In the previous Neurolab (STS-90) mission, a study showed that human cerebral autoregulation was preserved, and possibly even improved, by two weeks after space flight. However, the study might suffer from the small number of subjects or the special character of the mission as major limitations shared by most research in space. The specific aims of this study are to confirm reproducibility of the results from the Neurolab mission and to reveal the effects of prolonged space flight on cerebral circulation.
The main objective of the study is to determine the effects of short and long-duration space flight on cerebral blood flow autoregulation in humans by analyzing waveforms of arterial blood pressure and blood flow velocity in the middle cerebral artery recorded by transcranial Doppler (TCD).
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Waveforms of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) in the middle cerebral artery will be measured by a non-invasive ABP monitor (Cardiopres) and a TCD preflight, in-flight, and postflight. Cerebral autoregulation will be estimated by spectral and transfer function analysis of beat-by-beat changes in ABP and CBFV. If the study shows decreases in gain and coherence of transfer function indices during weeks in space, it means that short-duration space flight improves cerebral autoregulation and reproducibility of the previous results of the Neurolab is confirmed. Contrarily, if the study does not show improved cerebral autoregulation, the discrepancy would be resulted from the differences in the mission protocol between Neurolab and the International Space Station (ISS). In this situation, a periodic exposure to centrifugation in the Neurolab mission would be suggested to cause this discrepancy, and the centrifugation can possibly be used as a countermeasure in the future of human space exploration. Results after a couple of months in space would reveal the effects of long-duration space flight on cerebral circulation. Regardless of the results, this study would provide new information of human cerebral autoregulation during space flight.
Results will be available at a later date.