144 



RESPIRATION 



irregular distribution of fresh air to the alveoli, even though the 

 average distribution, as shown by the volume of air breathed, is 

 greatly increased. Hence the mixed arterial blood will be deficient 

 in oxygen, and grave anoxaemia may develop. Here, also, the 

 effects of oxygen administration will decide the diagnosis of the 

 condition. 



We found that the recumbent position greatly favors the de- 

 velopment of periodic breathing, and therefore of anoxaemia. 

 We also found that when a normal person assumes the recumbent 

 position, the usual result is that the breathing becomes slower and 

 deeper. In my own case, for instance, the frequency diminishes 

 from about 15 in the sitting or upright position to 7 or 8, while 

 the depth correspondingly increases, so as to keep the alveolar 

 CO2 pressure nearly the same (see Figure 47). The cause of this 

 phenomenon is not altogether clear, but is probably the increased 

 resistance thrown on the diaphragm in the recumbent position, 

 as the weight of the liver and other abdominal organs assists the 

 descent of the diaphragm in the upright position. Rontgen ray 



liiailiMiijiiiiiiii 



■iMilliMMilBtWil^ 



Figure 48. 

 Subject J. G. P. I. Breathing restricted by concertina — lying. 2. Breathing 

 restricted to same extent — sitting. 3. Breathing further restricted — sitting. Oxy- 

 gen given. Curves read left to right. Inspiration upstroke. Time marker = 

 seconds. 



photographs which we took to show the position of the diaphragm 

 favored this explanation ; and, assuming it to be correct, the effect 

 of the recumbent position may well be similar to the slowing 

 effect produced by resistance as shown in Chapter III. Whatever 



