Applied aspects of theoretical analysis of pulmonary gas exchange.

This paper gives a summary of the theoretical analysis of the processes of gas exchange in the lungs. It brings out the effect of changes in the rate of equilibration of gases across the membrane due to a variety of factors. It brings out that the length of the capillary over which complete equilibration occurs is infinitesimally small, hence a diffusion defect is seldom a cause of hypoxaemia in disease unless the character of membrane changes like in interstitial fibrosis or pneumoconiosis. The increase in length of capillary for complete equilibrium is significant in hypoxia of high altitude and left ventricular failure causing dilatation of pulmonary capillaries.