Numerical Study on Flow Behavior of Red Blood Cells through Symmetric Capillary Bifurcations

The red blood cell (RBC) partitioning properties at microvascular bifurcation are largely related to heterogeneous oxygen distributions in the microcirculatory networks. Here, three-dimensional, T-type symmetric capillary bifurcation models have been prepared and the flow behavior of RBCs through the capillary bifurcations has been investigated. Simulated blood flow was computed using the lattice Boltzmann method, in conjunction with the immersed boundary method, for incorporating fluid-membrane interactions between the flow field and deformable RBCs. To do this, first the straight vessel flow was simulated to determine the RBC flow at a parent vessel of the bifurcation model. The simulation results indicated two types of RBC arrangements according to the hematocrit: (i) zigzag-slipper and (ii) aligned-parachute shapes. Next, by adopting the RBC arrangements obtained from the straight vessel analysis, RBC partitioning in the capillary bifurcation was investigated. The simulation results were in agreement with the Pries' empirical model at high hematocrit. On the other hand, the bias of RBC flux for the parachute shape was larger than that of the empirical model at low hematocrit. These results suggest that the partitioning properties of RBCs in the microvascular bifurcation depend largely on the RBC arrangement in the parent vessel.