Prediction of oxygen transport rates in blood flowing in large capillaries.

A mathematical model has been developed to predict oxygen transport to and from blood flowing in tubes of the diameter of arterioles and larger (approximately 20 microns and larger). The resistance to oxygen transport in red cell suspensions is much higher than that of a comparable homogeneous hemoglobin solution. The increased resistance is associated with encapsulation of the hemoglobin in the red cells. Yet, somewhat paradoxically, for large capillaries relatively little resistance is within or in the immediate vicinity of the red cells. The great majority of the resistance is shown to be distributed in the plasma. Predictions of oxygen uptake and release are shown to be in excellent agreement with results of measurements taken on red cell suspensions flowing in capillaries of 27- and 100-microns diameter. The model seems to be the first for oxygen transport in flowing blood that is validated by detailed comparison with experimental results. It is a predictive model in that all parameters in the model are determined from independent measurements or from the literature.