A model for blood-tissue oxygen exchange and tracer water production

An axially distributed three-region multibarrier model was formulated for oxygen transport and metabolism in a generic capillary-tissue system. The model considers blood flow through arterial, capillary, and venular vessels, countercurrent solute exchange between arteriole and venule, differences in erythrocyte and plasma velocities, and differences in effective volumes of distribution for water versus oxygen. The formulation therefore incorporates higher velocity for RBCs compared to plasma. Additionally, because of the high affinity of O/sub 2/ to hemoglobin, the relative volume of distribution in blood compared to tissue is much higher for O/sub 2/ than for H/sub 2/O and the O/sub 2/ transit time is much less than that for H/sub 2/O. It was found that under conditions of high-permeability surface area, there are dramatic changes in the profiles of both O/sub 2/ and H/sub 2/O outflow curves with changes in O/sub 2/ consumption rates. The implications of these observations with respect to oxygen delivery to hypoxic tissues are discussed.<
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