Assessment of the influence of whole body vibration on Cochlear function

BACKGROUND: Whole body vibration (WBV) is a potentially harmful consequence resulting from the dissipation of energy by industrial machineries. The result of WBV exposure on the auditory system remains unknown. The objective of the present research was to evaluate the influence of WBV on cochlear function, in particular outer hair cell function. It is hypothesized that WBV impairs cochlear function resulting in decreased Distortion Product Otoacoustic Emission (DPOAE) levels (L(dp)) in rabbits subjected to WBV. METHODS: Twelve rabbits were equally divided into vibration and control groups. Animals in vibration group were exposed to 1.0 ms(-2) r.m.s vertical WBV at 4–8 Hz for 8 h/day during 5 consecutive days. Outer hair cell function was assessed by comparing repeated-measurements of DPOAE levels (L(dp)) across a range of f(2) frequencies in rabbits both exposed and unexposed to WBV. DPOAE level shifts (LS(dp)) were compared across ears, frequencies, groups, and times. RESULTS: No differences were seen over time in DPOAE levels in the non-exposed rabbits (p = 0.082). Post-exposure L(dp) in rabbits exposed to WBV were significantly increased at all test frequencies in both ears compared to baseline measures (p = 0.021). The greatest increase in L(dp) following exposure was seen at 5888.5 Hz (mean shift = 13.25 dB). Post-exposure L(dp) in rabbits exposed to WBV were not significantly different between the right and left ears (p = 0.083). CONCLUSION: WBV impairs cochlear function resulting in increased DPOAE responses in rabbits exposed to WBV. DPOAE level shifts occurred over a wide range of frequencies following prolonged WBV in rabbits.