Importance of diffusion and chemical reaction rates in O2 uptake in the lung

Abstract

The Bohr integration procedure for the approximate solution of the blood O₂ tension along the pulmonary capillary from known values of alveolar, mixed venous, and end capillary O₂ tensions and the O₂ hemoglobin dissociation curve assumes, among other things, that the dissolved O₂ in the blood is always in equilibrium with the hemoglobin, in other words that the exchange of O₂ between the red cells and the plasma is instantaneous. Previous work (J. Appl. Physiol. 16: 511, 1961) has shown that, on the contrary, the experimentally measured rates of O₂ uptake of the red cells are slow enough to limit the uptake of this gas in the alveolar capillaries. Therefore we have developed a method analogous to the Bohr integration for obtaining an approximate solution for the O₂ tension of the plasma and of the red cells along the pulmonary capillary where Dl is a function of O₂Hb saturation. Examples are given for a normal individual and an individual with severe anemia both breathing air and 14% O₂. Submitted on July 18, 1961