RESUMO
It has been recognized that noise levels generated during ear surgery may cause sensorineural hearing loss. However, there is a controversy about the main factor that may cause such hearing threshold alternations: drilling, suction or both of them. The purpose of this investigation was to measure the air-conduction noise levels generated by common drills, burrs and suction irrigators in mastoid surgery. Our evaluations were carried out in two states: isolated temporal bones [cadavers] and intraoperative recordings. Preliminary drillings were made on 10 cadavers, and intensity and frequency analysis of common diamond and cutting burrs were performed. Then, the noise levels generated by drilling, suction irrigation and simultaneous drilling and suction irrigation were measured from 15 patients under radical modified mastoidectomy. Data were analyzed by SPSS II software and 0.05 value was regard as significant level. The average noise levels of drilling ranged from 83 to 95 dB SPL, varying with burr used. Cutting burrs were found to be up to more intense than diamond burrs. Mean suction irrigation noise levels ranged from 77.45 to 78.65 dB SPL. The average of "intraoperative drilling" and "simultaneous drilling and suction irrigation" generated noise levels were 87.14 and 86.26 dB SPL, respectively. The comparison of resultant noise levels between cadaver and under operation situations was not statistically significant. Our results showed that the main factor contributing the highest noise level is drilling which is predominately apparent in cutting burrs. Exposure to these noise levels may account for shifts in the hearing thresholds