331 12.1 Acoustic Immittance

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shanamd2010
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142492
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331 12.1 Acoustic Immittance
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2012-03-19 12:55:49
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acoustic immittance
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acoustic immittance
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  1. acoustic immittance refers to either
    • acoustic impedance (Za or Ohms) - tests resistance to the flow of energy
    • acoustic admittance (Ya or mmhos) - tests ease of flow
  2. what does acoustic admittance test
    • not hearing.
    • it tells us how well the middle ear amplifies sound
  3. SPL and Middle Ear Status
    • arrow to far right = fluid build up
    • arrow middle = normal
    • arrow to far left = absorbs energy / ossicle chain busted
  4. tympanograms
    measure of change in SPL
  5. Three Immittance measures
    • tympanograms
    • static immittance
    • ear canal volume
  6. two classification systems for tympanograms
    • PAS System - pressure amplitude shape
    • The Jerger System - 3 types A B C
    • these test the ear drum
  7. Types of tympanograms
    back of slide 8
  8. PAS pressure
    • negative = E-Tube dysfunction (start of Otitis Media)
    • WNL = within normal limits
    • positive = AOM (rare) - ear drum about to rupture, people with this go to physicians
  9. PAS amplitude
    • increased = flaccid (loose) - the peak it very high
    • WNL = winthin normal limits
    • reduced = stiff - the peak is very low
  10. PAS shape
    • flat = fluid or perforation or ECV=0 - tympanogram is flat
    • increased (notched) = healed perf. - area of the ear drum with 2 layers instead of 3, occurs after a rupture heals
    • increased 'w' shape = disarticulation - break something, no ossicular chain
    • bumpy = glomus tumor - gets bumps per min
  11. 70 bumps/min means
    • you are hearing the heart beat
    • the tumor is hitting the ear drum
  12. 12 bumps/min
    • you are hearing the breathing
    • opening to Eustachian tube is flopping
  13. Jerger classification chart
    slide 12
  14. As means
    • stiff
    • pressure normal but shallower than normal
  15. A means
    • disarticulation
    • very flaccid
  16. B means
    flat
  17. C means
    normal but negative pressure
  18. Jerger charts
    slide 13 - 17
  19. Static Immitance units
    • Acoustic Impedance (Ohms)
    • Acoustic Admittance (mmhos)
    • Compliance (ml)
  20. static immittance usefullness
    almost useless because normal and abnormal have too much overlap
  21. tympanometric width is used for
    screening kids in schools
  22. ear canal volume
    • expressed in ml
    • if reduced = probe in cerumen or against wall of EAM, clean and do it again
    • if increased = perforated (hole) tympanic membrane, open PE tube
    • probe can tell the amount of volume between tip of probe and ear drum
  23. negative pressure on a tympanogram means
    E-tube dysfunction
  24. three types of acoustic reflex tests
    • presence or absencce of the reflex
    • acoustic reflex threshold (ART) - as you raise sound, the muscle contracts at a higher magnum
    • acoustic reflex decay - tumor testing
  25. presence/absense acoustic reflex tests 4 thing
    • 2 ipsilateral
    • 2 contralateral
  26. presence/absence flow charts
    slide 31 - 33
  27. ART in normal people
    • approximately 90 dB HL
    • reduced SL's imply sensory loss in cochlea
    • increased HL's imply Neural Loss - could be very serious (brain tumor)
  28. ART chart
    35 - 36
  29. acoustic reflex decay charts
    38 - 39

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