Abstract:
BACKGROUND : The primary aim of newborn hearing screening is to detect permanent hearing
loss. Because otoacoustic emissions (OAEs) and automated auditory brainstem response (AABR)
are sensitive to hearing loss, they are often used as screening tools. On the other hand, falsepositive
results are most often because of transient outer- and middle ear conditions. Wideband
acoustic immittance (WAI), which includes physical measures known as reflectance and
absorbance, has shown potential for accurate assessment of middle ear function in young infants.
OBJECTIVE : The main objective of this study was to determine the feasibility of WAI as a
diagnostic tool for assessing middle ear functioning in preterm neonates in the neonatal
intensive care unit (NICU) designed for premature and ill neonates. A further objective was to
indicate the difference between the reflectance values of tones and click stimuli.
METHOD : Fifty-six at-risk neonates (30 male and 26 female), with a mean age at testing of 35.6
weeks (range: 32–37 weeks) and a standard deviation of 1.6 from three private hospitals, who
passed both the distortion product otoacoustic emission (DPOAE) and AABR tests, were
evaluated prior to discharge from the NICU. Neonates who presented with abnormal DPOAE
and AABR results were excluded from the study. WAI was measured by using chirp and tone
stimuli. In addition to reflectance, the reflectance area index (RAI) values were calculated.
RESULTS : Both tone and chirp stimuli indicated high-power reflectance values below a frequency
of 1.5 kHz. Median reflectance reached a minimum of 0.67 at 1 kHz – 2 kHz but increased to
0.7 below 1 kHz and 0.72 above 2 kHz for the tone stimuli. For chirp stimuli, the median
reflectance reached a minimum of 0.51 at 1 kHz – 2 kHz but increased to 0.68 below 1 kHz and
decreased to 0.5 above 2 kHz. A comparison between the present study and previous studies
on WAI indicated a substantial variability across all frequency ranges.
CONCLUSION : These WAI measurements conducted on at-risk preterm NICU neonates (mean age at testing: 35.6 weeks, range: 32–37 weeks) identified WAI patterns not previously reported
in the literature. High reflective values were obtained across all frequency ranges. The age of
the neonates when tested might have influenced the results. The neonates included in the
present study were very young preterm neonates compared to the ages of neonates in previous
studies. WAI measured in at-risk preterm neonates in the NICU was variable with
environmental and internal noise influences. Transient conditions affecting the soundconduction
pathway might have influenced the results. Additional research is required to
investigate WAI testing in ears with and without middle ear dysfunction. The findings of the
current study imply that in preterm neonates it was not possible to determine the feasibility of
WAI as a diagnostic tool to differentiate between ears with and without middle ear pathology.
