Comparison of Viscometric Behaviour of Suspensions of Polystyrene Latex and Human Blood Cells

Abstract

THE viscosity of blood is a complex physical property determined by many factors. These factors include at least: (a) the physical characteristics of the blood cells (size, shape, deformability, etc.); (b) the concentration of the blood cells; (c) the composition of the plasma (especially the proteins) and the interactions between plasma and cells; (d) the shear rate. To examine the influence of cell shape and deformability on blood viscosity, we have compared, at low shear rates, the viscosities of suspensions of red blood cells and suspensions of rigid, spherical latex particles with diameters comparable to the major diameters of red cells in human blood. Polystyrene latex (Dow Chemical Co., Midland, Michigan) used for this purpose consisted of rigid spheres, with a mean diameter of 9.2µ, suspended in water with soap and stabilized with colloidal silica. Human red blood cells are biconcave disks with a mean major diameter of 7.2µ (ref. 1) and are deformable^2–4. In the work recorded here, plasma was removed from human blood and the cells washed and suspended in a protein-free solution (Ringer's solution), thus eliminating the influence of plasma proteins on blood viscosity and making the cell suspensions more comparable to the latex suspensions. Because of the dependence of the viscosity of cell suspensions on cell concentration and shear rate^5,6, viscosity measurements on cell suspensions and latex suspensions were made over a wide range of particle concentration and at shear rates varying from 50 sec⁻¹ to 0.02 sec⁻¹.