Introduction to Tympanometry

Useful terminology

1. 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).

2. Tympanometric peak pressure (TTP) / middle ear pressure (MEP)

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).

3. 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).

4. 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)

1. Type A

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

2. Type B

Type B characteristics

• Rounded line/no peak
• Usually no measureable/reduced MEP or SC
• ECV within normal range

3. Type C

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

4. Type As

Type As characteristics

• Sharp peak
• Normal MEP
• SC < 0.3cc (adults) (hypomobile)
• ECV within normal range

5. Type Ad

Type Ad characteristics

• Sharp peak
• Normal MEP
• SC > 1.6cc (adults) (hypermobile)
• ECV within normal range

6. Tympanic membrane (TM) perforation

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.

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 measurable 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.