Effects of Red Blood Cell Stiffness on Hemodynamics in a Model Microvessel

The deformability of red blood cells (RBCs) plays important roles in influencing hemodynamic characteristics and properties of blood flow in the microcirculation. Under healthy conditions RBCs are extremely deformable but can increase in stiffness due to disease or aging. Both the particulate nature of blood as well as individual RBC deformability influence the apparent viscosity of blood, in addition to other related characteristics such as the wall shear stress and blunted character to velocity profiles. Quantifying such considerations over a range of conditions is important to enable a more comprehensive understanding of blood characteristics in the microcirculation. Here we use 3D simulations resolving the deformation and dynamics of RBC suspensions in model microvessels to study the impacts of RBC stiffness on hemodynamic behavior. RBC suspensions are comprised of a specified distribution of healthy and stiff RBCs, and we define a stiff RBC as having a membrane shear elastic modulus ten times greater than a healthy RBC. We quantify distributions by the ratio of the number of stiff to healthy RBCs (Φ), with Φ=0,0.25,0.5,0.75. Suspensions are modeled in straight tubes, considering three different diameters (10,20,30μm), three hematocrit values (0.1,0.2,0.3), and three effective shear rates (25,50,100 sec^-1). Output is used to systematically quantify dependencies on apparent viscosity, wall shear stress, velocity profile bluntness, and separation characteristics of the RBC populations.