Presented at the EHDI Conference
Atlanta, GA
March 4, 2005

Strategies for Fitting Hearing Aids to Infants

Marlene Bagatto, Susan Scollie, Shane Moodie, Richard Seewald
National Centre for Audiology, University of Western Ontario
London, Ontario, Canada

EHDI Programs are committed to:
•	identifying infants with hearing loss by 3 months of age
•	initiating intervention by 6 months of age

Therefore, appropriate assessment and intervention protocols must be in place.

Published Protocols

Pediatric Working Group (1996) American Journal of Audiology, 5(1): 53-68.

American Academy of Audiology Pediatric Amplification Guidelines, October 2003
•	www.audiology.org/professional/positions/pedamp.pdf

Basic Components of an Assessment Protocol

•	High frequency immittance for infants 6 months of age and younger
•	Margolis, RH, Bass-Ringdahl, S, Hanks, WD, Holte, L & Zapala, DA, 2003. Tympanometry in newborn infants -- 1 kHz norms. JAAA, 14(7), 383-92.

•	Otoacoustic emissions
•	Pass/fail criteria based on level of emission, emission-noise floor ratio, and repeatability

•	Frequency-specific ABR
•	air and bone conduction
•	Stapells, D, 2000. Frequency-specific evoked potential audiometry in infants. A Sound Foundation Through Early Amplification: Proceedings of an International Conference. Ed. RC Seewald, pp. 13-32.

•	Equipment and parameter specific nHL corrections
•	Identify who is responsible for applying correction

•	Intervention is not postponed for behavioural assessment

Using ABR Data for Hearing Aid Fitting
	
Some Issues
•	ABR threshold values (nHL) are not equivalent to behavioural thresholds (HL)

•	Algorithms (eg., DSL [i/o]) use threshold information in HL to calculate the hearing aid prescription

A Solution
•	Apply a correction to ABR thresholds (nHL) to obtain the Estimated Hearing Level (eHL)

•	The corrected nHL value represents a behavioural threshold (HL)

Please Note:
•	Based on publications by D. Stapells
•	Equipment, calibration, and parameter specific

Ontario Infant Hearing Program Corrections:

500 Hz =   -20		2000 Hz = -10
1000 Hz = -15		4000 Hz =   -5

Components of an Amplification Protocol

Assessment
•	Correct FS-ABR threshold estimations (if not already corrected) and enter into DSL [i/o]

•	Measure RECD using new technique
•	Connect probe tube to tip using plastic film
•	Probe tube should extend about 2mm beyond sound bore (11mm insertion depth from canal opening)
•	Use predicted values if unable to measure 
•	Bagatto, MP, Scollie, SD, Seewald, RC, Moodie, KS, & Hoover, BM, 2002. Real-ear-to-coupler difference predictions as a function of age for two coupling procedures. JAAA, 13, 407-415.
•	See also www.dslio.com

Selection
•	Use evidence-based prescriptive formula (eg., DSL[i/o]) to calculate targets for gain and output across frequency

•	Consider the following options when selecting a hearing instrument for an infant:
•	Compression (WDRC)
•	Output compression limiting
•	Multiple channels
•	Pediatric filtered earhook
•	Direct audio input
•	Tamper proof battery door & volume control
•	Behind-the-ear style
•	FM system

•	Technologies that require a careful approach with infants:
•	Directional microphones
•	Noise reduction
•	Multiple memories
•	Feedback management/cancellation

Verification
•	Conduct simulated (coupler-based) REAR & RESR measurements (www.dslio.com)
•	Verify audibility of speech using soft, average, and loud speech signals
•	Verify MPO using 90-100dB pure tone
•	Check for feedback and use lubricant if needed

Follow-up
•	Conduct VRA using insert earphones coupled to personal earmolds
•	Use control trials to obtain a measure of reliability
•	Widen, JE, Folsom, RC, Cone-Wesson, B, Carty, L, Dunnell, JJ, Koebsell, K, Levi, A, Mancl, L, Ohlrich, B, Trouba, S, Gorga, MP, Sininger, YS, Vohr, BR, & Norton, SJ, 2000. Identification of neonatal hearing impairment: Hearing status at 8 to 12 months corrected age using a visual reinforcement audiometry protocol. Ear and Hearing, 21(5):471-87.

•	Measure the RECD using the earmold whenever the child obtains new ones
•	For accurate comparison of hearing assessment results over time, correct thresholds using the RECD to account for changes in ear growth (HLp)
•	Adjust hearing aids if there is a true shift in hearing levels

Contact information:

Marlene Bagatto
bagatto@nca.uwo.ca
(519) 661-2111 ext 88949