Oxygen Consumption. 1?5 



Oxygen Consumption. 



While the determination of the carbon dioxide excreted by man presents no 

 especially difficult problems other than the acurate analysis of the air, and the 

 measure of the total air expired, the case is very different when an attempt is 

 made to determine the total amount of oxygen consumed by man in any given 

 experimental period. 



METHODS FOR DETERMINING THE OXYGEN CONSUMPTION. 



Indirect Method. 



Two methods have been used to obtain this value ; one, the so-called indirect, 

 and the other the direct method. By the indirect method, careful records of the 

 changes in body-weight, weights of the total food and drink ingested and feces 

 and urine collected are made, and the total amounts of carbon dioxide excreted 

 and water vaporized are carefully determined. From these data a simple cal- 

 culation serves to show the oxygen consumption. The method was first brought 

 into prominence by Pettenkofer and Voit and has since been used with con- 

 siderable success by the Russian investigators, Sadovyen and Likhatscheff. 



The errors incidental to measuring each of the numerous factors which must 

 enter into the calculation of the oxygen by the indirect method are so great 

 that without the most careful technique the values obtained can only be con- 

 sidered as rough approximations. The error of Pettenkofer and Voit in attrib- 

 uting what subsequently proved to be a change in weight of the bedding of 

 the subject to a storage of oxygen in the body accentuates the difficulties attend- 

 ing the use of the indirect method for determining oxygen. 



Direct Method. 

 The second method involves the direct determination of oxygen used by the 

 subject. This may be done in two ways, first, by using a special nosepiece or 

 mouthpiece and carefully analyzing the inspired and expired air, or by measur- 

 ing the deficiency in oxygen in a large mass of air in which the subject remains 

 seated at rest or at work. The first is the basis of the methods of Speck, 1 

 Zuntz-Geppert, 2 Hanriot and Eichet, 3 and Chauveau and Tissot, 4 all of whom 

 used a special mouthpiece or nosepiece. Instead of using such an apparatus, 

 Jaquet 5 places his subjects in a large chamber, but by means of the most deli- 

 cate gas-analysis apparatus analyzes the incoming and outgoing air, and notes 

 the difference in the percentage of oxygen. Grafe 8 has employed Jaquet's 

 method, but the subject wears a helmet, instead of being inclosed in a large 

 respiration chamber. The principle involved in the determination of the 

 oxygen remains, however, the same. 



1 Speck, Physiologie des Menschlichen Athmens, Leipzig, 1892. 



2 Zuntz and Geppert, see detailed description by Magnus-Levy, Archiv f. d. ges. 

 Physiol., 1894, 55, p. 1. 



3 Hanriot and Richet, Comptes rendus, 1887, 104. p. 435. 



4 Chauveau and Tissot, Comptes rendus, 1899, 129, p. 249. 



5 Jaquet, Verhandl. Naturf. Gesellsch. Basel, 1904, 15, p. 252. 



6 Grafe, Deutsch. Archiv f. klin. Med., 1909, 95, p. 529. 



