Tympanometry with Stapedial Reflection
It evaluates the integrity of the tympanic membrane, ossicular chain and middle ear air cavities.
Tympanometry is a test developed to evaluate the mobility of the tympanic membrane during the variation of air pressure.
To perform tympanometry, the tip of a catheter is inserted into the external auditory canal until a hermetic seal is obtained. Subsequently, pressure is “applied” to facilitate the observation of the behavior of the system against changes in said pressure.
Components of a normal tympanogram:
Compliance. Mobility or elasticity of the middle ear system by reference to the ease of sound transmission through the ear. The unit of measure is cm2 or ml. This volume is measured through two registers: the first one is obtained when the tympanic membrane becomes more rigid by the application of a known air pressure (+200 mm H2O). After determining this volume, a second REGISTRY is taken, which corresponds to the equivalent volume measurement. This is done with the tympanic membrane in the state of maximum compliancy (when the air pressure in the middle ear is equivalent to that of the external auditory canal).
Gradient. It is calculated in different ways. One of them is to use the following formula to find the numerical value of the slope of the tympanogram curve:
Gradient = Compliance – (Yn + Yp) / 2 (ml)
This formula gives high gradient values for very outstanding and low tympanogram curves for flat tympanogram.
The tympanograms are classified in:
Ear studies. Tympanogram type “A”
We find the well defined maximum compliancy values at a pressure difference of 0 mm H20. This curve is most often seen in people with normal hearing or sensorineural hearing loss.
Tympanogram type “AD”
It is a variation of type A, in which a high and open peak (high compliance) is obtained given the hypermobility of the tympanic membrane; The pressure is within the normal range. This type of curve is characteristic in a discontinuity of the oscicular chain.
Timpanogram type “AS”
The tympanogram shows a limited compliance in relation to normal mobility, maintaining the air pressure within parameters of normality. It is characteristic of otosclerosis.
Tympanogram type “B”
It is characterized by the little variation of the compliancy when there are changes of air pressure. It does not observe maximum defined complicity at any air pressure. It is common in people with fluid in the middle ear (serous otitis media).
Tympanogram type “C”
The peak of complicity is well defined at negative pressures. The presence of an intact but retracted eardrum suggests an alteration in the Eustachian tube.
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