RESPIRATION 15 1 



samples of arterial blood drawn usually from the radial artery by 

 means of a syringe. In normal persons he found an average of 

 95 per cent saturation of the haemoglobin with oxygen ; and this 

 is about what might be expected in view of what has been said 

 above. In cases of pneumonia the saturation varied from 95 to 

 42 per cent; and as a rule the cases where the saturation was 

 below ^6 per cent ended fatally. Cardiac cases were soon after- 

 wards investigated by Harrop/^ who found that in many of them 

 there was imperfect saturation of the arterial blood. This was 

 almost certainly due, frequently, to partial failure of the respira- 

 tory center and consequent shallow breathing. 



The significance of these analyses will be evident from what 

 has been said in the previous and present chapters ; and the danger 

 to a patient of permitting any serious arterial anoxaemia to con- 

 tinue when it can be prevented is, I hope, already evident. 



As anoxaemia is such a common and often dangerous condition, 

 and can frequently be combated by the addition of oxygen to the 

 inspired air, it will be rfrT^tee'to" refer liere to clinical methods 

 of administering oxygen. In the first place it is necessary to have 

 clear ideas as to the objects aimed at, in administering oxygen. If 

 the oxygen is only given to enable a patient to surmount some quite 

 temporary crisis due to anoxaemia — produced, it may be, by one 

 of the sudden angina-like attacks of reflex restriction of breath- 

 ing referred above — a very simple method of administration will 

 suffice. A small cylinder of oxygen furnished with an india-rubber 

 tube by means of which a stream of oxygen may be directed into 

 the patient's open mouth will suffice; and such an arrangement 

 would probably often be useful in certain cases, as the oxygen 

 could be given promptly by a competent nurse at any time. 



In the great majority of cases, however, the cause of the an- 

 oxaemia is one which may last for a considerable time, so that 

 the administration of oxygen, in order to be useful, must be 

 continued. In this connection it should be clearly realized that 

 the object of the oxygen administration is not simply palliative, 

 but curative. By preventing the anoxaemia we not only avert 

 temporarily a cause of danger or damage to the patient ; but give 

 the body an interval for recovery from the original cause, what- 

 ever it may be, of the anoxaemia, or for adaptation. We also break 

 a vicious circle : for if the anoxaemia is allowed to continue, it 

 will itself make the patient worse, or tend to prevent the recovery 

 which would otherwise naturally occur. We are not dealing with 



" Harrop> Journ. of Exper. Med., XXX, p. 241, 19 19. 



