Brown University School of Engineering

Fluids Seminar: Fluid Mechanics of Pulsatile Flow in the Brain

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Tuesday, November 06, 2012 3:00pm - 4:00pm

William Olbricht School of Chemical and Biomolecular Engineering Cornell University Ithaca, NY Fluid Mechanics of Pulsatile Flow in the Brain We have used two-photon excited fluorescence (2PEF) microscopy to study time-dependent blood flow inside and outside cortical arterioles and capillaries of live, anesthetized rodents. The method provides sufficient spatial and temporal accuracy to determine velocity profiles as a function of heartbeat and respiration cycles. Detailed velocity measurements can also be made of the interstitial flow outside blood vessels in the surrounding brain parenchyma. We have applied this method and supporting analysis to two problems. First, we have studied effects of hematocrit on blood flow in arterioles and capillaries of the brain cortex. Elevated hematocrits are typical in a variety of diseases characterized by an overproduction of blood cells. Animals with elevated hematocrit exhibit altered velocity profiles in arterioles and an unusually large number of “stalled” capillaries with little or no blood flow. These capillary stalls, which may start owing to altered hemodynamics, can persist for long times as a result of leukocyte and platelet adhesion inside the stalled vessels. Second, we have used 2PEF microscropy to examine effects of blood flow pulsatility on interstitial flow in the perivascular space immediately outside the blood vessel wall. Here, pulsatility can have a strong effect on interstitial flow, which can have important consequences for drug delivery methods that deliver fluid containing therapeutics directly into the brain parenchyma to treat neurological disorders.