Brainstem auditory evoked potentials during a helium-oxygen saturation dive to 450 meters of seawater

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Brainstem auditory evoked potentials during a helium-oxygen saturation dive to 450 meters of seawater

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dc.contributor.author Lorenz, J en_US
dc.contributor.author Brooke, ST en_US
dc.contributor.author Petersen, R en_US
dc.contributor.author Torok, Z en_US
dc.contributor.author Wenzel, J en_US
dc.date.accessioned 2006-08-23T01:10:26Z
dc.date.available 2006-08-23T01:10:26Z
dc.date.issued 1995 en_US
dc.identifier.other Undersea Hyperb Med en_US
dc.identifier.uri PMID: 7580764 en_US
dc.identifier.uri http://archive.rubicon-foundation.org/2205
dc.description Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org ) en_US
dc.description.abstract When divers are exposed to extreme atmospheric pressures they may exhibit symptoms of the high pressure nervous syndrome (HPNS). Although clinical HPNS symptoms are well described, little is known about the underlying pathophysiologic mechanisms. Special HPNS signs like vertigo and tremor suggested sensory-motor hyperexcitability resulting from brainstem dysfunction. We therefore studied brainstem auditory evoked potential (BAEP) repeatedly in four divers during an experimental deep helium-oxygen saturation dive to 450 meters of seawater (msw). Wave I (auditory nerve response) latency decreased whereas interpeak latencies (IPLs) I-III and I-V, which indicate respective cochleo-pontine and cochleo-mesencephalic transmission time, prolonged during the dive. IPLs III-V also prolonged the dive, but with greater variability among divers. Two divers showed a marked reversal of the normal attenuation effect of increased stimulus presentation rates on IV and V amplitudes during compression, an effect that subsided during the stay at bottom depth. This finding might indicate a relative enhancement of synaptic excitability and is presumed to be a feature of HPNS. Wave I latency reduction might at least partly be caused by accelerated sound conduction in dense helium. Additionally, an upward shift of middle ear resonance frequencies in helium can induce a basal shift of the main cochlear portion responding to the wide band clicks. This effect may reduce wave I latency due to greater relative input from the basal high frequency-short latency-cochlear neurons. Pressure-induced decrease of nerve conduction velocity, delay of synaptic transmission, and inhibitory modulation of midbrain auditory afferents possibly contributed to observed interpeak latency prolongations. Clinical HPNS signs, such as tiredness, dizziness, postural and intentional hand tremor, ataxia, and opsoclonus, were noted in three divers after reaching 300 msw and continued throughout the 37-h stay at bottom depth. en_US
dc.format.extent 2003127 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.rights Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org ) en_US
dc.source.uri null en_US
dc.subject saturation en_US
dc.subject helium en_US
dc.subject heliox en_US
dc.subject ear en_US
dc.subject high pressure nervous syndrome en_US
dc.subject auditory evoked potentials en_US
dc.subject.mesh Adult Diving/physiology* Evoked Potentials, Auditory, Brain Stem/physiology* Helium/administration & dosage High Pressure Neurological Syndrome/physiopathology* Humans Neurologic Examination Oxygen/administration & dosage Seawater Substances: Helium Oxygen en_US
dc.title Brainstem auditory evoked potentials during a helium-oxygen saturation dive to 450 meters of seawater en_US

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