Exchange of carbon dioxide in the pregnant rhesus monkey: multicompartmental analysis of carbon dioxide kinetics.

The exchange of carbon dioxide in the pregnant rhesus monkey has been studied quantitatively using sodium bicarbonate-(14)C and applying the model of a system of seven compartments. The transfer rates among the various compartments, compartment sizes, and the rate of production of carbon dioxide by fetus and mother were determined with a computer programmed to fit the theoretical model to the data by adjusting the parameter values of the model until a "best fit" was obtained. It was confirmed that the exchange of carbon dioxide between fetal and maternal blood across the placenta is rapid, that between fetal blood and amniotic fluid is slow, and that there is no appreciable exchange between maternal blood and amniotic fluid. The mean net production of CO(2) by fetus was 0.476 +/-0.0402 mmoles/kg.min, and that by mother was 0.373 +/-0.0279 mmoles/kg.min.