GAS TRANSPORT SVST1':M— KAO 



59 



dogs, with sliixfiiiii;-. An increase in the \'K„.. occurs at high levels of oxygen con- 

 sumption. Since a change in V'Eo., indicates change in tlie alveolar r\.„,. it can he 

 predicted that the arterial Pfo^ and ventilation luust he inversely related in these 

 hypothermic dogs. Figure 3 shows this prediction is true. The dotted line in figure 3 

 is the predicted result, using the ventilation equation.' The solid line in figure 3 

 represents that filled to the availahle data. hVom these results, it can further he pre- 

 dicted that respiratory acidosis must occur during hypothermia without shivering 

 and respiratory alkalosis exists during hypothermia with shivering. This prediction 

 has heen verified hy experimental results. - 



Cardiac output increases in the hypothermic dogs when shivering occurs, Init it 

 decreases in ahsence of shivering. It is interesting to note that the circulatory equiva- 

 lent for oxygen is also curvilinearly related to oxygen consumption (fig. 4), indi- 

 cating that the cardiac output is more than adequate to transport oxygen at low levels 

 of oxygen consumption hut less adeciuate at high levels of oxygen consumption. 

 The significance of this finding as well as of the regulatory process of cardiac output 

 during hypothermia is at present not explained. 



During hypothermia in dogs, ventilation fails first, followed hy the failure of the 

 heart. The regulation of the gas transport system during hypothermia is of a com- 

 plex nature because of the numerous stimuli produced during hypothermia, in addi- 

 tion to those prevailing in the normal condition. 



100 



200 



300 



Pc02 mm Hg 



Fig. 3. — The relationship between ventilation and arterial Pcoo- The dotted Hne represents 

 the predicted results. The solid line is the line fitted to the data obtained during hypothermia, 

 both with and without shivering. 



