A method of analysis of the pulmonary gas exchange system.

This method of system analysis is based on O2 and CO2 concentration curves obtained simultaneously from expired air during constant flow expiration. First, theoretical equations for alveolar O2 and CO2 curves were derived by using a simple gas exchange model. By substituting them with the measured data on alveolar gas concentrations and volume, such parameters as O2 uptake VO2, pulmonary blood flow Q and venous PCO2 were estimated. Expired air was continuously analyzed by means of a glow discharge gas analyzer and the alveolar gas volume was measured immediately after the gas analysis using a body plethysmograph. The estimated Q value showed a dispersion of about 14% average standard deviation in each subject, but other parameters showed no large variation. The average Q values of several measurements, however, corresponded with those obtained by an acetylene inhalation method. The VO2 also corresponded well with that measured by spirometry. This coinciding data seemed to reveal that the model was reasonable for the analysis. CO2 output, by virtue of the Haldane effect, was examined through the analyses in both normoxia and hypoxia in 9 normal subjects. No significant effect was observed.