72 DONALD D. VAN SLYKE 



hour or less included the carpopedal spasm, Chvostek sign, Trousseau sign, 

 Erb's sign, and in one instance even a tetanic convulsion. The physio- 

 logical effects of abnormally high blood pll appear to be similar, whether 

 the increase is caused by increase in the numerator or fall in the de- 

 nominator of the TBHCO 3 : H 2 CO 3 ratio. 



{Alkali excess, or. Here the pH is normal, the 

 4. Compensated 4 ^^ 



[C0 2 excess 



BHCOg is high, but is balanced by a proportionally high H 2 CO 3 . The 

 state of the acid-base balance of the blood is the same, whether the original 

 disturbance was alkali retention (Area 1) or CO 2 retention (Area 7-8). 

 Hence the condition may be described as either compensated alkali excess 

 or compensated CO 2 excess, according to whether the primary disturbance 

 is due to alkali excess or CO 2 excess. 



The condition has been observed to arise from both causes. Alkali 

 excess is most commonly caused by therapeutic administration of sodium 

 bicarbonate. If, as is usually the case following oral administration, the 

 absorption is not rapid, CO 2 may be retained sufficiently to balance the 

 increased BHCO 3 , and the condition moves from that indicated by Area 

 5 to that of Area 4. If absorption is too rapid for simultaneous com- 

 pensation by CO 2 retention, the condition changes to that indicated by 

 Area 1. 



Compensated C0 2 excess is, it appears, the state observed by Scott(&) 

 (1920) in emphysema. The retarded gas exchange presumably leads to a 

 state of chronically increased CO 2 tension in the blood, and the body 

 raises the blood BHCO 3 high enough to balance the H 2 CO 3 and maintain 

 a normal reaction. 



It appears that this condition, primarily due to CO 2 retention, may 

 be differentiated from that in which alkali retention is the primary cause, 

 by the fact that a primarily respiratory CO 2 retention is associated with 

 cyanosis, either permanent or caused by slight exertion. Diffusion of 

 oxygen through membranes is so much slower than that of CO 2 (Krogh (a), 

 1919) that any hindrance retarding the alveolar gas exchange sufficiently 

 to affect CO 2 excretion would presumably be accompanied by still more 

 hindrance to oxygenation of the blood. This presumption is further sup- 

 ported by the work of Krogh and Krogh (1910) who found in rabbits 

 that while CO 2 tension in arterial blood and alveolar air are equal, oxygen 

 tension is lower, even when respiration is unhindered. 



Area 5. Normal Acid-Base Balance. The normal area represents the 

 balance that is practically always found in the resting individual in health 

 and at ordinary altitudes. It is possible that when the normal pH limits 

 of the plasma are more accurately defined, they may fall within a nar- 

 rower range. Parsons is inclined to place the normal range at more nearly 

 between pH 7.30 and 7.40 than the doubly wide range of 7.30-7.50 which 



