Capillary pore rheology of erythrocytes. I. Hydroelastic behaviour of human erythrocytes

Abstract Lighthill and Fitz-Gerald have recently examined erythrocyte motion in narrow capillaries (diam. 5–7 μm) from the point of view of lubrication theory. They found that nonlinear pressure-velocity behaviour could be theoretically expected for erythrocytes in capillaries through which they have to squeeze. With increasing cell velocity, resistance to movement was predicted to fall as a result of red cell deformation by lubrication pressures and drag forces in the plasma film separating the cells from the capillary wall. The possibility of lubrication failure (seize-up) was predicted at velocities below about 0.1 mm·sec −1 resulting from frictional sliding of the cells along the vessel wall. Recent experimental evidence has been equivocal in support of this hypothesis and to some extent contradictory. In the present work some of the problems making experimental progress difficult have been overcome. Evidence has been obtained for the elastohydrodynamic behaviour of erythrocytes traversing capillary pores of 7 μm diam. No evidence has yet been found for seize-up caused by lubrication failure. It appears that in the lowest velocity range (0–0.25 mm·sec −1 ), erythrocytes maintain an effectively constant separation from the capillary wall. Resistance to movement is constant up to a certain speed (about 0.25 mm·sec −1 ) beyond which lubrication forces produce erythrocyte deformation and reduced resistances with increasing cell velocity.