Effects of changes in hematocrit on red cell flows at capillary bifurcations.

A theoretical study was developed to evaluate effects of changes in hematocrit on red cell flow partitioning at narrow capillary bifurcations of unequal diameters. Non-Newtonian blood viscosity and non-linear relationships between blood and red cell flows at capillary bifurcations are taken into account. Results suggest that heterogeneity of diameters is a determinant of red cell and blood flows heterogeneity not only due to its influence on geometrical resistance but also as a result of its influence on capillary viscosity. Lowering hematocrit reduces differences in viscosities between the two branches. Then more homogeneous red cell flows are induced. Considering three possible relationships for entering blood flow vs. entering discharge hematocrit, the present study stresses that changes in red cell flow for individual capillaries are not parallel to changes in entering red cell flow. Therefore discussion on effects of hemodilution have to take into account not only red cell flow or oxygen arriving to an organ, but also changes in distribution of capillary flows induced by rheological changes due to lower hematocrit.