Effects of ear canal static pressure on the dynamic behaviour of outer and middle ear in newborns

Wideband frequency impedance for diagnosis of ossicular chain abnormality

BACKGROUND

The accurate estimation of the ossicular chain abnormalities using existing functional examinations has been difficult.

AIMS/OBJECTIVES

This study aimed to verify the accuracy of preoperative diagnosis of ossicular chain abnormalities using a wideband frequency impedance (WFI) meter, which can measure the dynamic characteristics of the middle ear.

MATERIAL AND METHODS

Retrospective cohort study. Fourteen ears of patients with ossicular chain abnormalities that were definitively diagnosed surgically were included in this study. The following data were collected for each participant: sound pressure level (SPL) curve measured using the WFI meter and a sweep frequency impedance (SFI) meter, WFI measurements plotted on the resonance frequency (RF)-ΔSPL plane, distribution map of the dynamic characteristics of the middle ear, preoperative audiometry results, and the definitive surgical diagnosis.

RESULTS

The SPL curve obtained using the WFI meter had lesser noise than that obtained using the SFI meter. The distribution map revealed that the ossicular chain separation range and ossicular chain fixation range were completely separated. The hearing data tended to be poor in cases with small ΔSPL.

CONCLUSIONS AND SIGNIFICANCE

WFI can potentially enhance the accuracy of SFI. In addition, it can also be used for the classification of ossicular chain separation and fixation as well as the quantification of fixation in cases of ossicular chain anomalies that cannot be diagnosed using conventional tests.

Longitudinal changes in dynamic characteristics of neonatal external and middle ears

OBJECTIVES

Neonates have smaller and less mature ears than adults. Developmental changes in structure and function continually occur after birth and may affect the diagnostic results obtained by audiometric assessment instrumentation, such as tympanometry and otoacoustic emission. In the present study, we investigated longitudinal changes in external and middle ear dynamic characteristics by performing sweep frequency impedance (SFI) tests.

METHODS

SFI tests were longitudinally performed on healthy Japanese neonates (1 female and 1 male) from birth to 3 and 5 months, respectively. A sound of sweeping sinusoidal frequency, ranging from 0.1 kHz to 2 kHz, was presented to the ear canal at 50-daPa intervals of static pressure from +200 to -200 daPa. Test results were expressed a curve showing the sound pressure level (SPL) relative to probe tone frequency, called SPL curve.

RESULTS

The first fluctuation in resonance frequency (RF₁) and SPL (ΔSPL₁), related to the external ear, showed significant developmental changes as chronological age increased; that is, RF₁ and ΔSPL₁ were respectively increased and decreased and thereafter became unmeasurable by 5 months of age. In contrast, the second fluctuation in resonance frequency (RF₂) and SPL (ΔSPL₂), related to the middle ear, did not show significant changes over the measurement period.

CONCLUSIONS

The present results suggest that the dynamic characteristics of the external ear canal wall changed with increases in chronological age; the resonance of the wall at about 0.3 kHz at birth tended to increase to about 0.7 kHz and to be unmeasurable by 5 months of age, while those of the middle ear did not significantly changed. These results showing how neonatal-ear dynamics changes with chronological age may be an important key in further hearing research and the development of hearing devices and diagnostic tools suitable for neonates.

Sweep frequency impedance measures in young infants: developmental characteristics from birth to 6 months

OBJECTIVE

International Journal of Audiology To study the developmental characteristics of sweep frequency impedance (SFI) measures in healthy infants from birth to 6 months.

DESIGN

All infants were assessed using high-frequency tympanometry (HFT), distortion product otoacoustic emission (DPOAE) and SFI tests. SFI measures consisted of measurement of resonance frequency (RF) and mobility (ΔSPL) of the outer and middle ear. A mixed model analysis of variance was applied to the SFI data to examine the effect of age on RF and ΔSPL.

STUDY SAMPLE

Study included 117 ears from 83 infants of different age groups from birth to 6 months.

RESULTS

The mean RF of the outer ear increased from 279 Hz at birth to 545 Hz at 4 months, whereas mean ΔSPL of the outer ear decreased from 7.9 dB at birth to 3.7 dB at 4 months of age. In contrast, the mean RF and ΔSPL of the middle ear did not change significantly with age up to 6 months.

CONCLUSIONS

Developmental characteristics should be considered when evaluating the function of the outer and middle ear of young infants (≤6 months) using the SFI. The preliminary normative SFI data established in this study may be used to assist with the evaluation.