Article
Experimental study concerning the effect of positive Gz – acceleration on human hearing
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Published: | July 22, 2009 |
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Background: Decreased blood flow and stagnant hypoxia are discussed to be main reasons for inner ear dysfunction, especially for a few types of sudden hearing loss (SHL) and noise induced hearing loss (NHL).Several types of hypoxia cause impairment of inner ear function [Ref. 1], [Ref. 2]. Changes of the DPOAE-signal are observed,
but only after centrifuge runs [Ref. 3]. This pilot study was aimed to find out if acceleration and stagnant hypoxia affect human hearing.
Methods: Using the high performance human centrifuge of the German Airforce Institute of Aviation Medicine, Distortion Product Otoacoustic Emissions (DPOAE) from 1 kHz to 4 kHz (f2) and eardrum impedance of 8 male volunteers were recorded during centrifuge runs with increasing acceleration up to +5 Gz (z-axis, head to foot).
Results: During increased positive acceleration starting at 3 g about 5–10 dB decreased DPOAE were observed at all frequencies of 8 male volunteers. DPOAE amplitudes were more reduced in the lower (1–2 kHz) than in the higher frequency range (3–4 kHz). Additionally eardrum impedance also increased with increasing acceleration.
Conclusions: Inner and middle ear function are affected by positive acceleration (z-axis, head to foot). To distinguish between perfusion and mechanical caused impairment of hearing further research is necessary. The effect of decreased cerebral perfusion might be compensated by anti-G-suits.
References
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- Mess K, Behnisch A, Suckfüll M. Audimont – eine wissenschaftliche Expedition zum Cho Oyu im Himalaya. Fortschritte in der Medizin-Orginalien. 2003;121(1):2003:1-4.
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- Johnson RE, Allen JR, Schultz T, Liening DA, Bell AF. The Effects of Linear Acceleration on Distortion Product Otoacoustic Emissions in Human Ears. Avat Space Envir Med. 1998;69(1):40-4.