Compensating for deviant middle ear pressure in otoacoustic emission measurements, data, and comparison to a middle ear model.
Hof JR., de Kleine E., Avan P., Anteunis LJ., Koopmans PJ., van Dijk P.
OBJECTIVE: Deviant middle ear pressure has a negative effect on the forward and backward transmission of stimulus and emissions through the middle ear. Resolving this deviant middle ear pressure is expected to lead to better middle ear transmission and, as a result of this, stronger otoacoustic emissions, which are better detectable. We investigated the effect of compensation o a deviant tympanic peak pressure on click-evoked otoacoustic emissions (CEOAEs). Second, we compared patient data to model predictions made by Zwislocki's middle ear model. SETTING: University Medical Center. PATIENTS: Fifty-nine children aged between 0.5 and 9 years (mean, 4.4 yr). INTERVENTION: Hearing investigations including CEOAE measurements at ambient and at compensated tympanic peak pressure (TPP). MAIN OUTCOME MEASURE: CEOAEs at ambient and compensated TPP. RESULTS: Compensation of TPP resulted in higher emission amplitudes below 2 kHz (increase of 8-11 dB). In addition, the compensated measurement showed an increased phase lag (up to one-fourth cycle). For ears with mild deviations of TPP, Zwislocki's model could describe these changes. Pressure compensation was well described by a compliance increase of the tympanic membrane, the malleus, and the incus. CONCLUSION: Compensating the ear canal pressure for negative tympanic peak pressure increased CEOAE amplitudes below 2 kHz and increased the phase lag. These changes can be predicted from an increase of the compliance of the tympanic membrane, incus, and malleus, as a consequence of the pressure compensation.