A Computational Model of Oxygen Transport in the Cerebrocapillary Levels for Normal and Pathologic Brain Function

Abstract

The oxygen exchange and correlation between the cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMRO 2 ) in the cortical capillary levels for normal and pathologic brain functions remain the subject of debate. A 3D realistic mesoscale model of the cortical capillary network (non-tree like) is constructed using a random Voronoi tessellation in which each edge represents a capillary segment. The hemodynamics and oxygen transport are numerically simulated in the model, which involves rheological laws in the capillaries, oxygen diffusion, and non-linear binding of oxygen to hemoglobin, respectively. The findings show that the cerebral hypoxia due to a significant decreased perfusion (as can occur in stroke) can be avoided by a moderate reduction in oxygen demand. Oxygen extraction fraction (OEF) can be an important indicator for the brain oxygen metabolism under normal perfusion and misery-perfusion syndrome (leading to ischemia). The results demonstrated that a disproportionately large increase in blood supply is required for a small increase in the oxygen demand, which, in turn, is strongly dependent on the resting OEF. The predicted flow-metabolism coupling in the model supports the experimental studies of spatiotemporal stimulations in humans by positron emission tomography and functional magnetic resonance imaging.

Hematocrit Distribution and Tissue Oxygenation in Large Microcirculatory Networks

“…For interpreting the spatiotemporal relationship between in vivo measurements, computational methods can play an important role. Several imaging studies [10,26,53,60] recognize the significance of computational models for investigating the functional relationship between cerebral angioarchitecture [19,25,34,62], blood flow [37,65], and oxygen exchange [8,40,44,54,61]. Computational models for microcirculatory hemodynamics need to account for the nonideal flow behavior of erythrocyte-bound oxygen, which, in turn, is necessary to predict tissue oxygenation.…”

The capillary bed offers the largest hemodynamic resistance to the cortical blood supply

“…3,[27][28][29][30][31] However, experimental evidence has been unable to identify a hierarchal order to blood pressure, 32 hematocrit, 33 red blood cell velocity, 34 or oxygen saturation. Other studies employed random geometric space filling methods 35,36 ; unfortunately, these structures did not conform to the vessel topology seen in microscopy. However, topology significantly affects oxygen exchange.…”

The Influence of Endothelium-Dependent Mechanisms of Vessel Tone Regulation on the Tissue Oxygenation Parameters in Patients With Ischemic Stroke at the Background of Arterial Hypertension Syndrome

“…В настоящее время остаются недостаточно изученными особенности обмена кислорода в тканях в остром периоде нарушений мозгового кровообращения [3][4][5]6]. Остаются дискусси-онными вопросы взаимоотношений оксигенации тка-ней, особенностей мозговой гемодинамики и систем-ного артериального давления.…”