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Speaker: Akshita Sharma, Program in Applied Mathematics
Title: Theoretical Model for Cerebral Blood Flow and Oxygen Transport: Adverse Effects of Impaired Flow Regulation Despite Maintained Perfusion
Abstract: The brain’s metabolic activity requires a sufficient supply of oxygen to all cells in the tissue, which is achieved by local control of blood flow which modulates diameters of feeding arterioles. Experimental observations under pathological conditions suggest that impaired vascular function can lead to local hypoxia and damage to neurons even when overall perfusion is maintained. The goal of this study is to analyze the effects of changes in arteriolar diameters on the microscale distribution of tissue oxygen level in the brain, and to test whether maldistribution of blood flow can lead to tissue hypoxia, even when overall perfusion is maintained. A theoretical model is used to simulate blood flow in large microvascular networks. A Green's function method is used to simulate the transport of oxygen by convection in the vessels and diffusion into the surrounding tissue. For a network with about 5000 segments observed in the mouse cortex, the penetrating arterioles are identified and the effects of varying their diameters on oxygenation of the surrounding tissue region are examined. Changing the diameter of an individual penetrating arteriole results in localized changes in tissue oxygen levels in a region supplied by the arteriole. These changes are seen over a scale of hundreds of micrometers. Simulations are also performed for a case in which diameters of several arterioles are altered, in such a way that the overall perfusion of the tissue region remains constant. In that case, the statistical distribution of tissue oxygen levels is shifted, with an increase in the amount of hypoxic tissue.