154 RESPIRATION 



livery of 2 liters a minute a 40- foot cylinder would last nearly 

 ten hours. 



The effects of continuous oxygen inhalation with this apparatus 

 on the arterial blood in pneumonia and bronchitis have quite 

 recently been investigated by Meakins. 13 He found that with 2 

 liters a minute the percentage saturation of the haemoglobin in a 

 pneumonia case with almost complete consolidation of one lung 

 rose from 82 per cent to 91 per cent, but went back on stopping the 

 oxygen to 84 per cent, slight cyanosis returning also. On then 

 giving 3 liters a minute, the saturation rose to 97 per cent, which 

 is 2 per cent above the normal value for healthy persons. In a 

 bronchitis case with slight cyanosis and orthopnoea, the satura- 

 tion rose from 88.6 to 97.0 per cent on giving 2 liters a minute, 

 and the cyanosis and orthopnoea disappeared. In a normal man 

 the saturation rose from 95.6 to 98.1 on giving 2 liters a minute. 



The plan of treating patients in an air-tight chamber contain- 

 ing a high percentage of oxygen was introduced towards the end 

 of the war at Cambridge under Barcroft's direction; 14 and a 

 similar chamber was erected at Stoke-on-Trent. Favorable results 

 were obtained in chronic cases of gas poisoning, as might be 

 anticipated in view of the disturbed nervous control of breathing, 

 already described in Chapters III and VII. It now seems evident 

 that the administration of air enriched with oxygen is likely to 

 be successfully introduced in the treatment of various illnesses 

 in which arterial anoxaemia is present. 



During considerable muscular exertion the rate at which oxy- 

 gen has to penetrate from the alveoli into the blood is enormously 

 increased. Hence it is during muscular work that we should ex- 

 pect to find any signs of anoxaemia in healthy persons breath- 

 ing normal air at normal atmospheric pressure. That a certain 

 amount of anoxaemia is commonly produced can be shown 

 indirectly in various ways. In the first place the alveolar CO 2 

 pressure, particularly in some persons, does not rise during mus- 

 cular exertion in the proportion that would be expected if the 

 increased breathing were simply due to the increased production 

 of CO 2 and consequent rise in the alveolar CO 2 pressure. Thus in 

 the experiments of Priestley and myself, my own alveolar CO 2 

 pressure rose only by .13 per cent, in place of an expected rise of 



11 Meakins, Brit. Med. Journ., March 5, 1920. A number of further cases have 

 still more recently been recorded by Meakins, Journ. of Pathol. and, Bacter., XXIV, 

 p. 79, 1921. 



14 Barcroft, Dufton, and Hunt, Quarterly Journ. of Medicine, XIII, p. 179, 

 1920. 



