Amplification for Infants At long last, universal hearing detection and intervention programs have been implemented in the majority of states across the nation and are identifying children with hearing loss at younger ages than ever before. The success of early hearing detection and intervention programs has highlighted the need for well-trained pediatric audiologists ... Features
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Features  |   April 01, 2002
Amplification for Infants
Author Notes
  • Kathryn laudin Beauchaine, is the coordinator of audiology at Boys Town National Research Hospital and an instructor in the department of otolaryngology and human communication at Creighton University. Her clinical interests focus on pediatric audiological assessment and amplification for children. Contact her by email at beauchaine@boystown.org.
    Kathryn laudin Beauchaine, is the coordinator of audiology at Boys Town National Research Hospital and an instructor in the department of otolaryngology and human communication at Creighton University. Her clinical interests focus on pediatric audiological assessment and amplification for children. Contact her by email at beauchaine@boystown.org.×
  • Patricia G. Stelmachowicz, is the director of audiology at Boys Town National Research Hospital and a professor in the department of otolaryngology and human communication at Creighton University. Her research interests include speech perception in hearing-impaired listeners and the determination of optimum amplification characteristics for children. Contact her by email at stelmach@boystown.org.
    Patricia G. Stelmachowicz, is the director of audiology at Boys Town National Research Hospital and a professor in the department of otolaryngology and human communication at Creighton University. Her research interests include speech perception in hearing-impaired listeners and the determination of optimum amplification characteristics for children. Contact her by email at stelmach@boystown.org.×
Article Information
Hearing Disorders / Hearing Aids, Cochlear Implants & Assistive Technology / Audiologic / Aural Rehabilitation / Professional Issues & Training / Features
Features   |   April 01, 2002
Amplification for Infants
The ASHA Leader, April 2002, Vol. 7, 6-12. doi:10.1044/leader.FTR2.07072002.6
The ASHA Leader, April 2002, Vol. 7, 6-12. doi:10.1044/leader.FTR2.07072002.6
At long last, universal hearing detection and intervention programs have been implemented in the majority of states across the nation and are identifying children with hearing loss at younger ages than ever before.
The success of early hearing detection and intervention programs has highlighted the need for well-trained pediatric audiologists to provide appropriate diagnostic and follow-up services, including provision of amplification.
Not all centers have a large enough infant caseload to feel confident or to be proficient at providing amplification for infants. For some clinics, resources may not be available to provide state-of-the-art services. These situations call for the development of centers of excellence in pediatric audiology. In lieu of this, many organizations are attempting to fill the gap by offering continuing education seminars and providing information through the Internet or in print.
Fitting hearing instruments on these very young infants is new to many audiologists. The research suggests that the listening needs of infants are different from adults’. Unlike adults and older children, infants cannot tell us what amplified speech sounds like or let us know if sounds are too loud. There are also obvious physical differences between infants and older children and adults that affect the fitting process.
The amplification process for infants requires a systematic, five-step approach: confirmation of hearing loss and referrals for intervention, selection of amplification, fitting and verification, hearing aid orientation, and follow-up services.
Step One: Confirmation of Hearing Loss and Referrals for Intervention
Today, it is not uncommon for an infant to be referred for diagnostic audiological testing within the first month of life. The purpose of the audiological test battery is to estimate the degree and configuration of hearing loss in each ear, to rule out treatable middle-ear dysfunction as a contributing factor, and to rule out auditory neuropathy. In most cases, the diagnostic test battery will include otoacoustic emissions, frequency-specific evoked potential measures, and immittance testing. When an infant has middle-ear dysfunction, it may be necessary to refer for treatment and retest when the ears are clear.
Some infants have other health concerns that may delay the assessment and use of amplification. For example, it may be difficult to assess an infant on a respirator because of interfering electrical noise and muscle artifact. Other infants may have serious medical conditions that take precedence over amplification until health has stabilized. For infants diagnosed with auditory neuropathy, there is no consensus about the best treatment approach, and amplification should be considered on a case-by-case basis.
Once hearing loss has been quantified, a number of referrals should be considered. One essential referral is for educational intervention. Audiologists need to be aware of local educational resources. Typically, the local school district is the first contact. Each state has a system in place with designated service coordinators who manage the educational intervention. Central to the educational intervention process is the establishment of an Individual Family Services Plan, which specifies the family’s goals for their infant’s education.
Contact with the child’s medical home should be established to discuss referrals to an otolaryngologist for examination and to obtain medical clearance for amplification; a medical geneticist to rule out concomitant medical problems and assess recurrence risk if the family desires this information; and a pediatric ophthalmologist to determine if vision is normal. Parents also may benefit from support groups or communication with other parents of children with hearing loss.
Step Two: Selection of Hearing Instruments
Selecting hearing instruments from the large field of possible choices can seem daunting. The selection of hearing instruments is a complex decision based on circuit type, infant-specific options such as a tamper-resistant battery case and volume cover, electroacoustic flexibility, and FM system compatibility. Other factors include size, warranty, and battery drain. Further, some parents might be limited in their ability to make maximum use of features associated with advanced hearing instruments.
Funding sources for amplification also will need to be identified. Although national funding resources exist, many funding sources are specific to each state. The cost of hearing aids is a factor for some families and agencies, and may preclude programmable or digital instruments.
Step Three: Fitting and Verification
A prescriptive approach to fitting amplification is essential. For infants, the most appropriate prescriptive approach is one that is audibility based and accounts for the physical differences between children and adults. One method developed specifically with children in mind is the Desired Sensation Level (DSL). This method provides targets for gain and output, as well as for compression ratio. Other prescriptive procedures are available, and most manufacturers provide proprietary algorithms or other prescriptive methods with their advanced technology devices.
For a variety of reasons, real-ear measures are the preferred method to document hearing instrument performance. Real-ear measures are reliable, can be obtained quickly, and have high resolution in both the frequency and intensity domains. Unlike functional gain, these measures provide information about gain for speech-level inputs and maximum sound pressure levels delivered to the ear. It is difficult to complete traditional real-ear probe-microphone measures on infants because of their random movements and lack of head control. A proven alternative to traditional probe-microphone measures is to obtain real-ear to coupler differences (RECD). The RECD, measured with the infant’s own earmold, can be used in combination with test-box measures to predict real-ear responses.
Regardless of the method used to fit hearing aids, it is important to estimate the audibility of aided speech for soft, average, and loud speech inputs. The DSL [i/o] and NAL-NL (National Acoustics Laboratories-Non-Linear) fitting procedures can provide this information. The Situational Hearing Aid Response Profile also can be used. It is important for parents and other caregivers to monitor changes in the infant’s auditory behavior with hearing aids. A large discrepancy between expectations and actual performance with the hearing aid alerts the audiologist to possible errors in diagnosis, the existence of additional disabling conditions, or changes in hearing.
Step Four: Hearing Instrument Orientation
After the hearing instruments have been chosen and shown to be appropriate for the degree and configuration of hearing loss based on prescriptive targets, it is necessary to ensure that the infant can wear the devices at the recommended settings without feedback. Parents and caregivers must be instructed in use and care of the instruments and earmolds, shown how to perform daily listening tests and battery checks, and taught troubleshooting basics. Before leaving the clinic, parents must be able to place the devices in the ears and confidently operate the controls. Supplemental written materials also should be provided. During the orientation, instruction also should include inf ormation about listening scenarios, minimizing background noise, proximity issues, and the need to carefully observe the infant’s responses in a variety of listening situations. In follow-up conversations with the parents and the early intervention specialist, these acoustic and auditory issues should be reiterated.
Step Five: Follow-Up
Fitting amplification begins a life-long process for the infant and family. The first follow-up conversation with the family may be by telephone during the week following the fitting. For infants, it is likely that the next appointment will be for new ear impressions, possibly within one month of the initial fitting. Rapid growth during infancy means multiple sets of earmolds, especially during the first year or two of life. New earmolds require new RECD measures and re-entering these RECDs into the prescriptive program to determine if adjustments are needed in the hearing instruments.
As soon as the infant is able to perform visual reinforcement audiometry, around 6–7 months of age, a behavioral hearing test should be obtained. For infants whose developmental delays preclude reliable behavioral results, provisions should be made to repeat the frequency-specific ABR measures within six months. Changes in thresholds require returning to the prescriptive program to re-establish amplification targets.
After the first behavioral audiogram is obtained, a typical follow-up schedule for audiograms and hearing instrument testing is every three months until 3 years of age, then every six months until 6 years of age, and annually thereafter. For children with significant developmental delays and no suspicion of progressive hearing loss, it may be adequate to repeat the ABR test annually, although hearing instruments should be analyzed electroacoustically more frequently.
The audiologist is often a catalyst in promoting communication with parents, early interventionists, physicians, and others involved in the child’s care, which is critical to success in using amplification.
As amplification is provided at younger ages, audiologists must increase their knowledge and skills in pediatric amplification. A systematic, research-based approach to this process is critical. Resources are available to support the audiologist in this important work.
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April 2002
Volume 7, Issue 7