OAE PRESENTATION,/ KUNNAMPALLIL GEJO

OTOACOUSTIC

EMISSIONS

KUNNAMPALLIL GEJO JOHN

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AUDIOLOGIST

KUNNAMPALLIL GEJO JOHN,

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Otoacoustic Emissions

Thomas Gold (1948)

Suggested active elements related to hair

cells and feedback system could produce

emissions

David Kemp (1978)

Demonstrated existence of evoked

otoacoustic emissions


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Anatomy of the ear


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Origins of


The cochlea functions as a sensitive nonlinear,

bio-mechanical amplifier

Active cochlear processes known as the

„cochlear amplifier‟ are responsible for high

sensitivity, sharp tuning & wide dynamic range

of the cochlea

OAE are thought to be a by-product of this

cochlear amplifier


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Origins of



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Physiologic Factors effecting Otoacoustic

Emission Testing

External ear

If the ear canal is blocked with cerumen or

vernix, may not be able to record OAE even

though it was produced by the cochlea .


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Physiologic Factors effecting Oto-acoustic

Emission Testing

Middle ear

must rule out middle ear dysfunction if OAE

is abnormal

• negative pressure,retracted TM, excessive

compliance of m.e. system, fixation of

ossicles, otitis media

The anatomy of the middle ear is helpful for

inward propagation of sound only. There is

about a 15 dB loss of intensity for outward

propagation of sound in the normal ear.


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Emission Testing- Cochlea The outer hair cells are the source of OAEs.

• Shearing effect causes receptor potentials

to trigger ionic changes. The cells respond

by lengthening and shortening at the

frequency of the stimulus. This is what we

record.

Complete loss of OHC elevates threshold 40-

50 dB.

OHC are susceptible to inflammation,

ototoxicity, trauma, acoustic trauma.

• ototoxic drugs (Remember, this is a test of

outer hair cell function only, some

ototoxic drugs affect only inner hair cells)


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Emission Testing

Stria vascularis

provides energy to cochlea

Decreased blood supply affects OHC motility.

Some drugs (e.g. lasix) affect stria vascularis.


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Emission Testing

Efferent auditory system

Inhibitory system-

• Stimulating the efferent fibers suppresses

OHC activity.

OAE may be larger in infants than adults

because the efferent nervous system is not

mature yet.


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Classes of Otoacoustic

Emissions

Spontaneous

only occur in 50% of normals

present more in women than in men

can effect Evoked OAE since EOAE rides on

SOAE

Evoked

observed in almost 100% of normals


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Evoked Otoacoustic Emissions

Transient

produced by click or tone burst

Stimulus frequency

produced by continuous pure tone

Distortion product

produced by 2 continuous pure tones


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Measurement Techniques

Bio-logic Systems Corp.

Measurement TechniquesDistortion Product Otoacoustic Emissions (DPOAE)


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DPOAE/TEOAE


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DPOAE measurement

Stimulus- two pure tones presented

simultaneously producing intermodulary

distortion

F1 is the lower frequency (more apical).

• L1 is intensity of F1.

F2 is the higher frequency (more basal).

• L2 is intensity of F2.


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Frequency

F2;F1

Use a ratio which produces the highest

amplitude of the DPOAE response

e.g. F2/F1= 1.2

Measure the DPOAE at 2F1-F2.

e.g. F1= 2,000, F2 =2,400 DP= 1,600

• 2(2,000) - 2,400=1,600

upper limits DPOAE: can test up to 10,000 Hz

(F2)

testing with F2 below 1,000 Hz is difficult due

to physiological noise. Remember, DP is

measured at a lower frequency than F2


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Intensity L2;L1

L1 and L2 must be at moderate intensity level

Avoid high intensity (>70dB) which will

cause false negative due to passive distortion

of the BM

best responses recorded when L2 is about 10

dB less than L1

recommendation: L1=65 dB, L2= 55 dB


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DPOAE Analysis


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DPOAE analysis

For an intensity ratio of F1=F2+10 dB, the

response from the cochlea is generated at the

F2.

So, use F2 as horizontal axis on the DP gram

For an intensity ratio of F1=F2, the response

from the cochlea is generated near the

geometric mean of F1 and F2

So, use geometric mean as horizontal axis on

the DP gram.


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DPOAE analysis

DP should exceed noise floor by at least 6 dB to

be valid.

absolute value of normal DP varies by

frequency (see normative data in OAE

program)

When comparing DPOAE to an audiogram, try

to obtain F2 as close to audiometric frequency

as possible, can use more points/octave.


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TEOAE collection

Collection

Stimulus- click

Equal energy at all frequencies (1,500- 5,000)


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TEOAE analysis

reproducability- related to TE-NF

overall

by frequency band

may set up pass refer criteria based on

reproducability


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Beginning to test


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Test procedure

Reduce noise in test area as much as possible.

If possible, perform otoscopic exam (probably

not possible in neonates).

If patient is old enough to follow instructions,

ask patient to remain quiet and still.

Clip probe to patient‟s clothing or other

stationary object to cut down on noise.

Insert probe in ear canal as deeply as possible

(be careful not to “canal” probe).

...


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Test procedure…(cont.)

do not need to test in sound booth, but

environmental noise ldo not need to test in

sound booth, but environmental noise levels

should be as low as possible

can test with patent PE tubes, helpful to have

patient hold their breath during the test

levels should be as low as possible

can test with patent PE tubes, helpful to have

patient hold their breath during the test


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New Patient File...


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Patient Information


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Reset hardware (optional)


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Begin Collection


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Setup


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Select Protocol


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DPOAE Collection Setup

Parameters


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DPOAE

Advanced Setup Parameters


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TEOAE Collection Parameters


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TEOAE Advanced Collection

Parameters


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DPOAE display Setup


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TEOAE Display Parameters


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Open Patient Data File


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Right/Left Side by Side


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Superimposed


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Separate


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File names example 98J20D00

98= year

J= 10th month (Oct.)

20= date

D= distortion product otoacoustic emission

(T= Transient otoacoustic emissions)

00= first test done that day


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Reference data for DPOAE

Use normative data to analyze patient‟s

response

Is the amplitude of the response within the

normal region for that frequency?

There is a large degree of variability in amplitude even

within the normal population

Must use use same collection parameters when using a

set of normative data.

Use normative data collected on same type of

equipment you are using KUNNAMPALLIL GEJO JOHN,

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Viewing Scout Windows DPOAE


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Pass/ Refer


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Reference Data


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Analysis-Activate Display

Setup


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Expanded Boys Town


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Expanded boys Town- normal DP above the top lines suggests normal OAE function

and therefor probably suggests normal hearing since so

few impaired fall at or above the top lines


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Expanded Boys Town- abnormal DP below the bottom lines suggests abnormal OAE

function or inability to measure a response (middle ear)

since so few normals have amplitude that low.

• i.e. DP approximately equal to NF


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Expanded Boys Town-indefinite Between the 2 sets of lines, there are normals with low

amplitude DP or hearing impaired with robust

emissions.

probably not worse than mild loss


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Transient Test Protocol


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TE Screen Protocol


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Practice


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Practice Information


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Troubleshooting Confirm that actual stimulus intensities plotted are

close to target stimulus intensities. If not, be sure probe

is still in ear and tubes are attached between speaker

and mike assemblies.

Check spectrum of stimulus in ear to be sure that there

are no large dips in ear canal acoustics.

If there large dips in stimulus spectrum that the

system cannot compensate for, try refitting probe in

ear.

if no sound or very low intensity sound is emitted from

probe, clean probe by removing mike from back of

probe and insert cleaning tool in mike port and 2

speaker ports


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Factors to consider when interpreting

OAE measurements May fail OAE and be audiometrically “normal”. Can

see the effect of excessive noise exposure in OAE even if

not seen in the audiogram (early warning sign).

May loose 20-30% of OHC and audiogram will be

the same

Cannot use audiogram “normal” cut off of 20dB when

comparing to OAE since if audiometric threshold is

20dB, it is actually 4 standard deviations from zero

…


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Factors to consider when interpreting

OAE measurements (cont.)...

Standing waves in ear canal can cause interference in

DP of up to 20 dB, especially in high frequency (>7

kHz)

Replicate- If questionable response is obtained,

remove probe tip and replace it. If standing wave,

responses will be out of synch

OHCs are pre-neural structures, so it is possible to

have no behavioral response to sound, no ABR and

normal Otoacoustic emissions (auditory neuropathy).

This is very rare, however.


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Age/Gender

Neonates have larger OAEs till one year after

birth

At 30 weeks gestational age cochlea is mature

(assuming normal development)

Advancing age does not affect OAE (corrected

for hearing loss)

Gender a factor only for Transients or

Spontaneous, but not Distortion Products but

not Distortion Products(females stronger

TEOAEs than males) KUNNAMPALLIL GEJO JOHN,

BASLP,MASLP

Applications

Neonatal hearing screening

Preschool and school age hearing screening

Ototoxicity

Functional hearing loss

Cochlear v.s. Retro-cochlear

Monitoring noise exposure

Tinnitus (confirms cochlear dysfunction)


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Neonatal hearing screening

Test at least 24 hours after birth, if possible, to

prevent false positives due to vernix. If infant

fails, re-test at least one more time before

discharge

If one ear fails, try to have baby lay so that the

failed ear is facing up for a while to clear vernix

before retest.

Only need to retest failed ear

OK to test while infant is nursing

Baby may have middle ear effusion


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CPT codes 92587 Evoked Otoacoustic emissions, limited

(single stimulus level, either transient and/or

distortion products

92588 Evoked Otoacoustic emissions,

comprehensive or diagnostic evaluation

(comparison of transient and/ or distortion

product Otoacoustic emissions at multiple

levels and frequencies

contact insurance companies to see what they

reimburse in your area


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AuDX Hardware Options AuDX I

one protocol, not programmable

10 test memory, label printer

AuDX II

three protocols, programmable via software

50 test memory (option for 100 test memory)

label printer option, AuDX link option

Data Link option, HATS AuDX database

option


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AuDX Hardware Options…(cont.)

AuDX Plus

three protocols, programmable via software

50 test memory (option for 100 test memory)

compatible with Scout OAE software for

PC-based collection

label printer option

Data Link option, HATS AuDX database

option


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AuDx Link


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Select file


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AuDX Link DP-gram


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AuDX Data link

To share information with OZ Sims

program


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NO

YES

What should you do if you are

having an equipment problem?


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OAE PRESENTATION,/ KUNNAMPALLIL GEJO