THE GAS TRANSPORT SYSTEM IN HYPOTHERMIA 



F. F. KAO 



One of the must important aspects of the physiology of liyputhermia is the change 

 in the gas transport system which normally is called npon to supply oxygen con- 

 tinuously to and remove carbon dioxide from the metaliolizing tissues. During the 

 hypothermic state, the body temperature as well as the oxygen consumption of the 

 organism increases during shivering- but decreases when shivering is aboHshed. The 

 adequacy of the adjustment of the gas transport system during hypothermia can be 

 evaluated by correlating ventilation and cardiac output with oxygen consumption. 

 In dogs, as in man, under normal resting condition, ventilation and cardiac output 

 are precisely regulated to meet metabolic demands, as evidenced by the constancy of 

 the ventilatory equivalent for oxygen (VEo^, defined as ventilation in liters per 

 minute BTPS divided by oxygen consumption in 100 ml. per minute STPD) and 

 the circulation equivalent for oxygen (CEo^. defined as cardiac out]nit in liters per 

 minute divided by oxygen consumption in 100 ml. per minute STPDj. 



During hypothermia, both VE,,^ and CE„^ change as a function of oxygen con- 

 sumption. The relationship between ventilation and oxygen consumption in 1 2 hypo- 

 thermic dogs (without shivering) is shown in figure 1, in which ventilation is curvi- 

 linearly related to oxygen consumption. The concavity of the curve faces the vertical 

 axis, indicating a decrease in the ventilatory equivalent for oxygen at low levels of 

 oxygen consumption caused by a decrease in body temperature. Figure 2 reveals 

 a similar relationship between ventilation and oxygen consumption in hypothermic 



02 CONSUMPTION mlVmin STPD 



l*"iG. 1. — Tlie rclatiunship between ventila- 

 tion and oxygen consumption during hypo- 

 thermia in dogs (without shivering). For 

 explanation see text. 



m 10 

 = 8 



J* 



in. 



„ iOO 200 300 



02 CONSUMPTION ml./mln.STPD 



Fig. 2. — The relationship betw'cen ventila- 

 tion and oxygen consumption during hypo- 

 tliermia in dogs with shivering. .A.s shown 

 by tlic curvilinear relationship between these 

 variables, the ventilatory equivalent for oxy- 

 gen increases at high oxygen consumi)tion 

 caused iiv sliivering during liyi)(illierniia. 



58 



