Changes of concentration of CO2 and O2 through rubber bladders were determined by a) exposing the bladders to atmospheric air, b) putting them into polythene bags and inflating the bags by 1) normal expired air and 2) by the same gas mixture as inside the bladders. Two different gas mixtures (of similar percentage composition to that of expired air samples obtained during light and moderate exercise) were used. The rate of diffusion was found to depend on the partial pressure gradient across the rubber wall and the type of gas. The higher the partial pressure gradient, the more rapid was the diffusion, and CO2 diffused at a higher rate than O2. Such a simple procedure as putting the bladders into polythene bags and inflating the bags by the operator's own expired air was found to reduce the change of concentration considerably. A correction can be utilized to obtain a more accurate gaseous percentage composition if there is a delay between the experiment and the gas analysis.
carbon dioxide; oxygen; diffusion of gases; indirect calorimetry
Submitted on October 17, 1963
- Copyright © 1964 the American Physiological Society