Acquisition and Repeatability of High-Frequency Distortion Product Otoacoustic Emissions Using Two Different Calibration Methods in Newborns

Distortion-product otoacoustic emissions (DPOAEs) elicited with high-frequency (HF; up to 16 kHz) stimuli are measurable and repeatable in normal-hearing adults and children, adult patients, and are sensitive to ototoxic insults in adults. However, objective tests for monitoring basal cochlear function in those too young to respond subjectively need to be developed. DPOAE levels recorded at frequencies <10 kHz are well characterized, but DPOAE levels measured up to 16 kHz do not exist for newborns. The goal of the current study is to determine if HF DPOAEs are measurable and repeatable in newborns. DPOAEs were measured from 2-16 kHz (f(2)/f(1) of 1.22; L-1/L-2 = 65/55 dB SPL) using two different calibration methods (forward pressure level-FPL and in-the-ear-SPL) in 26 newborns. To assess repeatability, the probe was removed then re-inserted for a second round of testing. Results indicate that HF DPOAEs can be evoked and are repeatable in newborns and the use of FPL calibration shows promise for measuring HF responses and maximizing repeatability. To be implemented in monitoring programs where the highest frequencies with responses are continuously tested, stimulus parameters used to evoke newborn HF DPOAEs and calibration methods need further exploration.