title: Orthostatic intolerance and motion sickness after parabolic flight.
abstract: Because it is not clear that the induction of orthostatic intolerance in returning astronauts always requires prolonged exposure to microgravity, we investigated orthostatic tolerance and autonomic cardiovascular function in 16 healthy subjects before and after the brief micro- and hypergravity of parabolic flight. Concomitantly, we investigated the effect of parabolic flight-induced vomiting on orthostatic tolerance, R-wave-R-wave interval and arterial pressure power spectra, and carotid-cardiac baroreflex and Valsalva responses. After parabolic flight 1) 8 of 16 subjects could not tolerate 30 min of upright tilt (compared to 2 of 16 before flight); 2) 6 of 16 subjects vomited; 3) new intolerance to upright tilt was associated with exaggerated falls in total peripheral resistance, whereas vomiting was associated with increased R-wave-R-wave interval variability and carotid-cardiac baroreflex responsiveness; and 4) the proximate mode of new orthostatic failure differed in subjects who did and did not vomit, with vomiters experiencing comparatively isolated upright hypocapnia and cerebral vasoconstriction and nonvomiters experiencing signs and symptoms reminiscent of the clinical postural tachycardia syndrome. Results suggest, first, that syndromes of orthostatic intolerance resembling those developing after space flight can develop after a brief (i.e., 2-h) parabolic flight and, second, that recent vomiting can influence the results of tests of autonomic cardiovascular function commonly utilized in returning astronauts.
authors.affiliation: Life Sciences Research Laboratories, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas 77058, USA. tschlege@ems.jsc.nasa.gov
authors.forename: T T
authors.initials: TT
authors.lastname: Schlegel
authors.forename: T E
authors.initials: TE
authors.lastname: Brown
authors.forename: S J
authors.initials: SJ
authors.lastname: Wood
authors.forename: E W
authors.initials: EW
authors.lastname: Benavides
authors.forename: R L
authors.initials: RL
authors.lastname: Bondar
authors.forename: F
authors.initials: F
authors.lastname: Stein
authors.forename: P
authors.initials: P
authors.lastname: Moradshahi
authors.forename: D L
authors.initials: DL
authors.lastname: Harm
authors.forename: J M
authors.initials: JM
authors.lastname: Fritsch-Yelle
authors.forename: P A
authors.initials: PA
authors.lastname: Low
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology; D017704:Baroreflex; D001794:Blood Pressure; D002339:Carotid Arteries / Q000503:physiopathology; D004244:Dizziness; D005260:Female; D006321:Heart / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D013026:Space Flight; D018489:Space Motion Sickness / Q000503:physiopathology; D016683:Supine Position; D014636:Valsalva Maneuver; D014839:Vomiting / Q000503:physiopathology