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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4507_Библиотеки_им_академика_М_И_Перельмана.pdf
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carefully to parents and pay attention to nonverbal as well as verbal expressions.
Clinical audiologists should be patient and not interrupt parents during the interview. Parents’ questions should be answered as clearly and simply as possible. A
sample pediatric anamnesis form is shown in Fig.11.3.
After completing the anamnesis process, the infant must be reevaluated at the
hearing aid clinic. The auricle and ear canal must be examined for any anomalies,
followed by an otoscopic examination. The audiologist must determine the following: Is the external ear normal in appearance? Does the auricle have an abnormality
such as a skin tag/skin pit? Is the pinna suitable for BTE hearing aid usage? Does
Fig. 11.3 Sample of pediatric anamnesis form
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
221
the ear canal adequately support an earmold? Is the baby’s ear canal clean enough
to take ear impressions? What is the type and degree of the baby’s hearing loss? Are
there any additional temporary obstacles, such as otitis media, or permanent anomalies that may prevent sound from traveling through the outer and middle ear?
If there is an abnormal appearance of the outer ear or an overlooked skin tag/skip
pit, referral to an ENT specialist for further evaluation of inner ear abnormalities is
recommended. If the ear canal is too narrow, parents should be referred to an otolaryngologist to evaluate the function of the ear canal. In addition, if there is wax in the
ear canal, it is essential to remove the earwax before taking an impression of the
earmold.
11.7.3.3 Deciding ontheAmplification Method
In addition to the audiologic examination and anamnesis performed in the hearing
aid clinic, the audiologist typically determines the hearing aid tting protocol by
analyzing the infant’s comprehensive audiologic and hospital medical records. In
general, traditional BTE models are preferred for infants with appropriate auricles
and ear canals, while bone conduction hearing aids are used for those with outer ear
deformities or narrow/closed ear canals that prevent sound transmission.
Bone conduction hearing aids are typically attached to a fabric or metal headband and provide amplication through bone conduction. Bone conduction hearing
aids are often used for babies with healthy inner ears who cannot use BTE hearing
aids due to malformations of the outer ear. When using this type of hearing aid, it is
important to place the bone conduction receiver on the mastoid with enough pressure to deliver sound directly to the cochlea. However, some families may misinterpret this pressure as harmful to the baby’s head and loosen the tape, which can
damage the amplication process. Therefore, it is necessary to explain to the family
that applying pressure is not harmful to the baby and is essential for adequate amplication. A bone conduction auditory brainstem responses (ABR) test of the infant’s
inner ear prior to bone conduction hearing aid tting provides a denitive diagnosis
of cochlear status and estimated hearing thresholds for hearing aid tting.
Hearing aids commonly utilized in the pediatric population include traditional
BTE models. These models offer standard BTE (85dB SPL) and BTE UP/SP (140+
dB SPL) options that provide audiologically appropriate gain and are durable
enough to withstand a baby’s biting and throwing attempts. Moreover, they possess
a waterproof feature that safeguards against being chewed or submerged in water. A
few hearing aid manufacturers produce BTE models explicitly designed for the
pediatric population. Common features of these models include LED light stimulators for parents and smaller horns for babies, as well as tamper-proof/locked battery
doors. Pediatric hearing aid manufacturers also offer remote microphones and FM
system accessories for hearing-impaired children to use at school and home.
RITE models are often preferred for school-aged children and adolescents. These
models have a small appearance and wireless connectivity, which can address the
growing desire for “aesthetics” and “communication” during adolescence. However,
it is not advisable to use custom hearing instruments during this period as they are
not compatible with accessories that increase SNR, such as remote microphones.
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B. Celikgun et al.
Nevertheless, an IIC model hearing aid may be preferred for an adolescent patient
who cannot control his or her aesthetic perception. It is better to use hearing aids
than to suffer from auditory deprivation, even without accessories.
Infants and children diagnosed with severe or profound sensorineural hearing
loss require careful monitoring of their speech and language development.
Abbreviations such as SNHL and CI should be explained at the time of initial
tting. Those who demonstrate incomplete responses to sound, inadequate vocalization or babbling, and limited or no word production should be considered for
cochlear implant surgery. This is especially important prior to the critical period
of language acquisition. It is recommended that infants who do not benet sufciently from hearing aids be evaluated for the use of cochlear implants without delay.
11.7.3.4 Informing theFamily About Hearing Loss andHearing Aid
Application Process
Before the birth of a hearing-impaired child, the parents, who probably have no idea
about hearing loss and its negative effects, should be informed about it. The normal
physiology of hearing, the baby’s hearing loss and degree of hearing loss, the negative impact of hearing loss on the child’s academic, social, and psychological status,
and these can be minimized with hearing aids should be explained to the parents.
They should be informed that even profound hearing loss can be corrected with
hearing aids or, if necessary, cochlear implants. It is important to explain that early
intervention by an audiologist can minimize the negative impact of hearing loss on
their child’s development.
11.7.3.5 Taking theEar Impressions forEarmolds
There are some obvious physical differences between the outer ear structures of
infants and adults. The auricles and ear canals of infants are smaller than those of
adults. The ear canal is shorter in length and the eardrum is positioned more
obliquely within the ear canal. Therefore, these physical differences should be considered when taking ear impressions of babies. On the other hand, children who are
very active around the age of 2 may not allow an ear impression to be taken and may
make sudden movements while the otoscope/light pen is in the ear. For this reason,
more care should be taken when taking ear impressions from babies and the mother
or father should provide support to keep the baby/child stable during the procedure
(Fig.11.4a). In addition, the baby should be kept from crying as much as possible
as mouth movements can affect the quality of the ear impression. While Fig.11.4b
shows the ear impression-taking equipment, Figs.11.4c and d show the appropriate
and inappropriate ear impression samples, respectively.
It is recommended that the earmolds be replaced, especially every 3 to 6months
for the rst 2years, as babies’ ears grow quickly compared to adults. It is also recommended to wash the earmolds at least twice a week with warm soapy water or
earmold cleaning solution and dry them at room temperature without exposing them
to heat sources. Some earmold manufacturers can also make “fun” earmolds in different colors for the pediatric group.
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
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223
d
Fig. 11.4 (a) Ear impression taking position, (b) Ear impression tools, (c and d) Appropriate and
inappropriate ear impression samples for earmold production
11.7.3.6 The Hearing Aid Fitting Software andConnection
toHearing Aids
Since the 1990s, hearing aid manufacturers have offered computer software for tting
hearing aids. Each manufacturer has developed specic software for its brand, which is
updated several times a year. The tting of hearing aids is done in detail thanks to the
tting software and all the technologies used in the hearing aids that can be adjusted by
it. In addition, the “data logging” function in the software, which is essential for the
pediatric group, can show how many hours a day the baby uses the hearing aid.
Hearing aid tting software usually consists of a “patient information” screen, a
“ne-tuning” screen, and nally the “controls” screen. The patient information part
of the tting software typically includes the patient’s rst and last name, gender,
age, address, phone number, audiogram information, and hearing preferences. The
ne-tuning section offers prescription formula preferences, tting band ne-tuning,
and hearing instrument technology options. Finally, the controls section offers
options such as data logging, light/sound alert options for hearing aids, and button
lock options for pediatric patients. Hearing instrument software and rmware
should be kept “up to date” in order to function properly. Occasionally, hearing aid
manufacturers may provide improvements to hearing aids with an update they
release for certain models.
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B. Celikgun et al.
Entering the required information into the hearing aid tting software is the rst
rule of good tting. Although information such as the patient’s age and gender may
seem unrelated to the hearing aid tting, it can be important for the prescription
formula or hearing gain calculation by the tting software. For example, the calculated hearing gains for males and females may be different in some frequency bands
even though they have the same audiogram and tting formula.
Some hearing aid manufacturers may offer a tting module specically designed
for the pediatric population. In general, pediatric tting modules automatically
implement some settings required for pediatric patients. For example, the pediatric
DSL-5 tting formula is selected, microphones are set to omnidirectional mode,
DNR is turned off, data logging is turned on, and the program/volume control buttons are turned off while the hearing instrument’s LED light alert is activated. In
addition, they have a special “threshold input section” for tonal ABR results. The
important point here is the reference to the ABR threshold data. If the clinician has
applied the “correction factors” to the obtained tonal ABR results, these new values
should be entered into the software as “Estimated HL/Ehl.” If the ABR thresholds
are entered into the tting software without applying the correction factors, then the
“Normalized HL/nHL” thresholds should be entered into the tting software. This
will allow the tting software to automatically apply correction factors to the thresholds entered in nHL and convert them to eHL.If the audiologist mistakenly enters
the already corrected thresholds into the software as nHL, the hearing gain offered
to the child will be inadequate because the software will apply the correction factor
again. Therefore, selecting the appropriate reference as nHL or eHL for tonal ABR
thresholds in the tting software is critical.
Fitting software requires hardware called a “bridge” to connect to hearing instruments. This bridge connects the hearing instruments to the tting software via a
wired or wireless connection. Wired connections are generally provided by the
Natus Hi-Pro 2, while wireless connections are provided by the HIMSA Noahlink
Wireless. Both devices are compatible with all manufacturers and all hearing instrument models. When tting hearing aids to babies/children who are very active, it is
more convenient to use “wireless” hardware because the cables can be removed in
an instant with hand-arm movements. It also allows the hearing care professional
the opportunity to observe the baby on the playground and intervene in the hearing
aid tting if necessary.
11.7.3.7 Hearing Aid Fitting
The hearing aid tting software uses the entered data to calculate a frequencyspecic gain and provides recommendations for the use of the technology. The auditory gain calculation is performed using prescription formulas. These formulas are
obtained by incorporating a wide range of variables into the calculations. Many
variables such as the patient’s age, gender, hearing thresholds, Loudness Discomfort
Levels (LDL), Long Term Average Speech Spectrum (LTASS), and Speech
Intelligibility Index (SII) data are calculated using the software’s preferred formula.
This “preset” is then veried using objective and subjective verication methods,
ne-tuned if necessary, and the tting is complete.
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
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In general, the hearing aid tting process consists of the following stages: prescription formula preference, objective and subjective verication, and ne-tuning.
Prescription Formula Preference
Prescription formulas commonly used in hearing aid tting are NL-1 and NL-2
developed by the National Acoustic Laboratories (NAL), Desired Sensation Level
(DSL) [i/o], DSL v5.0 and DSL 5 pediatric. The most commonly used formulas
today are NAL-NL2 and DSL v5.0 for adults, and DSL v5.0 pediatric for the pediatric group.
NAL-NL 1 was updated and introduced in 1999 to match digitized hearing aids.
The formula, which aims to provide maximum speech discrimination at optimal
loudness levels, was updated in 2011. The new formula, called NAL-NL 2, provides
more gain in the low and high frequencies compared to the old version, but slightly
less gain in the mid-frequencies. In addition, no gain is applied to frequencies below
50Hz and above 16kHz. While NAL-NL 1 provides ne-tuning at two input levels,
“Soft” and “Loud,” NAL-NL 2 provides ne-tuning at three input levels: “Soft,”
“Moderate,” and “Loud.” In addition, NAL-NL 2 calculates the gender effect, suggesting 2dB less gain for women at the “Moderate” input level. Finally, the formula
takes into account age and hearing instrument experience.
Research has shown that pediatric hearing aid users require more overall gain
than adults. Therefore, DSL v5.0 Pediatric, which provides more gain at all frequencies at all input levels, is generally preferred for infants and children. The rst DSL
formula was revised in 1995 during the digital era and was named DSL [i/o]. The
formula, which was found to provide more hearing gain than users expected, was
revised again in 2005 and renamed DSL m[i/o]. The letter “m” in the revised algorithm stands for “multistage,” indicating that the formula includes four stages of
signal processing: amplitude expansion, linear gain, amplitude compression, and
output limiting. This new formula, commonly referred to as DSL v5.0, is designed
to eliminate loud noise interference during hearing aid use, ensure audibility of
important acoustic cues in speech, provide a wide variety of speech inputs, adapt to
different listening needs in quiet and noisy environments, and develop a formula
that will be widely used in pediatric ttings.
The DSL v5.0 Pediatric Formula is specically designed for pediatric hearing
instrument users. It allows the calculation of electrophysiological results in pediatric patients whose hearing thresholds cannot be determined for hearing aid tting. It
also takes into account the acoustic properties of the external ear canal, which vary
with age. The formula also takes into account important factors such as the type of
hearing loss and the binaural summation effect. In a study comparing the differences between NAL-NL 2 and DSL v5.0, real ear measurement (REM) found that
the NAL-NL2 formula was successful in the low and high-frequency ranges at input
levels of 65 and 80dB SPL, and in the high-frequency range at an input level of
50dB SPL.On the other hand, DSL v5.0 was found to be more successful in the
mid-frequency bands at 65dB SPL input level and in the low and mid-frequency
bands at 50dB SPL input level. While DSL v5.0 was found to be more successful
in the SII calculation at moderate and loud input levels, NAL-NL 2 had better results
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at low input levels. In addition, the DSL v5.0 formula was found to be more successful in understanding speech in noise as assessed by the Hearing in Noise Test
(HINT). In general, amplication using the DSL v5.0 formula was found to provide
better “speech perception.” [53] It has also been reported that the DSL v5.0 formula
provides better speech understanding results in bimodal ttings for unilateral
cochlear implant users [54].
Verification ofHearing Aids: Objective andSubjective Tools
Since the expressive language skills of infants with hearing loss are not yet developed
and hearing-impaired children generally have limited language skills compared to
their peers, verication procedures of auditory gain after hearing aid tting are of
great importance. Verication procedures used in the pediatric population can be
divided into two main groups: objective and subjective verication tools. While REM
for children and Real Ear Coupler Difference (RECD) for infants provide direct verication of hearing gain, Cortical Auditory Evoked Potential (CAEP) responses such
as the Acoustic Change Complex (ACC) and P1-N1-P2 can indirectly indicate
whether sounds are reaching the auditory cortex. In addition to objective tools, visual
reinforcement audiometry/conditioned orientation reex audiometry (VRA/COR)
free-eld audiometry tests, the startle “eye blink” reex, observations of infants’ auditory responses on the playground at the hearing care center, observations of parents at
home, and various questionnaires developed for parents also provide subjective data
about infants’ hearing. The integration of the objective and subjective results of the
infant’s hearing is very valuable for pediatric hearing aid tting.
Objective Verification Tools
In pediatric hearing aid applications, the auditory gain can be veried using two
different REM applications: Insertion Gain Measurement and RECD.The classic
insertion gain application requires the child to sit quietly on the parent’s lap for at
least 5minutes. In clinical practice, probe microphone measurements can be easily
performed on cooperative children over the age of 2. For classic REM testing, the
child is seated on the parent’s lap, 0.5–1m away, and 0° azimuth to the REM loudspeaker. The sitting position is important for a true REM measurement. If the child
sits closer than this distance, the SNR ratio may increase, especially at low input
levels, and cause erroneous measurements. On the other hand, if the child sits further away, the REM process may not start. After the REM procedure has been
explained to the parents, the probe microphone is placed in the child’s “clean” ear
canal. Before the hearing instrument is placed on the ear, some probe measurements
are taken to measure the characteristics of the ear’s resonance. The hearing instrument is then placed on the ear and gain verication measurements are taken. The
probe microphone should be placed in the ear canal about 5mm from the eardrum.
Placing the probe can be challenging for most pediatric patients. Therefore, attaching the probe to the earmold with a strap may facilitate the REM procedure. After
the sound or speech stimuli presented at 50, 65, or 80dB SPL are measured by the
microphones with a hearing aid, the verication process is complete. Audiologists
should ensure that the information entered into the hearing aid tting software and
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
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the REM software is the same as that entered prior to the REM application in the
pediatric group. It is important that the correct hearing aid tting parameters are
entered into the REM software in addition to the candidate’s audiogram information. Data such as the selected hearing aid model, earmold type, prescription formula, age, and gender of the candidate should be entered into the REM software.
The more commonly used conrmation method in the pediatric group is the
RECD.When REIG measurements cannot be performed, the RECD can be used to
verify hearing aid gain. Due to the physical limitations of infants under 2years of
age, objective hearing aid verication procedures are often performed using the
RECD.The RECD measurement is the difference between the SPL levels measured
with the same input signal in the patient’s ear and a HA-1 2cc coupler. The RECD,
which is used on infants who are physically unable or unwilling to cooperate with a
REM measurement, copies the acoustic characteristics of the infant’s ear canal onto
a coupler. The hearing aid t is veried on a 2 cc coupler rather than on the
infant’s ear.
Two different probe tubes are used for RECD evaluation: the “normal” probe and
the “SPL” probe. The normal probe is the probe that is actively used for all other
probe measurements. The SPL probe is used for RECD testing and is thicker than
the normal probe tube. It is usually removed after the RECD test. Both probes
should be calibrated prior to use. After calibration, the SPL probe is connected to a
2cc coupler and an SPL measurement is made. The SPL probe is then connected to
the earmold tubing like a hearing aid. Later, the earmold is placed in the ear with the
regular probe tube and the SPL measurement of the ear canal is performed. After the
measurements, the REM software automatically calculates the difference between
the SPL measurements from the patient’s ear and the coupler. This is then displayed
on the measurement screen as the RECD.Finally, the hearing instrument is placed
on the coupler and Real Ear Aided Response (REAR) measurements are taken. If
the SPL measurement cannot be completed in the patient’s ear, the “estimated”
RECD values provided by the software can be used for the REAR measurement.
Caton’s studies in rabbits at the end of the nineteenth century found that acoustic
stimuli could be converted into electrical cortical potentials [55]. In 1939, Pauline
Davis discovered that electroencephalography (EEG) recordings contain a component dependent on acoustic stimuli, and late potentials were rst recorded using
acoustic stimuli [56]. Cortical responses, which provide information about the highest level of the auditory system, have been used clinically since the 1960s. CAEP
can be used clinically to evaluate auditory memory, study the central auditory system, diagnose functional hearing loss, and study central function in special clinical
situations such as schizophrenia, coma, and paralysis. In addition, CAEP can be
used to demonstrate the efcacy of hearing aid/cochlear implant use and neural
plasticity, especially in the pediatric group [57, 58]. This means that it is possible to
follow whether the sound transmitted by the hearing aid reaches the auditory cortex
and whether the auditory areas in the infant’s brain develop over time in a similar
way to their hearing peers. In addition, a 2017 study found that the use of CAEP in
the pediatric group reduced both hearing aid use and cochlear implant evaluation to
earlier ages [59].
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CAEP responses are generally studied as early and late responses. While early
responses provide information about the processing of the sensory stimulus, late
responses are related to higher cognitive functions such as selective attention and
memory [60]. Therefore, early response tests such as P1-N1-P2 and ACC are preferred to late response tests such as P300 and N400-P600 for pediatric hearing aid
evaluations. In addition, these tests are convenient to administer in the pediatric
population because they do not require the patient to be asleep or to participate in
the test (e.g., press a button). Although the test stimulus can be delivered directly
through the hearing aid, the most common method is to present the stimulus through
a loudspeaker. In free-eld testing, the baby sits on the mother’s lap and a cartoon is
presented to the baby through a computer or screen with the sound completely
turned off. The test is easy to administer because the infant’s attention does not need
to be focused on the stimulus.
The P1-N1-P2 test is typically used to determine if the baby can hear a stimulus
at a certain intensity level with hearing aids. In general, one-syllable speech such as
“ba” or “da” and a phoneme such as “m,” “g,” or “t” can be used as stimuli during
the test application. On the other hand, it is also known that this test does not provide information about sound discrimination. For this reason, the ACC test was
developed by modifying the stimulus presented in the P1-N1-P2 test. When obtained
in response to an acoustic change within a continuous sound, the resulting waveform is referred to as the ACC.Most importantly, both the P1-N1-P2 and ACC tests
show reasonable agreement with behavioral measures. Therefore, they can be used
to objectively verify hearing aids in the pediatric population [57]. A study conducted in 2022 to investigate the relationship between behavioral and objective
measures of sound intensity found that pupillometry can be used in addition to
CAEP for hearing aid verication [61].
Subjective Verification Tools
After the hearing aid verication, the behavior of the babies/children with hearing
aids to sounds should be checked in the clinic. These practical checks, performed by
the audiologist, verify that the babies are not disturbed by the sounds and that they
hear the sounds sufciently. It has been observed that some audiologists check
whether the baby is uncomfortable by clapping after the hearing aid tting. However,
the “clapping” sound peaks only in the 1–2kHz frequency range according to the
spectrogram. Instead, a drum can be used for low-frequencies, maracas for midfrequencies, and a bell for high-frequencies. This allows a wider range of frequencies to be controlled. For example, the hearing aid gain of a baby who is disturbed
only by low-frequency stimuli will not be reduced for all frequencies, but only for
the low-frequencies. In addition, Ling’s 6 sound cards can be used to attract the
baby’s attention. As a result of these loud sounds, the baby’s distress behaviors,
such as crying, putting a hand to the ear, and blinking, can be observed. In addition,
the baby’s response to softer sounds can be controlled by presenting these sounds
from a certain distance. The same toys can also be used to check the baby’s localization responses with hearing aids. The clinician should make sure that the baby can
hear equally from both sides.
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
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The infant’s free-eld thresholds (with/without hearing aids), startle responses to
loud sounds, and localization/lateralization abilities can be assessed in a “structured” environment using free-eld audiometry. This assessment is often performed
using two different test methods: VRA and COR. The VRA test uses one visual
amplier and one loudspeaker. It is possible to control hearing aid thresholds and
high tone startle response with this test, but localization ability cannot be controlled.
The COR test uses two visual reinforcers and loudspeakers, one on the right and one
on the left. In addition, one visual reinforcer can be used in the center line to keep
the baby/child’s interest in the center. The COR test can also test localization ability
in addition to VRA.In both testing techniques, the clinician can engage the infant/
child with a warble tone (WT), narrow band noise (NBN), or speech stimulus.
In addition to the tests and observations made in the clinic, some questionnaires,
usually lled in by the parents, can be used to observe the auditory behavior of
infants/children within a “system” and to follow their language development. The
use of these questionnaires such as Parents’ Evaluation of Aural/Oral Performance
of Children [62], Meaningful Auditory Integration Scale [63] allows both longitudinal follow-up of the patients and active participation of the family in the process by
taking responsibility.
Fine-Tuning
Although it is assumed that hearing aids veried by objective measurements provide optimal amplication for infants/children, minor changes in hearing aid gain
may be necessary based on subjective measurement results and family feedback.
Fitting software offered by hearing aid manufacturers includes a “ne-tuning”
screen for these changes. This screen typically includes frequency-based gain tting
bands in three different input levels (soft, moderate, and loud) and maximum power
out (MPO) tting bands. Frequency-specic compression settings can also be made
using these bands. In the 2010s, manufacturers determined the number of tting
bands based on the segment of the hearing instrument. Premium hearing aids used
to have more tting bands because more bands allowed for more detailed netuning. Today, however, almost all manufacturers offer enough tting bands, eight
or more. Some manufacturers include some automatic ne-tuning algorithms as a
result of their research. These are practical algorithms based on common user complaints such as “sounds are too loud” or “I have difculty hearing soft sounds.” They
attempt to address user complaints through changes in tting bands and technologies such as DNR.However, particularly in the pediatric group, it is important to
fully learn the tting software and perform manual ne-tuning to maintain auditory gain.
Auditory gain should be maintained at a level that does not cause discomfort to
the infant/child but provides adequate hearing. Therefore, ne-tuning should be
accomplished without reducing the “necessary” gain. After RECD verication,
when the baby’s Loudness Discomfort Level (LDL)/Uncomfortable Loudness
Level (ULL) is assessed with a speech stimulus, a blinking reex may be observed
in the baby’s eyes at loud sounds. In such situations, all frequencies should not be
turned down completely. Instead, the LDL should be assessed in each frequency