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Publication AbstractsEffect of 30-min +3 Gz Centrifugation on Vestibular and Autonomic Cardiovascular FunctionTodd T. Schlegel, Scott J. Wood, Troy E. Brown, Deborah L. Harm, and A. H. RupertAviat Space Environ Med 2003; 74:717-24 AbstractIntroduction: Repeated exposure to increased +Gz enhances human baroreflex responsiveness and improves tolerance to cardiovascular stress. However, it is not known whether such enhancements might also result from a single, more prolonged exposure to increased +Gz. Our study was designed to investigate whether baroreflex function and orthostatic tolerance are acutely improved by a single prolonged exposure to +3 Gz, and moreover, whether changes in autonomic cardiovascular function resulting from exposure to increased +Gz are correlated with changes in otolith function. Methods: We exposed 15 healthy human subjects to +3 Gz centrifugation for up to 30 min or until symptoms of incipient G-induced loss of consciousness (G-LOC) ensued. Tests of autonomic cardiovascular function both before and after centrifugation included: 1) power spectral determinations of beat-to-beat R-R intervals and arterial pressures; 2) carotid-cardiac baroreflex tests; 3) Valsalva tests; and 4) 30-min head-up tilt tests. Otolith function was assessed during centrifugation by the linear vestibulo-ocular reflex and both before and after centrifugation by measurements of ocular counterrolling and dynamic posturography. Results: Of the 15 subjects who underwent prolonged +3 Gz, 4 were intolerant to 30 min of head-up tilt before centrifugation but became tolerant to such tilt after centrifugation. The Valsalva-related baroreflex as well as a measure of the carotid-cardiac baroreflex were also enhanced after centrifugation. No significant vestibular-autonomic relationships were detected beyond a vestibular-cerebrovascular interaction reported earlier in a subset of seven participants. Conclusions: A single prolonged exposure to +3 Gz centrifugation acutely improves baroreflex function and orthostatic tolerance.
Keywords: orthostatic tolerance, otolith, baroreflex, Valsalva maneuver, motion sickness. Information on subscribing, and on obtaining copies of an article or of an entire issue. Table of Contents for Volume 74, Number 7 of the ASEM journal.
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