title: Effect of 4 hours HD -6 degrees on heart rate variability in symptomatic and non symptomatic subjects.
abstract: Orthostatic intolerance is the most serious symptom of cardiovascular deconditioning induced by microgravity exposure. In fact the neural control mechanisms of the cardiovascular system are significantly affected by this condition. Non-invasive measurement of Heart Rate Variability (HRV) have been used as a valuable tool to characterize the ability of neuroendocrine regulatory systems to modulate the cardiovascular function by analyzing the spontaneous fluctuations of arterial pressure and heart period on a beat-to-beat basis. Concerning this, conflicting results have been reported on the heart rate and blood pressure variability responses during exposure to microgravity. These differences seem to be due to different experimental designs used. Moreover, the different behavior of normal subjects in response to orthostatic stress after HD, i.e. Symptomatic (S) or Non Symptomatic (NS), could play some roles in producing these discrepancies. Therefore the aim of the present study was to examine BP and HR variability before and after 4 hours of HD in two groups of normal subjects with and without symptoms of orthostatic intolerance to orthostatic stress.
authors.affiliation: Centro Biomedicina Spaziale, Fisiopatologia Medica, Dip. Medicina Interna, Università di Roma "Tor Vergata".
authors.forename: G
authors.initials: G
authors.lastname: Raimondi
authors.forename: F
authors.initials: F
authors.lastname: Iellamo
authors.forename: R
authors.initials: R
authors.lastname: Balocchi
authors.forename: S
authors.initials: S
authors.lastname: Chillemi
authors.forename: S
authors.initials: S
authors.lastname: Sacco
authors.forename: J M
authors.initials: JM
authors.lastname: Legramante
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D018493:Cardiovascular Deconditioning / Q000502:physiology*; D005260:Female; D018475:Head-Down Tilt; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D008297:Male