Effects of the Mechanical Behaviors of Red Blood Cells on the Blood Flow.

To determine the mechanical properties of red blood cells (RBCs) that affect the blood flow, this chapter examines the range of dynamic behaviors from an individual RBC to collections of multiple RBCs. The elastic response and relaxation characteristics of an isolated RBC under tensile stretching and tube flow are examined. They show that the confinement of microvessels impedes the relaxation process of the RBC, particularly under the conditions of strong confinement. In addition, simulations of the flow of a suspension of RBCs in a straight microvessel demonstrate that elevated aggregation strength and deformability of RBCs can enhance the thickness of cell-free layer (CFL), thereby reducing the relative apparent viscosity and increasing the discharge hematocrit. The existence of stenosis results in an increase in blood flow resistance. An augmented Fahraeus-Lindqvist effect is observed in the presence of stenosis. Finally, the effects of RBC aggregation combined with reduced stenosis on blood flow dynamics are investigated. As RBC clusters traverse a stenotic region with a throat with a diameter comparable to that of the RBC core, the resistance to blood flow decreases in response to an increase in the strength of intercellular interaction. However, if the RBC core is significantly larger than the throat, a marked increase in blood flow resistance occurs under the condition of strong RBC aggregation, potentially contributing to the mechanism underlying microthrombus formation.