Identification of neonatal hearing impairment: Transient evoked otoacoustic emissions during the perinatal period

Objectives: 1) To describe transient evoked otoacoustic emission (TEOAE) le vels, noise levels and signal to noise ratios (SNRs) for a range of frequen cy bands in three groups of neonates who were tested as a part of the Ident ification of Neonatal Hearing Impairment multi-center consortium project. 2 ) To describe the relations between these TEOAE: measurements and age, test environment, baby state, and test time. Design: TFOAEs were measured in 4478 graduates of neonatal intensive care u nits (NICUs), 353 well babies with at least one risk indicator, and 2348 we ll. babies without risk factors. TEOAE: and noise levels were measured for frequency bands centered at 1.0, 1.5, 2.0, 3.0, and 4.0 kHz for a click sti mulus level of 80 dB SPL. For those ears not meeting "passing" stopping cri teria at 80 dB pSPL, a level of 86 dB pSPL was included. Measurement-based stopping rules were used such that a test did not terminate unless the resp onse revealed a criterion SNR in four out of five frequency bands or no res ponse occurred after a preset number of averages. Baby state, test environm ent, and other test factors were captured at the time of test. Results: TEOAE: levels,: noise levels and SNRs were similar for NICU gradua tes, well babies with risk factors and well babies without risk factors. Th ere were no consistent differences in response quality as a function of tes t environment, i.e., private room, unit, open crib, nonworking isolette, or working isolette. Noise level varied little across risk group, test enviro nment, or infant state other than crying, suggesting that the primary sourc e of noise in TEOAE measurements is infant noise. The most significant effe ct on response quality was center frequency. Responses were difficult to me asure in the half-octave band centered at 1.0 kHz, compared with higher fre quencies. Reliable responses were measured routinely at frequencies of 1.5 kHz and higher. Conclusions: TEOAEs are easily measured in both NICU graduates and well bab ies with and without risk factors for hearing loss in a wide variety of tes t environments. Given the difficulties encountered in making reliable measu rements for a frequency band centered at 1.0 kHz, its inclusion in a screen ing program may not be justified.