Document Detail

Postural control and venous gas bubble formation during hypobaric exposure.
MedLine Citation:
PMID:  11908882     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Earlier studies have shown that acute hypoxia at simulated altitudes up to 18,000 ft affects postural control. The main objective of this study was to investigate whether this is caused by hypoxia or by other effects of reduced barometric pressure. Doppler monitoring was included to rule out venous gas emboli (VGE) as a possible cause of disturbed postural control. A secondary objective was to evaluate two conventional altitude chamber training profiles regarding release of VGE. HYPOTHESIS: Chamber flights up to 18,000 ft affect postural control due to acute hypoxia or other effects of reduced barometric pressure such as bubble formation. VGE probably will not be formed at the altitude chamber flight profiles and procedures selected for this study. METHODS: Repeated registrations of postural control and Doppler monitoring for detection of possible VGE were performed on 12 subjects before, during, and after exposure to two different altitude chamber flight profiles. In chamber flight profile 1 the subjects were first preoxygenated for 45 min and then exposed to a normoxic environment at altitudes of 25,000, 18,000, 14,000, and 8000 ft. Chamber flight profile 2 consisted of an 80 min exposure to 14,000 ft without preoxygenation or supplemental oxygen for the first 60 min. RESULTS: In chamber flight profile 1, where normoxic conditions were achieved during all balance testing, no significant changes in postural control were found. No VGE were observed and no subjective dizziness was reported during this exposure. In chamber flight profile 2, a significant influence on postural control was reported for the eyes-open condition, when breathing air at 14,000 ft. These changes normalized when reaching ground level. VGE were observed in one of the 12 subjects after 75 min at 14,000 ft. Another subject complained of severe dizziness during the initial part of the decompression to 14,000 ft, and was excluded from further experiments. CONCLUSIONS: Changes in postural control at altitudes up to 18,000 ft is probably due to acute hypoxia. VGE may form during acute altitude exposure to 14,000 ft.
SteinHelgeGlad Nordahl; Torbjørn Aasen; Jan Risberg; Jan Ove Owe; Otto Inge Molvaer
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  73     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  2002 Mar 
Date Detail:
Created Date:  2002-03-22     Completed Date:  2002-09-10     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  184-90     Citation Subset:  IM; S    
Department of Otolaryngology/Head and Neck Surgery, Haukeland University Hospital, Bergen, Norway.
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MeSH Terms
Aerospace Medicine
Anoxia / physiopathology*
Embolism, Air / etiology*,  physiopathology,  ultrasonography
Middle Aged
Postural Balance*
Ultrasonography, Doppler

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

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