Repeated atmospheric pressure alteration effect on the cochlea in rats: Experimental animal study

Abstract

OBJECTIVE: This study aimed to evaluate the effects of repeated pressure alterations on cochlear structures in rats in an attempt to understand indirectly the inner ear status of flight crew who are repeatedly exposed to pressure alterations. METHODS: There were 12 adult Wistar albino rats equally divided into 2 groups: Group 1 (controls) and Group 2 (study group). The animals in Group 2 were exposed to repeated pressure changes in a pressure cabin which is regulated by manometers. The animals in Group 1 were placed in the cabin without being exposed to pressure changes. Auditory brainstem response (ABR) testing was performed in all animals at the beginning and at the end of the study. After 12 wk the animals were sacrificed and their cochleas were investigated using scanning electron microscopy (SEM). RESULTS: In the study group, hearing decreases at 2 kHz, 4 kHz, 6 dB at 8 kHz, and 32 kHz were encountered at the end of 3 mo. On SEM evaluation of the control group, the outer hair cells (OHC) and stereocilia were normal throughout the cochlea. In the study group, there were irregularities in lateral surface connections and separations, collapse, and adhesions in the basal segment of the cochlea and partial loss of stereocilia throughout the cochlea. CONCLUSION: Repeated alterations in the atmospheric pressure can lead to damage in the inner ear with subtle or evident hearing loss. Frequent flyers like air workers may be at risk of inner ear damage, which may be considered an occupational health problem.