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Cochlear degeneration in minipigs after repeated hyperbaric exposures.
M K Wilkes1, A C Palmer, P C Pearce
1Wellcome Laboratory for Comparative Neurology, Department of Clinical Veterinary Medicine, Cambridge, England.
Undersea Biomedical Research
|March 1, 1989
Summary
Repeated hyperbaric exposures caused significant auditory damage in minipigs, including hair cell loss and abnormal stereocilia. This suggests current decompression schedules may not be safe for compressed air workers.
Area of Science:
- Otoacoustic emissions
- Inner ear pathology
- Hyperbaric medicine
Background:
- Repeated hyperbaric exposures are common for compressed air workers.
- Standard decompression schedules are considered safe.
- Potential risks to auditory function from repeated hyperbaric exposures are not fully understood.
Purpose of the Study:
- To investigate the effects of repeated hyperbaric exposures on auditory function and cochlear pathology in minipigs.
- To evaluate the safety of a standard decompression schedule (Blackpool Tables) for repeated hyperbaric exposures.
Main Methods:
- Four minipigs underwent 21 hyperbaric exposures (4 ATA for 1 hour) with standard decompression.
- Control group of three minipigs received no hyperbaric exposure.
- Auditory function assessed using Brainstem Auditory Evoked Response (BAER) testing.
- Cochlear and vestibular pathology examined using light and scanning electron microscopy.
Main Results:
- All exposed minipigs showed significant hair cell loss in the cochlea.
- BAER testing revealed no response bilaterally in 3 and unilaterally in 1 exposed animal.
- Microscopy identified detached tectorial membranes, fused and giant stereocilia, and vestibular changes in the saccule.
Conclusions:
- Repeated hyperbaric exposures using the tested compression-decompression profile caused significant auditory and cochlear pathology in minipigs.
- The findings challenge the presumed safety of standard decompression schedules for repeated hyperbaric exposures.
- Further research is needed to understand the mechanisms of injury and to develop safer protocols for compressed air workers.