Cerebral autoregulation during exposure to artificial gravity

Abstract

Our work has previously shown that exposure to artificial gravity (AG) can improve orthostatic tolerance. The purpose of this work is to examine whether cerebral autoregulation is improved with AG in twelve hypovolemic men and women. The protocol consisted of an initial ~45 minutes of a “step up” tolerance period, used to determine participants' presyncopal limit, followed by ~45 minutes training period at GZ below participants presyncopal limit. Beat‐by‐beat blood pressure (Portapres), heart rate (ECG), middle cerebral artery blood flow velocity (Transcranial Doppler) and end‐tidal carbon dioxide (capnography) were collected on participants during short arm centrifugation. Cerebral autoregulation was assessed using transfer function analysis between mean arterial pressure (MAP) and mean cerebral blood flow velocity (MCBFV) in 3‐min intervals during the training period. Exposure to AG resulted in a significant positive correlation between GZ and MAP, MAP variability and MCBFV variability in the low frequency (LF) range (0.07–0.15 Hz). In addition, coherence between MAP and MCBFV in the LF range was positively correlated. There was no change in gain and phase between MAP and MCBFV in the same frequency range. With higher GZ, there was a significant positive correlation in coherence and significant negative correlation in gain between MAP and MCBFV in the very low frequency range (0.03–0.07 Hz). These data suggest that increasing GZ exposure is correlated to increasing MAP variability. However, despite this increased MAP variability gain values demonstrated a negative correlation with GZ, suggesting that cerebral autoregulation tended to improve with increasing GZ exposure. We expect increased coherence was a result of the increased MAP variability associated with higher GZ. These data may suggest that exposure to AG may be helpful to improve cerebral autoregulation. Therefore, one could speculate that AG may be a useful tool to consider as a countermeasure for post‐flight astronauts to improve their orthostatic tolerance as well as cerebral autoregulation and improve re‐adaptation to a gravity environment.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.