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AUD fall 2019 electrophys I > Week 5: DPOAEs > Flashcards

Week 5: DPOAEs Flashcards

1
Q

What are DPOAEs

A

distortions resulting from 2 tones presented together (looking at the interference between the 2)
—moderately loud sounds that are close together in freq

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2
Q

what is a basal distortion

A

has a higher frequency than the signals used to create it

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3
Q

what is an apical distortion

A

has a lower frequency than the signals used to create it

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4
Q

what would happen to DPOAEs if there is hair cell loss at F2

A

no DPOAE

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5
Q

what is higher in frequency: F1 or F2

A

F2

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6
Q

what would happen to DPOAEs if there is hair cell loss at F1

A

no DPOAE

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7
Q

what would happen if there was hair cell loss at 2F1-F2

A

there would still be interference between the two frequencies, so distortion would still be generated
—this is a mixed OAE because distortion and reflection and here the response would exist, but would not have the expected amplitude

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8
Q

HL in audiogram is correlated with frequencies at F1 or F2?

A

F2

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9
Q

what are the 2 theories of DPOAE propagation

A

1) backward traveling theory
2) compressional wave
- –research supports compressional wave

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10
Q

3 factors that would affect the measurement of DPOAEs

A
  • status of the external and middle ear
  • fit if the probe in the external canal
  • –the depth of insertion is important to avoid standing waves because the deeper the probe is makes the cavity smaller, creating a higher resonance frequency hopefully above that of the tones used
  • noise (ambient and physiological)
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11
Q

DPOAE test parameters: stimulus frequency

A
  • uses 2 stimuli: F1 which is lower in frequency and F2 which is higher (aka primary)
  • –the ratio between F2/F1 should be about 1.2 (between 1.15-1.3)
  • the cubic difference tone is what is being measured and is 2F1-F2
  • multiple sets of frequencies are presented within a given octave (between 2-8/octave)
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12
Q

fine structure of DPOAE stimulus frequency

A
  • is high resolution and shows the micropattern of fluctuating DPOAE levels
  • obtained by measuring every 100-200 Hz
  • really shows the 2 components of distortion and reflection
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13
Q

DPOAE test parameters: stimulus intensity

A

generally between 40-70 dB SPL

  • –below 40 is too low to generate measurable response
  • –above 70 is loud enough that OHCs done amplify so can’t measure response of OHCs
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14
Q

DPOAE intensity of F1 and F2

A

L1 and L2 for F1 and F2

  • –L1-L2= 10 to 15 dB
  • –L1 is generally 65 dB SPL
  • –L2 is generally 55 dB SPL
  • **L1 is louder
  • ——–can have L1=L2, but then the response is 3dB less in amplitude
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15
Q

number of tests as DPOAE parameter

A

will the test repeat on its own?

  • you can chose this
  • you want it to run twice to check for respeatability
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16
Q

2 ways DPOAEs can be displayed

A

1) DP-input-output function
- –less commonly used
- –increases F1 level and measure response amplitude (increase intensity of the same frequency)

2) DP-gram
- –clinically most often used
- –plots different frequencies on x-axis and is done at one intensity level (65 and 55 dB)
- —–x-axis represents the primary frequency (F2)
- –is associated with the configuration of the audiogram
* **same intensity, different frequencies

17
Q

DPOAE test protocol for infant hearing screening

A
  • intensity: L1=65 L2=55
  • frequency ratio: 1.21
  • frequency range: 2000-4000 Hz
  • 4-5 frequencies per octave
18
Q

DPOAE test protocol for general diagnostics

A
  • intensity: L1=65 L2=55
  • frequency ratio: 1.21
  • frequency range: 500-8000Hz
  • 3-5 frequencies per ocatve
19
Q

DPOAE test protocol for ototoxicity monitoring

A
  • intensity: 66-55; 55-45; 45-35
  • frequency ratio: 1.21
  • frequency range: 2000-8000
  • 8 per ocatve
20
Q

reliability with DPOAEs

A
  • have good reliability
  • do a test/ retest
  • want responses within 2 dB between the different tests, if it is more it is not reliable and should be repeated
21
Q

should you start with high or low frequencies with DPOAEs

A

start with high and then go to low because ambient noise is louder at lower so it will want to keep going and keep measuring the lows. if testing a child, they might quit cooperating within this time. if you test highs first and they quit at least you have some usable data (and the high frequencies are what we really care about)

22
Q

Boys-Town normative data for DPOAEs

A
  • based on norms of large number of people with HL and normal hearing to see where the amplitude of responses falls
  • plotted the 95th %ile of hearing impaired as the top line
  • plotted the 90th %ile of hearing impaired the second line from the top
  • plotted the 10th %ile of normal hearing the 3rd line from the top
  • plotted the 5th %ile of normal hearing as the bottom line
  • —-overall, the colored area is where they overlap and is called the area of uncertainty
  • —-in general, above this area is probs normal, below the area is probs hearing loss, and within the area is abnormal
23
Q

creating own normative data for DPOAEs

A
  • take a normal hearing group mean +/- 2 SD
  • this will give the 10th and 90th %ile for normal hearing
  • collect and average the DP amplitude and noise floor
24
Q

shortcut for not having norms for DPOAEs

A

basically, if the response is above 0dB SPL amplitude it is normal and below 0 DB SPL is absent or abnormal
—only reason to use is if there is no normative data

25
Q

why are norms important for DPOAEs

A

allow us to say if response is normal, reduced (abnormal) or absent
—note dont just say present or absent, but instead: present and normal, present and abnormal, or absent

26
Q

interpretation of DPOAEs

A
  • is it repeatable (within 2 dB between runs)
  • if the SNR is 6 or greater: normal OR present but abnormal
  • –basically you need a 6 dB SNR to be present but then classify if it is normal or abnormal based off norms
  • if the SNR is less than 6 dB: absent
27
Q

why might you have abnormal OAEs with a normal PTA

A
  • middle ear dysfunction
  • inner ear dysfunction
  • –subclinical sign
  • equipment error
28
Q

why might you have normal OAEs with abnormal PTA

A
  • inner ear and/or auditory nerve dysfunction
  • behavioral factors
  • equipment error
29
Q

10 factors that can affect OAE findings

A
  • time after birth
  • time after bath
  • age (term birth vs preterm)
  • no gender difference with DPOAEs
  • BGN
  • probe placement (depth and fit)
  • ear canal status
  • tester (knowledge and experience)
  • instrumentation
  • anesthesia
30
Q

how to troubleshoot DPOAEs when there is no OAE activity seen

A
  • could be due to middle ear disorder or cochlear damage
  • there could be inadequate stimulus:
  • –verify the stimulus matches the target level
  • –verify correct probe for the device
  • –verify the probe is calibrated
  • –verify probe fit
  • there could be external ear canal blockage
  • –do otoscopy and check probe ports for blockage
31
Q

how to troubleshoot DPOAEs when you are getting unexpected OAEs

A
  • might be from standing waves
  • –replace probe and repeat measures
  • –assess reliability of all test frequencies
  • –record TEOAEs and DPOAEs
  • –verify stimulus intensity level
32
Q

how to troubleshoot DPOAEs when there are high noise levels

A
  • might be from excessive ambient noise
  • –close test room door
  • –separate pt from noise sources
  • –improve probe fit
  • –orient test ear away from noise sources
  • –increase signal averaging
  • –limit stimulus frequencies to greater than 2000Hz
  • might also be from excessive physiological noise
  • –attempt to reduce pt movement
  • –verify pt is not chewing
  • –for infants, record OAEs during feeding or during sedation after ABR

AUD fall 2019 electrophys I (11 decks)

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