Correlation between shear dependent blood viscosity, electrical resistance and calculated width of the marginal layer in blood perfused capillary tubes.

Viscosity and shear dependent changes in electrical resistance (delta R) were measured simultaneously in blood perfused capillaries (I.D. = 0.58 mm, 1 = 300 mm, TW = 0.04 to 0.5 Pa). It appears that delta R is primarily caused by the development of a low resistant cell free marginal layer. Red cell aggregation strongly supports the development of delta R, while in non-aggregating blood the shear induced change in conductivity is rather small. Theoretical and experimental data become closely correlated if the calculated width of the marginal layer, being 1 to 5% of the capillary radius, is inserted into a modified form of Poiseuille's law. It is concluded that under the conditions of plug flow the non-Newtonian flow behavior of EDTA blood almost exclusively depends upon the width of the marginal layer, being a function of shear stress and hematocrit.