Otoacoustic emissions growth rate threshold: distortion product in neonates.

Background: Distortion product otoacoustic emission measures (DPOAE) verifies, among other characteristics, the emergence and growth rate of the DPOAE response according to sound stimulus intensity (growth curve).

Aim: To estimate the DPOAE threshold in neonates according to the DPOAE growth curve at 2 kHz and 4 kHz, with stimulus presentation ranging between 35 and 70 dB SPL.

Method: Participants were 51 neonates, with 24 to 84 hours of life and with no indication of risk for hearing impairment. The DPOAE were registered in the growth curve function at 2 kHz and at 4 kHz. Neonates were evaluated during the period of hospital stay, after birth. Three possible thresholds were considered (LIM 1, LIM 2 and LIM 3) based on the presence of response at 3 dB SPL in the signal to noise ratio.

Results: The average thresholds intensities ranged from 47.55 to 49.85 dB at 2 kHz and from 55.52 to 59.94 dB at 4 kHz. The mean amplitude response ranged from 6.67 to 8.27 dB at 2 kHz and from 6.99 to 11.35 dB at 4 kHz. There was significant difference between the three thresholds for the two studied frequencies.

Conclusion: The procedure was feasible for the neonatal population revealing mean thresholds of up to 60 dB for both frequencies. Even though participants presented elevated thresholds, robust amplitude responses were observed.