404 RELATION OF RESPIRATION TO OTHER PROCESSES [CH. XXVII. 



two things will happen: (1) The blood will take up in simple 

 physical solution about seven times as much oxygen as when exposed 

 to air, and this may be sufficient to carry on life ; (2) as regards the 

 saturation of the haemoglobin, the balance is now in favour of the 

 oxygen, weak as its affinity for haemoglobin is, and the carbon 

 monoxide gradually works its way out of the body. 



Cheyne-Stokes Respiration. 



This is a condition in which the breathing waxes and wanes to a 

 remarkable degree (fig. 310). It is an exaggeration of the type of 

 respiration which is often seen during sleep in perfectly healthy 

 people. The condition was first observed by the two Dublin 

 physicians whose names it bears. It may be induced in normal 

 persons if they make themselves pant violently for 1-2 minutes. 

 If then respiration is allowed to take its own course, there will first 



FIG. 310. Stethograph tracing of Cheyne-Stokes respiration in a man. The time is 

 marked in seconds. (Pembrey and Allen.) 



be a pause (apnoea), then Cheyne-Stokes respiration will be set up. 

 The groups will become less and less distinct, and respiration will 

 ultimately become normal. The explanation of this phenomenon 

 is as follows : 



The panting causes an undue amount of carbonic acid to leave 

 the body, with the result that the carbonic acid tension in the blood 

 and in the tissues sinks to perhaps a quarter or a third of its usual 

 value. Already we have seen that carbonic acid is an active stimulant 

 to the respiratory centre, and its removal causes respiration to cease, 

 hence the apnoea. But during the apnoeic period the arterial blood 

 becomes less and less oxygenated, with the result that lactic acid 

 formation (a constant result of oxygen want) takes place in the tissues ; 

 the lactic acid, like carbonic acid, stimulates the respiratory centre, 

 which remains active till the advent of oxygen causes oxidation of 

 the acid; there is then another pause, and so on. Cheyne-Stokes 

 breathing is dependent, then, on oxygen want. 



