Simulations of steady quaternary gas diffusion between alveolar and blood compartments.

Fick's law is usually employed to analyze diffusion phenomena in the lung. However, this law is only strictly applicable to two component mixtures. When there are more than two gases in the mixture. Stefan's equations are more appropriate. Under physiological conditions during respiration, at least three gases are involved (O2, CO2, N2). Furthermore, helium is often added in studies on the effect of density on pulmonary mixing. Features of quaternary gas diffusion (O2, CO2, N2, He), and computer simulations of physiologically relevant conditions are presented. The results of the simulations were found to be in agreement with results from studies on normal and disease lungs.