Scoping Review for a Global Hearing Care Framework: Matching Theory with Practice.

The hearing healthcare industry is evolving rapidly. A framework addressing provision options in contemporary hearing care could assist clinician and client navigate their options to find the most appropriate solution for each individual. A PRISMA approach was used followed by mapping, validation, and thematic analysis to produce a framework to better describe and discuss service and product delivery options in contemporary hearing care. No frameworks were identified to advise matching needs with current provision options in audiological care. Charting, mapping, and thematic analysis of the validation criteria and hearing care literature produced three core domains: Service, Channel, and Technology/Device. The framework developed in this review allows for an understanding of where innovation is occurring in hearing healthcare and differentiates between changes to technology, channel, and service. New questions open up such as whether one model is more effective than another or which model of hearing help is best for which type of person. This framework allows for the disambiguation of hearing health services, hearing loss technology, and the channel in which services and technology are delivered. It has potential to be a versatile and valuable addition to the industry of hearing healthcare.

Effectiveness of a teleaudiology approach to hearing aid fitting.

This research was conducted to evaluate the efficacy of an online speech perception test (SPT) for the measurement of hearing and hearing aid fitting in comparison with conventional methods. Phase 1 was performed with 88 people to evaluate the SPT for the detection of significant hearing loss. The SPT had high sensitivity (94%) and high selectivity (98%). In Phase 2, phonetic stimulus-response matrices derived from the SPT results for 408 people were used to calculate "Infograms™." At every frequency, there was a highly significant correlation (p < 0.001) between hearing thresholds derived from the Infogram and conventional audiograms. In Phase 3, initial hearing aid fittings were derived from conventional audiograms and Infograms for two groups of hearing impaired people. Unaided and aided SPTs were used to measure the perceptual benefit of the aids for the two groups. The mean increases between unaided and aided SPT scores were 19.6%, and 22.2% (n = 517, 484; t = 2.2; p < 0.05) for hearing aids fitted using conventional audiograms and Infograms respectively. The research provided evidence that the SPT is a highly effective tool for the detection and measurement of hearing loss and hearing aid fitting. Use of the SPT reduces the costs and increases the effectiveness of hearing aid fitting, thereby enabling a sustainable teleaudiology business model.

Psychophysical measures in patients fitted with Contour and straight Nucleus electrode arrays.

The objective of this study was to compare the psychophysical performance of patients using the Nucleus Contour electrode array with that of patients using the straight banded-electrode array. In particular, we wished to consider how psychophysical parameters would differ for an electrode array positioned closer to the modiolus, and how this might influence both patient benefits and the design of speech processing strategies. Nine subjects participated in the study: four used the Nucleus straight array and five used the Nucleus Contour electrode array. Radiographic analyses found that the Contour array lay closer to the modiolus, was more deeply inserted and spanned a larger fractional length of the basilar membrane than the straight banded-electrode array. The results were analysed in terms of array type and of the position of the individual electrode band, both distance from the modiolus and longitudinal placement. Mean threshold was lower for the Contour array but maximum comfortable level was similar. Whereas threshold varied significantly with distance of electrode band from the modiolus, maximum comfortable level did not. Pitch varied fairly regularly with longitudinal position of the stimulated electrode, with the exception of one Contour subject. The forward masking profiles, using moderately loud maskers, were narrower for the Contour array, indicative of more localized neural excitation.

Spatial spread of neural excitation: comparison of compound action potential and forward-masking data in cochlear implant recipients.

The feasibility of using the electrically evoked compound action potential (ECAP), measured with the NRT system (Neural Response Telemetry) and the NRT software (version 2.04), to quantify the longitudinal spread of neural excitation was examined in four subjects fitted with the Nucleus C124M cochlear implant. The ECAP and psychophysical forward-masking profiles were measured using stimulation on each of three electrodes, in basal, middle and apical positions. Spatial spread profiles derived from the ECAP measure produced broader functions than those derived from the psychophysical measure. These results, together with investigation of the change of ECAP spread pattern with stimulation current, suggest that functions derived from this 'simple' method were more influenced by the spread of electric field from excited neuron to electrode array than by breadth of the neural excitation pattern. The recently released NRT version 3.0 permits the masker and probe pulses to be delivered to separate electrodes, thus removing a fundamental limitation of version 2.04. Results from a pilot study, in which this capability was exploited, suggest that the spatial functions from this 'advanced' method may provide a better correlation with results from psychophysical forward masking.

Spatial spread of neural excitation in cochlear implant recipients: comparison of improved ECAP method and psychophysical forward masking.

This study introduces and evaluates a method for measurement of the longitudinal spread of electrically evoked neural excitation in the cochlea, using the Neural Response Telemetry system (NRT) available with the Nucleus((R)) 24 cochlear implant system. The recently released version of the NRT software (version 3.0) enables presentation of the 'masker' and 'probe' on different electrodes. In the present method the probe position was fixed, while the masker position was varied across the electrode array. The amplitude of the response to the partially masked probe provides a measure of the amount of masking, which is dependent on the extent of overlap of the excitation regions of the masker and probe. These measurements were performed in seven subjects implanted with the Nucleus 24 cochlear implant system (four with straight and three with Contour electrode arrays), for basal, middle and apical probe electrodes. Similar excitation profiles were obtained using either the standard NRT subtraction paradigm or an alternative 'Miller' method. The excitation profiles were compared with those obtained from psychophysical forward masking and good agreement was found. The widths of electrically evoked compound action potential (ECAP) and forward masking profiles did not differ significantly. Whereas the width of the ECAP measure was significantly correlated with both the maximum comfortable level and the distance of the electrode band from the modiolus, the width of the forward masking profile was not.

Threshold, comfortable level and impedance changes as a function of electrode-modiolar distance.

OBJECTIVE: The study investigated the hypothesis that threshold and comfortable levels recorded from cochlear implant patients would reduce, and dynamic range increase, as distance of the electrode from the modiolar wall (radial distance) decreases. Two groups of cochlear implant patients participated; one group using the Nucleus' 24 Contour electrode array, and one group using the Nucleus standard straight (banded) array. The Nucleus 24 Contour array has been shown in temporal bone studies to lie closer to the modiolus than the banded array. The relationship of electrode impedance and radial distance is also investigated. DESIGN: The study, conducted at three centers, evaluated 21 patients using the Contour array, and 36 patients using the banded array. For each patient, threshold, comfortable levels and dynamic range were measured at four time points. Common ground electrode impedance was recorded clinically from each patient, at time intervals up to 12 wk. An estimate of the radial distance of the electrode from the modiolus was made by analysis of Cochlear view x-rays. RESULTS: Threshold and comfortable levels were significantly lower for the Nucleus 24 Contour array than for the banded array. However, dynamic range measurements did not show the predicted increase. In a majority of subjects, a significant correlation was found between the estimated radial distance of the electrode from the modiolus and the measured threshold and comfortable levels. This trend was not observed for dynamic range. The analysis indicates that other factors than radial distance are involved in the resultant psychophysical levels. Clinical impedance measures (common ground) were found to be significantly higher for the Contour array. However, the electrodes on the Contour array are half-rings, which are approximately only half the geometric size of the full rings as electrodes of the standard array. When the geometric electrode area in the two array designs are normalized, the trends in the electrode impedance behavior are similar. CONCLUSIONS: The results support the hypothesis that the relationship between the radial distance of the electrode and the psychophysical measures are influenced by patterns of fibrous tissue growth and individual patient differences, such as etiology and neural survival. Impedance measures for the Nucleus 24 Contour electrode array were higher than the banded electrode array, but this is primarily due to the reduction in electrode surface area. The different outcomes in impedance over time suggest differences in the relative contributions of the components of impedance with the two arrays.