Anette G Therkildsen1, Michael Gaihede. 1. Department of Otolaryngology, Head and Neck Surgery, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
Abstract
HYPOTHESIS: Modern tympanometers run at higher rates of pressure change than older tympanometers, which increases the inaccuracy of determining the middle ear pressure. BACKGROUND: Tympanometric middle ear pressure may be susceptible to both the direction as well as the rate of pressure change, which is reflected by two different pressure peaks in a bidirectional recording. The resulting peak pressure difference results in an inaccuracy, which can amount to 25 daPa in older instruments with slower rates of pressure change. However, modern instruments often apply much faster rates, which may increase the peak pressure difference and thus the inaccuracy of middle ear pressure. METHODS: Middle ear pressure was measured for a negative and positive direction of pressure change at four different rates (50, 100, 200, and 400 daPa/s) in 38 normal adults. The peak pressure difference was calculated by the middle ear pressure determined in positive minus negative direction. RESULTS: The mean peak pressure differences ranged between 10 and 12 daPa (standard deviation = 8-11) in the four groups and were independent of the rate of pressure change (p = 0.321). CONCLUSION: The peak pressure differences found by the current tympanometer were consistently small for all rates of pressure change and were thus independent of the rate. This means that high rates can be used without decreasing accuracy, and the mean error is only 5 to 6 daPa, corresponding to the intrinsic hysteresis of the middle ear system.
HYPOTHESIS: Modern tympanometers run at higher rates of pressure change than older tympanometers, which increases the inaccuracy of determining the middle ear pressure. BACKGROUND: Tympanometric middle ear pressure may be susceptible to both the direction as well as the rate of pressure change, which is reflected by two different pressure peaks in a bidirectional recording. The resulting peak pressure difference results in an inaccuracy, which can amount to 25 daPa in older instruments with slower rates of pressure change. However, modern instruments often apply much faster rates, which may increase the peak pressure difference and thus the inaccuracy of middle ear pressure. METHODS: Middle ear pressure was measured for a negative and positive direction of pressure change at four different rates (50, 100, 200, and 400 daPa/s) in 38 normal adults. The peak pressure difference was calculated by the middle ear pressure determined in positive minus negative direction. RESULTS: The mean peak pressure differences ranged between 10 and 12 daPa (standard deviation = 8-11) in the four groups and were independent of the rate of pressure change (p = 0.321). CONCLUSION: The peak pressure differences found by the current tympanometer were consistently small for all rates of pressure change and were thus independent of the rate. This means that high rates can be used without decreasing accuracy, and the mean error is only 5 to 6 daPa, corresponding to the intrinsic hysteresis of the middle ear system.
Authors: Yi-Wen Liu; Chris A Sanford; John C Ellison; Denis F Fitzpatrick; Michael P Gorga; Douglas H Keefe Journal: J Acoust Soc Am Date: 2008-12 Impact factor: 1.840