Modeling and numerical simulation of the cerebral blood flow under acceleration.

When fighter aircrafts change directions, the pilots are subject to a centrifuge force. This force can be enough to induce the pilot loss of consciousness (LOC). The physiological cause of this LOC is a brain hypoxia which results from the increase of the hydrostatic pressure. Under gradual onset rate + Gz acceleration (GOR+Gz), the brain hypoxia occurs with visual prodromes familiar to fighter pilots. In this case, they feel a reduction of the peripheral vision (Grey-out), followed by a loss of the central vision (Black-out). The useful time of consciousness can be prolonged by using anti-G suit. Under rapid onset rate +Gz acceleration, a new symptomatology of the LOC, characterized by the absence of a grey or black-out, has been observed. The objective of this theoretical study is a better understanding of mechanisms which cause fighter pilot inflight LOC. A physical model has been developed. It allows to take into account the influence of the rate of change in acceleration on the cerebrovascular system behavior.