Time-Frequency Properties of Neonatal Transiently Evoked Otoacoustic Emissions Measured in Three Different Acquisition Modes

Differences between Pressurized and Non-Pressurized Transient-Evoked Otoacoustic Emissions in Neonatal Subjects

INTRODUCTION

Recently, Interacoustics presented a new otoacoustic emission protocol where the probe pressurizes the ear cavity, thus eliminates the risk of non-assessment (REFER outcome) due to a negative middle ear pressure. This study evaluated the characteristics and the performance of this new protocol on a newborn well-baby population.

METHODS

One hundred sixty-three newborns (age 2.7 ± 1.1 days) for a total of 294 ears were assessed randomly. Transiently evoked otoacoustic responses were acquired by the Titan device (Interacoustics), using the default and a pressurized TEOAE protocol. The data were analyzed in terms of signal to noise ratios (S/Ns) at 5 frequencies, namely, 0.87, 1.94, 2.96, 3.97, and 4.97 kHz. To assess any possible gestational age (GE) effects on the TEOAE variables, the responses were subdivided in 4 different age subgroups.

RESULTS

There were no significant differences between the left and right ear TEOAE responses, for age (in days), GE (in weeks), weight (in grams), and S/N at all 5 frequencies. Considering the pooled 294 ears, paired t tests between the default and the pressurized TEOAE data showed significant differences across all 5 frequencies (p < 0.01). The pressurized protocol generated TEOAE responses presenting larger S/Ns, and a positive additive effect of approximately 2.31 dB was observed at all tested frequencies. There were no significant GE effects on the pressurized TEOAE responses. In terms of performance, both protocols performed equally (same number of PASSes).

CONCLUSION

The pressurized TEOAE protocol generates responses with higher S/Ns which might be useful in borderline cases where the middle ear status might cause a REFER screening outcome.

Otoacoustic emissions in newborns evoked by 0.5kHz tone bursts

BACKGROUND

Otoacoustic emissions (OAEs) are currently widely used in newborn hearing screening programs. OAEs evoked by transients (TEOAEs) in newborns are usually characterized by large response levels at higher frequencies but lower frequencies are affected by physiological noise. The purpose of the present study was to acquire responses at lower frequencies by measuring OAEs evoked by 0.5kHz tone bursts (TBOAEs).

METHODS

Otoacoustic emissions (OAEs) were recorded from 49 newborns. Measurements were made using the ILO 292 equipment from Otodynamics. In each ear, three measurements were made: first with a standard click stimulus at 80dB pSPL (CEOAEs), a second using a 0.5kHz tone burst at 80dB pSPL (TBOAEs), and a third recording of spontaneous OAEs (SOAEs). Global and half-octave-band values of OAE signal-to-noise ratio (SNR) and response level were used to assess statistical differences between CEOAEs and 0.5kHz TBOAEs. Additionally, time-frequency (TF) analysis of signals was performed using the matching pursuit method.

RESULTS

Global levels were highest for CEOAEs. However, at low frequencies (0.7-1kHz), 0.5kHz TBOAEs had significantly higher levels and SNRs than CEOAEs. At these frequencies, SNRs of CEOAEs were usually below 0dB. At 0.5kHz there were no statistically significant differences between CEOAEs and TBOAEs. In ears with recordable SOAEs, CEOAEs and TBOAEs had higher levels and SNRs than in ears without SOAEs.

CONCLUSIONS

Use of 0.5kHz TBOAEs may be a useful addition to standard CEOAE tests in newborns. They provide information about lower frequencies, a region where CEOAEs are usually prone to noise. The presence of SOAEs affects the magnitudes of both CEOAEs and TBOAEs.