Blood flow in microvessels lined with a poroelastic wall layer

It is well known that the cross-sectional distribution of red blood cells in microvessels leads to a cell-rich core and a relatively thin plasma-rich zone near the vessel wall. The fact that the endothelial-cell surface glycocalyx may occupy a substantial fraction of the plasma-rich zone has important implications for the apparent viscosity of blood in the microcirculation. A new semi-empirical model is presented for blood flow in glycocalyx-lined microvessels greater than 20 mu m in diameter. The variation in blood viscosity over the vessel cross section is estimated from experimental observations of the cross-sectional hematocrit distributions within microvessels. The blood is modeled as a viscous fluid having a radially varying viscosity and the glycocalyx is modeled as a hydrated poroelastic wall layer. The model predicts an increase in flow resistance in a 20-mu m vessel lined with a 1/2-mu m-thick glycocalyx of over 30% relative to the corresponding value in a 20-mu m glass tube.