Hemodynamics

Abstract

Blood is composed of blood cells suspended in plasma. The viscosity of blood varies with clinical conditions that influence blood cell aggregation and the hematocrit, and involves hemodynamic changes in vessels directly [1-3]. Generally, in arteries with diameters larger than 3 mm, the viscosity of blood is essentially constant when the shear rate exceeds 100 s-1 [4]. By contrast, in capillaries with diameters smaller than 400 μm, the decrease in the vessel diameter reduces the viscosity of blood by redistributing blood cells at the center of the vessel [5]. Therefore, we should consider non-Newtonian blood flow behavior according to the flow conditions in blood vessels. This section briefly describes the basics of fluid mechanics that might be useful for understanding cerebral hemodynamics. © 2010 Springer-Verlag Tokyo.