Studies on lung volume. IV. Investigations on admixture of air in the lungs with other air

Several methods of importance for the study of the physiology and pathology of respiration and circulation require (1) that it is possible to produce full admixture of air within the lungs with other air and (2) that the exact conditions necessary for full mixture can be ascertained in a given case. This and the following paper is a short report of experiments dealing with questions.

Technique. 3 liters of oxygen (Allen-Pepys' method) or of hydrogen plus oxygen (Davy-Durig's method) are introduced in a 5 to 6 liter rubber bag. Starting either from full inspiration or full expiration the subject rebreathes uniformly and almost as deeply as possible from the bag a certain number of times. The connection between the mouth and the bag is a 35 cm. long, 2 cm. wide rubber tube and a 3-way stopcock. The frequency of respiration has always been betwen 8 and 20, usually about 10-15 per minute. During the experiments several small samples (15-20 c. c.) of air were drawn (1) from the bag, and (2) from the very last part of the expiration. In the last instance therefore, alveolar air was obtained. The samples were drawn into evacuated recipients without interrupting or interfering with the breathing. By such a procedure (Fig. 1) one can follow the changes in the composition of the air in the two most important places (bag and alveoli) of the closed system during the rebreathing experiment. In the oxygen experiments the changes in the nitrogen percentage were followed and in the hydrogen experiments the changes in the hydrogen percentage were observed.

Results. In Table I an example of oxygen experiments are given and in Table II an example of hydrogen experiments. Figs. 2 and 3 correspond to Tables I and II respectively.