FLUCTUATIONS IN MICROVASCULAR BLOOD-FLOW PARAMETERS CAUSED BY HEMODYNAMIC MECHANISMS

We have developed a mathematical model of microvascular network blood flow in which the nonlinear flow properties of blood and the nonunifor m axial distribution of red blood cells in each vessel, as well as dis proportionate cell partitioning at bifurcations, are all accounted for . The movements of red blood cells in the network are tracked; hence, the model is able to simulate temporal variations in local flow parame ters in the network due to hemodynamic mechanisms. The model was appli ed to four rat mesenteric networks for which the topology, boundary co nditions, blood velocity, and discharge hematocrit (Hct(d)) had been m easured for each branch. Temporal variations in Hct(d) and blood veloc ity after simulation convergence were predicted. In some cases of the three vessels connected to a node, Hct(d) of one vessel fluctuates in a simple periodic form, Hct(d) of the second one oscillates in a more complex periodic form, whereas the Hct(d) of the third one does not os cillate at all. These variations were obtained with constant flow boun dary conditions and, therefore, are due to hemodynamic factors alone. The temporal variations in flow parameters predicted by the model simu lations are caused by hemorheological mechanisms and would be superimp osed on variations caused by other mechanisms (e.g., vasomotion). The frequencies of the predicted fluctuations in blood velocity are in qua litative agreement with observed in vivo variations in dual-slit veloc ity in the arterioles of the cremaster muscle of anesthetized Golden h amster.