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Introduction to Tympanometry

This is an introduction to understanding and reporting on tympanometry measurements. This guide should be used in conjunction with your own clinic’s protocols and current research in the area of acoustic immittance testing.

Some Useful Terminology

Ear Canal Volume
“The equivalent ear canal volume (ECV) is an estimate of the volume of air medial to the probe, which includes the volume between the probe tip and the tympanic membrane if the tympanic membrane is intact, or the volume of the ear canal and the middle ear space if the tympanic membrane is perforated” (Fowler & Shanks, 2002, p. 180).

Tympanometric Peak Pressure/Middle Ear Pressure
Tympanometric peak pressure (TTP) or middle ear pressure (MEP) is the ear canal pressure at which the peak of the tympanogram occurs (Margolis & Hunter, 2000).

Static Compliance
Static compliance (SC) “is the greatest amount of acoustic energy absorbed by the middle ear system (the vertical peak of the tympanic tracing)” (Onusko, 2004, p. 1716).

Gradient
“Tympanogram gradient is an objective measure that describes the steepness of the slope of the tympanogram near the peak” (Fowler & Shanks, 2002, p.182). The gradient is not commonly used in Australia to analyse tympanograms.

TYMPANOGRAM TYPES (as proposed by Jerger)

Type A		Type B
Type A Characteristics Sharp peak MEP between +50 to -99 mmH2O SC = 0.3 to 1.6cc (adults)/0.2 to 0.9cc (children 3 – 5 yrs) ECV within normal range		Type B Characteristics Rounded line/no peak Usually no measureable/reduced MEP or SC ECV within normal range
Type C		Type As
Type C Characteristics Sharp peak MEP less than -99mm (significant negative MEP) SC = 0.3 to 1.6cc (adults)/0.2 to 0.9cc (children 3 – 5 yrs) ECV within normal range		Type As Characteristics Sharp peak Normal MEP SC < 0.3cc (adults) (hypomobile)  ECV within normal range
Type Ad		Tympanic Membrane (TM) Perforation
Type Ad Characteristics Sharp peak Normal MEP SC > 1.6cc (adults) (hypermobile) ECV within normal range		TM Perforation Characteristics Rounded/flat line (no peak) Usually no measureable/reduced MEP or SC Large ECV (as measurements takes into consideration middle ear cavity)

N.B. Classification of tympanogram types differ between many clinics and audiologists. This is a guide only and should be used in conjunction with your own research and clinical protocols.

Reasons for repeating Tympanometry

• Client swallows, talks, laughs, coughs etc during the test
• You get an odd result that doesn’t look correct or doesn’t match audiogram findings. When in doubt, repeat the test to check your results are repeatable.

Reporting
These are some common sentences used to report on tympanometry results.

N.B. Tympanometry results should be looked at in conjunction with other audiological results in the test battery (audiometry, speech audiometry etc) when giving recommendations/impressions in reporting.

Type A
Tympanometry showed normal middle ear pressure and static compliance.

Type B
Tympanometry showed no measureable middle ear pressure or static compliance, consistent with middle ear pathology.

Type C
Tympanometry showed significant negative middle ear pressure in the presence of normal static compliance, consistent with Eustachian tube dysfunction/middle ear pathology.

Type As
Tympanometry showed normal middle ear pressure with decreased static compliance, consistent with a hypomobile tympanic membrane.

Type Ad
Tympanometry showed normal middle ear pressure with increased static compliance, consistent with a hypermobile tympanic membrane.

Large ECV
Tympanometry results showed a large ear canal volume, consistent with a tympanic membrane perforation or patent grommet. 

References
Fowler, C. G., & Shanks, J. E. (2002). Tympanometry. In J. Katz (Ed.), Handbook of clinical audiology (5th ed.). (pp. 175 – 204). Baltimore: Lippincott Williams & Wilkins.

Margolis, R. H., & Hunter, L. L. (2000). Acoustic Immittance Measurements. In R. J. Roeser, M. Valente & H. Hosford-Dunn (Ed.), Audiology diagnosis. (pp. 381 - 423). New York: Thieme Medical Publishers, Inc.

Onusko, E. (2004). Tympanometry. American Family Physician, 70 (9), 1713 – 1720.

Srireddy, S. V., Ryan, C. E., & Niparko, J. K. (2003). Evaluation of the patient with hearing loss. In J. Niparko & L. R. Lustig (Ed), Clinical neurotology: Diagnosing and managing disorders of hearing, balance and the facial nerve. (pp. 65 – 80). London: Martin Dunitz Publishing.