Lesson 14 Tympanometry

Identifies a measure of the dynamic compliance of the tympanic membrane (TM) and reflects the algebraic sum of the factors influencing middle ear performance.

Answers the question of "Should this patient be referred for medical follow-up?"

+200mm H2o to 0mm H2o to -200mm H2o.

The TM is free to move, this neutral pressure status permits the maximum passage of acoustic energy through...

The peak reflects the "point of maximum compliance" of the TM.

the pressure exerted in the chamber matches the pressure level in the middle ear.

the TM is being pulled out into the canal and again, becomes stiffened by the combination of the shape and resistance of the TM itself.

1. Is not a hearing test.  It is possible for a dead ear to produce a normal tympanogram.

2. Middle ear muscles (i.e., the stapedial reflex) in general, require acoustic stimulation (hearing) for activation of that activity, even under the most "normal" of middle ear conditions

3. The patient can be awake or asleep, and the results will be the same.

"Normal" and the range of static compliance runs from .4cc to roughly 1.6cc

"Shallow A" there is a stiffness somewhere through the transfer of energy. 

Static compliance is ranging UP TO .4cc

Ossicular fixation

Other possible causes could be a scar tissue or thickened epithelial tissue on the lateral margin of the TM

"Deep A" Still has an intact TM as well as normal eustachean tube function. 

Static compliance range falls ABOVE 1.6cc

1. Ossicular discontinuity, or an incomplete "chain" causing "flaccid" movement of the membrane.

2. A monomeric membrane, in which a recovering perforation produces a weak spot when the epithelial (or outer) layer grows back.

"Flat"

• 1. Obstruction in the canal
• 2. Perforation of the TM
• 3. Middle Ear fluid
• 4. Misapplication of the probe tip

• Substantial negative pressure in the middle ear space.
• Referred to as a retracted tympanic membrane.

retracted tympanic membrane

Reduction of output by 2-3 dB, b/c the transfer of energy through the middle ear mechanism is highly efficient and therefore more energy passes through.

Small addition to the output by 2-3 dB to allow for compensation for the additional stiffness of the system.