PREDICTION OF MICROCIRCULATORY OXYGEN-TRANSPORT BY ERYTHROCYTE HEMOGLOBIN SOLUTION MIXTURES/

A mathematical model has been developed to predict oxygen transport by erythrocyte/acellular hemoglobin solution mixtures flowing in arterio lar-sized vessels (20 to 100 mu m diameter). The model includes erythr ocyte and extracellular hemoglobin solution phases, radial hematocrit and velocity gradients, axial convection, and radial diffusion of both oxygen and oxyhemoglobin. Model simulations were compared with experi mental data from an in vitro capillary model where all of the geometri c, physical, and transport parameters are known accurately. A new appr oach to shear augmentation of transport in 25-mu m-diameter conduits w as developed. Comparison of theory with experiment suggests that shear augmentation in this flow regime is primarily an extracellular phenom enon produced by cell-cell interactions. Negligible shear augmentation was seen in erythrocyte suspensions in plasma due to the relatively l ow solubility of oxygen in the plasma phase. Good agreement was found between the theoretical simulations and experimental data for release experiments even neglecting shear augmentation. However, treatment of shear augmentation significantly improved agreement between theoretica l simulations and experimental data for oxygen uptake. The model was u sed to determine the effects on oxygen transport of varying extracellu lar hemoglobin concentration and extracellular hemoglobin oxygen bindi ng characteristics. It is known that hemoglobin solutions transport ox ygen more efficiently than erythrocyte suspensions of the same overall hemoglobin content. Model simulations show that erythrocyte/hemoglobi n solution mixtures with 30% extracellular hemoglobin transport oxygen with virtually the same efficiency as pure hemoglobin solutions of th e same overall hemoglobin content. Additional simulations predict that erythrocyte/hemoglobin solution mixtures transport oxygen more effici ently than Rbc suspensions, even if the extracellular hemoglobin has a high oxygen affinity. (C) 1998 Academic Press.