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)

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