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A Model of Cerebral Blood Flow During Sustained Acceleration

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Technical Report

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Defence and Civil Institute of Environmental Medicine Toronto, Ontario Canada

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Radial accelerations generated in modern combat aircraft maneuvers Gz may result in impaired vision or loss of consciousness G-LOC. We are interested in developing mathematical models of cerebral blood flow during exposure to Gz. Our previous model 1 showed that intracranial vascular resistance does not change with Gz since the vessels are protected from collapse by the cerebrospinal fluid and that reduction of the blood flow to the brain is mainly due to the increased vascular resistance of the large extracranial veins. Based on the previous results, we propose a model with simplified presentation of the arteries and intracranial vessels and a more detailed description of the jugular veins. The extracranial arteries are accounted for by the hydrostatic pressure drop from the heart to the head level. The intracranial vessels are represented by a resistance independent of the mechanical effects of Gz. However, a model of cerebral autoregulation is incorporated, which involves actives active change in the cranial vascular resistance in reaction to the change in blood pressure at the head level. The jugular veins are modeled using one dimensional equations of fluid dynamics and a non-linear relation between the transmural blood minus external pressure and the local vessel cross-sectional area. The central arterial and venous pressures are taken to be 105 mmHg and 55 mmHg respectively and Gz was varied from -5 to 10.

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