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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

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.



What does this tell us
What does this tell us? like?

  • 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?







Summary of this survey
Summary of this survey like?

  • 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? like?

  • “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? like?

  • 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 like?

  • 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 like?

  • 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 like?

  • 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: like?

  • 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: like?

  • 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: like?

  • 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 like?

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


Example two
Example Two like?

  • 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



Infant hearing assessment
Infant Hearing Assessment like?

  • 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 …… like?

  • 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 like?

  • 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…. like?

ABR Thresholds (nHL)

Threshold Estimates for Hearing Aid fitting(eHL)


Fitting hearing aids from hl data
Fitting Hearing Aids From like?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: like?

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 like?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 like?

  • 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 like?

All service providers:

  • Attend training sessions

  • Use same equipment

  • Follow same procedures


Amplification services1
Amplification Services like?

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 like?

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 like?

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 like?

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 like?

  • 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 like?

  • 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 like?

  • 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: dsl@nca.uwo.ca

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