Effects of Changes in the Apparent Viscosity of Blood with Vessel Sizeon Retinal Microcirculation: Significance of the Fahraeus-Lindqvist Effect

摘要

The purpose of this study was to quantitatively assess the influence of the Fahraeus-Lindqvist effect on the microcirculation in the arteriovenous network of the human retina. A mathematical model was used to simulate the arteriovenous distributions of hemodynamic parameters within a microvascular network of successive, symmetric bifurcating branches that were constructed based on both flow conservation and a modified Murray's law with a diameter exponent of 2.85. The vessel calibers ranged from a 108-pm arteriole and a 117μm venule down to the 5μm capillaries. The distributions of vascular resistance, pressure drop, and wall shear stress as a function of vessel diameter within the retinal microcirculatory network with the Fahraeus-Lindqvist effect were lower than those without the Fahraeus-Lindqvist effect. The efficiency of blood transport to tissues in the microvascular bed, which was evaluated in terms of the inverse of the mechanical energy cost of the product of the driving pressure and blood flow, was 44% greater with the Fahraeus-Lindqvist effect than without the Fahraeus-Lindqvist effect. These results quantitatively demonstrated that the Fahraeus-Lindqvist effect plays an important role in reducing the physical energy required to transport blood that flows through the microcirculatory network. The integrated and interactive relationships between shear stress, circumferential wall stress, vessel radius, and wall thickness in response to acute and chronic increases in perfusion pressure are discussed with regard to their coordinating roles in the control of blood flow and pressure in microcirculation.