Evaluating Intravascular Transport of Nitric Oxide with the Heat-Mass Transfer Analogy

To investigate how intravascular transport of nitric oxide (NO)/nitrite varies across arterial scale, we assessed species transport with high-resolution three-dimensional idealized models of bifurcating arteries. Morphological and hemodynamic input parameters such as parent-daughter branching area ratios and flow rates were estimated with available in vivo data. To enhance computational efficiency of the advection-diffusion models in ANSYS Fluent, we utilized the heat-mass transfer analogy through matching nondimensional Schmidt and Prandtl numbers thus allowing useful translation of relative temperature changes to changes in NO/nitrite concentration ([NO_x]) at each arterial scale. Convection dominated flows in large arteries result in the formation of near-wall [NO_x] boundary layers; however, bifurcations induce scale-dependent mixing of boundary layers with core flow in >200 μm diameter arteries reducing [NO_x]. In contrast, NO/nitrite diffusion in arterioles <100 μm diameter raised cross-sectionally averaged [NO_x] to the nanomolar range. We investigate the effect of additive propagation of NO/nitrite from large arteries on vasodilation and red blood cell absorption of circulating NO/nitrite.