Fitting amplification by 6 months of age best practices
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Fitting Amplification by 6 months of age: Best Practices. Susan Scollie, Ph.D. & Marlene Bagatto, M.Cl.Sc. National Centre for Audiology The University of Western Ontario. Is Amplification Important?.

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Fitting Amplification by 6 months of age: Best Practices

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Fitting amplification by 6 months of age best practices

Fitting Amplification by 6 months of age: Best Practices

Susan Scollie, Ph.D. & Marlene Bagatto, M.Cl.Sc.

National Centre for Audiology

The University of Western Ontario


Is amplification important

Is Amplification Important?

  • Hearing aid use carries a substantial risk of harm, if excessive amplification is provided.

  • Hearing aids confer substantial benefit, if fitted appropriately.


Ehdi program guidance manual

EHDI Program Guidance Manual

We “cannot solely rely on technology … Comprehensive programs and systems must be in place to ensure infants transition smoothly through other key EHDI components, including rescreening, audiologic and medical evaluation, intervention, and family to family support services.”


Ehdi program guidance manual1

EHDI Program Guidance Manual

  • “Goal 2:

    • All infants who screen positive will have a diagnostic audiologic evaluation before 3 months of age.

  • Goal 3:

    • All infants identified with a hearing loss will begin receiving appropriate early intervention services before 6 months of age.”

Do we have a smooth transition between Goal 2 and Goal 3?

What protocols ensure success in Goal 3?


Ehdi program guidance manual2

EHDI Program Guidance Manual:

  • Program Objectives: Audiologic services.

    All infants identified with hearing loss will receive appropriate audiologic services before 6 months of age.


3 areas that need specific protocol

3 areas that need specific protocol:

  • Using diagnostic information (from ABR) for the first hearing aid fitting.

  • Specific procedures for prescribing, fitting, and verifying hearing aids for infants.

  • Appropriate use of advanced technologies with infant hearing aid fittings.


Commonly cited sources for consensus based protocols

Commonly-cited sources for consensus-based protocols

  • Pediatric Working Group (1996) American Journal of Audiology,

    5(1): 53-68

  • American Academy of Audiology

    Pediatric Amplification Guidelines

    October, 2003

    http://www.audiology.org/professional/positions/pedamp.pdf


Commonly cited sources for consensus based protocols1

Commonly-cited sources for consensus-based protocols

  • Shared features:

    • Consistent use of terminology to describe the stages of hearing aid prescription and fitting.

    • Consistent recommendations, such as:

      • Minimum assessment data required Use of nonlinear technology

      • Procedures for real-ear verification (with updates)

      • Important physical features


What does current practice in infant amplification look like

What does current practice in infant amplification look like?

Bamford, Beresford, Mencher, DeVoe, Owen, & Davis (2001). Provision and Fitting of new Technology Hearing Aids: Implications from a Survey fo some “Good Practice Services” in UK and USA. In: Seewald & Gravel, eds., A Sound Foundation through Early Amplification: Proceedings of the second international conference.

Surveyed 27 “good practice” clinics in the United States, regarding their amplification practices.


Did the surveyed clinics fit hearing aids in infancy

Did the surveyed clinics fit hearing aids in infancy?


What does this tell us

What does this tell us?

  • For most levels of hearing loss, hearing aid fitting precedes audiologic certainty by several months.

  • How is this dealt with across programs, clinics, and clinicians?

    • A hearing aid fitting based on uncertain thresholds should err on the side of caution (i.e., low gain). How is this being done?


Amplification procedures

Amplification Procedures


Training priorities

Training Priorities


Level of comfort with higher technology hearing aids

Level of comfort with higher technology hearing aids…


Factors contributing to positive outcomes

Factors contributing to positive outcomes…


Barriers to improvement in amplification services

Barriers to improvement in amplification services


Summary of this survey

Summary of this survey

  • Even in “best-practice” clinics, significant procedural variation was present, in the area of hearing aid fitting.

  • Specific training needs related to amplification were among the highest-priority needs identified.


What are these clinicians trying to say

What are these clinicians trying to say?

  • “I’ve spent the last few years learning a lot about infant hearing screening & assessment. In the mean time, hearing aids have changed a lot. I know that appropriate hearing aid fitting is important for good outcomes, but I’m not always sure how to handle specific devices or cases. I think I need some update training and/or newer protocols.”


Do our current protocols provide the necessary guidance

Do our current protocols provide the necessary guidance?

  • Several state-level amplification protocols were reviewed, to assess:

    • Is there a protocol publicly available?

    • Are the protocols consistent?

      • With one another?

      • With current state-of-the-science?

    • Is the level of detail specific enough to ensure consistent implementation?


Strengths

Strengths

  • Most publicly-available protocols tend to follow the 1996 Pediatric Working Group consensus statement.

  • Like the EHDI guidelines and JCIH position statements, they endorse the importance of appropriate hearing aid fitting as a component of intervention programs.


Some possible limitations

Some possible limitations

  • Protocols that are less than entirely specific leave us open to practice variation due to interpretation.

    • Is that what we want? (sometimes)

    • The devil is in the details. What may seem like a very specific protocol on the surface may actually produce very different hearing aid fittings when applied in the clinic.


Some possible limitations1

Some possible limitations

  • Pediatric amplification practice has changed a lot in recent years. New information is available and needs to be reflected in our protocols.

  • Witness: the differences between the 1996 and 2003 (AAA) position statements.

    • Role of higher technologies

    • Greater consensus on infant-friendly procedures


In particular

In particular:

  • Most prescriptive formulae now offer specific targets for compression hearing aids.

    • These targets differ significantly from the older, linear versions of the same formulae.

    • They are not interchangeable.

    • Some higher technologies are very appropriate for the infant population. Others are not.

  • Infant-friendly real-ear measurement procedures are available. Adult-friendly procedures are not likely to be successful with the 6 month old population.


In particular1

In particular:

  • Most older protocols have few specifics on higher-technology hearing aids, e.g.:

    • Level-dependent processing

    • Noise reduction processing

    • Feedback reduction

    • Directional microphones

  • Yet: this is what most audiologists have questions about… we need to provide some guidance.


Summary next steps

Summary & Next Steps:

  • We have witnessed tremendous growth in knowledge & practice regarding screening, assessment, and diagnosis of hearing status in infancy.

  • One of our current challenges is to improve the level of consistency, documentation, and data tracking in the area of amplification in EHDI programs.

  • Two examples…


Example one

Example One

  • Without specific protocols, how do we ensure accurate data transfer from electrophysiological assessment to hearing aid fitting?


Example two

Example Two

  • Hearing aid fitting in infancy requires appropriate accounting for the effects of:

    • The small, variable, and growing infant ear

    • The signal processing characteristics of modern hearing aids


Using abr thresholds for hearing aid fitting in infants

Using ABR Thresholds for Hearing Aid Fitting in Infants


Infant hearing assessment

Infant Hearing Assessment

  • Estimates of hearing sensitivity are derived from FS-ABR measurements in infants under 6 months

  • Hearing aid selection and fitting proceeds using ABR threshold estimates

    • Do not postpone intervention for behavioural data


Some issues

Some issues ……

  • ABR threshold values (nHL) are not equivalent to behavioural thresholds (HL)

  • A correction is applied to ABR thresholds to obtain the Estimated Hearing Level (eHL)


Correction to abr thresholds

Correction to ABR Thresholds

  • Protocols must be in place to ensure that the ABR (nHL) thresholds are only corrected once

  • Protocol must indicate specific correction values to be used

    • Based on equipment type and parameter settings


Gap in the procedure

Gap in the Procedure….

ABR Thresholds (nHL)

Threshold Estimates for Hearing Aid fitting(eHL)


Fitting hearing aids from hl data

Fitting Hearing Aids From HL Data

  • Many programs use DSL for prescribing hearing aids for infants

  • DSL, like other prescriptive formulae, takes in threshold information in HL

  • Therefore, corrections from nHL to eHL are needed before the hearing aid prescription can be calculated


Converting nhl to ehl

Converting nHL to eHL:

nHL

  • If more than one audiologist is involved, how do we ensure that this is done correctly, and only once?

  • Anything else risks over- or under-amplification

-correction

eHL

Prescription


Challenges in fitting hearing aids from ehl data

Challenges in fitting Hearing Aids From eHL Data

  • ABR (eHL) corrections

    • do not have ANSI standardized calibration

    • vary with stimulus and test parameters

      • Click corrections: up to 15 dB

      • Tone pip corrections: up to 30 dB

    • are largely based on older children, with significant maturation between the nHL and HL test sessions

  • We have an ongoing research project to determine feasibility of using eHL in prescriptive software


We can use protocols to bridge this gap

We can use protocols to bridge this gap

  • Ontario Protocol Safeguards:

    • Audiologist who performs the ABR is responsible for converting to eHL. Corrections are standardized across the program.

    • This is reinforced by the database:

      • Only eHL data may be entered

      • All candidacy & referral guidelines are stated in eHL units

    • Amplification audiologists are trained in nHL to eHL, so that they know it has been done and what type of data to expect.


Amplification services

Amplification Services

All service providers:

  • Attend training sessions

  • Use same equipment

  • Follow same procedures


Amplification services1

Amplification Services

Amplification Training:

  • 6 hours; small groups

    • 73 prescribing; 48 dispensing

  • Lecture and hands-on

  • Follow-up consultation available

  • Repeat training as requested or needed


Amplification services2

Amplification Services

Prescription Process:

  • Define hearing levels and ear canal acoustics of the infant

  • Select hearing aid(s) and features

  • Verify that specified targets have been achieved

  • Validation of device effectiveness


Amplification services3

Amplification Services

Prescription Shall Include:

  • Specification of type of aid(s) and earmold(s) to be fitted

  • Appropriate settings

  • Must be conducted by a registered audiologist


Amplification services4

Amplification Services

Do:

  • Measure each infant’s RECD

  • Use DSL [i/o] prescriptive targets

  • Use RECD-corrected coupler targets

    Don’t:

  • Use the Aided Audiogram for verifying hearing aid fitting – only as an outcome measure

  • Use Insertion Gain measures


Amplification services5

Amplification Services

  • Use newly developed RECD predictions if necessary

    • Bagatto, et al, 2001

  • Advanced Technologies

    • Directional microphones

    • Noise reduction

    • Multi-memory

    • Feedback management/cancellation


Amplification services6

Amplification Services

  • We use an electroacoustic test system that can:

    • Evaluate all hearing aids accurately, regardless of signal processing abilities

    • This ability is dependent on the test signals used by the equipment


Amplification is important

Amplification Is Important

  • Hearing aid use carries a substantial risk of harm, if excessive amplification is provided.

  • Hearing aids confer substantial benefit, if fitted appropriately.

  • www.dslio.com, or: [email protected]

  • www.audiology.org/professional/positions/pedamp.pdf


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