The effect of red blood cell flexibility on blood flow through tubes with diameters in the range 30 to 500 microns

Simultaneous measurement of apparent viscosity and mean tube hematocrits have been made at various shear rates for the flow of red blood cell suspensions through glass capillaries with diameters in the range 30 to 500 microns. Two types of red blood cell (RBC) suspensions, namely normal and heated RBC suspensions, have been used in the investigation to study the effect of erythrocyte deformability. The effect of heating on the shape and size of erythrocytes was studied through scanning electron microscopy. The hematocrit of the suspensions ranged from 5 to 65 % in the large tubes whereas in the smaller tubes it was maintained around 40 % for both the suspensions. Experimental results on the apparent viscosity and hematocrit defect for normal RBC suspensions are found to be in good agreement with the published data in literature. The decreased deformability of the heated erythrocytes resulted in an increase in the apparent viscosity as measured in all the tubes. However, the extent of this increase was observed to depend on tube diameter, the effect being more pronounced in smaller tubes. Further, the hematocrit defect in the heated RBC suspensions was found to be less than that for the normal RBC suspensions under comparable flow conditions.