Computational analysis of nitric oxide biotransport in a microvessel influenced by red blood cells.

It is pivotal that endothelium-dependent Nitric Oxide (NO) consumed by hemoglobin (Hb) inside red blood cells (RBCs) membrane, regulates the vascular tone. The whole processes of NO transport in vessel containing flowing RBCs is still not clear, such as NO production in endothelium, diffusion in plasma and consumption inside RBCs. In this work, the motion of RBCs in a microvessel is investigated by using immersed boundary lattice Boltzmann method (IB-LBM) first and the deformability of RBCs is expressed by using spring network model which is based on the minimum energy principle. Furthermore, the interaction between RBCs is considered. Based on the wall shear stress (WSS), NO production rate originated from endothelium was obtained by using a hyperbolic model. NO distribution inside the microvessel with multiple RBCs was computed by using immersed boundary finite difference method (IB-FDM). The result shows that a large (small) WSS exists at locations with a relatively wide(narrow) gap between the wall and cell. In terms of mass transfer, an increase of RBC membrane permeability leads to a decrease of NO concentration in the vessel and the surrounding endothelium significantly. In addition, with the increasing of hematocrit (Hct) value, NO concentration distribution in the whole vessel decreases both in the lumen and vascular wall. Finally, the thickness of RBCs-depleted layer gradually decreases with the weakened deformability of RBCs membrane, and the change degree of cell free layer (CFL) thickness decreases as the bending stiffness is relatively higher. Thus, when bending stiffness is higher, the NO concentration in vascular wall is reduced resulting from the thinner CFL.