1. TOPIC 5 NONBEHAVIORAL ASSESSMENT MEASURES IMMITANCE AUDIOMETRY

2. The Functions of Immittance Audiometry Detection of middle ear pathology Differentiating cochlear from retrocochlear pathology Estimate sensitivity Use in cross-check with pure tone results

3. Advantages of Immittance Audiometry Non-invasive Non-behavioral

4. Instrumentation Major components Probe tone oscillator and loudspeaker Monitor microphone Pressure pump and manometer Ipsilateral reflex oscillator and loudspeaker Probe tip

5. Measurement Technique “Immittance is a physical characteristic of all mechanical vibratory systems, of which the middle ear is one example”

6. Compliance vs Impedance Compliance Ease with which energy flows through a system Impedance Resistance to energy flow through a system

7. Auditory Immittance “ A way of assessing the manner in which energy flows through the outer and middle ear into the cochlea”

8. Immittance Relationships Probe tone energy passed Probe tone energy reflected Compliance High impedance LowHighLow Low impedance HighLowHigh

9. Basic Immittance Measures Tympanometry Acoustic Reflex Thresholds Acoustic Reflex Threshold Decay

10. Tympanometry “A way of measuring how acoustic immittance of the middle ear system changes as air pressure is varied in the external ear canal”

11. Tympanometry Concepts of immittance applied in practice

12. Normal Tympanogram

13. Impedance as Equivalent Volume When the amount of reflected probe tone pressure is high, it’s as if the volume has decreased. As volume increases, sound pressure decreases

14. What’s a Normal Tympanogram? Shape Pressure: -100 mm H 2 O or DaPa Compliance: 0.3-1.6 cc

15. Common Tympanograms Normal tympanogram (Type A) Shape? Pressure? Compliance?

16. Common Tympanograms Type A s Shape? Pressure? Compliance?

17. Common Tympanograms Type A d Shape? Pressure? Compliance?

18. Common Tympanograms Type B Shape? Pressure? Compliance?

19. Assessing PE Tubes

20. Common Tympanograms Type C Shape? Pressure? Volume?

21. Basic Immittance Measures Tympanometry Acoustic Reflex Thresholds

22. The Middle Ear Muscles and the Acoustic Reflex Tensor tympani muscle (top figure) Stapedius muscle (bottom figure)

23. Acoustic Reflex Pathways Ipsilateral Right ear Left ear Contralateral Probe right Probe left

24. Acoustic Reflex Threshold “the lowest intensity at which a middle ear immittance change can be detected in response to sound”

25. Instrumentation for Acoustic Reflex Thresholds

26. Normal Acoustic Reflex Threshold Levels

27. Interpretation of an Absent Acoustic Reflex Threshold Possible pathologies that might lead to an absent contralateral probe left reflex (right crossed)

28. Basic Immittance Measures Tympanometry Acoustic Reflex Thresholds Acoustic Reflex Threshold Decay

29. Time Course of the Acoustic Reflex Threshold Decay The test is carried out by presenting a 10 s signal at 10 dB above the ART.