(0946) Measurement of Sound and Vibrational Noise During Mastoidectomy

Introduction: The acoustic trauma that patients are exposed to during otologic surgery drill use is unclear, as previous studies have not captured the vibrational noise transmitted to the inner ear. To fill this knowledge gap, we have examined inner ear noise directly via intracochlear pressure changes during a mastoidectomy and cochleostomies.

Methods: Inner ear stimulation was measured using fiber optic pressure sensors inserted into the cochlea of cadaveric heads using a trans-canal approach. A tympanomeatal flap was elevated, and cochleostomies were made into the scala vestibuli and tympani, through which the sensors were placed and secured to the cochlear promontory with adhesive. Intracochlear pressures were measured with different drill bits, at different speeds, during mastoidectomy and cochleostomy. The equivalent sound pressure level in the ear canal was calculated from the measurements using the middle ear transfer function to estimate equivalent noise exposures. Microphones were also placed in the surgeon’s ear, cadaver ear, and within three feet of drilling to capture acoustic noise exposure in the room.

Results: Preliminary results show significant pressures during mastoidectomy, which could exceed 115 dB SPL (equivalent ear canal SPL) in scala vestibular and tympani during drilling. The highest values were seen during the cochleostomy portion of the experiment.

Conclusions: Results reveal significant changes in intracochlear pressure during mastoidectomy, with levels high enough to potentially induce acoustic trauma. This data will be used to characterize the noise exposure mastoidectomy patients and surgeons experience in relation to occupational exposure to provide guidelines for safe maximum noise exposure and duration for patient and surgeon.