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Acute acoustic trauma (AAT) is a sudden sensorineural hearing loss caused by exposure of the hearing organ to acoustic overstimulation, typically an intense sound impulse, hyperbaric oxygen therapy (HOT), which favors repair of the microcirculation, can be potentially used to treat it. Hence, this study aimed to assess the effects of HOT on guinea pigs exposed to acoustic trauma. Fifteen guinea pigs were exposed to noise in the 4-kHz range with intensity of 110 dB sound level pressure for 72 h. They were assessed by brainstem auditory evoked potential (BAEP) and by distortion product otoacoustic emission (DPOAE) before and after exposure and after HOT at 2.0 absolute atmospheres for 1 h. The cochleae were then analyzed using scanning electron microscopy (SEM). There was a statistically significant difference in the signal-to-noise ratio of the DPOAE amplitudes for the 1- to 4-kHz frequencies and the SEM findings revealed damaged outer hair cells (OHC) after exposure to noise, with recovery after HOT (p = 0.0159), which did not occur on thresholds and amplitudes to BAEP (p = 0.1593). The electrophysiological BAEP data did not demonstrate effectiveness of HOT against AAT damage. However, there was improvement of the anatomical pattern of damage detected by SEM, with a significant reduction of the number of injured cochlear OHC and their functionality detected by DPOAE.

Auditory conditioning consists of the pre-exposure to low levels of a potential harmful agent to protect against a subsequent harmful presentation. The agent that was first tested was noise. This paradigm was more recently successfully tested with other agents. Nonetheless, the vast majority of the studies utilize the same agent to condition and to cause the trauma. The aim of this study was to verify whether conditioning with an agent different from the agent used to cause the trauma can also be effective. Thus, the following groups were organized: group Cont, which is the noise trauma control group, was exposed to 110-dB broadband noise centered at 4 kHz for 72 h; group Gent, which is the gentamicin conditioning control group, was administered 30 mg/kg of gentamicin daily for 30 consecutive days; and group Expt was conditioned with gentamicin similarly to group Gent and then subjected to a noise trauma similarly to group Cont. The animals were functionally and morphologically evaluated through the measurement of the auditory brainstem response and scanning electron microscopy, respectively. The following variables were investigated: outer hair cell injury and auditory threshold shift. The group that was conditioned with the drug exhibited significantly less outer hair cell damage, 10.8 and 22.9 %, respectively (p = 0.0146), although did not maintain the proper functioning of the auditory system. We, therefore, conclude that conditioning with a different agent from that used to cause the trauma is effective, which suggests that both agents that were used promote similar mechanisms of self-protection.

As investigações sobre os efeitos da oxigenoterapia hiperbárica (OHB) em lesão por ruído são escassas e apontam para diferentes efeitos em função do momento de intervenção. Dentre os trabalhos já descritos foi observado efeito lesivo da OHB quando aplicada imediatamente ao trauma acústico, contudo, efeito positivo foi observado quando aplicada após 2 e 6 horas. Com relação aos tratamentos usados para trauma acústico, alguns estudos descrevem o uso de corticoides como melhor alternativa, mas recentemente estudos apontam para a sua combinação com OHB como a terapêutica com maior beneficio nas lesões por ruído. O presente estudo teve como objetivos avaliar o momento da intervenção pela OHB após 2, 4 e 6 horas de repouso auditivo após exposição ao ruído e avaliar a associação terapêutica entre a OHB e corticoterapia (CT). Cobaias albinas foram expostas a um ruído branco na faixa de 4 kHz com intensidade igual a 110dB NPS por 72h e divididas em cinco grupos terapêuticos: OHB com início após 2, 4 e 6h de repouso auditivo após exposição ao ruído, CT isolada e OHB após 6 horas de repouso associada a CT. O tratamento durou 5 dias, sendo uma sessão terapêutica por dia. Todos os animais tiveram a função auditiva avaliada pelo Potencial Evocado Auditivo de Tronco Encefálico (PEATE) e pelas Emissões Otoacústicas Produtos de Distorção (EOAPD) em três momentos: pré-ruído, pós-ruído e pós-tratamento. Após a eutanásia dos animais e preparação dos espécimes cocleares, todas as cócleas foram analisadas através de Microscopia Eletrônica de Varredura (MEV). Não houve diferença estatística significativa entre os momentos de intervenção pela OHB após 2, 4 e 6 horas, contudo, os dados de MEV demonstraram que uma maior otoproteção ocorreu quando a intervenção foi realizada após um maior repouso auditivo. Apesar da não diferença estatística significativa, os achados anatômicos e funcionais permitiram concluir que a associação terapêutica entre a OHB e a corticoterapia desempenhou um melhor efeito otoprotetor e terapêutico se comparada a essas mesmas terapias isoladas. Investigations on the effects of hyperbaric oxygen therapy (HBOT) in noise injury are scarce and point to different effects depending on the time of intervention. Among the work already described has been observed damaging effect of HBOT when applied immediately after the acoustic trauma, however, positive effect was observed when applied after 2 and 6 hours of rest after the trauma. Studies describe the use of corticosteroids as the best alternative to treat acoustic trauma, but recent studies point to their combination with HBOT as the major benefit in lesions by noise. This study aimed to evaluate the time of intervention by HBOT after 2, 4 and 6 hours of rest after hearing noise exposure and to evaluate the association between HBOT and corticoid. Female guinea pigs were exposed to a white noise on 4kHz at 110dB SPL during 72 hours and divided into five treatment groups: HBOT after 2, 4 and 6 hours of rest after the noise exposure, corticosteroid therapy and HBOT combined with corticoid. The treatment lasted five days, being a therapy session per day. All animals were exposed to Distortion Product Otoacoustic Emissions (DPOAE) and Auditory Brainstem evoked Response (ABR) in three moments: before and after exposure to the noise and after the treatment. All cochleae were examined by scanning electron microscopy (SEM). There was no statistically significant difference between the moments of intervention by HBOT after 2, 4 and 6 hours, however, the SEM data showed that a greater otoprotection occurred when the intervention was performed after a higher auditory rest. Although not statistically significant, the anatomical and functional findings concluded that the association between HBOT and corticosteroid therapy played a better otoprotective and therapeutic effect compared to those same therapies alone.

Studies describe the use of corticosteroids as the best alternative to treat acoustic trauma, but recent studies point to their combination with hyperbaric oxygen therapy (HBOT) as the major benefit in lesions by noise. This study aimed to evaluate the association between HBOT and corticoid therapy (CT). Female guinea pigs were exposed to a white noise on 4 kHz at 110 dB SPL during 72 hours and divided into three treatment groups: HBOT, CT and the combination of both therapies (HBOCT). The treatment lasted five days, being a therapy session per day. All animals were exposed to Distortion Product Otoacoustic Emissions and Brainstem Auditory Evoked Potentials in three moments: before and after exposure to the noise and after the treatment. All cochleae were examined by scanning electron microscopy. Although not statistically significant, the anatomical and functional findings concluded that the association HBOCT played a better otoprotective and therapeutic effect compared to those same therapies alone.