Blood flow and cell-free layer in microvessels.

Blood is modeled as a suspension of red blood cells using the dissipative particle dynamics method. The red blood cell membrane is coarse-grained for efficient simulations of multiple cells, yet accurately describes its viscoelastic properties. Blood flow in microtubes ranging from 10 to 40 μm in diameter is simulated in three dimensions for values of hematocrit in the range of 0.15-0.45 and carefully compared with available experimental data. Velocity profiles for different hematocrit values show an increase in bluntness with an increase in hematocrit. Red blood cell center-of-mass distributions demonstrate cell migration away from the wall to the tube center. This results in the formation of a cell-free layer next to the tube wall corresponding to the experimentally observed Fahraeus and Fahraeus-Lindqvist effects. The predicted cell-free layer widths are in agreement with those found in in vitro experiments; the results are also in qualitative agreement with in vivo experiments. However, additional features have to be taken into account for simulating microvascular flow, e.g., the endothelial glycocalyx. The developed model is able to capture blood flow properties and provides a computational framework at the mesoscopic level for obtaining realistic predictions of blood flow in microcirculation under normal and pathological conditions.