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

The influence of varying shear forces (4–10 N·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 Rdecreased by about 3%, while more rigid cells evoked a shear dependentincrease 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.