Chapter 44. Tympanometry

• • Tympanometry directly measures the compliance of the tympanic membrane and ossicular chain, estimating middle ear pressure.

  • Tympanometry is primarily used to detect the presence of middle ear fluid, enhancing the diagnosis of acute otitis media and otitis media with effusion.

  • The procedure is also useful for detecting tympanic membrane perforation, ossicular chain disruption, and the patency of eustachian tubes.

  • Tympanometry is commonly performed as part of the early evaluation of hearing loss.

Absolute

• • Age younger than 7 months. Studies have shown that tympanometry in infants 0–7 months of age is inaccurate due to the high compliance of the ear canal in these patients.

  • Recent ear surgery, such as stapedectomy, myringoplasty, or tympanoplasty.

Relative

• • Blocked ear canal.

  • Ear canal with copious drainage.

  • Uncooperative or screaming patient.

• • Otoscope.

  • Ear curettes.

  • Tympanometer with probe tips.

  • • All instruments use acoustic energy to measure the combined admittance (compliance) of the ear canal and middle ear.

    • The most commonly used instruments deliver a probe tone of 225 Hz.

    • High-frequency instruments, sometimes used in infants, deliver a tone of 678 Hz.

• • Before beginning the procedure, make sure that the probe assembly is securely fastened together; leaks will obscure the test results.

  • Also, ensure that the probe tube and tips are dry; wet equipment may clog, making it impossible to continue the test.

• • Describe the procedure to the parents and patient and answer any questions.

  • Be sure to inform the patient that he or she will be hearing some brief, but potentially loud, sounds.

• • The child needs to sit still during the procedure; if necessary, have the child sit on a parent’s lap for reassurance.

• • Hearing results from the conduction of sound into the ear canal. Sound stimulates the tympanic membrane, which then vibrates.

  • The malleus (the first bone of the ossicular chain, attached to the eardrum) also starts vibrating, which sets the incus and stapes into motion (Figure 44–1).

• • The stapes is set in the oval window, the opening of the inner ear. The sound is conducted into the inner ear, which translates sound energy into nerve impulses to the brain.

  • The eustachian tube, an extension of the nasopharynx, equalizes middle ear pressure with atmospheric pressure (the pressure within the ear canal).

• • Using an otoscope, examine the ear canal and remove any occluding cerumen.

  • Choose the appropriate sized ear tip for the patient’s ear canal and affix it to the probe.

  • Grasp the helix and pull back and up gently to straighten the ear canal.

  • Insert the probe into the entrance of the ear canal, obtaining an airtight seal. ...