Ternary diffusion and effective diffusion coefficients in alveolar spaces.

An experimentally verified mathematical model of non-equimolar ternary gas diffusion is applied to simulate the conditions existing in the alveolar spaces. When a fictitious gas film is erected a certain distance away from the alveolar membrane, and when the compositions at the two boundaries of the film are, respectively, the alveolar gas composition and a proportional mixture of inspired gas with the alveolar gas, the resulting fluxes of O2 and CO2 are essentially linearly related to their respective partial pressure gradients. From the slopes of these flux lines, effective diffusion coefficients are obtained. Ramifications of the effective diffusion coefficients approach are discussed.