Document Detail

Simulations of gravitational stress on normovolemic and hypovolemic men and women.
MedLine Citation:
PMID:  24754201     Owner:  NLM     Status:  In-Process    
BACKGROUND: Earth-based simulations of physiologic responses to space mission activities are needed to develop prospective countermeasures. To determine whether upright lower body positive pressure (LBPP) provides a suitable space mission simulation, we investigated the cardiovascular responses of normovolemic and hypovolemic men and women to supine and orthostatic stress induced by head-up tilt (HUT) and upright LBPP, representing standing in lunar, Martian, and Earth gravities.
METHODS: Six men and six women were tested in normovolemic and hypovolemic (furosemide, intravenous, 0.5 mg x kg(-1)) conditions. Continuous electrocardiogram, blood pressure, segmental bioimpedance, and stroke volume (echocardiography) were recorded supine and at lunar, Martian, and Earth gravities (10 degrees, 20 degrees, and 80 degrees HUT vs. 20%, 40%, and 100% bodyweight upright LBPP), respectively. Cardiovascular responses were assessed from mean values, spectral powers, and spontaneous baroreflex parameters.
RESULTS: Hypovolemia reduced plasma volume by approximately 10% and stroke volume by approximately 25% at supine, and increasing orthostatic stress resulted in further reductions. Upright LBPP induced more plasma volume losses at simulated lunar and Martian gravities compared with HUT, while both techniques induced comparable central hypovolemia at each stress. Cardiovascular responses to orthostatic stress were comparable between HUT and upright LBPP in both normovolemic and hypovolemic conditions; however, hypovolemic blood pressure was greater during standing at 100% bodyweight compared to 80 degree HUT due to a greater increase of total peripheral resistance.
CONCLUSIONS: The comparable cardiovascular response to HUT and upright LBPP support the use of upright LBPP as a potential model to simulate activity in lunar and Martian gravities.
Qingguang Zhang; Charles F Knapp; Michael B Stenger; Abhijit R Patwardhan; Samy C Elayi; Siqi Wang; Vladimir I Kostas; Joyce M Evans
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  85     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  2014 Apr 
Date Detail:
Created Date:  2014-04-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  407-13     Citation Subset:  IM; S    
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