oae presentation,/ kunnampallil gejo
Post on 29-Nov-2015
113 Views
Preview:
DESCRIPTION
TRANSCRIPT
OTOACOUSTIC
EMISSIONS
KUNNAMPALLIL GEJO JOHN
BASLP,MASLP
AUDIOLOGIST
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
Origins of
Otoacoustic Emissions
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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 .
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
Physiologic Factors effecting Oto-acoustic
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)
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
Physiologic Factors effecting Oto-acoustic
Emission Testing
Stria vascularis
provides energy to cochlea
Decreased blood supply affects OHC motility.
Some drugs (e.g. lasix) affect stria vascularis.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
Physiologic Factors effecting Oto-acoustic
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.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
Measurement Techniques
Bio-logic Systems Corp.
Measurement TechniquesDistortion Product Otoacoustic Emissions (DPOAE)
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
TEOAE collection
Collection
Stimulus- click
Equal energy at all frequencies (1,500- 5,000)
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
TEOAE analysis
reproducability- related to TE-NF
overall
by frequency band
may set up pass refer criteria based on
reproducability
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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).
...
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
…
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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.
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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)
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
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
KUNNAMPALLIL GEJO JOHN,
BASLP,MASLP
top related