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Tympanometry & Clinical Applications


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Published in: Health & Medicine

Tympanometry & Clinical Applications

  1. 1. Dr. Mona Hassan Selim Prof. of Audiology Cairo University Dr. Mona Selim
  2. 2. Acoustic immittancemetry• Acoustic immittance is a general term used to refer to an acoustic energy transfer regardless of the manner in which it is measured. Dr. Mona Selim
  3. 3. Acoustic impedance (ZA):• The middle ear opposes the transfer of energy to some extent. This opposition is termed acoustic impedance(in ohms).Acoustic admittance (YA)• The resulting energy flow or transfer of air pressure changes at the eardrum into movements within the cochlear fluid is termed acoustic admittance(in mhos). Dr. Mona Selim
  4. 4. TympanometryI) Definition: Dynamic measure of the acoustic immittance in the ext. ear canal, as a function of ear canal air pressure change.II) Principle: Air pressure is varied +ve and -ve relative to ambient or atmospheric pressure and is measured by detecting reflected SPL from T.M. Dr. Mona Selim
  5. 5. III) Instrumentation:a) Preliminary steps: * Otoscopic examination. * Instructions to patient. * Achieving air tight seal.b) Equipment for M.E immittance measurements: Dr. Mona Selim
  6. 6. 1. Loudspeaker: emits puretone (incident wave).2. Microphone: picks sound in the ear canal (both incident wave +reflected wave from eardrum).3. Air pump: creates +ve or -ve pressure (1dapa= 1.02 mmH2O).4. A.R activator source (ipsilateral). Dr. Mona Selim
  7. 7. IV) Measurement of static compliance of ME:1. Ensure clean ear canal.2. Ear tip is pressed into canal.3. ↑ pressure with air pump until air tight seal is obtained.4. ↑ pressure  200 daPa (C1). C1 = equivalent volume in cm3. = compliance of the outer ear. Dr. Mona Selim
  8. 8. 5. ↓ pressure gradually until ear drum achieves max. compliance (pressure on both sides of drum is equal). (C2). C2= Compliance of outer + middle ear. Cx = Static compliance of M.E (Ytm) Cx = C2-C1 Normally: 0.28-2.5 cm3 Dr. Mona Selim
  9. 9. • A 1 cm3 volume of air at sea level under reference conditions, has an acoustic admittance of 1 acoustic mmho for a 226-Hz probe tone. 1 cm3 ~ 1 mmho Dr. Mona Selim
  10. 10. Ytm= Ya-Vea.Ya= total admittance Ytm= admitt. at t.m Vea= vol. of ext. canal Dr. Mona Selim
  11. 11. A compensated (Baseline) tympanogramThe contribution of the ext. canal has been removed Dr. Mona Selim
  12. 12. Physical volume test (PVT): Equivalent E.C. volume (Vec).• An interesting application of Vec measure has been suggested to identify a perforation of the ear drum or a patent PE tube.• Both conditions will lead to an ↑ in C1 volume than normal:• Vec adults ~ 0.6-1.5 cm3 children ~ 0.4-0.9 cm3 Dr. Mona Selim
  13. 13. N.B.:• An ↑ in volume between 2 ears > 0.4cm3 children > 0.87cm3 adults is suggestive of a perforation.• An abnormally small C1 volume – Impacted cerumen. – Probe impacted against wall.• Normal C1 volume + type B tympan. – ME effusion. – Neoplasm. – Lateral ossicular fixation. Dr. Mona Selim
  14. 14. Pinhole Perforation• Vec = within normal range.• Ytm = can be normal.• However, a unique tympanometric pattern can be detected: Dr. Mona Selim
  15. 15. Dr. Mona Selim
  16. 16. Interpretation of flat tymp. using Veca = Vec normal  M.E effusion.b = Vec small  improper placement or cerumen.c = Vec large  perforation or patent tube Dr. Mona Selim
  17. 17. • Large Vec  suggests perforation.• Normal Vec  DOES NOT exclude the existence of a perforation. There may be associated: – ME effusion. – Cholesteatoma. – Obliteration of the mastoid air cells. Dr. Mona Selim
  18. 18. Clinical uses of tympanograms:1. Determination of TPP.2. Amplitude of tympanogram  admittance at T.M (Peak compensated static acoustic admittance) (peak Ytm).3. Vec.4. Tympanometric shape and width: variety of patterns associated with different pathologies. Dr. Mona Selim
  19. 19. VI) Classification of tympanometric shapes:A) Jerger-Liden classification• Categorized according to shape and tympanometric peak pressure.Type (A)• It is the normal tympanogram.• The peak is at or near zero pressure (dapa).• It reflects normal air filled middle ear.• -100 +50 dapa. Dr. Mona Selim
  20. 20. Dr. Mona Selim
  21. 21. Type AD:• It is a tympanogram with abnormally high peak > 2.5 mmhos.• Found in cases of T.M and ossicular abnormalities (e.g disruption).Type AS:• It is a tympanogram with reduced amplitude < 0.28 mmhos.• Found in: – Ossicular fixation. – Some forms of otitis media (adhesive, serous). – Tympanosclerosis. Dr. Mona Selim
  22. 22. Dr. Mona Selim
  23. 23. Type B• Flat.• Represents non-mobile T.M.• Occurs in the presence of ME effusion.• Or space occupying lesion. Dr. Mona Selim
  24. 24. It can be seen with large C1 volume in:• T.M perforation.• Patent PE tube.It can be seen with abnormal small C1 volume:• Impacted cerumen.• Improperly placed immittance probe. Dr. Mona Selim
  25. 25. Type C• -ve peak pressure• Indicating -ve M.E pressure with intact mobile T.M with poor ET function.Type D Shows sharp notching characteristic of:• Scarred eardrums.• Normal hypermobile T.M. Dr. Mona Selim
  26. 26. Type E• Brood, smooth notching• most commonly found in cases of partial or complete ossicular discontinuity. Dr. Mona Selim
  27. 27. Dr. Mona Selim
  28. 28. Tympanogram Width (TW)• Used to quantify the tympanogram shape in the vicinity of the peak and is sometimes called the tympanogram gradient.• Measured as the WIDTH in pressure (daPa) of the tympanogram at half of the height from the peak to the tail. Dr. Mona Selim
  29. 29. • Normally ~ 100 daPa∀ ↑ TW  ME effusion (TW > 275 daPa).∀ ↓ TW  TM abnormalities (scarring, tympanosclerosis), ossicular fixation. Dr. Mona Selim
  30. 30. Feldman ClassificationBased on analysis of:• Tympan. Peak pressure.• Amplitude.• Shape.1) Tympanometric peak pressure Normal -ve +ve Flat Dr. Mona Selim
  31. 31. Pathologies with –ve M.E pressure:• Serous otitis media.• E.T malfunction.Pathologies with +ve M.E pressure:• Early acute O.M.• Physiological conditions. Valsalva/sneezing/ coughing. Dr. Mona Selim
  32. 32. Pathologies with normal pressure:• Ossicular fixation.• Ossicular discontinuity.• Adhesive O.M.• Scarring T.M.Absent pressure peak (flat):• Adhesive O.M.• Secretory O.M.• Tiny perforation.• Seal against wall. Dr. Mona Selim
  33. 33. 2) Amplitude:• It is a function of the compliance of the system.Increased amplitude:• Monomeric T.M (Hypermobile).• Ossicular discontinuity. Dr. Mona Selim
  34. 34. Decreased amplitude:• Ossicular fixation: – Congenital. – Otosclerosis. – Paget disease.• Adhesive O.M.• Cholesteatoma, polyps, Granuloma.• Glomus tumors.• Fluids, mass.Normal amplitude:• Eust. Tube malfunction.• Early acute O.M. Dr. Mona Selim
  35. 35. 3) Shape Slope Smoothness• Tymp. shape is related to amount and not viscosity of M.E effusion.• Presence of a peak  presence of air in the M.E. with or without effusion (good prognosis in O.M). Dr. Mona Selim
  36. 36. SLOPEFlattened slope:• Secretory O.M.• Ossicular fixation.• Tumors of the M.E.Peaked or ↑ slope:• Ossicular discontinuity• TM abnormalities. Dr. Mona Selim
  37. 37. Notched:• Monomeric drum.N.B.: Pathologies altering tympanometric smoothness.• Scarring of T.M.• Ossicular discontinuity.• Vascular tumours.• Patulous E.T.• Adhesive O.M. Dr. Mona Selim
  38. 38. VII) Procedural variables affecting tympan. amplitude and shape.1) Rate of ear canal pressure changeAmplitude∀ ↑ in amplitude when pressure rate was increased from 200 dapa/sec  400 dapa/sec.Shape• More frequent notching at high rates of pressure change (esp. high frequency tympanograms). Dr. Mona Selim
  39. 39. 2) Direction of ear canal pressure change• In normal ears: Mean acoustic admittance is greater for increasing (-ve  +ve) than for decreasing (+ve  -ve) press. change.• Not consistent across individuals.• Higher incidence of notched tympanograms in increasing vs decreasing ear canal pressure change. Dr. Mona Selim
  40. 40. 3) Number of consecutive pressure sweeps:• Test-retest reliability is enhanced if two tymp. sweeps were completed prior to data collection.∀ ↑ in no. of trials  ↑ static admittance due to viscoelastic changes of M.E due to repeated extremes of pressure change. Dr. Mona Selim
  41. 41. VIII) Tympanometry in infants:Neonates• Tympanograms recorded from infant ears are influenced by developmental changes in the anatomy of the ext. ear.• Bony floor of the ext.canal is not well formed in neonates  highly compliant ext. canal wall  higher incidence of notched tympanograms.• By the age of 10 days, notched tympanograms decline to about 20%.• Older infants: adult form nearly by the 3rd month. Dr. Mona Selim
  42. 42. X) Advantages of tympanometry:• Quick.• Inexpensive.• Non-invasive.• Easily tolerated by most subjects.• Requires no behavioral response.• Reveals M.E abnormalities that may not be detected by behavioral tests.• No need for sound – treated room. Dr. Mona Selim
  43. 43. XI) Limitations of tympanometryA) Subject:• Uncooperative (child, M.R).• Ear atresia.• Affected by movement.• Old age  collapsed ear canal.• Dual lesion.B) Equipment:• Calibration.C) Physician:• Unqualified. Dr. Mona Selim
  44. 44. Eustachian Tube Function TestsA) Intact T.M.• TPP near atmospheric pressure  no ET dysfunction suspected.• TPP significantly -ve  ask patient to perform Valsalva, then repeat tympanogram  -ve pressure should resolve (good ET function). Dr. Mona Selim
  45. 45. Eustachian Tube Function TestsB) Perforated T.M.• E.T is normally closed.• +ve or –ve press. can be built through perforated T.M. (if not)  patulous E.T.• After swallowing  change in pressure occurs (good ET function). Dr. Mona Selim
  46. 46. Eustachian Tube Function TestsIf NO change occurs after swallowing:• Ask patient to perform valsalva or Toynbee• Repeat tympanogram*Change in pressure *No change in pressureET works under pressure Poor ET function Dr. Mona Selim
  47. 47. Diagnosis of patulous E.T (with).intact T.M• Perform tympanometry.• Hold the pressure at TPP.• Switch system to the AR decay mode with stimulus turned off.• Perform 3 recordings. Dr. Mona Selim
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  49. 49. Dr. Mona Selim