Hearing acuity of anesthesiologists and alarm detection

With rapid technological advances in anesthesiology, we are acquiring an ever increasing number of auditory alarm systems in the operating room the value of which depend on the hearing acuity of the anesthesiologist monitoring the patient. Presbycusis, the effect of aging on the auditory system, characteristically results in a bilaterally symmetric neurosensory high-frequency hearing loss ( > 2,000 Hz). In this study we attempt to assess the impact of this common hearing disorder on alarm detection.

We measured air conduction hearing acuities of 188 anesthesiologists who volunteered to participate. Subjects were divided into six age groups (25-34, 35-44, 45-54, 55-64, and > 75 yr of age). Abnormal audiograms were compared to the intensity and frequency of alarms in our operating room to determine which alarms were out of hearing range. Subjects with a history of chronic or excessive noise exposure were excluded from the study. The median hearing threshold for each age group of study subjects was compared to the median hearing threshold of similar age groups in the general population.

Overall, 66% of the subjects had an abnormal audiogram, and 7% had one or more alarm intensities less than their detectability threshold (14% unilateral, 86% bilateral). Median hearing threshold was worse than the general population for men and women less than 55 yr of age. Hearing acuity worse than the general population occurred at the lower frequencies while acuity at the higher frequencies was equal or slightly better. However, inability to hear alarms occurred only with those alarms that have frequencies of 4,000 Hz or greater.

Although high-frequency hearing acuity of individuals in our study was better than that of the general population, hearing deficits at high frequencies were of the magnitude to interfere with alarm detection. Also background noise levels vary greatly in different operating rooms. These two problems create a hindrance to alarm detection for certain anesthesiologists. From our data we conclude that the aging human ear may not be capable of accurately detecting some auditory alarms in the operating room. Alarm design should consider hearing acuity because high-frequency alarms may go undetected.