Document Detail

Physical and physiological effects on otoacoustic emissions in hypobaric hypoxia.
MedLine Citation:
PMID:  20689333     Owner:  NLM     Status:  MEDLINE    
Tinnitus and dizziness are symptoms of acute mountain sickness. We investigated the mechanism by which high altitude (i.e. hypobaric hypoxia) affects inner ear function by measuring transient evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) under conditions of normobaric normoxia (1,013 hPa; 760 mm Hg) and hypobaric hypoxia (540 hPa; 405 mm Hg). The possibility that air pressure effects on the eustachian tube impacted our findings was excluded by the use of tympanograms. The nonphysiological effects of hypobaric hypoxia on TEOAE and DPOAE were also assessed using an ear simulator. Under conditions of hypobaric hypoxia, both TEOAE and DPOAE levels were reduced. The amount of reduction that occurred was approximately 4 dB in the total echo power and signal-to-noise ratio of the TEOAE, and in the 2f(1) - f(2) element level of the DPOAE. Stimulus levels that were measured using an ear simulator were also reduced by approximately 4 dB under conditions of hypobaric hypoxia. These results do not indicate that stimulus levels affected TEOAE and DPOAE levels because these levels were actually only slightly affected by changes in the stimulus level. Instead, this reduction was likely due to the nonphysiological hypobaric effects of the sound pressure emitted from the tympanic membrane. We conclude that the impact of hypobaric hypoxia on cochlear function was negligible up to pressures of 540 hPa.
Rika Ide; Tatsuhiko Harada; Sho Kanzaki; Hideyuki Saito; Masako Hoshikawa; Takashi Kawahara; Kaoru Ogawa
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Publication Detail:
Type:  Comparative Study; Journal Article     Date:  2010-07-30
Journal Detail:
Title:  ORL; journal for oto-rhino-laryngology and its related specialties     Volume:  72     ISSN:  1423-0275     ISO Abbreviation:  ORL J. Otorhinolaryngol. Relat. Spec.     Publication Date:  2010  
Date Detail:
Created Date:  2010-08-19     Completed Date:  2011-01-04     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0334721     Medline TA:  ORL J Otorhinolaryngol Relat Spec     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  225-32     Citation Subset:  IM    
Copyright Information:
Copyright 2010 S. Karger AG, Basel.
Department of Otorhinolaryngology, Keio University School of Medicine, Tokyo, Japan.
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MeSH Terms
Anoxia / physiopathology*
Auditory Threshold / physiology*
Eustachian Tube / physiopathology*
Middle Aged
Otoacoustic Emissions, Spontaneous / physiology*
Pressure / adverse effects
Reference Values

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