title: Does bed rest produce changes in orthostatic function comparable to those induced by space flight?
abstract: Use of bed rest to simulate microgravity exposure is not well validated. We compared heart rate (HR) and blood pressure (BP) responses to standing in bed-rest (BR) subjects (n=11) to those of two astronaut groups. One astronaut group (n=28) fluid loaded (FL) before landing by consuming a water and salt tablet mixture, the second astronaut group (n=8) did not (NL). Bed-rest or microgravity exposure lasted approximately 7.0 days. Preexposure, the responses to standing did not differ between groups. Postexposure, all groups demonstrated an increased HR response (p<0.01), a decreased SBP response (p<0.05), no change in DBP response, and a reduced PP response (p<0.05) compared to preexposure. Change in HR response was lowest for the FL group, presumably due to increased plasma volume induced by fluid consumption. These findings generally support bed rest as a valid simulator of microgravity.
authors.affiliation: KRUG Life Sciences, Houston, TX 77058, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Moore
authors.forename: J B
authors.initials: JB
authors.lastname: Charles
authors.forename: S M
authors.initials: SM
authors.lastname: Lee
authors.forename: S F
authors.initials: SF
authors.lastname: Siconolfi
authors.forename: M C
authors.initials: MC
authors.lastname: Greenisen
mesh_terms: D000328:Adult; D001510:Bed Rest / Q000009:adverse effects*; D001794:Blood Pressure / Q000502:physiology*; D005440:Fluid Therapy; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000209:etiology* / Q000503:physiopathology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume / Q000502:physiology; D011187:Posture / Q000502:physiology; D013026:Space Flight; D014893:Weightlessness / Q000009:adverse effects*; D018544:Weightlessness Countermeasures; D018474:Weightlessness Simulation / Q000379:methods