Inert gas elimination from lungs with stratified inhomogeneity: theory

The effects of diffusion limitation in alveolar space (stratified inhomogeneity) on steady state inert gas elimination by the lung from blood are studied in theory. The lung models used for the calculations are characterized by a diffusion barrier in the alveolar space, which is quantified by a diffusive conductance (diffusing capacity), D'. In both homogeneous and inhomogeneous lung models (with log-normal distribution of VA, Q and D') increasing stratified inhomogeneity (decreasing D') is shown to diminish inert gas elimination. The effect, which depends on the solubility of the gases, is similar to the effect of alveolar dead space ventilation.