impedancemetry

Impedancemetry is a diagnostic test used to assess the function of the middle ear and the mobility of the tympanic membrane and ossicles. It is a non-invasive objective measure, meaning it does not require the patient's conscious participation and is therefore useful for testing infants and children. The test is performed using a small probe inserted into the ear canal. This probe emits a sound tone and measures how much of that sound is reflected back by the eardrum.

The device used for impedancemetry is called an impedance meter or tympanometer. It typically consists of a pump to vary the air pressure in the ear canal, a loudspeaker to emit a pure tone, and a microphone to measure the sound pressure level. As the air pressure is changed, the impedance of the middle ear system is measured. This data is plotted on a graph called a tympanogram.

A normal tympanogram shows a peak at zero daPa (decaPascals) of pressure, indicating that the middle ear pressure is at atmospheric pressure and the eardrum and ossicles are moving freely. Abnormal tympanograms can indicate a variety of conditions, such as middle ear effusion (fluid in the middle ear), tympanic membrane perforation (a hole in the eardrum), or ossicular discontinuity (a disruption in the chain of middle ear bones). Impedancemetry is often performed in conjunction with audiometry, the standard hearing test, to provide a more complete picture of hearing function. It can help differentiate between conductive hearing loss, which affects the outer or middle ear, and sensorineural hearing loss, which affects the inner ear or auditory nerve.