Effects of Pressure Sweep Factors on Acoustic Immittance Measures in Ears with Normal/Low and High Acoustic Admittance

Abstract

Normal middle-ear function has a tympanometric peak pressure (TPP) of ~0 daPa, with a sharp decline as the air pressure withdraws away from 0 daPa. However, there is no information about variations in the TPP because of changes in pressure sweep direction and sweep rate in ears with different acoustic admittance values. This study investigated the effects of pressure sweep direction and rate on the TPP and acoustic admittance values in individuals with high- and normal-/low acoustic admittance middle-ears (25 ears with healthy middle-ear acoustic admittance [Group I] and 19 ears with high middle-ear acoustic admittance [Group II]). We explored changes in ipsilateral acoustic reex thresholds (ARTs) monitored with the obtained TPPs. Tympanometry was performed under four experimental conditions in two pressure directions (conventional and reverse) and at two pressure rates (high and low). In addition, we measured ipsilateral ARTs at octave frequencies from 500 to 4000 Hz for the obtained TPPs. We observed significant differences in the TPPs, but not in acoustic admittance measures, in both groups. Analysis of ipsilateral ARTs monitored at different TPPs showed significant differences between the four experimental conditions in Group II at octave frequencies >1000 Hz but not in Group I. Low (better) ARTs were elicited with lower variability at a TPP obtained in the conventional pressure sweep direction but at a low pressure sweep rate of 50 daPa/s. Therefore, tympanometric measurements are suggested to be performed at a low pressure sweep rate and in a conventional pressure sweep direction, especially for people with increased acoustic admittance.