Document Detail

Cardiovascular deconditioning and venous air embolism in simulated microgravity in the rat.
MedLine Citation:
PMID:  9025798     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Astronauts conducting extravehicular activities undergo decompression to a lower ambient pressure, potentially resulting in gas bubble formation within the tissues and venous circulation. Additionally, exposure to microgravity produces fluid shifts within the body leading to cardiovascular deconditioning. A lower incidence of decompression illness in actual spaceflight compared with that in ground-based altitude chamber flights suggests that there is a possible interaction between microgravity exposure and decompression illness. HYPOTHESIS: The purpose of this study was to evaluate the cardiovascular and pulmonary effects of simulated hypobaric decompression stress using a tail suspension (head-down tilt) model of microgravity to produce the fluid shifts associated with weightlessness in conscious, chronically instrumented rats. METHODS: Venous bubble formation resulting from altitude decompression illness was simulated by a 3-h intravenous air infusion. Cardiovascular deconditioning was simulated by 96 h of head-down tilt. Heart rate, mean arterial blood pressure, central venous pressure, left ventricular wall thickening and cardiac output were continuously recorded. Lung studies were performed to evaluate edema formation and compliance measurement. Blood and pleural fluid were examined for changes in white cell counts and protein concentration. RESULTS: Our data demonstrated that in tail-suspended rats subjected to venous air infusions, there was a reduction in pulmonary edema formation and less of a decrease in cardiac output than occurred following venous air infusion alone. Mean arterial blood pressure and myocardial wall thickening fractions were unchanged with either tail-suspension or venous air infusion. Heart rate decreased in both conditions while systemic vascular resistance increased. CONCLUSIONS: These differences may be due in part to a change or redistribution of pulmonary blood flow or to a diminished cellular response to the microvascular insult of the venous air embolization.
R R Robinson; M F Doursout; J E Chelly; M R Powell; T M Little; B D Butler
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  67     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  1996 Sep 
Date Detail:
Created Date:  1997-03-06     Completed Date:  1997-03-06     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  835-40     Citation Subset:  IM; S    
Dept. of Anesthesiology, University of Texas-Houston Medical School 77030, USA.
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MeSH Terms
Blood Gas Analysis
Cardiovascular Deconditioning / physiology*
Decompression Sickness / etiology,  physiopathology*
Embolism, Air / etiology,  physiopathology*
Fluid Shifts
Head-Down Tilt
Leukocyte Count
Lung Compliance
Weightlessness / adverse effects*
Weightlessness Simulation / adverse effects*
M R Powell / JSC; B D Butler / U TX, Houston

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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