Guidelines for the Audiologic Management of Adult Hearing Impairment
Audiology Today
Valente, M., Abrams, H., et al. (2006).
Audiology Today, 18(5), 1-44.
This guideline from the American Academy of Audiology provides recommendations for the audiologic management of hearing loss in adults regarding the selection, verification, and validation of hearing aids.
American Academy of Audiology
When fitting hearing aids for adults with hearing loss, recommendations for noise reduction and feedback suppression programming include the following:
<ul>
<li>"[Digital noise reduction] DNR processing may be helpful for enhancement of sound quality and patient comfort. Not all implementations of DNR are equivalent, and data specific to individual implementations should be evaluated prior to selection" (Grade D Evidence; p. 15).</li>
<li>"[Digital feedback suppression/cancellation] DFS processing may be helpful for reduction of feedback and allow for a wider vent that may be beneficial to reduce the occlusion effect. Not all implementations of DFS are equivalent, and data specific to individual implementations should be evaluated prior to selection" (Grade B Evidence; p. 15).</li>
</ul>
For adults with hearing loss who use hearing aids, "the use of [hearing assistive technology] HAT should be considered in the management of each patient as personal hearing aids may not address all of the patient's communication and safety needs" (Grades B, C, and D Evidence; p. 32). [Frequency modulated] FM systems and other technologies should be considered for "patients with extremely poor speech understanding in noise" (Grade B Evidence). "Counseling, instruction, and coaching should be included to ensure optimal use of FM systems" (Grades B and C Evidence; p. 32).
When fitting hearing aids for adults with hearing loss, "at least four to eight frequency handles (bands) for gain shaping are recommended to optimize audibility. Greater numbers of handles (bands) may be desirable to increase the precision with which the frequency response of the hearing aid follows the slope of the audiogram, but evidence does not support improved audibility" (Grade B Evidence; p. 15).
For adults with hearing loss who use hearing aids, "post-fitting counseling and follow-up should be provided to new hearing aid users and offered to experienced users who have not received these services or who may want a 'refresher' course" (Grade A Evidence; p. 38). Counseling should include the patient's primary communication partner(s) and can be provided in group or individual format (Grade B Evidence). Counseling should address the following topics:
<ul>
<li>basic anatomy and physiology of the hearing process;</li>
<li>understanding the audiogram;</li>
<li>problems associated with understanding speech in noise;</li>
<li>appropriate and inappropriate hearing and listening behaviors;</li>
<li>listening and repair strategies;</li>
<li>controlling the environment;</li>
<li>assertiveness;</li>
<li>realistic expectations;</li>
<li>stress management;</li>
<li>community resources;</li>
<li>hearing assistive technology;</li>
<li>hearing aid use and care;</li>
<li>hearing aid features (multiple programs, telephone coil, directional microphone settings, direct audio input, and other special features);</li>
<li>insertion/removal;</li>
<li>battery use (size, how to change, disposal, purchase options);</li>
<li>comfort;</li>
<li>feedback;</li>
<li>telephone use;</li>
<li>warranty protection;</li>
<li>wearing schedule;</li>
<li>goals and expectations;</li>
<li>adjusting to amplification: family, social, school, and work settings;</li>
<li>speechreading;</li>
<li>monaural/binaural hearing aid use; and</li>
<li>post-fitting care (Grade A and B Evidence).</li>
</ul>
For adults with hearing loss, the physical fit of hearing aids should be assessed to ensure ease of insertion/removal, subjective comfort, appearance, microphone angle, and a lack of audible feedback (Grade C Evidence).
A hearing aid fitting evaluation of adults with hearing loss should include a comprehensive case history, otoscopic inspection, cerumen management, hearing assessment, and needs assessment that result in:
<ul>
<li>diagnosis of type and extent of hearing loss;</li>
<li>medical referral as necessary;</li>
<li>provision of audiometric results and counseling on treatment options;</li>
<li>determination of candidacy for amplification and patient attitude toward treatment;</li>
<li>lifestyle assessment; and</li>
<li>need for medical clearance.</li>
</ul>
When fitting hearing aids for adults with hearing loss, recommendations regarding microphone directionality include the following:
<ul>
<li>"[A switchable directional/omnidirectional microphone] is recommended for patients with complaints of speech understanding in noise" (Grade B Evidence; p. 15).</li>
<li>"Fixed (non-switchable) directional technology is not recommended in the majority of cases" (Grade B Evidence; p. 15).</li>
<li>"[An] adaptive directional microphone technology is recommended for patients who experience difficult listening situations with relatively discrete noise source location" (Grade B Evidence; p. 15).</li>
</ul>
For adults with hearing loss, hearing aid verification should include the following:
<ul>
<li>All hearing aids (new and repaired), hearing aid features, and physical parameters should be electroacoustically verified (Grade D Evidence). "Such verification may include confirmation of earmold/shell style, ordered vent size, color, type, as well as a number of hearing aid processing (memories, automatic switches, etc.) and mechanical (directional microphones, t-coil, integrated FM, etc.) features" (Grade D Evidence; p. 24).</li>
<li>Aided soundfield thresholds may be problematic in some instances as a result of binaural summation or open fittings.</li>
<li>Aided soundfield threshold "measurements may be useful for the evaluation of audibility of soft sounds: however, it should be noted that audibility of speech has not been shown to be correlated with hearing aid benefit (though it may lead to increased use) (Grade A Evidence), and excessive audibility of soft sounds may lead to complaints of noisiness and intolerance" (Grade D Evidence; p. 26).</li>
<li>"Those features which cannot be verified through physical examination or standard electroacoustic verification methods should be verified through a listening check" (Grade D Evidence; p. 24).</li>
</ul>
For adults with hearing loss, bone-anchored hearing aids "are recommended for patients with conductive/mixed hearing loss and unilateral deafness" (Grade B Evidence; p. 16).
For adults with hearing loss, "post-fitting administration of these [self-assessment] instrument(s) is necessary to validate benefits/satisfaction from amplification" (Grade B Evidence; p. 7).
When fitting hearing aids for adults with hearing loss, "the magnitude of the [occlusion effect] OE should be assessed informally to ensure that the quality of the hearing aid wearer's own voice is not problematic due to occlusion. In cases in which occlusion problems are suspected, verification of the magnitude of occlusion should be verified using probe microphone techniques or with a device designed to measure real-ear occlusion effect" (Grade B Evidence; p. 26). Routine measurement of OE "is generally recommended given that it requires only a very brief period of time beyond that required for probe microphone verification of gain and output" (p. 26).
When providing pre-fitting counseling to adults with hearing loss, the following considerations should be addressed to establish realistic expectations with the hearing aid user:
<ul>
<li>"Audiologists should be aware of the non-auditory factors that may impact successful prognosis" (Grades A, B, and D Evidence; p. 8).</li>
<li>All patients should be questioned or screened for issues related to general health, manual dexterity, near vision, support systems, motivation, and prior experience with amplification (Grades A, B, C, and D Evidence).</li>
<li>"Each patient should receive formal self-assessment instrument(s)/inventory(s) prior to fitting to establish communication needs, function, and goals" (Grade B Evidence; p. 7).</li>
<li>"Self-assessment scales, visual analog scales, or semantic differential scales can be used to assess hearing aid readiness" (Grades A, B and D Evidence; p. 8).</li>
<li>"Cognitive abilities or personality assessments should be assessed by a professional specially trained in these areas" (Grades B and D Evidence; p. 8).</li>
<li>"Audiologists should have a list of professionals trained to deal with the above-mentioned issues to whom patients might be referred" (Grade D Evidence; pp. 8-9).</li>
<li>"Patients should be informed that the full benefits from amplification may not be immediately apparent and that there may be a period of adjustment and/or acclimatization" (Grade B Evidence; p. 38).</li>
</ul>
When fitting adults with hearing loss, hearing aid programming recommendations include the following:
<ul>
<li>"Initial selection of target gain for average speech input levels should be based on a validated prescriptive procedure. This recommendation is based on evidence that validated prescriptive methods appear to be a reasonable starting point and are time efficient" (Grade B Evidence; p. 14).</li>
<li>The Threshold of Discomfort should be measured for individual patients and the OSPL90 should be set such that it does not exceed the Threshold of Discomfort (Grade B Evidence).</li>
</ul>
Recommendations for hearing aid features include the following:
<ul>
<li>"Volume controls (VC) are recommended for many patients regardless of the type of gain processing (linear or compression)" (Grade B Evidence; p. 14).</li>
<li>Direct auditory input and telecoil circuitry should be considered, when appropriate (Grade C Evidence).</li>
<li>"Multiple memories are useful when specific signal processing is beneficial in some environments, but not others. The most obvious case is that of directional versus omnidirectional microphone modes" (Grade A Evidence; p. 15).</li>
</ul>
Hearing aid laterality and style recommendations include the following:
<ul>
<li>"Binaural amplification is recommended for most patients [Grade B Evidence]. However, monaural fittings may be warranted based on specific patient needs and in particular cases of asymmetry, binaural interference, and financial and/or cosmetic concerns" (Grade C Evidence; p. 14).</li>
<li>"The choice of hearing aid style should be based on factors such as gain and output requirements, ear canal size and geometry, ease of insertion and manipulation, skin sensitivity, need for specific features (e.g., directional microphone, direct auditory input, telecoil), comfort, occlusion considerations, and cosmetic concerns" (Grades B and C Evidence; p. 14).</li>
</ul>
Recommendations regarding compression circuitry in hearing aids include the following:
<ul>
<li>"Hearing aids with a low compression threshold (CT) are recommended for patients with reduced dynamic range (DR) of hearing ... though linear signal processing with compression limiting (CL) may be preferred to low CT" (Grade A Evidence; p. 14).</li>
<li>"The evidence relative to the number of compression channels is mixed" (Grades A and D Evidence; p. 14). No more than three to five channels of compression are recommended.</li>
<li>"CL is recommended over peak clipping (PC) for output limitation. PC may be preferred by some patients with profound hearing loss having prior experience with PC hearing aids" (Grade B Evidence; p. 15).</li>
<li>"Use of compression for patients with severe to profound hearing loss should be limited to compression that minimizes the alteration of speech cues, particularly in the temporal domain (i.e., CL or low CT with few compression channels, low compression ratios, and long time constants)" (Grade B Evidence; p. 15).</li>
<li>"It is recommended that proportional frequency compression hearing aids be experimentally considered for patients with severe-to-profound hearing loss, especially when other treatments (such as conventional amplification and/or cochlear implants) have failed or may not be an option" (Grade B Evidence; pp. 15-16).</li>
</ul>
For adults with hearing loss who use hearing aids,<strong> </strong>electroacoustic verification of their device should include the following:
<ul>
<li>"Prescribed gain from a validated prescriptive method should be verified using a probe microphone approach that is referenced to ear canal [sound pressure level] SPL" (Grade A, B and C Evidence; p. 26).</li>
<li>"The probe microphone technique of front-to-back ratio (FBR) is recommended as a time-efficient and reliable method for quantifying that the directional microphone is functioning. This method is impacted by compression parameters and is not useful for prediction of benefit, but is advocated for within-patient quality control and examination of the impact of fitting effects such as venting" (Grade C Evidence; p. 27).</li>
<li>Simulated real-ear techniques should verify the maximum hearing aid output, OSPL90 (Grade B Evidence).</li>
<li>"Actual speech or a speech-like signal should be used when attempting verification of prescriptive methods for which the targets are based on speech inputs.... This would require that the test signal adequately represent the frequency, intensity, and temporal aspects of speech" (Grade B Evidence; p. 25).</li>
</ul>
