audiometry (impedance)

Last reviewed 03/2023

Tympanometry:

• the tympanometer (handheld or desktop)
  • is a useful, affordable diagnostic tool in general practice (1)
  • is a device that provides quantitative information on the function of structures and the presence of fluid in the middle ear
• the tympanogram is the graphic display of this data (1)
• this provides useful quantitative information about the following (1):
  • presence of fluid in the middle ear
  • mobility of the middle ear system
  • ear canal volume
• its uses include
  • the evaluation of otitis media with effusion and to a lesser extent in acute otitis media (1)
  • to assess middle ear compliance or to assess nerve deafness in children
  • it provides a convenient method for screening children for glue ear.
• it is based upon two principles:
  • when sound energy passes down the ear canal, some will be absorbed by the eardrum and some will be reflected back
  • the proportion of the sound reflected will increase as the pressure in the middle ear falls and the ear drum is stiffened
• a tympanogram is constructed by altering the pressure in the external auditory meatus and at each setting, passing sound to the ear and measuring the sound energy reflected. A three channel tympanometer is used - with separate channels for each function.
• a pneumatic otoscopic examination of the tympanic membrane should be done prior to tympanometry (1)

Reference:

• (1) Edward Onusko. Tympanometry.Am Fam Physician 2004;70:1713-20