Tomographic Analysis of the Effect of Hematocrit on the Distribution of Erythrocytes in Blood Flow in Glass Capillaries of Various Diameters

Abstract

Blood flow through the cardiovascular system is a complex phenomenon which has been analyzed by in vitro and in vivo investigations. Although in vitro experiments are not the exact representation of the in vivo conditions, still these developments have contributed significantly to the growth of this field. Some of these include the decrease of blood viscosity in capillaries with decrease of radius [1] and increase of shear rate [2], its increase with hematocrit [3] and deviation of velocity profile from that of parabolic in blood flow [4]. It has further been observed that the capillary hematocrit is less than that of reservoir hematocrit [5,6]. In these analyses the distribution of erythrocytes in capillary flow has not been well accounted. According to Taylor [7] the erythrocytes migrate towards the axis, thus forming a cell-free layer of plasma, the thickness of which decreases with increasing hematocrit. Thus leading to the assumption of two- or three-layered models for theoretical analysis of blood flow [8]. From the contributions of Segré and Silberberg for solid suspensions [9] and Goldsmith for rigid erythrocytes [10], in vertical tubes, it has been evident that the particles or cells also move away from the axis leading to the formation of their high concentration at the intermediate regions between the wall and the axis of the tube. Besides these, Dix and Scott Blair [11] have also indicated the formation of multi-laminae and have suggested that the flow through a tube should be obtained by summation rather than the conventional integration method.