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AUD fall 2019 electrophys I > Week 4: TEOAEs > Flashcards

Week 4: TEOAEs Flashcards

transient evoked otoacoustic emissions

1
Q

what are the 4 critical factors that can interfere with recording OAEs

A
  • the external and middle ear status
  • noise (ambient and physiological)
  • fit of the probe
  • stimulus characteristics and stability
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2
Q

non-pathologic factors of the external ear canal that can affect OAEs

A
  • standing waves
  • cerumen/debris
  • vernix caseose
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3
Q

pathologic factors of the external ear canal that can affect OAEs

A
  • fungal infections
  • external otitis
  • stenosis
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4
Q

non-pathologic factors of the middle ear that can affect OAEs

A
  • mesenchyme (fluid in the ME of newborns

* ventilation tubes

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5
Q

pathologic factors of the middle ear that can affect OAEs

A
  • TM perf
  • ETD
  • neg middle ear pressure
  • Hx of ear disease
  • OM
  • otosclerosis and ossicular dislocation
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6
Q

relationship between OAEs and the backwards transmission of waves

A
  • normal OAEs argue strongly for normal middle ear function
  • OAEs rarely have measured amplitude higher than 10 dB SPL
  • animal models show 30 dB greater inside cochlea
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7
Q

how ambient and physiologic noise can affect OAEs

A
  • normal/expected noise level is ower for adults than children
  • equipment has normative data in it, it is okay to use of you test a small group and then compare to the norms data base b/c the norms don’t give info on the environment where collected
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8
Q

how probe fit can affect OAEs

A
  • only use the recommended tips by the manufacturer
  • determine probe tip size and proper depth (rubber vs foam)
  • secure probe fit minimized problems with ambient noise and maintains intensity level
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9
Q

stimulus verification with OAEs

A
  • monitor stability of the stimulus (particularly with young children)
  • calibration of the stimulus is very critical for recording reliable OAEs
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10
Q

what are the 7 parameters of TEOAEs

A
  • type
  • stimulus temporal waveform
  • stimulus spectrum
  • intensity
  • stimulus stability
  • polarity
  • rate
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11
Q

type of stimulus with TEOAEs

A
  • click about 100 microseconds
  • –transducer affects the freqs of the click
  • —-inserts fall off after-kHz so frequency range is to about that point
  • tone burst
  • –a freq specific stimulus, but not a pure tone b/c it is brief so there is energy splatter to nearby freqs
  • can use a chirp, but not common
  • non-linear mode of presentation: a set of stimuli and every set has a reverse phase stimulus ( 3 together and one opposite to minimize stimulus artifact in ear canal
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12
Q

stimulus temporal waveform with TEOAEs

A
  • 0.3 Pa which is about 83.5 dB SPL
  • –PE= peak equivalent which is used to measure click stimulus because it is fast and hard to capture and measure; so present click through oscilliscope to capture amount of voltage and plot, then present 1000 Hz one and keep changing the level until you find the = voltage
  • –no ringing more than 2-3ms should happen with a click
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13
Q

stimulus spectrum with TEOAEs

A
  • bottom right small pic and is the x-axis= frequency on an print out
  • can see stimulus fall off after 4kHz on click and peak around 1000Hz on an 1000 Hz tone burst
  • –technically the spectrum should be flat with no peaks for a click, so need to reposition probe if not flat
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14
Q

intensity of TEOAEs stimulus

A

80-86 dB peSPL (about 50 dB HL)

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15
Q

stimulus stability of TEOAEs

A
  • basically how stable was the stimulus throughoout the measure? (want close to 100% if possible, will accept 90% or better)
  • look in notes for math to see how this plays out*
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16
Q

rate of stimulus with TEOAEs

A

*not something you really choose, but means how many clicks are presented per second (manipulated in evoked potentials, not here)

17
Q

stimulus polarity with TEOAEs

A

not manipulated much, but is nonlinear presentation

18
Q

name the 4 TEOAE acquisition parameters

A
  • TEOAE magnitude
  • background noise level
  • TEOAE temporal waveform and spectrum
  • reliability/reproducibility
19
Q

relationship between TEOAE magnitude and background noise level

A
  • go hand in hand
  • always trying to measure a TEOAE response stronger than the the noise floor (looking for 6 dB SNR minimum)
  • –TE (magnitude) - NR (SNR)
20
Q

TEOAE temporal waveform and spectrum (of the response itself)

A
  • spectrum is in the top right under response FFT and waveform is the big picture in the middle when looking at a printout
  • –waveform is not measured within the 1st 3 msec to make sure the stimulus is not being measured (remember it should not ring more than 3 msec)
  • –waveform reflects the time on the basalar membrane, 1st comes highs from the base and then lower from the apex depicting the fact the signal takes time to travel and then come back
  • ——so looking at the temporal waveform can know what part of the cochlea it is coming from
21
Q

reliability/ reproducibility of TEOAE responses

A
  • only for TEOAES
  • equipment presents many clicks and averages them, but stores the response of 1/2 the clicks in one spot and 1/2 in another and compares to make sure they are very similar (even #ed clicks go to one buffer and odd #ed to another for example)
  • —on pic they will show up as different colored lines, but you should not be able to tell them apart
  • this measure gives confidence in scores
  • some equipment plots A+B and A-B, if the waveforms are v similar, A-B should be 0 and A + B should be largish
  • —-if they do not cancel out when subtracted, it is not a response
22
Q

how can the TEOAE test protocol be modified under certain conditions

A
  • under optimal conditions, as few as 20-50 clicks
  • default 260, 540, or even 1040 clicks
  • more presentations will always results in a more confident identification of TEOAEs
23
Q

how does the TEOAE test protocol change for newborn hearing screening

A
  • analysis time are sometimes reduced from 20 msec to 10 msec
  • –20 msec allows to measure lower freqs
  • –10 msec is mostly high freqs, so eliminate effects of ambient noise which is at lower freqs
  • —–this is okay because high freqs are most commonly affected by congenital HL or flat loss
  • –shortening the analysis time should be done with care as it can result in a loss of sensitivity to middle ear issues
24
Q

two things we need to be confident in TEOAE results

A
  • low noise floor
  • stability
  • –to verify, we need reproducibility value >70% but could use 90% to be more conservative
25
Q

how to analyse TEOAE test results

A

is the OAE to noise floor difference greater than 6 dB?

  • –yes= OAEs are present
  • –no= OAEs are absent
26
Q

screening algorithm for TEOAEs

A
  • automated clincial devices have an analysis of 50-100 points within 5-10 msec, statistical test certainty 99%
  • –early criteria: 3 dB SNR and as low as 50% reproducibility which gave a lot of false negatives
  • –currently need 6dB SNR and 70% reproducibility
27
Q

at what amount of hearing loss might TEOAEs not show up at all?

A

more than 35 dB

28
Q

how do TEOAEs change with age

A

the response amplitude from babies has been reported to exceed the amplitude of adults by more than 10 dB

29
Q

TEOAE difference between men and women (#)

A

2.4-2.7 dB difference (larger for women)

30
Q

TEOAE difference between right vs left ear

A

1.2-1.5 dB difference (larger in right)

31
Q

at what level do we want the noise floor to be at at the highest?

A

-10 dB (ideally less)

AUD fall 2019 electrophys I (11 decks)

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