Kanka Nattikan, Murakoshi Michio, Hamanishi Shinji, Kakuta Risako, Matsutani Sachiko, Kobayashi Toshimitsu, Wada Hiroshi
Department of Mechanical Engineering, Kagoshima University, Kagoshima, Japan.
Faculty of Frontier Engineering, Kanazawa University, Kanazawa, Japan.
Int J Pediatr Otorhinolaryngol. 2020 Jul;134:110061. doi: 10.1016/j.ijporl.2020.110061. Epub 2020 Apr 22.
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.
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.
The first fluctuation in resonance frequency (RF) and SPL (ΔSPL), related to the external ear, showed significant developmental changes as chronological age increased; that is, RF and ΔSPL were respectively increased and decreased and thereafter became unmeasurable by 5 months of age. In contrast, the second fluctuation in resonance frequency (RF) and SPL (ΔSPL), related to the middle ear, did not show significant changes over the measurement period.
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.
新生儿的耳朵比成年人更小且发育更不成熟。出生后，耳朵的结构和功能会持续发生发育变化，这可能会影响通过听力评估仪器（如鼓室图和耳声发射）获得的诊断结果。在本研究中，我们通过进行扫频阻抗（SFI）测试，研究了外耳道和中耳动态特征的纵向变化。
对健康的日本新生儿（1名女性和1名男性）分别从出生到3个月和5个月进行纵向SFI测试。以50 daPa的静态压力间隔（从+200到-200 daPa），向耳道施加频率范围为0.1 kHz至2 kHz的扫频正弦波声音。测试结果以一条显示相对于探测音频率的声压级（SPL）的曲线表示，称为SPL曲线。
与外耳道相关的共振频率（RF）和SPL（ΔSPL）的首次波动显示，随着月龄增加，有显著的发育变化；也就是说，RF和ΔSPL分别增加和减少，到5个月大时变得无法测量。相比之下，与中耳相关的共振频率（RF）和SPL（ΔSPL）的第二次波动在测量期间没有显示出显著变化。
目前的结果表明，外耳道壁的动态特征随着月龄增加而变化；出生时约0.3 kHz的壁共振倾向于增加到约0.7 kHz，到5个月大时变得无法测量，而中耳的动态特征没有显著变化。这些显示新生儿耳朵动态如何随月龄变化的结果，可能是进一步听力研究以及开发适合新生儿的听力设备和诊断工具的重要关键。
