Theoretical analysis of oxygen consumption by vascular walls exposed to hemodynamic stress in the human retinal microvascular network

The rates at which endothelial and smooth muscle cells in vessel walls should consume oxygen during blood transport along the length of a microvascular network are highly controversial. We examined the arteriovenous distribution of oxygen consumption by a microvesselwallexposed to circumferentialwallstress and fluid shear stress. A model of retinal microcirculation in which a network that branched dichotomously at every bifurcation depended on both a flow conservation law and a modified Murray's law with a diameter exponent of 2.85 was used. Oxygen consumption was calculated from the integration of the number of branches multiplied by the consumption rates of the endothelial and smooth muscle cells per branch unit. The oxygen consumption by all of the microvessel walls was only about 1.9% of the totaloxygen consumption throughout the microvascular network, including the surrounding tissues. This result suggests that the oxygen that had diffused across the microvessel walls was mainly consumed by the surrounding tissues. Also, based on the circumferential and shear stresses, the microvascular flow and pressure control system is presumably designed to optimize the vessel tone of the arteriolar network so that the microcirculation can accommodate material exchange.