Red cell flexibility, electrical resistance and viscosity of blood flowing through small glass capillaries

The influence of varying shear forces (4-10 microN.cm-2) generated by a pulsating flow of 4 cycles/min, on the longitudinal electrical resistance (R) of a blood perfused small glass capillary (I.D. = 0.12 mm, l = 30 mm) was determined. Red cells were stiffened by stepwise addition of bile or by sterile incubation during 24-48 h. The shear dependent changes in R were closely related to red cell flexibility and apparent blood viscosity. In normal defibrinized blood R decreased by about 3%, while more rigid cells evoked a shear dependent increase in R of 1-5%. The measurements performed demonstrate that the typical shapes of the electrical signals provide more information of rheological significance of red blood cell flexibility than the results of viscosity determination alone.