RESPIRATION AND ACIDOSIS 311 



symptoms of acidosis. Furthermore one of the laboratory procedures 

 for establishing the extent of the acidosis is the estimation of the 

 amount of the reduction in the carbon dioxide concentration of the 

 alveolar air which accompanies the hyperpnea. This indirect index 

 of acidosis may be determined in a few minutes. (For methods see 

 page 319.) 



A rather more satisfactory method for the study of acidosis is the 

 direct determination of the " buffer , value" or " alkali reserve" of the 

 blood. This consists in saturating a given volume of blood plasma with 

 carbon dioxide and in measuring the volume of carbon dioxide given off 

 from this blood plasma when acid is added. A decrease in the carbon 

 dioxide indicates a depletion of the bicarbonate of the blood and hence 

 a lowering of the blood's "buffer value" or " alkali reserve." 



The alkali reserve may also be determined by administering sodium 

 bicarbonate. Normal urine is acid in reaction. When bicarbonate is 

 given to a normal person in small amount the reaction of the urine 

 becomes alkaline. In acidosis, however, an increased amount of car- 

 bonate is necessary to produce a change in the urinary reaction. The 

 amount of alkali needed to cause the urine to become alkaline is an 

 index of what is commonly called the "tolerance to alkalies." 



Because of the fact that it varies so little from the normal under 

 any circumstances, the determination of the hydrogen ion concentration 

 of the blood is of less value in the diagnosis of acidosis than either the 

 determination of the "alkali reserve" of. the blood, the "carbon dioxide 

 tension" of the alveolar air or the "alkali tolerance" of the patient. 



METHODS 



i. Alkali Reserve. Direct Method, (a) Carbon dioxide ca- 

 pacity of the plasma. (Van Slyke and Cullen. 1 ) 



Principle. The plasma from oxalated blood is shaken in a 

 separatory funnel filled with an air mixture whose carbon dioxide 

 tension approximates that of normal arterial blood, by which treatment 

 it combines with as much carbon dioxide as it is able to hold under 

 normal tension. A known quantity of the saturated plasma is then 

 acidified within a suitable pipette, and its carbon dioxide is liberated 

 by the production of a partial vacuum. The liberated carbon dioxide 

 is then placed under atmospheric pressure, its volume carefully 

 measured, and the volume corresponding to 100 c.c. of plasma 

 calculated. 



Apparatus. The apparatus 2 used in the estimation of the carbon 



1 Van Slyke & Cullen: Jour. Biol. Chem., 30, 289, 1917; Van Slyke: Jour. Biol. Chem. t 

 30, 347, 1917- 



2 The apparatus is manufactured by the Emil Greiner Company, 55 Fulton Street, 

 New York. 



