Rethinking the clinical utility of distortion-product otoacoustic emission (DPOAE) signal-to-noise ratio

OBJECTIVE

Distortion-product otoacoustic emission (DPOAE) levels are repeatable over time in normal-hearing individuals making DPOAE levels an ideal measurement for monitoring cochlear status in clinic and research applications. However, if DPOAE signal-to-noise ratio (SNR) values instead of levels are used for monitoring, the repeatability of this value needs to be established. This retrospective, cross-sectional study sought to determine DPOAE SNR repeatability in younger children, older children, young adults and a patient population with normal hearing.

DESIGN

Each participant attended four sessions where DPOAE discrete frequency sweeps were collected at conventional (≤ 8 kHz) and/or extended-high frequencies (> 8 kHz). To examine the extent of variability to be expected for DPOAE SNR, average absolute SNR differences-between-trials were determined and compared to average absolute DPOAE level differences-between-trials.

STUDY SAMPLES

One hundred forty-five participants, incorporating four different groups from three different studies. Ages ranged from 3 to 55 years.

RESULTS

Average SNR differences-between-trials across all frequencies are greater than differences for average DPOAE levels. Improved calibration methods result in SNR differences-between-trials that are similar across all frequencies.

CONCLUSIONS

When monitoring cochlear health over an extended bandwidth, DPOAE levels are less variable across trials than SNR values, thus allowing earlier indicators of cochlear damage.

Descriptive Characterization of High-Frequency Distortion Product Otoacoustic Emission Source Components in Children

PURPOSE

Distortion product otoacoustic emissions (DPOAEs) provide an objective assessment of cochlear function and are used for serial ototoxicity monitoring in pediatric cancer patients. DPOAEs are modeled as having distortion (near f2) and reflection (near 2f1-f2) component sources, and developmental changes are observed in these components' relative strengths in infants compared with adults. However, little is known about source component strengths in childhood or at extended high frequencies (EHFs; > 8 kHz). Thus, the purpose of this study was to describe the effects of age and stimulus frequency on DPOAE components in children.

METHOD

DPOAEs were collected with varied frequency ratios (f2/f1 = 1.1-1.25) for a wide range of frequencies (2-16 kHz) in 39 younger (3-6 years) and 41 older (10-12 years) children with constant levels (L1/L2) of 65/50 dB SPL. A depth-compensated simulator sound pressure level method of calibration was employed. A time waveform representation of the results across various ratios was created to estimate peak pressures and latencies of each DPOAE component.

RESULTS

Estimated peak pressures of DPOAE components revealed the greatest differences in DPOAE sources between children occurring at the highest frequencies tested, where the peak pressure of both components was largest for younger compared with older children. Latency differences between the children were only noted at higher frequencies for the distortion component.

CONCLUSIONS

These results suggest that DPOAE levels decrease with age and reflection emissions are vulnerable to cochlear change. This work guides optimization of protocols for pediatric ototoxicity monitoring, whereby including EHF otoacoustic emissions is clearly warranted and choosing to isolate DPOAE sources may prove beneficial.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23669214.

Influence of tinnitus, lifetime noise exposure, and firearm use on hearing thresholds, distortion product otoacoustic emissions, and their relative metric

Distortion product otoacoustic emissions (DPOAEs) and hearing thresholds (HTs) are widely used to evaluate auditory physiology. DPOAEs are sensitive to cochlear amplification processes, while HTs are additionally dependent upon inner hair cells, synaptic junctions, and the auditory nervous system. These distinctions between DPOAEs and HTs might help differentially diagnose auditory dysfunctions. This study aims to differentially diagnose auditory dysfunctions underlying tinnitus, firearm use, and high lifetime noise exposure (LNE) using HTs, DPOAEs, and a derived metric comparing HTs and DPOAEs, in a sample containing overlapping subgroups of 133 normal-hearing young adults (56 with chronic tinnitus). A structured interview was used to evaluate LNE and firearm use. Linear regression was used to model the relationship between HTs and DPOAEs, and their regression residuals were used to quantify their relative agreement. Participants with chronic tinnitus showed significantly elevated HTs, yet DPOAEs remained comparable to those without tinnitus. In contrast, firearm users revealed elevated HTs and significantly lower DPOAEs than predicted from HTs. High LNE was associated with elevated HTs and a proportional decline in DPOAEs, as predicted from HTs. We present a theoretical model to interpret the findings, which suggest neural (or synaptic) dysfunction underlying tinnitus and disproportional mechanical dysfunction underlying firearm use.

Clinical Considerations for Routine Auditory and Vestibular Monitoring in Patients With Cystic Fibrosis

Purpose Specific classes of antibiotics, such as aminoglycosides, have well-established adverse events producing permanent hearing loss, tinnitus, and balance and/or vestibular problems (i.e., ototoxicity). Although these antibiotics are frequently used to treat pseudomonas and other bacterial infections in patients with cystic fibrosis (CF), there are no formalized recommendations describing approaches to implementation of guideline adherent ototoxicity monitoring as part of CF clinical care. Method This consensus statement was developed by the International Ototoxicity Management Working Group (IOMG) Ad Hoc Committee on Aminoglycoside Antibiotics to address the clinical need for ototoxicity management in CF patients treated with known ototoxic medications. These clinical protocol considerations were created using consensus opinion from a community of international experts and available evidence specific to patients with CF, as well as published national and international guidelines on ototoxicity monitoring. Results The IOMG advocates four clinical recommendations for implementing routine and guideline adherent ototoxicity management in patients with CF. These are (a) including questions about hearing, tinnitus, and balance/vestibular problems as part of the routine CF case history for all patients; (b) utilizing timely point-of-care measures; (c) establishing a baseline and conducting posttreatment evaluations for each course of intravenous ototoxic drug treatment; and (d) repeating annual hearing and vestibular evaluations for all patients with a history of ototoxic antibiotic exposure. Conclusion Increased efforts for implementation of an ototoxicity management program in the CF care team model will improve identification of ototoxicity signs and symptoms, allow for timely therapeutic follow-up, and provide the clinician and patient an opportunity to make an informed decision about potential treatment modifications to minimize adverse events. Supplemental Material https://doi.org/10.23641/asha.16624366.

Emerging Distortion Product Otoacoustic Emission Techniques to Identify Preclinical Warning Signs of Basal Cochlear Dysfunction Due to Ototoxicity

Hundreds of medications commonly prescribed for anticancer treatments and some infections are known to cause hearing damage, referred to as ototoxicity. Preventing or minimizing ototoxicity is critical in order to preserve quality of life for patients receiving treatment and to reduce the societal burden of hearing loss. Current clinical evaluations are restricted to a limited frequency range (≤8 kHz); however, this approach does not permit the earliest detection of ototoxicity, most likely to be observed at the highest frequencies (9–20 kHz). Distortion product otoacoustic emissions (DPOAEs) offer a noninvasive, objective approach to monitor cochlear health in those unable to respond via conventional methods. The current report analyzes different DPOAE paradigms used in patients undergoing chemotherapy treatments with various platinum derivatives. Individualized serial monitoring protocols were completed at the highest frequencies with measurable DPOAEs. This allowed the exploration of potential clinical translation opportunities for further quantification of the earliest signs of underlying cochlear damage, which may go undetected with conventional methods. Clinical practice has the potential to be enhanced by emerging DPOAE applications, including targeted monitoring protocols and high-frequency stimuli to assess cochlear function, especially at the highest frequencies, and advanced calibration techniques to ensure the stability of serial measurements.

Development of Natural Product-Conjugated Metal Complexes as Cancer Therapies

Platinum-based drugs have revolutionized cancer care, but are unfortunately associated with various adverse effects. Meanwhile, natural product scaffolds exhibit multifarious bioactivities and serve as an attractive resource for cancer therapy development. Thus, the conjugation of natural product scaffolds to metal complexes becomes an attractive strategy to reduce the severe side effects arising from the use of metal bearing drugs. This review aims to highlight the recent examples of natural product-conjugated metal complexes as cancer therapies with enhanced selectivity and efficacy. We discuss the mechanisms and features of different conjugate complexes and present an outlook and perspective for the future of this field.

Conventional audiometry, extended high-frequency audiometry, and DPOAEs in youth recreational firearm users

To determine if conventional audiometry, EHFA, and pDPOAEs are useful as early indicators of cochlear damage from recreational firearm impulse noise exposure in youth firearm users. Quantitative cross-sectional descriptive pilot study. Descriptive statistics and MANOVA with post hoc Tukey Honestly Significant Difference test were used to compare pDPOAEs (1-10 kHz), conventional audiometry (0.25-8 kHz), and EHFA (10-16 kHz) in YFUs. 25 YFUs (n = 11 7-12 years; n = 14 13-17 years) with self-reported poor compliance with hearing protector device wear. Conventional audiometric thresholds at 2-, 3- and 4 kHz were significantly poorer than normal but did not distinguish between older and younger YFUs or between the GBE and the contralateral ear. EHFA thresholds at 14- and 16 kHz were significantly poorer than for other frequencies, and differentiate between older and younger youths, but do not distinguish the GBE from the contralateral ear. Finally, pDPOAE levels were significantly reduced at 8- and 10 kHz but did not show any differences for the younger versus older YFUs or for the GBE from the contralateral ear. Conclusion: Both EHFA and pDPOAEs provide early evidence of NIHL in YFUs, and may be useful for the early detection of NIHL in YFUs.

Applying U.S. national guidelines for ototoxicity monitoring in adult patients: perspectives on patient populations, service gaps, barriers and solutions

OBJECTIVES

To promote establishment of effective ototoxicity monitoring programs (OMPs), this report reviews the U.S. national audiology guidelines in relation to "real world" OMP application. Background is provided on the mechanisms, risks and clinical presentation of hearing loss associated with major classes of ototoxic medications.

DESIGN

This is a non-systematic review using PubMed, national and international agency websites, personal communications between ototoxicity experts, and results of unpublished research. Examples are provided of OMPs in various healthcare settings within the U.S. civilian sector, Department of Defense (DoD), and Department of Veterans Affairs (VA).

STUDY SAMPLE

The five OMPs compared in this report represent a convenience sample of the programs with which the authors are affiliated. Their opinions were elicited via two semi-structured teleconferences on barriers and facilitators of OMP, followed by a self-administered questionnaire on OMP characteristics and practices, with responses synthesized herein. Preliminary results are provided from an ongoing VA clinical trial at one of these OMP sites. Participants were 40 VA patients who received cisplatin chemotherapy in 2014-2017. The study arms contrast access to care for OMP delivered on the treatment unit versus usual care as provided in the audiology clinic.

RESULTS

Protocols of the OMPs examined varied, reflecting their diverse settings. Service delivery concerns included baseline tests missed or completed after the initial treatment, and monitoring tests done infrequently or only after cessation of treatment. Perceived barriers involved logistics related to accessing and testing patients, such as a lack of processes to help patients enter programs, patients' time and scheduling constraints, and inconvenient audiology clinic locations. Use of abbreviated or screening methods facilitated monitoring.

CONCLUSIONS

The most effective OMPs integrated audiological management into care pathways of the clinical specialties that prescribe ototoxic medications. More OMP guidance is needed to inform evaluation schedules, outcome reporting, and determination of actionable ototoxic changes. Guidance is also lacking on the use of hearing conservation approaches suitable for the mass testing needed to support large-scale OMP efforts. Guideline adherence might improve with formal endorsement from organizations governing the medical specialty stakeholders in OMP such as oncologists, pulmonologists, infectious disease specialists, ototolaryngologists and pharmacists.