Abstract
As a contribution to solving the problem of pH disequilibrium in arterial blood, the results of two modes of gas exchange in the lung have been calculated using an equilibrium state model of the blood. In both cases the HCO3 /Cl exchange was assumed to occur after the gas exchange in the pulmonary capillaries. When the gas exchange was assumed to be dependent on intra-erythrocytic carbonic anhydrase. the plasma pH in the arterial blood increased. Whe plasma and erythrocytes were assumed to equilibrate separately with the alveolar gas due to presence of extra-erythrocytic carbonic anhydrase, plasma pH in the arterial blood decreased. In each case there was a slight increase inpCO2 after the blood had left the pulmonary capillaries.