Department of Otolaryngology, Head and Neck Surgery, Eberhard-Karls-University Tübingen, Tübingen, Germany.
Section of Physiological Acoustics and Communication, Department of Otolaryngology, Eberhard-Karls-University Tübingen, Tübingen, Germany.
Ear Hear. 2024;45(5):1326-1338. doi: 10.1097/AUD.0000000000001522. Epub 2024 May 29.
To date, there is no international standard on how to use distortion-product otoacoustic emissions (DPOAEs) in serial measurements to accurately detect changes in the function of the cochlear amplifier due, for example, to ototoxic therapies, occupational noise, or the development of regenerative therapies. The use of clinically established standard DPOAE protocols for serial monitoring programs appears to be hampered by multiple factors, including probe placement and calibration effects, signal-processing complexities associated with multiple sites of emission generation as well as suboptimal selection of stimulus parameters.
Pulsed DPOAEs were measured seven times within 3 months for f2 = 1 to 14 kHz and L2 = 25 to 80 dB SPL in 20 ears of 10 healthy participants with normal hearing (mean age = 32.1 ± 9.7 years). L1 values were computed from individual optimal-path parameters derived from the corresponding individual DPOAE level map in the first test session. Three different DPOAE metrics for evaluating the functional state of the cochlear amplifier were investigated with respect to their test-retest reliability: (1) the interference-free, nonlinear-distortion component level ( LOD ), (2) the time course of the DPOAE-envelope levels, LDP ( t ), and (3) the squared, zero-lag correlation coefficient ( ) between the time courses of the DPOAE-envelope pressures, pDP ( t ), measured in two sessions. The latter two metrics include the two main DPOAE components and their state of interference.
Collated over all sessions and frequencies, the median absolute difference for LOD was 1.93 dB and for LDP ( t ) was 2.52 dB; the median of was 0.988. For the low ( f2 = 1 to 3 kHz), mid ( f2 = 4 to 9 kHz), and high ( f2 = 10 to 14 kHz) frequency ranges, the test-retest reliability of LOD increased with increasing signal to noise ratio (SNR).
On the basis of the knowledge gained from this study on the test-retest reliability of pulsed DPOAE signals and the current literature, we propose a DPOAE protocol for future serial monitoring applications that takes into account the following factors: (1) separation of DPOAE components, (2) use of individually optimal stimulus parameters, (3) SNR of at least 15 dB, (4) accurate pressure calibration, (5) consideration of frequency- and level-dependent test-retest reliabilities and corresponding reference ranges, and (6) stimulus levels L2 that are as low as possible with sufficient SNR to capture the nonlinear functional state of the cochlear amplifier operating at its highest gain.
迄今为止，尚无关于如何在连续测量中使用畸变产物耳声发射（DPOAE）来准确检测耳蜗放大器功能变化的国际标准，例如，由于耳毒性治疗、职业噪声或再生治疗的发展。临床上采用既定的标准 DPOAE 方案进行连续监测计划似乎受到多种因素的阻碍，包括探头放置和校准效应、与多个发射源相关的信号处理复杂性以及刺激参数的选择不理想。
在 10 名听力正常的健康参与者（平均年龄 32.1 ± 9.7 岁）的 20 只耳朵中，在 3 个月内进行了 7 次频率为 f2=1 至 14 kHz、L2=25 至 80 dB SPL 的脉冲 DPOAE 测量。L1 值是根据第一个测试会话中相应的个体 DPOAE 水平图中的个体最佳路径参数计算得出的。使用三种不同的 DPOAE 指标来评估耳蜗放大器的功能状态，研究其测试-重测可靠性：（1）干扰自由、非线性失真分量水平（LOD）；（2）DPOAE 包络水平的时间过程，LDP（t）；（3）在两个会话中测量的 DPOAE 包络压力 pDP（t）之间的平方、零滞后相关系数（）。后两个指标包括两个主要的 DPOAE 分量及其干扰状态。
汇总所有会话和频率，LOD 的中位数绝对差为 1.93 dB，LDP（t）的中位数绝对差为 2.52 dB，的中位数为 0.988。对于低频（f2=1 至 3 kHz）、中频（f2=4 至 9 kHz）和高频（f2=10 至 14 kHz）频率范围，LOD 的测试-重测可靠性随着信噪比（SNR）的增加而增加。
基于本研究中关于脉冲 DPOAE 信号的测试-重测可靠性的知识和当前文献，我们提出了一种用于未来连续监测应用的 DPOAE 方案，该方案考虑了以下因素：（1）DPOAE 分量的分离；（2）使用个体最佳刺激参数；（3）至少 15 dB 的 SNR；（4）准确的压力校准；（5）考虑频率和水平依赖性的测试-重测可靠性及其相应的参考范围；（6）刺激水平 L2 尽可能低，同时具有足够的 SNR 以捕获以最高增益运行的耳蜗放大器的非线性功能状态。
