Vestibular and Cardiovascular Responses After Long-Duration Spaceflight

BACKGROUND: The vestibulo-sympathetic reflex operates during orthostatically challenging movements to initiate cardiovascular responses in advance of a baroreceptor-mediated response. The objective of this study was to determine whether there was an association between changes in vestibular function and cardiovascular responses during a prone-to-stand movement in astronauts after return from long-duration spaceflight.METHODS: Thirteen crewmembers who participated in International Space Station missions were tested before spaceflight and 1 d after landing. Vestibular function was evaluated by computerized dynamic posturography while their head was erect and while they performed dynamic head tilts. Heart rate and mean arterial blood pressure were measured while the subjects were in prone and standing positions.RESULTS: The 21.4% increase in the astronauts' heart rate during the prone to stand maneuver after spaceflight correlated significantly with their spaceflight-induced 48.7% decrease in postural stability during dynamic head tilts. The larger mean arterial pressure in the prone position after spaceflight compared to preflight (+7%) also correlated with the postflight decrease in postural stability during dynamic head tilts.CONCLUSION: These results indicate that an appropriate vestibular function is important to evoke optimum vestibulo-sympathetic response during orthostatically challenging voluntary movements performed after spaceflight. They also suggest that there may be a greater need to generate an anticipatory cardiovascular response after spaceflight.Deshpande N, Laurie SS, Lee SMC, Miller CA, Mulavara AP, Peters BT,Reschke MF, Stenger MB, Taylor LC, Wood SJ, Clément GR, Bloomberg JJ.