title: Hypovolemic men and women regulate blood pressure differently following exposure to artificial gravity.
abstract: OBJECTIVE
  In addition to serious bone, vestibular, and muscle deterioration, space flight leads to cardiovascular dysfunction upon return to gravity. In seeking a countermeasure to space flight-induced orthostatic intolerance, we previously determined that exposure to artificial gravity (AG) training in a centrifuge improved orthostatic tolerance of ambulatory subjects. This protocol was more effective in men than women and more effective when subjects exercised.
  
  
  METHODS
  We now determine the orthostatic tolerance limit (OTL) of cardiovascularly deconditioned (furosemide) men and women on one day following 90 min of AG compared to a control day (90 min of head-down bed rest, HDBR).
  
  
  RESULTS
  There were three major findings: a short bout of artificial gravity improved orthostatic tolerance of hypovolemic men (30 %) and women (22 %). Men and women demonstrated different mechanisms of cardiovascular regulation on AG and HDBR days; women maintained systolic blood pressure the same after HDBR and AG exposure while men's systolic pressure dropped (11 ± 2.9 mmHg) after AG. Third, as presyncopal symptoms developed, men's and women's cardiac output and stroke volume dropped to the same level on both days, even though the OTL test lasted significantly longer on the AG day, indicating cardiac filling as a likely variable to trigger presyncope.
  
  
  CONCLUSIONS
  (1) Even with gender differences, AG should be considered as a space flight countermeasure to be applied to astronauts before reentry into gravity, (2) men and women regulate blood pressure during an orthostatic stress differently following exposure to artificial gravity and (3) the trigger for presyncope may be cardiac filling.
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA. jevans1@uky.edu.
authors.forename: Joyce M
authors.initials: JM
authors.lastname: Evans
authors.affiliation: Wyle Science, Technology and Engineering Group, Houston, TX, USA.
authors.forename: L Christine
authors.initials: LC
authors.lastname: Ribeiro
authors.affiliation: NASA Ames Research Center, Moffett Field, CA, USA.
authors.forename: Fritz B
authors.initials: FB
authors.lastname: Moore
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA.
authors.forename: Siqi
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA.
authors.forename: Qingguang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Kostas
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA.
authors.forename: Connor R
authors.initials: CR
authors.lastname: Ferguson
authors.affiliation: Veterans Affairs New Jersey Health Care System, East Orange, NJ, USA.
authors.forename: Jorge
authors.initials: J
authors.lastname: Serrador
authors.affiliation: Veterans Affairs New Jersey Health Care System, East Orange, NJ, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Falvo
authors.affiliation: Wyle Science, Technology and Engineering Group, Houston, TX, USA.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Stenger
authors.affiliation: Medical University of Graz, Graz, Austria.
authors.forename: Nandu
authors.initials: N
authors.lastname: Goswami
authors.affiliation: NASA Ames Research Center, Moffett Field, CA, USA.
authors.forename: Jon C
authors.initials: JC
authors.lastname: Rask
authors.affiliation: NASA Ames Research Center, Moffett Field, CA, USA.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Smith
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Knapp
mesh_terms: D000328:Adult; D001794:Blood Pressure; D005260:Female; D006801:Humans; D020896:Hypovolemia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D054971:Orthostatic Intolerance / Q000209:etiology / Q000503:physiopathology*; D012737:Sex Factors; D014893:Weightlessness / Q000009:adverse effects*
keywords: Cardiac output; Cardiovascular deconditioning; Centrifugation; Heart rate; Orthostatic tolerance; Stroke volume