Audiometry, Hearing Loss

Audiometry, Hearing Loss

Synonym/acronym: N/A.

Common use

To evaluate hearing loss in school-age children but can be used for all ages.

Area of application

Ears.

Contrast

N/A.

Description

Tests to estimate hearing ability can be performed on patients of any age (e.g., at birth before discharge from a hospital or birthing center, as part of a school screening program, or as adults if indicated). Hearing loss audiometry includes quantitative testing for a hearing deficit. An audiometer is used to measure and record thresholds of hearing by air conduction and bone conduction tests. The test results determine if hearing loss is conductive, sensorineural, or a combination of both. An elevated air-conduction threshold with a normal bone-conduction threshold indicates a conductive hearing loss. An equally elevated threshold for both air and bone conduction indicates a sensorineural hearing loss. An elevated threshold of air conduction that is greater than an elevated threshold of bone conduction indicates a composite of both types of hearing loss. A conductive hearing loss is caused by an abnormality in the external auditory canal or middle ear, and a sensorineural hearing loss by an abnormality in the inner ear or of the VIII (auditory) nerve. Sensorineural hearing loss can be further differentiated clinically by sensory (cochlear) or neural (VIII nerve) lesions. Sensorineural hearing loss is permanent. Additional information for comparing and differentiating between conductive and sensorineural hearing loss can be obtained from hearing loss tuning fork tests. Every state and territory in the United States has a newborn screening program that includes early hearing loss detection and intervention (EHDI). The goal of EHDI is to assure that permanent hearing loss is identified before 3 mo of age, appropriate and timely intervention services are provided before 6 mo of age, families of infants with hearing loss receive culturally competent support, and tracking and data management systems for newborn hearing screens are linked with other relevant public health information systems.

This procedure is contraindicated for

    N/A

Indications

  • Determine the need for a type of hearing aid and evaluate its effectiveness
  • Determine the type and extent of hearing loss and if further radiological, audiological, or vestibular procedures are needed to identify the cause
  • Evaluate communication disabilities and plan for rehabilitation interventions
  • Evaluate degree and extent of preoperative and postoperative hearing loss following stapedectomy in patients with otosclerosis
  • Screen for hearing loss in infants and children and determine the need for a referral to an audiologist

Potential diagnosis

If findings are normal the patient should have normal hearing. The test is conducted using earphones and/or a device placed behind the ear to deliver sounds of varying intensities. Results are categorized using ranges of pure tone recorded in decibels.

ASHA CategoryPure Tone Averages
Normal range or no impairment–10–15 dB
Slight loss16–25 dB
Mild loss26–40 dB
Moderate loss41–55 dB
Moderately severe loss56–70 dB
Severe loss71–90 dB
Profound lossGreater than 91 dB
dB = decibel.

Normal findings

  • Normal pure tone average of −10 to 15 dB for infants, children, or adults

Abnormal findings related to

  • Causes of conductive hearing loss
    • Impacted cerumen
    • Hole in eardrum
    • Malformed outer ear, ear canal, or middle ear
    • Obstruction of external ear canal (related to presence of a foreign body)
    • Otitis externa (related to infection in ear canal)
    • Otitis media (related to poor eustachian tube function or infection)
    • Otitis media serous (related to fluid in middle ear due to allergies or a cold)
    • Otosclerosis
  • Causes of sensorineural hearing loss
    • Congenital damage or malformations of the inner ear
    • Ménière’s disease
    • Ototoxic drugs administered orally, topically, as otic drops, by IV, or passed to the fetus in utero (aminoglycoside antibiotics, e.g., gentamicin or tobramycin, and chemotherapeutic drugs, e.g., cisplatin and carboplatin, are known to cause permanent hearing loss; quinine, loop diuretics, and salicylates, e.g., aspirin are known to cause temporary hearing loss; other categories of drugs known to be ototoxic include anesthetics, cardiac medications, mood altering medications, and glucocorticosteroids, e.g., cortisone, steroids)
    • Presbycusis (gradual hearing loss experienced in advancing age related to degeneration of the cochlea)
    • Serious infections (meningitis, measles, mumps, other viral, syphilis)
    • Trauma to the inner ear (related to exposure to noise in excess of 90 dB or as a result of physical trauma)
    • Tumor (e.g., acoustic neuroma, cerebellopontine angle tumor, meningioma)
    • Vascular disorders

Critical findings

    N/A

Interfering factors

  • Factors that may impair the results of the examination

    • Effects of ototoxic medications can cause temporary, intermittent, or permanent hearing loss.
    • Failure to follow pretesting preparations before the procedure may cause the procedure to be canceled or repeated.
    • Improper earphone fit or audiometer calibration can affect results.
    • Inability of the patient to cooperate or remain still during the procedure because of age, language barriers, significant pain, or mental status may interfere with the test results.
    • Noisy environment or extraneous movements can affect results.
    • Tinnitus or other sensations can cause abnormal responses.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient/caregiver this procedure can assist in detecting hearing loss.
  • Obtain a history of the patient’s complaints, including a list of known allergens.
  • Obtain a history of the patient’s known or suspected hearing loss, including type and cause; ear conditions with treatment regimens; ear surgery; and other tests and procedures to assess and diagnose auditory deficit.
  • Obtain a history of the patient’s symptoms and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Address concerns about pain and explain that no discomfort will be experienced during the test. Inform the patient that an audiologist or health-care provider (HCP) specializing in this procedure performs the test in a quiet, soundproof room, and that the test can take up to 20 min to evaluate both ears. Explain that each ear will be tested separately by using earphones and/or a device placed behind the ear to deliver sounds of varying intensities. Address concerns about claustrophobia, as appropriate. Explain and demonstrate to the patient how to communicate with the audiologist and how to exit from the room.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.
  • Ensure that the external auditory canal is clear of impacted cerumen.
  • Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

Intratest

  • Potential complications: N/A
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
  • Instruct the patient to cooperate fully and to follow directions. Instruct the patient to remain still during the procedure because movement produces unreliable results.
  • Perform otoscopy examination to ensure that the external ear canal is free from any obstruction (see monograph titled “Otoscopy”).
  • Test for closure of the canal from the pressure of the earphones by compressing the tragus. Tendency for the canal to close (often the case in children and elderly patients) can be corrected by the careful insertion of a small stiff plastic tube into the anterior canal.
  • Place the patient in a sitting position in comfortable proximity to the audiometer in a soundproof room. The ear not being tested is masked to prevent crossover of test tones, and the earphones are positioned on the head and over the ear canals. Infants and children may be tested using earphones that are inserted into the ear, unless contraindicated. An oscillating probe may be placed over the mastoid process behind the ear or on the forehead if bone conduction testing is to be performed as part of the hearing assessment.
  • Start the test by providing a trial tone of 15 to 20 dB above the expected threshold to the ear for 1 to 2 sec to familiarize the patient with the sounds. Instruct the patient to press the button each time a tone is heard, no matter how loudly or faintly it is perceived. If no response is indicated, the level is increased until a response is obtained and then raised in 10-dB increments or until the audiometer’s limit is reached for the test frequency. The test results are plotted on a graph called an audiogram using symbols that indicate the ear tested and responses using earphones (air conduction) or oscillator (bone conduction).
  • Air Conduction

  • Air conduction is tested first by starting at 1,000 Hz and gradually decreasing the intensity 10 dB at a time until the patient no longer presses the button, indicating that the tone is no longer heard. The intensity is then increased 5 dB at a time until the tone is heard again. The tone is delivered to an infant through insert earphones or ear muffs, and the auditory response is measured through electrodes placed on the infant’s scalp. This is repeated until the same response is achieved at a 50% response rate at the same hertz level. The threshold is derived from the lowest decibel level at which the patient correctly identifies three out of six responses to a tone at that hertz level. The test is continued for each ear, testing the better ear first, with tones delivered at 1,000 Hz; 2,000 Hz; 4,000 Hz; and 8,000 Hz, and then again at 1,000 Hz; 500 Hz; and 250 Hz to determine a second threshold. Results are recorded on a graph called an audiogram. Averaging the air conduction thresholds at the 500-Hz; 1,000-Hz; and 2,000-Hz levels reveals the degree of hearing loss and is called the pure tone average (PTA).
  • Bone Conduction

  • Bone conduction testing is performed in a similar manner to air conduction testing; a vibrator placed on the skull is used to deliver tones to an infant. The raised and lowered tones are delivered as in air conduction using 250 Hz; 500 Hz; 1,000 Hz; 2,000 Hz; and 4,000 Hz to determine the thresholds. An analysis of thresholds for air and bone conduction tones is done to determine the type of hearing loss (conductive, sensorineural, or mixed).
  • In children between 6 mo and 2 yr of age, minimal response levels can be determined by behavioral responses to test tone. In the child 2 yr and older, play audiometry that requires the child to perform a task or raise a hand in response to a specific tone is performed. In children 12 yr and older, the child is asked to follow directions in identifying objects; response to speech of specific intensities can be used to evaluate hearing loss that is affected by speech frequencies.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Instruct the patient to resume usual activity, as directed by the HCP.
  • Recognize anxiety related to test results, and be supportive of impaired activity related to hearing loss or perceived loss of independence. As appropriate, instruct the patient in the use, cleaning, and storing of a hearing aid. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Profound hearing loss can have a long-range impact personally, socially, and professionally. Consideration needs to be given to support groups that may guide the patient toward a realistic transition toward life management with an auditory deficit. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the National Center for Hearing Assessment and Management (http://infanthearing.org) or for the American Speech-Language-Hearing Association (www.asha.org) or for assistive technology at ABLEDATA (sponsored by the National Institute on Disability and Rehabilitation Research, www.abledata.com). When caring for a patient with altered auditory function, forms of communication should be adapted to meet the patient’s needs. The process of communication chosen should be documented on the plan of care to ensure consistency and decrease frustration.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. As appropriate, instruct the patient in the use, cleaning, and storing of a hearing aid. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include analgesic and antipyretic drugs, antrimicrobial drugs, cultures bacterial (ear), evoked brain potential studies for hearing loss, gram stain, newborn screening, otoscopy, spondee speech reception threshold, and tuning fork tests (Webber, Rinne).
  • Refer to the table of tests associated with the Auditory System at the end of the book.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners