Capillary blood flow: I. Erythrocyte deformation in glass capillaries

Abstract

High-speed motion photography is used to study the deformation and orientation of individual red cells as they move through 4- to 10-μ glass capillaries at cell velocities between 0 and 2 mm/sec. The results of the study indicate that in most cases red cells tend to move in an edge-on orientation with the cell shape becoming more nearly axisymmetric at high velocities. The apparent thickness of the peripheral plasma layer (a measure of the degree of cell deformation) increases with velocity in the range 0–1 mm/sec. The plasma layer thickness is essentially constant for velocities greater than 1 mm/sec. Average limiting (high velocity) values for the apparent plasma layer thickness are about 0.6, 1.1, 1.4, and 1.9 μ for respective capillary diameters of 4.5, 6.7, 7.6 to 8.5, and 9.7 μ. From these observations it is concluded that the relative apparent viscosity (relative to plasma) for blood flow in capillaries is nonlinear with minimum relative apparent viscosity occurring at velocities which are greater than 1 mm/sec.