Knowledge translation in audiology: promoting the clinical application of best evidence.

The impetus for evidence-based practice (EBP) has grown out of widespread concern with the quality, effectiveness (including cost-effectiveness), and efficiency of medical care received by the public. Although initially focused on medicine, EBP principles have been adopted by many of the health care professions and are often represented in practice through the development and use of clinical practice guidelines (CPGs). Audiology has been working on incorporating EBP principles into its mandate for professional practice since the mid-1990s. Despite widespread efforts to implement EBP and guidelines into audiology practice, gaps still exist between the best evidence based on research and what is being done in clinical practice. A collaborative dynamic and iterative integrated knowledge translation (KT) framework rather than a researcher-driven hierarchical approach to EBP and the development of CPGs has been shown to reduce the knowledge-to-clinical action gaps. This article provides a brief overview of EBP and CPGs, including a discussion of the barriers to implementing CPGs into clinical practice. It then offers a discussion of how an integrated KT process combined with a community of practice (CoP) might facilitate the development and dissemination of evidence for clinical audiology practice. Finally, a project that uses the knowledge-to-action (KTA) framework for the development of outcome measures in pediatric audiology is introduced.

An integrated knowledge translation experience: use of the Network of Pediatric Audiologists of Canada to facilitate the development of the University of Western Ontario Pediatric Audiological Monitoring Protocol (UWO PedAMP v1.0).

Pediatric audiologists lack evidence-based, age-appropriate outcome evaluation tools with well-developed normative data that could be used to evaluate the auditory development and performance of children aged birth to 6 years with permanent childhood hearing impairment. Bagatto and colleagues recommend a battery of outcome tools that may be used with this population. This article provides results of an evaluation of the individual components of the University of Western Ontario Pediatric Audiological Monitoring Protocol (UWO PedAMP) version 1.0 by the audiologists associated with the Network of Pediatric Audiologists of Canada. It also provides information regarding barriers and facilitators to implementing outcome measures in clinical practice. Results indicate that when compared to the Parents' Evaluation of Aural/Oral Performance of Children (PEACH) Diary, audiologists found the PEACH Rating Scale to be a more clinically feasible evaluation tool to implement in practice from a time, task, and consistency of use perspective. Results also indicate that the LittlEARS(®) Auditory Questionnaire could be used to evaluate the auditory development and performance of children aged birth to 6 years with permanent childhood hearing impairment (PCHI). The most cited barrier to implementation is time. The result of this social collaboration was the creation of a knowledge product, the UWO PedAMP v1.0, which has the potential to be useful to audiologists and the children and families they serve.

A critical review of audiological outcome measures for infants and children.

Outcome evaluation is an important stage in the pediatric hearing aid fitting process, however a systematic way of evaluating outcome in the pediatric audiology population is lacking. This is in part due to the need for an evidence-based outcome evaluation guideline for infants and children with hearing loss who wear hearing aids. As part of the development of a guideline, a critical review of the existing pediatric audiology outcome evaluation tools was conducted. Subjective outcome evaluation tools that measure auditory-related behaviors in children from birth to 6 years of age were critically appraised using a published grading system (Andresen, 2000). Of the tools that exist, 12 were appraised because they met initial criteria outlined by the Network of Pediatric Audiologists of Canada as being appropriate for children birth to 6 years of age who wear hearing aids. Tools that were considered for the guideline scored high in both statistical and feasibility criteria. The subjective outcome evaluation tools that were ultimately chosen to be included in the guideline were the LittlEARS Auditory Questionnaire (Tsiakpini et al., 2004) and the Parents' Evaluation of Aural/Oral Performance of Children (PEACH) Rating Scale (Ching & Hill, 2005b) due to the high grades they received in the critical review and their target age ranges. Following this critical review of pediatric outcome evaluation tools, the next step was for the Network Clinicians to evaluate the guideline (Moodie et al., 2011b).

Adaptation of the BKB-SIN test for use as a pediatric aided outcome measure.

BACKGROUND: There is a need for objective pediatric hearing aid outcome measurement and thus a need for the evaluation of outcome measures. We explored a commercially available pediatric sentence-in-noise measure adapted for use as an aided outcome measure. PURPOSE: The purposes of the current study were (1) to administer an adapted BKB-SIN (Bamford-Kowal-Bench Speech-in-Noise test) to adults and children who have normal hearing and children who use hearing aids and (2) to evaluate the utility of this adapted BKB-SIN as an aided, within-subjects outcome measure for amplification strategies. RESEARCH DESIGN: We used a mixed within and between groups design to evaluate speech recognition in noise for the three groups of participants. The children who use hearing aids were tested under the omnidirectional, directional, and digital noise reduction (DNR) conditions. Results from each group were compared to each other, and we compared results of each aided condition for the children who use hearing aids to evaluate the test utility as an aided outcome measure. STUDY SAMPLE: The study sample consisted of 14 adults with normal hearing (aged 22-28 yr) and 15 children with normal hearing (aged 6-18 yr), recruited through word of mouth, and 14 children who use hearing aids (aged 9-16 yr) recruited from local audiology clinics. DATA COLLECTION AND ANALYSIS: List pairs of the BKB-SIN test were presented at 50 dB HL as follows: four list pairs to each participant with normal hearing, four list pairs in the omnidirectional condition, and two list pairs in the directional and DNR conditions. Children who use hearing aids were fitted bilaterally with laboratory devices and completed the BKB-SIN test aided. Data were plotted as mean percent of key words correct at each signal-to-noise ratio (SNR). Further, we conducted an analysis of variance for group differences and within-groups for the three aided conditions. RESULTS: Adult participants outperformed children with normal hearing, who outperformed the children who use hearing aids. SNR-50 (signal-to-noise ratio at which listener can obtain a speech recognition score of 50% correct) scores demonstrated reliability of the adapted test implementation. The BKB-SIN test measured significant differences in performance for omnidirectional versus directional microphone conditions but not between omnidirectional and DNR conditions. CONCLUSIONS: We conclude that the adapted implementation of the BKB-SIN test can be administered reliably and feasibly. Further study is warranted to develop norms for the adapted implementation as well as to determine if an adapted implementation can be sensitive to age effects. Until such norms are developed, clinicians should refrain from comparing results from the adapted test to the test manual norms and should instead use the adapted implementation as a within-subject measure.

Fit to targets, preferred listening levels, and self-reported outcomes for the DSL v5.0 a hearing aid prescription for adults.

STUDY OBJECTIVE: This study evaluated how closely the DSL v5.0 a prescription could be approximated with hearing aids, its relationship to preferred listening levels (PLLs) of adults with acquired hearing loss, and the self-reported outcomes of the resulting fittings. PARTICIPANTS: Thirty adults with varying degrees and configurations of hearing loss ranging from mild to severe. METHODS: Hearing aid output was measured after the initial fitting to DSL v5.0 a targets and after determination of the PLL after approximately 90 days. The Client Oriented Scale of Improvement (COSI) was used to evaluate outcome. RESULTS: The 95% confidence interval of fits to target ranged from 5.8 to 8.4 dB across frequency. The DSL v5.0 a adult algorithm approximated the PLLs of the participants within 2.6 dB on average. Hearing aid fittings provided positive subjective outcome improvements on the COSI. CONCLUSIONS: Findings suggest that the use of DSL v5.0 a for the fitting of hearing aids on adults with acquired hearing loss was feasible and provided an appropriate initial fitting.

Prescribed real-ear and achieved real-life differences in children's hearing aids adjusted according to the NAL-NL1 and the DSL v.4.1 prescriptions.

This paper examined how hearing aids adjusted for comparing NAL-NL1 with DSLv.4.1 prescription formulas matched prescriptive targets. The real-ear-to-coupler differences (RECD) of 48 children (24 in Australia and 24 in Canada) were measured and used to derive coupler gain targets. Verification of gain and output were carried out in an HA2-2cc coupler. Electroacoustic measurements revealed a minimal difference between NAL-NL1 and DSLv.4.1 frequency-response slopes due to practical limitations of the devices, even though the prescribed differences were large (up to 13 dB/octave). The difference in overall gain was generally achieved in the hearing aids, with DSLv.4.1 prescribing higher overall gain than NAL-NL1. The mean RECD at 4 kHz was 5 dB higher for children in Australia than in Canada. As the same RECDs were used in deriving targets for both prescriptions, this is unlikely to affect the results of the comparison. The impact of a gain difference between prescriptions on children's performance and preferences in real life is reported in separate papers.

Children's speech perception and loudness ratings when fitted with hearing aids using the DSL v.4.1 and the NAL-NL1 prescriptions.

This paper reports speech and loudness measures on a group of children in a double-blind cross-over trial comparing the NAL-NL1 and DSL[i/o] prescriptions. Twenty-four children with hearing impairment were fitted with digital WDRC hearing aids at each site (Australia, Canada). Speech recognition was measured for nonsense syllables and for the 50% correct threshold for sentence recognition in noise. Loudness ratings for sentences were made on a 7-point scale. Measures were made at fitting and repeated following 8-week trials. Fitting orders were randomized and counterbalanced. Significant differences in consonant recognition occurred for individual children. On average, scores at the 80 dB SPL presentation level were better with the NAL-NL1 fitting. Loudness ratings differed at baseline but did not differ following home trials. Speech recognition scores revealed a small but significant interaction of prescription with level in quiet but not in noise. Individual children had significant performance differences. Loudness ratings showed significant acclimatization effects for children at both sites.

Evaluation of the NAL-NL1 and the DSL v.4.1 prescriptions for children: Paired-comparison intelligibility judgments and functional performance ratings.

This paper reports intelligibility judgments and real-life functional performance of 48 children in a double-blind, cross-over trial comparing the NAL-NL1 and the DSL v.4.1 prescriptions. Intelligibility judgments were obtained by using a paired-comparisons procedure with audiovisual stimuli. Functional performance of children during two eight-week periods, each with hearing aids adjusted to one prescription, was assessed by parents and teachers (PEACH and TEACH) and by children's self reports (SELF). Consistently across reports, performance was significantly better in quiet than in noise. On average, better performance in noise (a higher Noise subscale score) was associated with NAL-NL1 than with DSL v.4.1, both for the PEACH and the SELF. This difference was significant for the SELF in Australia. Intelligibility judgments revealed preferences that were equally split between prescriptions in both countries, on average. In the Australian sample, intelligibility judgments agreed with the questionnaire ratings and with parents' ratings. An increase in preference for NAL was significantly associated with lesser hearing loss. The effect was not significant in the Canadian sample.

A cross-over, double-blind comparison of the NAL-NL1 and the DSL v4.1 prescriptions for children with mild to moderately severe hearing loss.

The relative effectiveness of the NAL-NL1 and the DSL4.1 prescriptions for 48 children with mild to moderately severe hearing loss was studied using a double-blind, four-period, two-treatment cross-over design in Australia and in Canada. Evaluations included speech perception tests, loudness ratings, reports from parents and teachers on functional performance in real life, children's self-reports, paired-comparison judgements of intelligibility, and children's preferences in real-world environments. Electroacoustic measures of hearing aids revealed that gain differences dominated the comparison. Across trials and measures, individual Australian children consistently preferred either the NAL-NL1 or the DSL v.4.1 prescription. An overall figure of merit (FOM), calculated by averaging the standardized difference scores between prescriptions for all measures, revealed that the strongest prescription-related differences were found in Australia. On average, an advantage and preference for the NAL-NL1 prescription was associated with lesser degrees of hearing loss. This research provides evidence on the effectiveness of the NAL-NL1 and DSL v.4.1 prescriptions, and highlights the need for evaluating and fine-tuning amplification to meet the diverse needs of individual children in real life.

Evaluation of the NAL-NL1 and DSL v4.1 prescriptions for children: Preference in real world use.

This paper reports real world preferences of children in a double-blind, cross-over trial comparing NAL-NL1 and DSL v.4.1 prescriptions. Twenty-four children wore digital WDRC hearing aids at each site (Australia, Canada). Multi-memory hearing aids provided the NAL and DSL programs in each of two memories. Diaries were completed during two counterbalanced trials, providing overall preference, situational preference, and preference comments. Ratings were reliable, and situational preferences factored into quiet/low level situations versus noisy/reverberant/high level situations. Children at both sites used DSL v4.1 for hearing low level speech, or when they wanted to hear loudly and clearly. Children used NAL-NL1 when they wished to hear sounds at a lower level, or to reduce background noise. Children expressed strong preferences for having the choice of both programs. Canadian children were more likely to prefer DSL than were the Australian children. Factors such as listening environment and prior listening experience are discussed in interpreting these findings.

Protocol for the provision of amplification within the Ontario infant hearing program.

This document describes the protocol for the provision of amplification to infants and preschool children registered with the Ontario infant hearing program (OIHP) in Canada. The provision of amplification includes the prescription and dispensing of hearing instruments to infants and preschool children identified with permanent childhood hearing impairment (PCHI) in the province of Ontario. The first section deals with the structure and processes of the program, while the second section specifies the clinical procedures that are applied in providing hearing instruments to infants and young children with hearing impairment.

Evaluation of nonlinear frequency compression: clinical outcomes.

This study evaluated prototype multichannel nonlinear frequency compression (NFC) signal processing on listeners with high-frequency hearing loss. This signal processor applies NFC above a cut-off frequency. The participants were hearing-impaired adults (13) and children (11) with sloping, high-frequency hearing loss. Multiple outcome measures were repeated using a modified withdrawal design. These included speech sound detection, speech recognition, and self-reported preference measures. Group level results provide evidence of significant improvement of consonant and plural recognition when NFC was enabled. Vowel recognition did not change significantly. Analysis of individual results allowed for exploration of individual factors contributing to benefit received from NFC processing. Findings suggest that NFC processing can improve high frequency speech detection and speech recognition ability for adult and child listeners. Variability in individual outcomes related to factors such as degree and configuration of hearing loss, age of participant, and type of outcome measure.

Evaluation of the desired sensation level [input/output] algorithm for adults with hearing loss: the acceptable range for amplified conversational speech.

OBJECTIVES: This study had two related purposes: first, to define the range of optimal ear canal levels of aided speech in both high frequency and low frequency regions for adults, using both subjective and objective definitions of optimal; and second, to determine whether a prescribed frequency response, such as that given by Desired Sensation Level [Input/Output], falls within the adult listener's optimal range. DESIGN: Twenty-three adult listeners with mild to moderately severe sensorineural hearing loss were selected from a pool of research volunteers. They were fitted in the laboratory with the Siemens Signia hearing instrument and tested with 20 nominally different frequency responses. All advanced processing options of the hearing instrument were disabled. Subjective ratings of loudness and quality and objective measures of consonant identification were obtained for every frequency response. RESULTS: These adult listeners had, on average, a 10 dB range of measured responses in both the low and the high frequencies that resulted in optimal performance on all the measurements. The range did not vary with degree or configuration of hearing loss, or previous hearing aid experience. Desired-Sensation-Level Input/Output targets were within the optimal range for the low frequencies, and 3 dB above the optimal range for the high frequencies. CONCLUSIONS: A range of aided ear canal frequency responses was determined within which adults with mild to moderately severe hearing loss performed optimally on both objective and subjective outcomes. Clinical implications of this finding include the following: prescriptive methods providing different targets may all result in optimal fittings; and a range of targets may be more appropriate than a single target when setting the frequency-gain characteristics of the hearing instrument.

Evaluation of a probe-tube insertion technique for measuring the real-ear-to-coupler difference (RECD) in young infants.

A common strategy for measuring the real-ear response of the real-ear-to-coupler difference (RECD) in the pediatric population is to insert a probe-tube separately from the eartip. This strategy is at times difficult to implement while attempting to obtain the measurement from a young infant. An RECD probe-tube insertion technique that involves connecting the probe-tube to an eartip with plastic film for simultaneous insertion was examined on 30 infants. Repeated measurements were completed on each infant to obtain within-session test-retest reliability data. Probe-tube insertion depth was also examined across participants to provide a guideline for the infant population. Findings indicate that reliable RECD values can be obtained in infants when the probe-tube is extended approximately two to four millimeters (mm) beyond the eartip or 11 mm from the entrance to the ear canal. Clinical implications of this work are discussed.

The DSL method for pediatric hearing instrument fitting: historical perspective and current issues.

The Desired Sensation Level (DSL) Method was originally developed in the early 1980s to provide clinicians with a systematic, science-based approach to pediatric hearing instrument fitting that ensures audibility of amplified speech by accounting for factors that are uniquely associated with the provision of amplification to infants and young children who have hearing loss. This review identifies and describes several of the primary factors that have been considered in the development of the DSL Method. Specifically, the issues discussed relate to: (1) the definition and measurement of relevant acoustic, electroacoustic and audiometric variables; (2) how the external ear acoustics of infants and young children are accounted for in the DSL Method for both audiometric assessment and in the fitting of amplification; and (3) how the DSL Method has evolved concurrently with developments in hearing instrument and electroacoustic measurement technologies. Finally, current issues in the field are identified that have motivated the development of version 5.0 of the DSL Method for hearing instrument fitting.

Clinical protocols for hearing instrument fitting in the Desired Sensation Level method.

A discussion of the protocols used particularly in the clinical application of the Desired Sensation Level (DSL) Method is presented in this chapter. In the first section, the measurement and application of acoustic transforms is described in terms of their importance in the assessment phase of the amplification fitting process. Specifically, the implications of individual ear canal acoustics and their impact on accurately defining hearing thresholds are discussed. Detailed information about the statistical strength of the real-ear-to-coupler difference (RECD) measurement and how to obtain the measure in young infants is also provided. In addition, the findings of a study that examined the relationship between behavioral and electrophysiologic thresholds in real-ear SPL is described. The second section presents information related to the electroacoustic verification of hearing instruments. The RECD is discussed in relation to its application in simulated measurements of real-ear hearing instrument performance. In particular, the effects of the transducer and coupling method during the RECD measurement are described in terms of their impact on verification measures. The topics of insertion gain, test signals, and venting are also considered. The third section presents three summary tables that outline the hearing instrument fitting process for infants, children, and adults. Overall, this chapter provides both clinical and scientific information about procedures used in the assessment and verification stages of the DSL Method.

The Desired Sensation Level multistage input/output algorithm.

The Desired Sensation Level (DSL) Method was revised to support hearing instrument fitting for infants, young children, and adults who use modern hearing instrument technologies, including multichannel compression, expansion, and multimemory capability. The aims of this revision are to maintain aspects of the previous versions of the DSL Method that have been supported by research, while extending the method to account for adult-child differences in preference and listening requirements. The goals of this version (5.0) include avoiding loudness discomfort, selecting a frequency response that meets audibility requirements, choosing compression characteristics that appropriately match technology to the user's needs, and accommodating the overall prescription to meet individual needs for use in various listening environments. This review summarizes the status of research on the use of the DSL Method with pediatric and adult populations and presents a series of revisions that have been made during the generation of DSL v5.0. This article concludes with case examples that illustrate key differences between the DSL v4.1 and DSL v5.0 prescriptions.

An approach for ensuring accuracy in pediatric hearing instrument fitting.

Hearing instrument fitting with infants and young children differs in several important ways relative to the fitting process with adults. In developing the Desired Sensation Level method, we have attempted to account for those factors that are uniquely associated with pediatric hearing instrument fitting. Within this article we describe how the external ear acoustics of infants and young children have been systematically accounted for in developing the Desired Sensation Level method. Specific evidence-based procedures that can be applied with infants and young children for the purposes of audiometric assessment, electroacoustic selection, and verification of hearing instrument performance are described.

Evaluation of electroacoustic test signals I: comparison with amplified speech.

OBJECTIVE: To evaluate the ability of clinical test signals to match the aided levels of real speech, across a range of hearing aid circuit types and strengths. DESIGN: Hearing aids (N = 41) were set to DSL targets for moderate, severe, and profound hearing losses. These hearing aids were tested with three test signals (Fonix Pure Tones, Fonix Composite Noise, and Audioscan Swept), as well as with running speech. The difference between the aided test signal and the aided speech was calculated. RESULTS: Accuracy of matches between aided test signals and aided speech levels depended on circuit type, signal type, and test level. CONCLUSIONS: Clinical test signals can more accurately match the aided levels of speech for all types of hearing aids if they are 1) speech-weighted and 2) temporally modulated. Matches were more accurate at low to moderate test levels (i.e., 50 to 70 dB SPL), and less accurate at high test levels (i.e., 85 dB SPL).