-rate. The fall of pressure lasts a short time only (ten 
to twenty seconds), and is followed often by a temporary 
rise above the normal. 
ll.—This fall of systemic arterial pressure depends on 
two factors: greater flow of blood to the skin when the air 
around the animal is rarefied, and greater accumulation of 
blood in the lungs when they are distended. 
111.—Of these two factors, accumulation of blood in the EXPERIMENTS IN THE PNEUMATIC CABINET. 
lungs is the more effective; for, if the animal breathes air 
from the cabinet and not from outside, rarefaction of air 
within the cabinet (in this case accompanied by no special 
expansion of the thorax) has but a trivial effect in lowering 
arterial pressure. 
IY.—When the animal is breathing external air, rare- 
faction of the air within the cabinet usually has no effect 
upon the respiratory rate or the extent of individual respira- 
tory acts, unless the fall of blood-pressure is considerable. 
If it is considerable, symptoms of anaemia of the medulla 
oblongata are seen. In most cases there is more forcible 
dyspnoeic breathing; in some there are dyspnoeic convul- 
sions similar to those which occur when an animal is bled 
todeath, and due to the same cause, viz., deficient blood-flow 
to the respiratory center. 
Y.—The rapid recovery of general arterial pressure, 
while the animal is still in a rarefied atmosphere but breath- 
ing external air, is probably due to excitation of the vaso- 
motor center, which, as is well known, is excited whenever 
its blood-supply is defective. 
Yl.—The brain, inclosed in a rigid box, which is prac- 
tically unaffected by variations in atmospheric pressure, has 
its circulation more disturbed in the pneumatic cabinet than 
any other organ except the lungs. 
Yll.—Compression of the air within the cabinet, while 
the lungs are in communication with the exterior air, causes 
a considerable but transient rise of blood-pressure. This is 
probably mainly due to the forcing of blood from the cu- 
taneous vessels; but we have not yet had opportunity to 
thoroughly investigate this point. 
Ylll.—Compression of air within the cabinet, while the 
lungs are in communication with the exterior air, slows the 
pulse as the arterial pressure rises. This is probably due to 
excitation, by increased intra-cranial blood-pressure, of the 4 
EXPERIMENTS IN THE PNEUMATIC CABINET 
cardio-inhibitory center; but further experiments are neces- 
sary before this can be positively stated. 
IX.—ln certain cases, when the air within the cabinet 
is rarefied and the animal is breathing external air, the re- 
spiratory movements cease altogether for several seconds. 
As to the cause of this physiological “ apncea ” we are not 
yet ready to form an opinion. It may be due to the extra 
accumulation of air in the alveoli of the lungs, or to disten- 
sion of the lungs exciting those fibers of the pneumogastric 
which tend to check inspiration. 
Such, in brief, being the physiological effect of rarefied 
and compressed air as applied in the Ketchum cabinet, how 
should this knowledge affect the practical use of this appa- 
ratus ? It having been found that even very great rarefac- 
tion of the air in the cabinet produces but slight effect on 
the circulation, provided the animal is breathing the air 
within the cabinet, I conclude: 
1. That rarefaction of the air when the person first en- 
ters the cabinet (as directed by Mr. Ketchum), in order that 
the residual air may expand and so drive out any plugs of 
mucus in the lungs, may be done without danger to the in- 
dividual. In view of the great and sudden fall of arterial 
pressure when the animal is breathing outside air and the 
air within is rarefied, I conclude : 
2. That the air in the cabinet should never be suddenly 
rarefied, and that the motion of exhaust should invariably 
be slowly made, and the amount of rarefaction small, par- 
ticularly at the first treatments. This sudden fall of arterial 
pressure depending as it does upon an increased blood-flow 
to the skin and an accumulation of bipod in the distended 
veins and lung alveoli, I conclude : 
3. That, before deciding a person to be a proper subject 
for treatment by pneumatic differentiation, thorough exami- 
nation should be made of the heart; and that no person EXPERIMENTS IN THE PNEUMATIC CABINET. 
5 
found to have pronounced insufficiency or stenosis of the 
mitral valve or the slightest tricuspid regurgitation should, 
under any condition, he placed in the pneumatic cabinet; 
for it is plain that rarefaction of the air would be most dan- 
gerous in such cases. The fall of arterial pressure would 
seem to depend chiefly upon the accumulation of blood in 
the lungs, for, if the animal breathes air from the cabinet 
and not from outside, rarefaction of air within the cabinet 
has but a trivial effect upon arterial pressure. From this 
fact I conclude: 
4. That the liability to pulmonary hsemorrhage is very 
slight, though greater perhaps than Dr. Williams has sup- 
posed. It having been proved that compression of the air 
within the cabinet while the animal breathes external air 
causes a considerable rise in arterial pressure, and slows the 
pulse from the increase of intra-cranial blood-pressure, I 
conclude: 
5. That old persons, with possibly atheromatous arteries, 
are not, generally speaking, proper subjects for the pneu- 
matic chamber, especially where their trouble is emphysema 
or asthma, and compression of the air within the cabinet is 
made use of in order to assist expiration. 
Again, in view of the sudden and pronounced fall in 
arterial pressure following rarefaction, and of the consider- 
able though transient rise of the same following compression 
of the air in the cabinet, I conclude that the method of dif- 
ferentiation should be practiced with much care and dis- 
crimination in all cases, and that the actual movements of 
exhaust and compression should be made always very slowly 
and gently. 
Finally, the Ketchum cabinet should be in the hands of 
careful auscultators only, for in those of the inexperienced 
or careless great harm may be done. REASONS WHY 
Physicians sM4 Sterile 
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