22 



SCIENCE PROGRESS 



When it is remembered that as a general rule the more 

 shallow the respirations the more rapid they become, the 

 rise of concentration in alveolar air in the ioo c.c. respirations 

 would be relatively still more rapid than the table indicates. 

 For instance, if eight of the shallow respirations corresponded 

 in point of time to six of the deep, then a percentage of 1*65 

 in alveolar air in the case of the deep respirations would 

 occur after the same period of time as a percentage of 2*17 

 in alveolar air in the case of the shallow respirations. 



Considerations such as these abundantly prove the need 

 of extreme caution in administering a higher concentration of 

 chloroform when the breathing becomes more shallow. More 

 especially is caution necessary since it so frequently happens 

 that the respirations become more shallow because the patient 

 has already received an overdose of chloroform. It seems to the 

 writer that the only legitimate alteration to make on the 

 respirations becoming shallower is a reduction and not an 

 increase of concentration administered. 



So far we have regarded the supplemental and residual air 

 as constant in amount. Any variation in their bulk, however, 

 will alter the rate of increase of alveolar concentration. The 

 following table illustrates this fact. The data on which it is 

 constructed are given below : 



(1) Percentage of anaesthetic in alveolar air . 1*3 



(2) Percentage of anaesthetic in inspired air . 2*0 



(3) Depth of respirations 250 c.c. 



After 1st respiration 

 „ 2nd „ 



» 3rd 



Supplemental + 



Residual Air. 



1,000 c.c. 



Alveolar per cent. 

 I -44 



1 '64 



Supplemental + 



Residual Air. 



2,000 c.c. 



Alveolar per cent. 

 1-38 



1 "45 

 1-51 



Supplemental + 



Residual Air. 



3,000 c.c. 



Alveolar per cent. 



i'35 

 1 '40 



i"4S 



It is thus apparent that the smaller the proportion between the 

 tidal air and the sum of the supplemental and the residual air, 

 the slower is the rise in the alveolar concentration. Pulmonary 

 emphysema supplies an excellent example of an increase in 

 supplemental and residual air. One would, therefore, expect 

 that an emphysematous patient would be difficult to anaesthetise, 



