Fatiga auditiva / Auditory fatigue

Introducción y objetivos: Ante posibles pérdidas de audición a causa de sobrecargas sonoras y la escasa referencia de procedimientos objetivos para su estudio, aportamos una técnica que suministra datos precisos sobre el perfil audiométrico y el factor reclutamiento. El objetivo del estudio es la determinación de la fatiga auditiva temporal a través de la respuesta microfónica coclear ante estímulos de sobrecarga de presión sonora y medida del tiempo de recuperación. Material y método: Instrumentación específica para el estudio de microfónicos cocleares, más un generador que nos proporciona estímulos sonoros de diversa intensidad y componente armónico. Utilizamos ratas Wistar. Medimos la respuesta microfónica normal y después el efecto que sobre ella ha ejercido la aportación de sobrecarga acústica. Resultados: Utilizando un tono puro a 60 dB obtenemos una respuesta microfónica. Fatigando de inmediato con 100 dB en la misma frecuencia, a los 15 min obtenemos una pérdida de 11 dB, a partir de los cuales el deterioro se lentifica y no supera los 15 dB. Mediante sonidos de banda compleja aleatoria o ruido blanco no se produce fatiga ni a niveles de 100 dB durante una hora de sobreestímulo. Conclusiones: No existe fatiga a nivel de los receptores sensoriales. El deterioro de la respuesta mediante intenso sobreestímulo posiblemente se deba a alteraciones bioquímicas de desensibilización por agotamiento. La fatiga auditiva en pruebas clínicas subjetivas afecta a tramos supracocleares. Las pruebas de fatiga auditiva encontradas no coinciden con las obtenidas subjetivamente en clínica ni en psicoacústica (AU)

Introduction and objectives: Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. Material and method: We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. Results: Using a 60 dB pure tone acoustic stimulation, we obtained a microphonic response at 20 dB. We then caused fatigue with 100 dB of the same frequency, reaching a loss of approximately 11 dB after 15 minutes; after that, the deterioration slowed and did not exceed 15 dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100 dB and over an hour of overstimulation. Conclusions: No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials (AU)

[Auditory fatigue]. / Fatiga auditiva.

INTRODUCTION AND OBJECTIVES: Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. MATERIAL AND METHOD: We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. RESULTS: Using a 60dB pure tone acoustic stimulation, we obtained a microphonic response at 20dB. We then caused fatigue with 100dB of the same frequency, reaching a loss of approximately 11dB after 15minutes; after that, the deterioration slowed and did not exceed 15dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100dB and over an hour of overstimulation. CONCLUSIONS: No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials.

Latencia de los microfónicos cocleares / Cochlear microphonic latency

Introducción y objetivo: Empleando la instrumentación adecuada, venimos constatando que los microfónicos cocleares (MC) evocados adelantan o retrasan su aparición en función de la presión sonora que los genera. Esta variación en el tiempo es del orden de microsegundos. No hemos encontrado referencia alguna de este comportamiento, razón por la cual damos conocer el hallazgo. Material y método: Se emplea instrumentación específica para el estudio de los MC. El método se basa en el desplazamiento de fase de los MC en función de la intensidad del estímulo. Resultados: Se constata la latencia en los MC y se observa que la misma disminuye a medida que se incrementa la intensidad del estímulo. Conclusiones: Desde el estímulo sonoro a la traducción en potencial bioeléctrico encontramos un periodo de tiempo en microsegundos, menor a mayor potencia. Esto sugiere que traducción mecano-eléctrica no es un simple proceso de naturaleza mecánica (AU)

Introduction and objective: By using appropriate instrumentation, we have found that cochlear microphonics (CM) advance or delay their appearance, depending on the sound pressure that generates them. This time variation is on the order of microseconds. We have not found any reference to this behaviour, which is why we make the finding known. Material and method: We used the standard instrumentation specified for the study of CM. The method was based on the phase shift function of the CM according to the intensity of the stimulus. Results: Latency was observed in CM, and we determined that latency time diminishes as the intensity of the stimulus increases. Conclusions: From the sound stimulus to the bioelectric potential transduction, there is a time period of microseconds, the shorter the more powerful the stimulus. This suggests that electromechanical transduction is not a simple mechanical process (AU)

[Cochlear microphonic latency]. / Latencia de los microfónicos cocleares.

INTRODUCTION AND OBJECTIVE: By using appropriate instrumentation, we have found that cochlear microphonics (CM) advance or delay their appearance, depending on the sound pressure that generates them. This time variation is on the order of microseconds. We have not found any reference to this behaviour, which is why we make the finding known. MATERIAL AND METHOD: We used the standard instrumentation specified for the study of CM. The method was based on the phase shift function of the CM according to the intensity of the stimulus. RESULTS: Latency was observed in CM, and we determined that latency time diminishes as the intensity of the stimulus increases. CONCLUSIONS: From the sound stimulus to the bioelectric potential transduction, there is a time period of microseconds, the shorter the more powerful the stimulus. This suggests that electromechanical transduction is not a simple mechanical process.

[A procedure to obtain the recruitment using cochlear microphonic potentials]. / Procedimiento para obtener el reclutamiento mediante microfónicos cocleares.

OBJECTIVE: To present an objective procedure for recruitment measure. Nowadays all recruitment methods are based on the patients' subjective responses. This procedure is based on the ratio between an increase in the cochlear microphonic potential and the increase in stimuli intensity. The system allows recruitment to be measured down to one tenth of a decibel; the precision necessary to differentiate the auditory capacity of patients. METHOD: We used a specific technique to detect cochlear microphonic potentials. We have compared the results obtained with this new technique with those determined by the Luscher method. We present 10 adults with no statistic AIM. We first tested the physical accuracy followed by measures with laboratory animals and humans. RESULTS: We obtained a maximum deviation of 0.3 dB with respect to the patients' subjective appreciation. During the repetition of the objective measure with the same patients, we obtained identical results, whereas significant differences were observed with the repetitions in the subjective study. CONCLUSIONS: The possibility of an objective measurement for recruitment opens up new perspectives for early diagnosis. This technique may be of assistance in the decision to place an implant or how to adapt a hearing aid. Through automatic volume control as well as the correct adjustment of the selective gain in frequency, we can also obtain the threshold audiometric profile simultaneously.

Procedimiento para obtener el reclutamiento mediante microfónicos cocleares / A procedure to obtain the recruitment using cochlear microphonic potentials

Objetivo: Aportar un procedimiento objetivo para la obtención del factor de reclutamiento (recruitment). En la actualidad todos los métodos están basados en la respuesta subjetiva del paciente. La relación entre el aumento del potencial microfónico coclear (MC) y el incremento del estímulo es la base de esta aportación. El sistema permite la apreciación de décimas de decibelio, precisión necesaria para determinar el poder diferencial de amplitud auditiva en los pacientes. Método: Se ha empleado un equipo específico para el estudio de los potenciales MC. Hemos comparado los resultados obtenidos con esta nueva técnica con los determinados subjetivamente por el método de Lüscher. Se presenta a 10 adultos sin propósito estadístico. Previamente se comprobó la precisión física del equipo, y luego se practicaron determinaciones en animales de experimentación y, por último, en humanos. Resultados: Obtenemos mediante MC una desviación máxima de 0,3 dB respecto a la apreciación subjetiva de los pacientes. En la repetición de la prueba objetiva se obtienen idénticos resultados en el mismo paciente, mientras que en el estudio subjetivo se observan discrepancias en las repeticiones. Conclusiones: La posibilidad de estudiar el reclutamiento objetivamente abre nuevas perspectivas en diagnóstico precoz y nos capacita para optar más acertadamente respecto a la colocación de un implante o la adaptación de un audífono, con un control automático de volumen correcto unido al ajuste de la ganancia selectiva en frecuencia, ya que obtenemos simultáneamente el perfil audiométrico umbral

Objective: To present an objective procedure for recruitment measure. Nowadays all recruitment methods are based on the patients’ subjective responses. This procedure is based on the ratio between an increase in the cochlear microphonic potential and the increase in stimuli intensity. The system allows recruitment to be measured down to one tenth of a decibel; the precision necessary to differentiate the auditory capacity of patients. Method: We used a specific technique to detect cochlear microphonic potentials. We have compared the results obtained with this new technique with those determined by the Luscher method. We present 10 adults with no statistic aim. We first tested the physical accuracy followed by measures with laboratory animals and humans. Results: We obtained a maximum deviation of 0.3 dB with respect to the patients’ subjective appreciation. During the repetition of the objective measure with the same patients, we obtained identical results, whereas significant differences were observed with the repetitions in the subjective study. Conclusions: The possibility of an objective measurement for recruitment opens up new perspectives for early diagnosis. This technique may be of assistance in the decision to place an implant or how to adapt a hearing aid. Through automatic volume control as well as the correct adjustment of the selective gain in frequency, we can also obtain the threshold audiometric profile simultaneously

[Conventional audiometry versus cochlear microphone audiometry]. / Audiometría convencional comparada con la audiometría microfonicococlear.

OBJECTIVE: The recording and processing of cochlear microphone potentials in hearing studies is currently in the definitive validation phase against results obtained with other objective procedures. The purpose of this work is to contribute to its validation. MATERIAL AND METHOD: The equipment used was exclusively designed for recording cochlear microphone potentials. The study has been carried out in adults to compare subjective audiometric results with those obtained from cochlear microphones. RESULTS: We present a statistical concordance study between subjective audiometry and cochlear microphone audiometry. CONCLUSIONS: In view of the results obtained, this method is particularly valid for early diagnosis. We obtained an identical profile to the subjective audiogram at audiometric frequencies of 250, 500, 1000, 2000, and 4000 Hz.

Audiometría convencional comparada con la audiometría microfonicococlear / Conventional audiometry versus cochlear microphone audiometry

Objetivo: Actualmente el estudio de la audición mediante el registro y el procesamiento de los potenciales microfónicos cocleares está en fase de validación definitiva respecto a los resultados que se obtienen mediante otros procedimientos objetivos. El propósito de esta aportación es contribuir a esa validación. Material y método: Se ha empleado equipo destinado exclusivamente al registro de los microfónicos cocleares realizando el estudio en adultos para poder comparar los resultados audiométricos subjetivos con los obtenidos mediante microfónicos cocleares. Resultados: Presentamos una concordancia estadística entre la audiometría subjetiva y la audiometría microfonicococlear. Conclusiones: Dada la equidad de resultados, el procedimiento resulta válido muy especialmente en el diagnóstico precoz, en el que se consigue un perfil idéntico al del audiograma subjetivo en las frecuencias audiométricas 250, 500, 1.000, 2.000 y 4.000 Hz

Objective: The recording and processing of cochlear microphone potentials in hearing studies is currently in the definitive validation phase against results obtained with other objective procedures. The purpose of this work is to contribute to its validation. Material and method: The equipment used was exclusively designed for recording cochlear microphone potentials. The study has been carried out in adults to compare subjective audiometric results with those obtained from cochlear microphones. Results: We present a statistical concordance study between subjective audiometry and cochlear microphone audiometry. Conclusions: In view of the results obtained, this method is particularly valid for early diagnosis. We obtained an identical profile to the subjective audiogram at audiometric frequencies of 250, 500, 1000, 2000, and 4000 Hz