Determinant of the optimal hematocrit

Abstract

In glass tubes, blood flow changes exponentially over a wide range of hematocrit ratio. Data on viscosity, as measured in glass tubes as well as that measured with the cone viscosimeter, are adequately described by an exponential equation for viscosity. However, in biological systems, blood flow appears to change linearly with changes in the hematocrit ratio over the range of hematocrit ratio of from 20 to 60, and based on this linearity, another equation for blood viscosity may be derived. Since it is necessary to determine the O2 transport equation in terms of the hematocrit ratio in order to evaluate the con-ditions for optimum transport of O2, both viscosity formulas are evaluated and shown to have a relationship. From the O2 transport equation, by differentiation, it is determined that the conditions for optimum transport of O2 occur when the hematocrit ratio is inversely equal to the decay constant of the exponential equation for viscosity, and this factor appears to be most affected by changes in vessel diameter.