Erythrocyte sedimentation rate I. Volume fraction dependence in saline solution

Abstract

We have measured volume fraction dependence of the sedimentation curve of swine erythrocytes in a physiological saline solution at 10°C, 20°C, 30°C and 40°C. The sedimentation curves were found to consist of initial constant velocity region and final plateau region at the lower temperatures of 10°C and 20°C. while modified S-shaped curves were observed at the higher temperatures of 30°C and 40°C. The volume fraction dependence of the initial slope ν of the sedimentation curve was fitted well to the following exponential type equation at all the temperatures: $$\mathit{\nu }={\mathit{\nu }}_{\mathrm{s}\mathrm{,}exp}\mathrm{(}1-\mathrm{H}\mathrm{)}exp-\mathrm{(}\mathrm{BH}+{\mathrm{CH}}^2\mathrm{)}$$ where ${\mathit{\nu }}_{\mathrm{s}\mathrm{,}exp}$ is the velocity in infinite dilution corresponding to the Stokes velocity and H is the volume fraction of erythrocytes. The volume fraction dependence of the relative velocity $\mathit{\nu }\mathrm{/}{\mathit{\nu }}_{\mathrm{s}\mathrm{,}exp}$ was in close agreement with a semi-empirical equation derived for slurrys in the field of chemical engineering at the lower temperatures. while a small deviation between the observed and calculated curves was found at the higher temperatures. The volume fraction dependence of ν at 20°C was also analyzed on a theory recently developed by Oka. The explicit functional form of the medium up-flow factor ϕ(H) and the deformability factor f in the theory were determined using the experimental data.