Brief Exposure To –2 G Z Reduces Cerebral Oxygenation In Response To Stand Test

The aim of the present experiment was to determine whether a single 30 s of exposure to –2 G z (foot-to-head inertial forces) as orthostatic stress results in altered brain oxygenation control in response to active standing. Cerebral oxygenation (oxy-Hb), cerebral blood volume (CBV), and mean arterial blood pressure at brain level (MAP brain) were recorded in 12 subjects in supine and then in standing position (10 min), before and after –2 G z centrifugation. The decrease in oxy-Hb (-5 ± 9 vs –9 ± 10 μ M, P 0.001) and in CBV (-2 ± 11 vs –4 ± 12 μ M, P 0.05) upon standing was more important after –2 G z centrifugation, with unchanged MAP brain (-6 ± 7 vs –6 ± 9 mmHg). These findings suggest a downward shift in the static cerebral autoregulation curve.