Pressurizing the transient evoked otoacoustic emission (TEOAE)

Summary of: Hof, J. R., de Kleine, E., Avan, P., Anteunis, L. J., Koopmans, P. J., & van Dijk, P. (2012). Compensating for deviant middle ear pressure in otoacoustic emission measurements, data, and comparison to a middle ear model. Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 33(4), 504–511. https://doi.org/10.1097/MAO.0b013e3182536d9f

Otoacoustic emissions (OAEs) describe soft sounds measured in the ear canal that originate in the cochlea via transmission through the middle ear. The presence of OAEs indicate normally functioning outer hair cells within the inner ear. However, OAE detection also depends upon the integrity of conductive path via the middle ear.  Therefore, a middle ear pathology may preclude OAE detection, even though outer hair cell function is normal. Such middle ear involvement may include the presence of middle-ear pressure that deviates from the ambient pressure in the ear canal, e.g., negative middle ear pressure, which has been shown to attenuate OAEs in the low frequencies. Matching the pressure in the sealed ear canal to the deviant pressure in the middle ear cavity may improve OAE detection assuming that the outer hair cell function is normal. The current study describes the effect of compensating for deviant middle-ear pressure on the amplitude and phase of transient-evoked OAEs (TEOAEs) in 59 children with near-normal and more severe deviant tympanic peak pressure. Subsequent to normalizing abnormal middle ear pressure in pathologic ears, results indicate that the OAEs increase in amplitude and phase lag, and hence, improve detectability.  Specifically, ears with mild negative middle ear pressure between -120 and -40 daPa show an average increase of 8 dB near 1 kHz, no level change above 1.5 kHz and a phase increase by 0.4 pi near 1.5 kHz; ears with moderate negative pressure between -200 and -120 daPa show an increase up to 11 dB near 1 kHz and extending up to 2 kHz, and a phase increase by 0.5 pi up to 5 kHz; and finally, ears with the largest negative pressure between -280 and -200 daPa do not show an increase in amplitude but do show a slight increase in phase for the frequencies above 2 kHz  over the moderate group. Comparisons made to a Zwislocki middle ear model suggest that the effect of compensating for negative middle ear pressure is a function of a decrease in the stiffness of the middle ear structures. This result supports the notion that compensating for negative middle ear pressure in the measurement of OAEs, as is possible in the Titan TEOAE module, increases the robustness of OAE detection.