Electrophysiological assessment and pharmacological treatment of blast-induced tinnitus.

Tinnitus, the phantom perception of sound, often occurs as a clinical sequela of auditory traumas. In an effort to develop an objective test and therapeutic approach for tinnitus, the present study was performed in blast-exposed rats and focused on measurements of auditory brainstem responses (ABRs), prepulse inhibition of the acoustic startle response, and presynaptic ribbon densities on cochlear inner hair cells (IHCs). Although the exact mechanism is unknown, the "central gain theory" posits that tinnitus is a perceptual indicator of abnormal increases in the gain (or neural amplification) of the central auditory system to compensate for peripheral loss of sensory input from the cochlea. Our data from vehicle-treated rats supports this rationale; namely, blast-induced cochlear synaptopathy correlated with imbalanced elevations in the ratio of centrally-derived ABR wave V amplitudes to peripherally-derived wave I amplitudes, resulting in behavioral evidence of tinnitus. Logistic regression modeling demonstrated that the ABR wave V/I amplitude ratio served as a reliable metric for objectively identifying tinnitus. Furthermore, histopathological examinations in blast-exposed rats revealed tinnitus-related changes in the expression patterns of key plasticity factors in the central auditory pathway, including chronic loss of Arc/Arg3.1 mobilization. Using a formulation of N-acetylcysteine (NAC) and disodium 2,4-disulfophenyl-N-tert-butylnitrone (HPN-07) as a therapeutic for addressing blast-induced neurodegeneration, we measured a significant treatment effect on preservation or restoration of IHC ribbon synapses, normalization of ABR wave V/I amplitude ratios, and reduced behavioral evidence of tinnitus in blast-exposed rats, all of which accorded with mitigated histopathological evidence of tinnitus-related neuropathy and maladaptive neuroplasticity.

Assessment of Safe Listening Intentional Behavior Toward Personal Listening Devices in Young Adults.

Recreational noise-induced hearing loss (RNIHL) is a highly preventable disorder that is commonly seen in teenagers and young adults. Despite the documented negative effects of RNIHL, it is still challenging to persuade people to adopt safe listening behaviors. More research is needed to understand the underlying factors guiding listeners' intentions to engage in safe listening habits. We used the Theory of Planned Behavior (TPB) to identify attitudes, social norms, and behavioral control in 92 young adults toward two intentional behaviors related to safe listening habits while listening to their personal listening devices: (1) lowering the intensity of loud music, and (2) shortening the listening duration of loud music. Using a Qualtrics survey, the major factors of the TPB model as they relate to the participants' intention to engage in risk-controlling behavior were assessed. Behavioral intentions to turn the music down and listen for shorter durations were thought to be predicted by the TPB factors (attitudes, social norms, and perceived behavioral control). Linear regression findings indicated that the overall TPB models were significant. Positive attitudes toward turning the music down and shortening the durations were significantly associated with intentions to engage in non-risky behavior, more so for the former behavior.

Distortion product oto-acoustic emission: a superior tool for hearing assessment than pure tone audiometry.

OBJECTIVE: Hearing plays a crucial role in the performance of a soldier and is important for communication and speech processing. Service personnel are constantly exposed to high levels of noise and hence predisposed to occupational health disabilities, principally noise-induced hearing loss (NIHL) and tinnitus. NIHL is a significantly common impairment in the military and can affect the warfare performances. Parochial awareness about the effects of uproarious noise which exacerbates their hearing, acceptance rate of use of hearing protection devices and follow-up audiological tests have become the major drawback for prevention of NIHL and are less pondered upon. METHOD: The present study focuses on the effects of noise on the hearing of service crew operating and maintaining military equipment and explores the efficacy of DPOAE's to substitute pure tone audiometry as a quick, easy to operate and implementable test technique for monitoring of hearing status. RESULTS: The results suggest that DPOAE test is important and more coherent than audiometry alone for the early detection of cochlear injury due to noise from military operations and efficacious for detecting NIHL.

Incident Angle Correction Algorithm For Impulse Noise Injury Assessment.

Objectives: We developed an empirical algorithm to account for the effect of the change in the A-weighted sound exposure level (SELA) as a result of the change in angle of incidence (AoI) of the impulse noise on the prediction of hearing loss. The product is the upgraded software tool, Auditory 4.5 that incorporates the incident angle correction algorithm. Methods: The SELA calculated from free-field pressure data is used as the dose metric that was corrected for AoI. The angle-dependent eardrum pressure was measured by performing shock tube tests with the Acoustical Testing Fixture varied over a wide range of orientation angles. The yaw angle was varied from 0 to 360° and the pitch angle from -60° to +90° in 15° steps. The algorithm was constructed by calculating a correction factor, ΔSELA for any given AoI at the ear relative to the SELA at normal incidence. The ΔSELA values were applied to correct the dose values to predict injury for all AoI. Results: A three-dimensional contour of ΔSELA as a function of the AoI was produced. The largest ΔSELA was 9.81 dB at pitch = -15° and yaw = 255°. ΔSELA values compared well against available benchmark data. Conclusions: A new capability has been incorporated in Auditory 4.5 to predict the effects of AoI on impulse noise injury.

Costs and effectiveness of hearing conservation programs at 14 US metal manufacturing facilities.

OBJECTIVE: This study characterised overall and specific costs associated with hearing conservation programmes (HCPs) at US metal manufacturing sites, and examined the association between these costs and several noise-induced hearing loss (NIHL) outcomes. DESIGN: We interviewed personnel and reviewed records at participating facilities. We also measured noise for comparison to the ten-year average of measurements made by each facility. NIHL outcomes assessed included rates of standard threshold shifts (STS) and high-frequency hearing loss, as well as prevalence of hearing impairment, for each participating facility. We used linear regression to identify per-person HCP costs that best predicted the NIHL outcomes. STUDY SAMPLE: We evaluated 14 US metal manufacturing facilities operated by a single company. RESULTS: Annual HCP costs ranged from roughly $67,000 to $397,000 (average $308 ± 80 per worker). Our full-shift noise measurements (mean 83.1 dBA) showed good agreement with the facilities' measurements (mean 82.6 dBA). Hearing impairment prevalence was about 15% overall. Higher expenditures for training and hearing protector fit-testing were significantly associated with reduced STS prevalence. Higher training expenditures were also related to lower hearing impairment prevalence and high-frequency hearing loss rates. CONCLUSIONS: HCP costs were substantial and variable. Increased workplace spending on training and fit-testing may help minimise NIHL.

Analytical and numerical modeling of the hearing system: Advances towards the assessment of hearing damage.

Hearing is an extremely complex phenomenon, involving a large number of interrelated variables that are difficult to measure in vivo. In order to investigate such process under simplified and well-controlled conditions, models of sound transmission have been developed through many decades of research. The value of modeling the hearing system is not only to explain the normal function of the hearing system and account for experimental and clinical observations, but to simulate a variety of pathological conditions that lead to hearing damage and hearing loss, as well as for development of auditory implants, effective ear protections and auditory hazard countermeasures. In this paper, we provide a review of the strategies used to model the auditory function of the external, middle, inner ear, and the micromechanics of the organ of Corti, along with some of the key results obtained from such modeling efforts. Recent analytical and numerical approaches have incorporated the nonlinear behavior of some parameters and structures into their models. Few models of the integrated hearing system exist; in particular, we describe the evolution of the Auditory Hazard Assessment Algorithm for Human (AHAAH) model, used for prediction of hearing damage due to high intensity sound pressure. Unlike the AHAAH model, 3D finite element models of the entire hearing system are not able yet to predict auditory risk and threshold shifts. It is expected that both AHAAH and FE models will evolve towards a more accurate assessment of threshold shifts and hearing loss under a variety of stimuli conditions and pathologies.

Commentary on the regulatory implications of noise-induced cochlear neuropathy.

OBJECTIVE: A discussion on whether recent research on noise-induced cochlear neuropathy in rodents justifies changes in current regulation of occupational noise exposure. DESIGN: Informal literature review and commentary, relying on literature found in the authors' files. No formal literature search was performed. STUDY SAMPLE: Published literature on temporary threshold shift (TTS) and cochlear pathology, in humans and experimental animals, as well as the regulations of the US Occupational Safety and Health Administration (OSHA). RESULTS: Humans are less susceptible to TTS, and probably to cochlear neuropathy, than rodents. After correcting for inter-species audiometric differences (but not for differences in susceptibility), exposures that caused cochlear neuropathy in rodents already exceed OSHA limits. Those exposures also caused "pathological TTS" (requiring more than 24 h to recover), which does not appear to occur with human broadband noise exposure permissible under OSHA. CONCLUSION: It would be premature to conclude that noise exposures permissible under OSHA can cause cochlear neuropathy in humans.

Hearing testing in the U.S. Department of Defense: Potential impact on Veterans Affairs hearing loss disability awards.

Hearing loss is the second most common disability awarded by the U.S. Department of Veterans Affairs (VA) to former members of the U.S. uniformed services. Hearing readiness and conservation practices differ among the four largest uniformed military services (Air Force, Army, Marine Corps, and Navy). Utilizing a data set consisting of all hearing loss claims submitted to the VA from fiscal years 2003-2013, we examined characteristics of veterans submitting claims within one year of separation from military service. Our results indicate that having a hearing loss disability claim granted was significantly more likely for men, individuals over the age of 26 years at the time of the claim, individuals most recently serving in the U.S. Army, and those with at least one hearing loss diagnosis. Importantly, individuals with at least one test record in the Defense Occupational and Environmental Health Readiness System-Hearing Conservation (DOEHRS-HC) system were significantly less likely to have a hearing loss disability claim granted by the VA. Within the DOEHRS-HC cohort, those with at least one threshold shift or clinical hearing loss diagnosis while on active duty were more than two and three times more likely to have a hearing loss disability claim granted, respectively. These findings indicate that an established history of reduced hearing ability while on active duty was associated with a significantly increased likelihood of an approved hearing loss disability claim relative to VA claims without such a history. Further, our results show a persistent decreased rate of hearing loss disability awards overall. These findings support increased inclusion of personnel in DoD hearing readiness and conservation programs to reduce VA hearing loss disability awards.

Percepção e conhecimento dos profissionais da saúde da atenção primária sobre notificação da perda auditiva induzida pelo ruído em Curitiba - Paraná / Primary care health professionals' perception and knowledge on notification of noise-induced hearing loss in Curitiba - Paraná

RESUMO Objetivo Analisar a percepção e o conhecimento dos profissionais de saúde que atuam na rede de Atenção Primária à Saúde do Município de Curitiba - Paraná sobre a notificação compulsória da Perda Auditiva Induzida pelo Ruído (PAIR) no, Sistema de Informação de Agravos de Notificação (SINAN). Método Utilizando como método o estudo transversal na cidade de Curitiba, analisando a percepção e o conhecimento dos profissionais de saúde que atuam na rede de Atenção Primária à Saúde do Município de Curitiba sobre a notificação compulsória da PAIR no SINAN. Aplicou-se ainda um questionário semiaberto em profissionais de saúde da atenção básica sobre conhecimento sobre a PAIR e sua notificação. Resultados Dos profissionais da atenção básica, 50% eram médicos com faixa etária de 26 a 30 anos. Dentre os profissionais, 56,2% relataram estarem preparados para identificar problemas de saúde relacionados ao trabalho, porém apenas 43,7% sentem-se aptos a identificar casos de PAIR. Entre as facilidades na notificação, relataram descentralização da assistência à saúde próxima à residência do usuário, encaminhamento para referência em medicina do trabalho e prontuário eletrônico na UBS; como dificuldades, relataram a não formação específica em saúde do trabalhador e falta de capacitação, tempo reduzido para consultas e receio. Conclusão os profissionais de saúde conhecem as características e sentem-se aptos para identificar os casos de PAIR, mas ainda não notificam os casos suspeitos de PAIR e não percebem a Saúde do Trabalhador como um programa institucionalizado fazendo parte do serviço.

ABSTRACT Objective The article aims to analyze the perception and knowledge of health professionals working in primary health care networks in the Municipality of Curitiba – Paraná, regarding the compulsory notification of Induced Hearing Loss Noise (NIHL) in the National Notifiable Diseases Information System (SINAN). Methods We performed a transversal cohort study in Curitiba, analyzing perception and knowledge of health professionals working in the primary health care networks in the Municipality of Curitiba, regarding the compulsory notification of NIHL in SINAN, from 2007 to 2014, featuring the reported cases and exploring the situational analysis of the NIHL notification, through a questionnaire and a structured news conference. Results The primary care professionals’ survey showed that 50% were doctors and the predominant age group was 26-30 years, with 56.2% reported as being able to identify health problems related to work, but only 43.7% feel able to identify cases of NIHL. Conclusion It was found that health professionals know the features and feel able to identify cases of NIHL, but still do not report suspected NIHL cases and do not consider occupational health an institutionalized program that is part of the service.

Primary care health professionals' perception and knowledge on notification of noise-induced hearing loss in Curitiba - Paraná. / Percepção e conhecimento dos profissionais da saúde da atenção primária sobre notificação da perda auditiva induzida pelo ruído em Curitiba - Paraná.

OBJECTIVE: The article aims to analyze the perception and knowledge of health professionals working in primary health care networks in the Municipality of Curitiba - Paraná, regarding the compulsory notification of Induced Hearing Loss Noise (NIHL) in the National Notifiable Diseases Information System (SINAN). METHODS: We performed a transversal cohort study in Curitiba, analyzing perception and knowledge of health professionals working in the primary health care networks in the Municipality of Curitiba, regarding the compulsory notification of NIHL in SINAN, from 2007 to 2014, featuring the reported cases and exploring the situational analysis of the NIHL notification, through a questionnaire and a structured news conference. RESULTS: The primary care professionals' survey showed that 50% were doctors and the predominant age group was 26-30 years, with 56.2% reported as being able to identify health problems related to work, but only 43.7% feel able to identify cases of NIHL. CONCLUSION: It was found that health professionals know the features and feel able to identify cases of NIHL, but still do not report suspected NIHL cases and do not consider occupational health an institutionalized program that is part of the service.

Educating teenagers about hearing health by training them to educate children.

OBJECTIVE: We investigated the change in hearing-health behaviour amongst teenagers trained to deliver the Dangerous Decibels programme to younger children. DESIGN: The Dangerous Decibels programme uses a two-stage process to train 8-12 year-old children to protect their hearing from noise: (1) a team of experts train 'Educators' who (2) give classroom training to children in schools. Training teenagers as Educators may add a second level of benefit if teenagers internalize the hearing-health messages that they present and thus protect their own hearing better. They were assessed before training, immediately after, and three months later (after all had presented the classroom training) using a questionnaire. In addition, a focus group was conducted with a subgroup of the Educators to assess their subjective experience. STUDY SAMPLE: We trained 44 Educators aged 14-17 years. RESULTS: Results were generally positive: there were significant and sustained improvements in knowledge, self-reported behaviour, and perceived supports towards protecting hearing, and trends but not significant changes in attitudes or perceived barriers to hearing protection. CONCLUSIONS: Providing training to teenagers had benefits beyond the delivery of training to younger children, but improvements in the delivery model may increase the uptake and impact on the teenagers.

Assessment of Synaptic Plasticity via Long-Term Potentiation in Young Mice on the Day after Acoustic Trauma: Implications for Tinnitus.

OBJECTIVE: This experimental study evaluated the pathophysiological association of long-term potentiation (LTP)-mediated synaptic plasticity in tinnitus in 30 BALB/c mice. MATERIALS AND METHODS: Baseline hearing levels and tinnitus perception were examined with startle reflex time and gap detection time measurements using an acoustic stimulus of a 6-kHz pure tone at 90 dB sound pressure level (SPL) on post-natal day 16. The acoustic trauma group was exposed to 6-kHz pure tone at 120 dB SPL on post-natal day 16. On post-natal day 17, the acoustic trauma group underwent re-measurements of hearing levels and tinnitus perception using an acoustic stimulus of 6-kHz pure tone at 100 dB SPL. Fifteen tinnitus-induced and fifteen control subjects were sacrificed on post-natal day 17, and LTP in the dorsal cochlear nuclei of each animal was examined. RESULTS: With respect to gap detection time, there were no statistically significant between-group differences; however, there was a statistically significant difference between the pre- and post-trauma period in the acoustic trauma group. Moreover, LTP was significantly higher in the acoustic trauma group than in the control group. CONCLUSION: The results suggest that LTP underlies tinnitus pathogenesis.

Assessment of the noise-protective action of the olivocochlear efferents in humans.

It has been demonstrated in different mammals that the medial olivocochlear efferents (MOC) exert a noise-protective effect on the cochlea. In humans such an effect has not unambiguously been shown as of yet. The objective of this study was to assess the relationship between MOC activity and susceptibility of the cochlea to noise-induced hearing loss in humans. In 40 normally hearing human subjects, we measured the following: (1) magnitude of temporary threshold shift (TTS) after exposure to 60 min broadband noise of 94 dB SPL and (2) contralateral suppression (CS) of distortion product otoacoustic emissions (which reflects MOC activity) using two different measurement paradigms. CS was measured in duplicate on 2 measurement days. The relationship between TTS and CS was assessed. Individual TTS in the most affected frequencies (4 > 3 > 8 kHz) ranged from 9 to 28 dB HL, with an average maximum TTS of 18.4 dB HL. The amount of CS ranged between 0.3 and 3 dB. The repeatability of CS, evaluated by Cronbach's α value, ranged from 0.76 (acceptable repeatability) to 0.86 (good repeatability). One of the two different measurement paradigms showed a statistically significant inverse correlation between CS magnitude and amount of TTS, which was hypothesized. This is the first study on the relationship between TTS and CS in humans employing TTS induced under controlled laboratory conditions and two different MOC paradigms. The findings are compatible with the hypothesis that MOC activity is noise protective in humans. Future perspectives include modified CS paradigms, longitudinal cohort studies or efforts to also monitor lateral efferent effects in humans.

The role of high-frequency oscillatory ventilation in the treatment of acute respiratory failure in adults.

PURPOSE OF REVIEW: High-frequency oscillatory ventilation (HFOV) is increasingly used in adults with the acute respiratory distress syndrome (ARDS), who remain hypoxemic during conventional mechanical ventilation. In this review, we will summarize the trials evaluating HFOV in adults with ARDS and discuss issues relevant to the clinician regarding the use of HFOV. RECENT FINDINGS: Several observational and randomized trials support the safety of HFOV and improvements in oxygenation in adult patients with severe ARDS, who remain hypoxemic during conventional mechanical ventilation. SUMMARY: HFOV theoretically meets the goals of lung-protective ventilation. On the basis of the current evidence, HFOV is associated with improvements in oxygenation in severe, adult ARDS. However, whether HFOV influences mortality, length of ICU stay, ventilator-free days, quality-of-life factors and is cost-effective remains to be determined. Large, prospective, randomized controlled trials such as the ongoing OSCAR and OSCILLATE trials will help further define the role of HFOV in adult ARDS.

Is it necessary to penalize impulsive noise +5 dB due to higher risk of hearing damage?

It is studied whether the +5 dB penalty for impulsiveness established by ISO 1999:1990 accounts for a higher risk of noise-induced hearing loss. A total of 16 normal-hearing human subjects were exposed for 10 min to two types of binaural industrial-recordings: (1) a continuous broad-band noise normalized to L(EX,8 h)=80 dBA and (2) the combination of the previous stimulus with an impulsive noise normalized to L(EX,8 h)=75+5(db penalty)=80 dBA (peak level 117 dBC and repetition rate of 0.5 impacts per second). Distortion product otoacoustic emissions (DPOAEs) were measured in a broad frequency range before and in the following 90 min after the exposure. The group results show that the continuous exposure had a bigger impact on DPOAE levels, with a maximum DPOAE shift of approximately 5 dB in the frequency range of 2-3.15 kHz during the first 10 min of the recovery. No evident DPOAE shift is seen for the impulsive + continuous stimulus. The results indicate that the penalty overestimated the effects on DPOAE levels and support the concept that the risk of hearing loss from low-level impulses may be predicted on an equal-energy basis.

Kurtosis corrected sound pressure level as a noise metric for risk assessment of occupational noises.

Current noise guidelines use an energy-based noise metric to predict the risk of hearing loss, and thus ignore the effect of temporal characteristics of the noise. The practice is widely considered to underestimate the risk of a complex noise environment, where impulsive noises are embedded in a steady-state noise. A basic form for noise metrics is designed by combining the equivalent sound pressure level (SPL) and a temporal correction term defined as a function of kurtosis of the noise. Several noise metrics are developed by varying this basic form and evaluated utilizing existing chinchilla noise exposure data. It is shown that the kurtosis correction term significantly improves the correlation of the noise metric with the measured hearing losses in chinchillas. The average SPL of the frequency components of the noise that define the hearing loss with a kurtosis correction term is identified as the best noise metric among tested. One of the investigated metrics, the kurtosis-corrected A-weighted SPL, is applied to a human exposure study data as a preview of applying the metrics to human guidelines. The possibility of applying the noise metrics to human guidelines is discussed.

[Sensorineural hearing loss after dull head injury or concussion trauma]. / Innenohrschwerhörigkeit nach stumpfem Schädelhirntrauma bzw. Kopfanpralltrauma.

A dull head injury can lead to isolated damage of the inner ear (cochlear labyrinthine concussion) or damage of the otolithe organ (vestibular labyrinthine concussion) due to a bone conduction pressure . A typical sign is a high frequency SNHL in form of a c5-dip. The c5-dip can be bilateral or unilateral or different on each side - dependant on the side of injury. In case of a unilateral skull base fracture a contralateral labyrinthine concussion is also possible. Moreover a lot of cases also show an accompanying tinnitus. This knowledge is based on animal and human experiments, as well as data from clinical and medical report examinations over decades. It is important to differentiate between a SNHL caused by accident or uni- or bilateral endogenic degenerative hearing loss.

Physiological and morphological assessment of the saccule in Guinea pigs after noise exposure.

OBJECTIVE: To investigate whether the saccule exhibits temporary or permanent functional loss resembling threshold shifts in auditory brainstem response (ABR) of guinea pigs following noise exposure. DESIGN: Randomly bred guinea pigs were divided into 3 groups: A (short-term noise exposure, 30 minutes, n = 15), B (long-term noise exposure, 40 hours, n = 9), and C (no noise exposure, n = 5). SETTING: University hospital. MAIN OUTCOME MEASURES: All animals underwent vestibular-evoked myogenic potential (VEMP) and ABR tests. Chronological changes of VEMP and ABR responses following noise exposure were analyzed and compared. After audiovestibular function testing, animals were killed for morphological study with light and electron microscopy. RESULTS: In group A, temporary VEMP loss and ABR threshold shifts recovered 2 and 4 days, respectively, after short-term noise exposure, with an interval of 2 days earlier in the recovery of VEMPs than that of ABR thresholds. In contrast, in group B, 78% and 83% of the ears exhibited permanent VEMP loss and ABR threshold shifts, respectively, 10 days following long-term noise exposure. In group C, all animals showed normal VEMPs and ABRs throughout the study period. Light and electron microscopic studies confirmed that loss of VEMPs correlated with saccular lesion. CONCLUSIONS: The saccule can exhibit temporary or permanent functional loss resembling hearing threshold shifts in guinea pigs following noise exposure. Recovery of VEMP precedes restoration of hearing threshold after damage from short-term noise exposure. Conversely, permanent VEMP loss after long-term noise exposure may reflect permanent hearing threshold shifts.

An assessment of threshold shifts in nonprofessional pop/rock musicians using conventional and extended high-frequency audiometry.

The clinical value of extended high-frequency audiometry for the detection of noise-induced hearing loss has not been established conclusively. The purpose of this study was to assess the relative temporary threshold shift (TTS) in two frequency regions (conventional versus extended high frequency). In this exploratory study, pure-tone thresholds from 0.5 to 14 kHz were measured in both ears of 16 nonprofessional pop/rock musicians (mean age, 35 yr; range, 27 to 49 yr), before and after a 90-minute rehearsal session. All had experienced repeated exposures to intense sound levels during at least 5 yr of their musical careers. After the rehearsal, median threshold levels were found to be significantly poorer for frequencies from 0.5 to 8 kHz (Wilcoxon signed rank test, p