Modeling of oxygen transport in blood-perfluorocarbon emulsion mixtures - Part 1: Oxygen uptake in tubular vessels

Perfluorocarbon (PFC) emulsions are usually used as mixtures with blood to enhance its capacity for oxygen, because stand alone PFC emulsions cannot perform the normal regulatory functions of blood. These mixtures have been found to be very effective in increasing the tissue oxygen tension, especially at high oxygen partial pressures, and many experimental observations exist in the literature in support of this fact. The explanations for these observations are still speculative and unquantified, however. In this work, models have been developed to describe oxygen transport in uniform and nonuniform mixtures of blood and PFCs. For the latter case, the extreme situation of central migration of erythrocytes is considered, wherein the erythrocytes occupy the central core region of the vessel surrounded by a plasma annulus. The predictions of the proposed models have been examined using a fixed wall oxygen tension, and the oxygen transport characteristics of mixtures have been presented with reference to blood alone. It was found that at high oxygen tensions the addition of PFCs significantly increases the oxygen wall flux into the tube. This increased flux, coupled with effects of competing oxygen sinks (erythrocytes and PFC droplets), leads to an anomalous increase in the average oxygen tension for short distances from the tube entrance. It has been shown that a near wall excess of PFC droplets is not necessary to cause this increase, as mentioned by Vaslef and Coldstick. For longer distances, however, the addition of PFCs leads to a decrease in the average oxygen tension.