Distribution of respiratory gases in a closed breathing circuit. I. In normal subjects

In the preceding paper (1) we have shown that in a small closed breathing circuit of steadily di-minishing volume (due to absorption of oxygen and CO2), any inert gas in the system will not be evenly distributed, when mixture of all respira-tory gases reaches equilibrium. Due to the fact that the lungs are a reservoir containing air from many earlier breaths with correspondingly lower concentrations of nitrogen (or other foreign inert gas), the pulmonary air at any moment contains a lower nitrogen concentration than the spi-rometer. It was found that with quiet breathing by nor-mal subjects, tidal air was sufficiently well dis-tributed through pulmonary spaces, so that b