Audiology, an autonomous profession that encompasses both health care and educational professional areas of practice, is involved with the study of hearing and balance and their related disorders. The audiologist is the independent hearing health care professional who provides comprehensive diagnostic and habilitative/rehabilitative services for all areas of auditory, vestibular, and related disorders. These services are provided to individuals across the entire age span from birth through adulthood, which is in concert with the goals of a life care plan; to individuals from diverse language, ethnic, cultural, and socioeconomic backgrounds; and to individuals who have multiple disabilities (ASHA, Spring 1996).
Within life care planning, the audiologist should be involved in pediatric and adult rehabilitation efforts when clients experience decreased hearing sensitivity, auditory processing problems, auditory neuropathy (auditory dys-synchrony), or balance problems. Clients may experience auditory deficits, due to genetic or natural aging factors, ear disease, brain injury, auditory processing dysfunction, environmental noise exposure, or reactions to medications that are ototoxic or vestibulotoxic.
Life care planners seeking information on current audiology preferred practices, technical papers, position statements, reimbursement codes, standards, and certification and licensure (Appendix 10.1) will find the American Speech-Language-Hearing Association (ASHA) web- portal (www.professional.asha .org or www.asha.org) the most comprehensive site for peer- reviewed documentation of practice issues and currency of reimbursement codes. The ASHA Code of Ethics (ASHA, 2003), revised January 1, 2003; scope of practice (ASHA, Spring 2004); preferred practice patterns for the profession of audiology (ASHA, 2006); Joint Audiology Committee Clinical Practice (1999) statements and algorithms; and current reimbursement code funding are documents (ASHA, 2007) of significant interest to life care planners seeking best practices information and quality hearing health care for their clients. The information is also available on the ASHA webportal.
Services provided by audiologists include the ability to
¦ Test and diagnose hearing and balance disorders
¦ Select, fit, and dispense hearing aids and assistive devices
¦ Provide audiologic/aural (re)habilitation services
¦ Educate consumers and professionals on prevention of hearing loss
¦ Participate in hearing conservation programs to help prevent workplace-related and recreational hearing loss
¦ Consult for federal, state, and local agencies in reducing community noise
¦ Conduct research
Audiology services are available in the following work settings:
¦ Colleg es and universities
¦ Public and private schools
¦ Hospitals
¦ Community-based hearing and speech centers
¦ State and local health departments
¦ Private practices
¦ Rehabilitation centers
¦ Nursing care facilities
¦ Industry
¦ State and federal governmental agencies
¦ Military
Audiology can be categorized by either the setting in which one practices or the population one serves. Bess and Humes (1995) identified the following specialty areas in which audiologists generally practice (see Figure 10.1). The pediatric audiologist concentrates on the audiologic management of children of all ages. The pediatric audiologist is often employed in a children’s hospital or a health care facility primarily serving children. The medical audiologist works with patients of all ages and is more concerned with establishing the site and cause of a hearing or balance problem. Medical audiologists are typically employed in hospitals as part of either a hearing and speech department or a department of otolaryngology (i.e., ear, nose, and throat). Some audiologists who work in a medical environment perform intraoperative monitoring, which involves monitoring central and peripheral nerve function during surgical procedures. The rehabilitative/dispensing audiologist focuses on the management of children or adults with hearing impairment. Rehabilitative audiologists are often in private practice and may specialize in the direct dispensing of hearing aids in addition to offering other audiologic rehabilitation services. Rehabilitative audiologists are also employed by a variety of health care facilities (e.g., hospitals and nursing homes). The industrial audiologist provides consultative hearing conservation services to companies whose workers are exposed to high noise levels. The industrial audiologist may be in private practice or work on a part-time basis. The forensic audiologist serves as an expert witness in legal issues related to hearing and balance. The forensic audiologist may serve as an expert witness for the plaintiff or defense in compensation cases and may also serve as a consultant in community or environmental noise issues. Finally, the educational audiologist serves children in the schools and is employed or contracted by the educational system. Many audiologists, not just those in academic environments, engage in basic and applied research that is not only essential to understanding human auditory function but also necessary in order to develop testing materials and procedures and improved amplification systems.
When referring a patient to an audiologist for a basic audiologic assessment, one may expect certain basic procedures to be conducted to quantify and qualify hearing loss on the basis of responses to acoustic stimuli and to screen for other associated communication disorders. These include a pure tone hearing test (ASHA, 1978), speech audiometry (ASHA, 1988), and acoustic immit- tance (ASHA, 1991b) procedures accomplished in accordance with American National Standards
Institute standards (ANSI, 1981, 1986, 1987, 1991, 1992, 1996) and under Centers for Disease Control (CDC) standard health care precautions guidelines (CDC, 1988; U.S. Department of Labor, 1998). Of course, the basic audiologic procedures may be modified depending on the age or level of cooperation of the patient.
The clinical process for a basic audiologic evaluation includes the following (ASHA, 1999):
¦ A case history
¦ Otoscopic evaluation
¦ External ear canal examination and cerumen management, if necessary
¦ Assessment, which includes:
- Air conduction and bone conduction threshold measures with appropriate masking (pure tone testing)
- Speech recognition thresholds or speech awareness thresholds with appropriate masking
- Word recognition (speech discrimination) measures with appropriate masking
- Acoustic immittance testing (tympanometry, static compliance, and acoustic reflex measures)
- Other procedures, which include, but are not limited to, otoacoustic emissions screening, speech and language screening, communication inventories, and screening for APDs and other related auditory disorders
The external ear canal examination is performed to remove debris from the ear canal to allow the audiologist to perform the assessment or to perform rehabilitative or hearing aid procedures. The need for cerumen (ear wax) management is required when there is an accumulation of debris that would preclude the audiologist from obtaining valid and reliable assessment results and, in many cases, improve auditory sensitivity. Established procedures include the following (ASHA, 1991a; Roeser & Crandell, 1991; Ballachandra & Peers, 1992):
¦ Mechanical removal
¦ Irrigation
¦ Suction
It should be noted that in some states, cerumen management is not within the scope of practice of audiologists. Reimbursement for the service varies by state and region and also from third-party payers.
An audiologist using a calibrated electronic device called an audiometer measures hearing. An audiogram is a graphic representation of hearing. It relates intensity (loudness) as a function of frequency (pitch). Frequency, measured in hertz (Hz), is plotted along the abscissa, and intensity, measured in decibels (dB), is plotted along the ordinate.
A person wears earphones and the audiologist presents tones at varying frequencies and intensities for each ear. When the individual hears the tone, she responds by raising her hand. When the tone is heard at the lowest intensity level two out of three times, the audiologist records this intensity level for each frequency on the audiogram. This level is called threshold. Thresholds for the left ear are plotted with a blue X and thresholds for the right ear are plotted with a red 0. Normal hearing is considered to be between —10 and +15 dB HL. Hearing level (HL) is the number of decibels relative to normal hearing, which is 0 dB HL on the audiogram. The example audiogram indicates normal hearing in the left ear and a hearing loss in the right ear.
The area enclosed by the two wavy lines is called the speech banana. This area represents the frequencies and intensities of spoken English and assists the audiologist in explaining how a hearing loss may affect a person’s ability to understand speech. In the example audiogram, the person will not be able to hear speech sounds above 1000 Hz in the right ear because his thresholds are out of the speech banana. Were this person to have this degree of hearing loss in both ears, he may be expected to have difficulty understanding high-frequency speech sounds such as s, f th, p, t, k, sh, and ch, for example. In addition, he may be expected to have considerable difficulty understanding conversational speech in the presence of background noise, such as in a cafeteria.
Audiograms are very important because they can indicate whether a person has a hearing loss and also the type and degree of loss she has. There are three principal types of hearing loss directly associated with the peripheral auditory mechanism: conductive (a problem in the outer or middle ear), sensorineural (a problem in the inner ear or the eighth cranial nerve, which carries the auditory signals to the brain), and mixed conductive and sensorineural loss. Other nonperipheral auditory deficits may include auditory processing disorders and an auditory neuropathy (auditory dys-synchrony).
A second part of the basic testing includes speech audiometry where the audiologist evaluates how well a person can hear and understand speech. Speech audiometry consists of speech threshold and word recognition (understanding) or speech discrimination testing. Speech threshold testing determines how soft a speech sound a person can recognize, whereas word recognition testing tells the audiologist what percentage of conversational speech is correctly understood at a particular intensity level. One method of obtaining a word recognition/speech discrimination score is called the articulation gain function (Figure 10.4) (or performance intensity/phonetic balance function). This method assures that the patient’s maximum score possible will be identified (ASHA, 1988).
Most people understand conversational speech maximally at approximately 40 dB above their speech threshold. The evaluator starts by presenting the speech level at 40 dB above the patient’s speech threshold and reading a list of 50 single-syllable words with the person instructed to repeat back each word.
The percentage correct score at 40 dB above a person’s threshold is then plotted. If 100% correct is not achieved, the test is repeated using a similar list of words at 50 dB above the person’s threshold, and that score is plotted. This procedure is repeated until the person’s best score is obtained. The score in the example graph indicates that the person will understand speech 90% of the time as long as it is 60 dB above threshold.
Acoustic immittance, sometimes referred to as acoustic impedance, measures the mobility of the middle ear system. The middle ear is basically a vibratory system consisting of the eardrum and the three middle ear bones: the malleus, incus, and stapes. The middle ear is responsible for taking acoustic energy (sound) and transferring it via mechanical energy from the outer ear to the fluids in the inner ear. The functioning of the middle ear affects the way people hear. Tympanometry is a measure of the mobility of the middle ear (compliance) as a function of middle ear pressure, measured in dekapascals (daPa). The results are displayed on a graph called a tympanogram (Figure 10.5), and interpretation of these results can help indicate the site of the lesion or what is causing a hearing loss (ASHA, 1991b).
An electroacoustic immittance meter is used to measure the middle ear function. A plug is inserted into the ear canal, and the instrument takes the measurements and graphs the information.
There are five basic types of tympanograms:
Middle ear pressure is between +100 and 150 daPa. Compliance is normal.Middle ear pressure is normal.Middle ear pressure is normal.Middle ear pressure cannot be measured due to fluid.Middle ear pressure is reduced.Middle ear pressure (daPa) Type BMiddle ear pressure (daPa)
Type CMiddle ear pressure (daPa)Although these procedures are typically conducted during an audiologic evaluation, they may be modified to meet the special needs of children and other difficult-to-test patients. For patients who cannot or will not tolerate earphones, test signals (tones and speech) can be presented through loudspeakers strategically placed within the sound-attenuated test booth. The patient will either look toward the sound or be taught to place a peg in a board, ring on a peg, block in a box, and so on, in response to the sound. At that moment, the patient’s positive response behavior will be reinforced. Successive trials will enable the audiologist to establish threshold or an acceptable estimate of hearing level.
Pediatric audiologic assessment is usually conducted on infants and young children (under 5 years of age) (ASHA, 1993) and other individuals whose developmental levels preclude the use of standard adult audiologic assessment procedures. The assessment typically requires an audiologist skilled in pediatric assessment and will involve multiple office visits. The clinical process is essentially the same as that for a basic audiologic assessment prior to attempting to obtain test results. The assessment may include one or more assessment tools (acoustic immittance measures, audiologic (re)habilitation and education needs assessment, otoacoustic emissions (OAE), electro- physiologic assessment, and other developmentally appropriate behavioral procedures). Behavioral testing measures include the following:
¦ Visual Reinforcement Audiometry (VRA)
¦ Conditioned Play Audiometry
¦ Tangible Reinforcement Operant Conditioning Audiometry (TROCA)
¦ Visual Reinforcement Operant Conditioning Audiometry (VROCA)
¦ Behavioral Observation Audiometry (BOA)
¦ Prenatal Causes of Hearing Loss
Prenatal causes refer to adverse effects on the cochlea during embryological and fetal development, resulting in congenital hearing loss. Development of the external, middle, and inner ear takes place between the fourth and eighth weeks of gestation. Some infants have hereditary factors that put them at risk for hearing loss. Genetic abnormalities such as a variety of sensorimotor impairments; difficulty with balance and coordination; mental retardation; musculoskeletal anomalies; thyroid disorders; abnormal skin pigmentation; visual disorders; cleft palate; and skull, facial, and external ear deformities may accompany the hearing loss. Combinations of these various disorders are referred to as syndromes, and a combination of genetic and in utero environmental factors is referred to as multifactorial genetic consideration.
Teratogens are environmental agents that result in malformations and anomalies of specific organs and systems that are undergoing rapid development in the embryo or fetus. Exposure to teratogens may result in maj or congenital anomalies. Some of these teratogens and infectious diseases are drugs (alcohol, cocaine, cigarette smoke), congenital HIV and AIDs, rubella, cytomegalovirus (CMV), herpes simplex-type virus, toxoplasmosis, congenital syphilis, and thalidomide (the most notorious teratogen in history). Table 10.1 summarizes categories of risk factors for hearing loss in infants and young children.
Family history of childhood hearing loss Congenital infections (TORCH)*
Craniofacial anomalies
Low birth weight (less than 3.5 lbs or 1.6 Kg)
Hyperbilirubinemia requiring blood exchange
Bacterial meningitis
Asphyxia
Ototoxic medication
Mechanical ventilation of more than 10 days Syndromes that include hearing lossNote: *TORCH is an acronym describing congenital perinatal infections, including toxoplasmosis, other infections (like syphilis), rubella, CMV, and herpes simplexMany children are born with significant hearing impairments but are not identified and provided appropriate intervention (Folge, 2008). These children lose their ability to acquire fundamental speech, language, cognition, and social skills required for later schooling and success in society. Early intervention is needed for them to develop communication skills on par with their normal hearing peers (Hayes & Northern, 1997; Vaughn, 2005). Hearing screening may be a luxury in many nations, but it is becoming increasingly important in nations with the resources to provide the procedures. Hayes and Northern (1997) stated that the prevalence of significant hearing disorders in newborns may be as high as 6 in every 1000 live births. Simmons, McFarland, and Jones (1980) found hearing loss in 1 out of 50 infants who had been discharged from neonatal intensive care units. Infants with low Apgar scores are considered at risk for hearing impairments. Some newborns may pass a hearing screening and still be at high risk for hearing loss, therefore it is important to perform regular follow-up hearing screenings for at least several months (Mann, Cuttler, & Campbell, 2001). Readers are referred to Table 10.2.
ASHA has a model bill for states, called the Early Hearing Detection and Intervention (EHDI) advocacy campaign, designed to help states reduce the number of infants lost to follow-up after hearing screening, expand early intervention services, and promote culturally sensitive family support programs.
Launched in 1999, ASHA’s Phase I EHDI campaign, developed in 2000 and revised in 2004, focused on federal seed grants and state legislation to expand universal newborn screening and other policies to build the infrastructure to support state EHDI programs. Since then, the number of infants screened for hearing loss has increased from 20% to 92% nationwide. Although not all states mandate hearing screening for all newborns, all states have a hearing screening program in place.
1. An illness or condition requiring admission of 48 hours or greater to a NICU.2. Stigmata or other findings associated with a syndrome known to include sensorineural or conductive hearing loss.3. Family history of permanent childhood sensorineural hearing loss.4. Craniofacial anomalies, including morphological anomalies of the pinna and ear canal.5. In-utero infection such as cytomegalovirus, herpes, toxoplasmosis, or rubella.29 days to 24 months
1. All of the above, plus the following.2. Parent or caregiver concern regarding hearing, speech, language, developmental delay, or a combination of these.3. Postnatal infections associated with sensorineural hearing loss, including bacterial meningitis.4. Recurrent or persistent otitis media with effusion for at least 3 months.5. Neonatal indicators—specifically, hyperbilirubinemia at a serum level requiring blood exchange transfusion, persistent pulmonary hypertension of the newborn associated with mechanical ventilation, and conditions requiring the use of extracorporal membrane oxygenation.6. Syndromes associated with progressive hearing loss such as neurofibromatosis, osteoporosis, and Usher’s syndrome.7. Neurodegenerative disorders such as Hunter’s syndrome, kyphosis, gargoylism, or sensorimotor neuropathies such as Friedreich’s ataxia and Charcot-Marie-Tooth syndrome.8. Recurrent or persistent otitis media with effusion for at least 3 months.9. Head trauma.The Phase II advocacy campaign builds on the principles of the 2007 Joint Committee on Infant Hearing (JCIH) Statement and the Early Hearing Detection and Intervention Act of 2007 (H.R. 1198 and S.N. 1069). ASHA’s goal is to have the federal EHDI legislation passed in 2009.
The EHDI model bill focuses on follow-up services. It calls for an enhanced tracking system to monitor newborns and infants with hearing loss. It also provides the following:
¦ A broad range of early intervention services, including family support programs
¦ Comprehensive insurance coverage for intervention services and devices for children with hearing loss
¦ Coverage for children with mild, moderate, and unilateral hearing loss
Although the majority of infants are screened for hearing loss, almost 60% of infants who do not pass the screening are lost to follow-up, either because they do not receive follow-up services or because their follow-up is not tracked effectively. In addition, services recommended in Phase II—early intervention services, family support programs, and devices—are either not provided or
not covered by health plans. ASHA’s model legislation addresses that gap by calling for improved tracking systems and by mandating insurance coverage for early intervention services, family support programs, and devices.
The model legislation is structured so that states can adapt it to fit their needs and availability of resources. Some states, such as Rhode Island and Virginia, already mandate coverage for early intervention services, and at least nine states mandate hearing aid coverage for children.
One important aspect of the Phase II follow-up and early intervention services requires states to mandate that family information and support are timely, culturally competent, and family centered. Phase II stipulates that families receive unbiased information and are offered the full range of early intervention services and treatment options available for children with hearing loss.
At press time of the third edition of this text, the following update on EDHI is available. New state laws are on the books in Maine and Tennessee that enhance early hearing detection and intervention (EHDI) efforts, reflecting a national trend to improve EHDI programs.
Maine’s governor approved legislation on April 17, 2008, to help ensure that newborns with suspected or confirmed hearing loss receive the necessary follow-up care in a timely manner from qualified professionals. The legislation implements the recommendations of a working group that studied the effectiveness and timeliness of early identification and intervention for children with hearing loss.
The new law requires a hospital or birthing center to schedule a newborn whose screening result is “refer” for a follow-up audiology appointment. Parental approval is necessary. The appointment must be scheduled prior to discharge, and the hospital or center must notify the newborn’s primary care provider in writing of the screening result and appointment prior to discharge. In addition, the Maine Department of Health and Human Services’ Newborn Hearing Program must report to a joint standing committee of the legislature about barriers to access to audiologists for the continued evaluation of hearing loss in newborns.
Tennessee’s governor signed legislation on April 21, 2008, to enhance the state’s newborn hearing screening program by mandating hearing screenings and follow-up care for all newborns. Claire’s Law requires that every newborn infant in Tennessee be screened for hearing loss before discharge from the hospital, unless the child’s parents object on religious grounds. For children born outside of a hospital setting, or in a hospital that does not provide screening, the attending health care professional must refer the child to the Department of Health or to an appropriate provider for a hearing screening. In addition, any medical or audiologic provider performing follow-up tests must report the results. Children who do not pass the hearing screening test are then referred to the Tennessee Early Intervention System (TEIS) of the Department of Education for follow-up. Children who have been identified with hearing loss or are at high risk for hearing loss must also be referred to the TEIS. Finally, the law requires certain insurance plans to cover hearing screenings.
Perinatal causes of hearing loss are those that occur during the birth process. Infants who must be admitted to neonatal intensive care units (NICUs) are 20 times more likely to have hearing problems than infants in normal newborn nurseries (Simmons et al., 1980). Hearing loss in infants who were in NICUs is often associated with the identifiable disorders that caused the need for the NICU or treatment for the disorders. Respiratory distress syndrome (RDS/hyaline membrane disease) is the most common respiratory disease in premature infants. Infants with RDS receive treatment by invasive procedures such as intubation and suctioning, putting them at an additional
risk of infections. If infants become septic (generalized infection), general treatment is with antibiotics with potential ototoxic properties, placing them at a higher risk for hearing loss.
Congenital heart disease (CHD) is among the most common birth defects, affecting as many as 1 in 100 newborns (Fogle, 2008), and may exhibit cyanosis, respiratory distress, congestive heart failure, or a combination of these. In addition, these infants frequently exhibit failure-to- thrive and feeding problems. CHD is often associated with syndromes such as growth deficiencies, mental retardation, Down syndrome, and external ear anomalies. Again, ototoxic drugs may be needed to fight the infections.
Central nervous system disorders may have hearing loss as one component of the disorder, including cerebral hemorrhage, hydrocephalus, hypoxic encephalopathy, and neonatal seizures. Any individual who experiences hypoxia may have compromised neurological status and hearing abilities.
Postnatal causes of cochlear hearing loss are factors occurring after birth. These include bacterial meningitis, measles, mumps, chicken pox, influenza, and viral pneumonia. Most viral-producing hearing losses are bilateral, except for mumps. The body’s natural reaction to infection is elevation of temperature; however, when fever becomes excessive, cellular damage can occur, including cells of the cochlea. Treatments may warrant ototoxic antibiotics. Diabetes mellitus and kidney disease have been implicated in sensorineural hearing loss, as have head traumas, which cause both neurological disorders and hearing loss (Fogle, 2008). Table 10.1 lists some of the risk factors for hearing loss in infants and young children.
In older children (and adults), one of the most preventable is noise-induced hearing loss. Most people will have reduced hearing as they grow older (especially after the age of 60); however, there are things individuals can do to try to preserve their hearing. Noise-induced hearing loss, once called “blacksmith’s deafness” from the continual clanging of metal on metal, dates back hundreds of years. During World War II it received much more attention because of the heavy artillery used in the war. Acoustic trauma from a single exposure may cause permanent hearing loss. Gradual hearing loss from repeated exposure to excessive sound can damage or destroy the delicate hair cells in the cochlea. Hearing conservation programs and hearing research programs (ASHA 2006) have developed public education campaigns to alert people, especially adolescents and teenagers, to the damage caused to hearing with loud music. Wearing ear plugs or ear muffs to help block the loud sounds or music, limiting the time of an iPod session with breaks to allow your hearing to rest, and keeping the volume reduced are just a few suggestions included in a hearing conservation program. Table 10.3 shows the readers the decibel levels of some of the most common environmental sounds, and Table 10.4 lists the decibel levels of some musical instruments as well as some types of music. Table 10.5 shows the noise exposure of sound in decibels for certain periods of time that may create hearing risk.
Many infants and children have repeated ear infections requiring pressure-equalizing (PE) tubes. The surgical procedure is called a myringotomy, performed with a small surgical incision into the tympanic membrane to relieve pressure and release fluid or pus from the middle ear. A small suction device may be inserted through the incision to delicately suction out the fluid and pus. Antibiotics are given before and continued afterward to manage infection (Mosby, 2006).
Source: Adapted from Northern, J. L. & Downs , M. P. Hearing in Children (5th ed.). Baltimore, MD: Lippincott Williams & Wilkins, 2002; Van Bereijk, W., Pierce, J., & David, E., Science, 131, 219-220, 1960; and American Industrial Hygiene Association, 2007.
Source: Adapted from HeadWize, www.headwise .com/articles /hearing_art.htm.
Following the myringotomy and cleaning of the middle ear, the otolaryngologist may insert a PE tube through the incision in the tympanic membrane. The tube is plastic, tiny, and hollow with a flange on each end that prevents the tube from falling into the middle ear or falling out of the tympanic membrane prematurely. The tube allows direct ventilation of the middle ear and
Note: When 2 or more periods of noise exposure occur, the combined effect should be considered rather than the individual effect of each. Exposure to impulse or impact noise should not exceed 140 dB peak sound pressure level.
functions as an artificial Eustachian tube to maintain normal middle ear pressure. The tube may remain in place from several weeks to several months, after which time it extrudes (pushes out) naturally into the external auditory canal, usually without the child noticing. Newer-designed tubes may remain in place indefinitely.
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