SURGICAL SHOCK 27 



After several voluntary deep breaths, there is a 

 quiescent interval, called apncea, due to the reduction 

 of the carbon dioxide to such a low figure that it is 

 some time before it reaches an amount sufficient to 

 stir the centre into activity again. 



It will be noted that it is not lack of oxygen that 

 excites the respiratory centre, but the rise of the CO.^ 

 above a certain percentage. This has been shown 

 not only by blood-gas analyses of the arterial and 

 venous blood, but also and more especially by an 

 estimation of the carbon dioxide in the air contained 

 in the alveoli of the lungs. This percentage is a 

 constant for the individual. In the open air or in a 

 crowded room the ventilation by the lungs is so 

 regulated as to maintain this constant. It does not 

 vary in the alveoli, because it varies only within the 

 narrowest limits in the blood. The amount of 

 oxygen, on the other hand, is by no means constant. 



Now, so far, there is no apparent application to 

 surgical shock. But Henderson's thesis is that, not 

 only does lack of carbon dioxide induce apncea, that 

 is, cessation of the activity of the respiratory centre, 

 but it also reduces other important functions, so that 

 the heart beats more quickly and the blood-pressure 

 falls. This reduction of the COj is called acapnia, 

 and the suggestion is that acapnia is the prime cause 

 of shock [a = lack of ; capnos = smoke). 



According to Henderson, the deep and rapid 

 breathing which, as we all know, is induced by pain, 

 excitement, or exposure and handhng of the intestines, 

 reduces the CO.^ in the blood to a very low figure, 

 whilst the oxygen, of course, is increased. This is 



