[Simulated diving tests in guinea pigs]

Simulated diving tests with helium oxygen mixture were carried out in guinea pigs. The water depth was 100M (1.1Mpa). Hearing ability of guinea pigs changes and inner ear lesions occurred after decompression. The tests proved that hearing changes were especially evident in 0.5-1.0 kHz in slow decompression group and were induced by barotrauma. In the fast decompression group, the hearing impairment in 0.5-1.0 kHz range was more prominent than that in the 2-8kHz. The hearing thresholds of the 3 guinea pigs having vestibular symptoms (nystagmus, rotatory movement of the body) were elevated in the 0.5-8.0 kHz range. The vestibular symptoms and the elevation of hearing threshold of these 3 guinea pigs were induced by inner ear decompression sickness. The middle ears showed bleeding, effusion and cell infiltration. Ultrastructural changes were derangement and lodging of stereocilia of hair cells and changes of organelle.