Transcript No Slide Title

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?
• 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
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 Manual
• “Goal 2:
– All infants who screen positive will
have a diagnostic
Do we have audiologic
a smooth
evaluation
before
3 months
transition
between
Goal 2 of age.
• Goal 3:
and Goal 3?
What
protocols with
ensure
– All infants
identified
a hearing
success
in Goal 3?appropriate
loss will begin
receiving
early intervention services before 6
months of age.”
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:
• 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
• 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 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?
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?
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
100
% of clinics
0-36 mo
80
60
40
20
0
REIR
REAR
RECD
Procedure
PRESC
Training Priorities
Priority (USA clinics only)
Rank
New hearing aids
Latest research findings
1
2
Non-linear fitting
Software skills
Social/cultural
3
4
5
Later agency working
Working with families
Handling young babies
Assessment skills
6
7
8
9
Level of comfort with higher
technology hearing aids…
Factors contributing to
positive outcomes…
Barriers to improvement in
amplification services
Top Two Barriers
(USA clinics only)
Limited resources
Lack of evidence on cost
effectiveness of new hearing aid
technology
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?
• “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?
• 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
• 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
• 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 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:
• 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 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:
• 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
• Without specific protocols, how do
we ensure accurate data transfer
from electrophysiological
assessment to hearing aid fitting?
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
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 ……
• 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
• 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….
ABR
Thresholds
(nHL)
Threshold
Estimates for
Hearing Aid
fitting(eHL)
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:
nHL
-
correction
eHL
Prescription
• If more than one
audiologist is
involved, how do
we ensure that this
is done correctly,
and only once?
• Anything else risks
over- or underamplification
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
• 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
All service providers:
• Attend training sessions
• Use same equipment
• Follow same procedures
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 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 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 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 Services
• Use newly developed RECD
predictions if necessary
–
Bagatto, et al, 2001
• Advanced Technologies
–
–
–
–
Directional microphones
Noise reduction
Multi-memory
Feedback management/cancellation
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
• 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