Impedance audiometry part 1
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Transcript of Impedance audiometry part 1
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IMPEDANCE AUDIOMETRYAditya Ghosh RoyPGT2MS ENT
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IMPEDANCE AUDIOMETRY
•USE
• TESTTYMPANOMETRY
EUSTACHIAN TUBE FUNCTIONSTAPEDIAL
REFLEX
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SOUND WAVE
SOUND WAVESOLID
RELECTED SOUND
WAVE
AIR
AIR
ABSORBED SOUND
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SOUNDAIR
SOLIDREFLECTED SOUND
IMPEDANCE
STIFFNES
S
MASS
FRICTION
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IMPEDANCE
AIR
COCHLEA
SOUNDMIDDLE EAR IMPEDANCE MATCHING
DEVICE
COCHLEA
EAC
TM
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TYMPANOMETRY (DEF)
• CHANGE IN PRESSURE --- CHANGE IN TM STIFFNESS ---SOUND ENERGY REFLECTED BACK DEPENDS ON STIFFNESS OF TM OR PRESSURE CHANGE
PROBE TONE AMPLIFIER
MANOMETER
SOUND
TYMPANIC MEMBRANE
REFLECTED
SOUND
PRESSURE
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• THEREFORE TYMPANOMETRY MAY BE DEFINED AS MEASUREMENT OF CHANGE IN IMPEDANCE OF MIDDLE EAR CAVITY AT THE TM PLANE IN RELATION TO CHANGE IN PRESSURE IN EAC.
• TYMPANOGRAM
Y or ORDINATEIMPEDANCE OR
STIFFNESS
X OR ABSCISSAAIR PRESSURE
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• IMPEDANCE
• NONE OF THE PARAMETERS MEASURED INDIVIDUALLY
SO AS A RESULT ACOUSTIC ADMITTANCE IS MEASUREDADMITTANCE IS RECIPROCAL OF IMPEDANCE
STIFFNESSMASS
FRICTION
IMPEDANCEOPPOSITION TO FLOW OF
ENERGYACOUSTIC OHM
ADMITTANCEEASE TO FLOW OF ENERGY
ACOUSTIC MHO
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• AUDIOMETERS STILL AUDIOMETERS DO NOT MEASURE ADMITTANCE DIRECTLY COMPLIANCE
LOW FREQUENCY PROBE TONE USED IMPEDANCE
EASE OF MOVEMENT OR SPRINGINESS OF MIDDLE EAR SYSTEM
IS ALSO RECIPROCAL OF STIFFNESS
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• HENCE IF COMPLIANCE IS MEASURED USING LOW FREQUENCY TONE
• IMPEDANCE OF MIDDLE EAR SYSTEM
• MOST OF THE IMPEDANCE AUDIOMETERS MEASURE COMPLIANCE
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IMPORTANT POINTS
• C1 – COMPLIANCE VALUE AT +200mm water
• C2 – COMPLIANCE VALUE AT (MAXIMUM)
• CX – STATIC COMPLIANCE (C2- C1=CX)
STATIC COMPLIANCE IS DEFINED AS COMPLIANCE OF AUDITORY CONDUCTIVE PATHWAY AT TM.
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MIDDLE EAR PRESSURE
• PRESSURE AT WHICH COMPLIANCE VALUE IS MAXIMUM IS CALLED AS MIDDLE EAR PRESSURE IE PRESSURE OF AIR IN MIDDLE EAR CAVITY.
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PHYSICAL VOLUME TEST VALUE
THE COMPLIANCE VALUE AT +200mM water IS THE VOLUME OF EAC .
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TYMPANOMETRY
MEASUREMENT OF STATIC
COMPLIANCE
MEASUREMENT OF MIDDLE EAR PRESSURE
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MEASUREMENT OF STATIC COMPLIANCE
• cc/ ml if COMPLIANCE• Millimho if SUSPECTANCE
• IF A 220 Hz PROBE– 1MILLIMHO OF SUSPECTANCE = 1 CC/ML OF COMPLIANCE
TYMPANOGRAM
ABSOLUTE
RELATIVE
COMPENSATED
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• BASELINE IS COMPLIANCE AT +200
• SHADED AREA IS VOLUME OF EAC
• ALSO CALLED NON COMPENSATED TYPE
ABSOLUTE
• BASELINE IS 0 AT ORDINATE• BRACKET PORTION IS
COMPLIANCE
RELATIVE
• BASELINE IS 0 AT ORDINATE• BRACKET PORTION IS
COMPLIANCE• SHADED AREA BESIDE THE
TYMPANOGRAM IS VOLUME OF EAC
COMPENSATED
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• NORMAL RANGE COMPLIANCE
• IMP POINT– CLINICAL CONDITION OF TM TO BE ALWAYS NOTED
• STUDY BY A.S. FELDMAN– HEALED TM INVALIDATES COMPLIANCE AS ONE OF THE TESTS OF TYMPANOMETRY
.35 TO 1.40 ML
>2.50mL
<.28 mL
AB
NO
RMAL
LY
HIG
H
ABNO
RMALL
Y LOW
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LARGE TM
OSSICULAR DISCONTINUITY
SCARED/HEALED TM
POST STAPEDECTOMY EAR
OTITIS MEDIA WITH EFFUSION
OSSICULAR FIXATION
TYMPANOSCLEROSIS
OTOSCLEROSIS
TUMOUR OF MIDDLE EAR
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MEASUREMENT OF MIDDLE EAR PRESSURE• EXPRESSED IN mm WATER / DEKA PASCAL
(daPa)
• 1mm WATER = 1.20 DEKA PASCAL
• RANGE = +50 TO -50 mm WATER
• MEP NEGATIVE WHEN P < -100 mm WATER
• PAED AGE GROUP-- +25 TO -100mm WATER
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NORMAL MEP• SCARRED TM• OSICULLAR FIXATION• OSICULLAR DISCONTUINITY• STAPEDIAL OTOSCLEROSISNEGATIVE MEP• ET DYSFUNCTION• SECRETORY OTITIS
MEDIA/EFFUSION
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ABSENCE OF PEAK• PERFORATED TM• ADHESIVE OTITIS MEDIA• ARTIFACT• PATENT GROMET IN TM• CERUMEN
POSITIVE MEP•EARLY ACUTE OTITIS MEDIA
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IMP POINT--POSITIVE PRESSURE PEAK
• SWALLOWING• CHILD CRYING PHYSIOLOGICAL• VALSALVA• HOLD BREATH IN EXPIRATION
• IN EARLY AOM PUS FORMED IN MEC AND ET DYSFUNCTION
DECREASE VOLUME + INCREASE PRESSURE OF MEC
POSITIVE PRESSURE PEAK
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TYPES AND SHAPES OF TYMPANOGRAMS
TYMPANOGRAMS
J. JERGER
A
B
A.S. FELDMAN
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TYPE A
• SHARP MAXIMUM AT 0 mm WATER• NORMAL EAR AND SOME CASES OF
OTOSCLEROSIS
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TYPE AD• NORMAL MIDDLE EAR PRESSURE WITH
HIGH COMPLIANCE• SEEN IN OSSICULAR CHAIN
DISCONTUINITY OR SCARRING OF TM• NOTCHED PEAK OR DOUBLE MAX AT 0
mm USUALLY SEEN WITH A HIGH FREQUENCY PROBE IN OSSICULAR DISCONTUINITY
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TYPE AS
• NORMAL MIDDLE EAR PRESSURE WITH LOW COMPLIANCE
• OTOSCLEROSIS AND THICKENED TM
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TYPE B
• FLAT TYMPANOGRAM• LITTLE OR NO COMPLIANCE AND NO SHARP PEAK• SEEN IN ADHESIVE OTITIS MEDIA, OTITIS MEDIA
WITH EFFUSION, PERFORATION OF TM
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TYPE C
• NEGATIVE MIDDLE EAR PRESSURE WITH NORMAL COMPLIANCE
• ET DYSFUNCTION WITHOUT EFFUSION
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TYPE CS
• NEGATIVE MIDDLE EAR PRESSURE WITH LOW COMPLIANCE• ET DYSFUNCTION WITH OTITIS MEDIA WITH EFFUSION
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CLASSIFICATION BY A.S. FELDMAN
PEAK PRESSURE
TYPE OF CONFIGURATION
OF TYMPANOGRAM
COMPLIANCE OR AMPLITUDE
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1.NORMAL TYMPANO GRAM• GOOD COMPLIANCE AND PEAK PRESSURE AT 0
mm WATER• CORRESPONDS TO JAGER TYPE A
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2.NORMAL MIDDLE EAR PRESSURE WITH HIGH COMPLIANCE • IF 226HZ PROBE USED THEN EITHER OSSICULAR
CHAIN DISCONTUINITY OR SCARRING OF TM• BUT IF A 660 OR 800 HZ PROBE USED THEN A
NOTCHED PEAK OR DOUBLE MAX AT 0 mm USUALLY SEEN IN OSSICULAR DISCONTUINITY
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3.NORMAL MIDDLE EAR PRESSURE WITH LOW COMPLIANCE• OTOSCLEROSIS OR OSSICULAR FIXATION AND
THICKENED TM
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4. FLAT TYMPANOGRAM• LITTLE OR NO COMPLIANCE AND NO SHARP PEAK• SEEN IN ADHESIVE OTITIS MEDIA, OTITIS MEDIA
WITH EFFUSION, PERFORATION OF TM .• CORRESPONDS TO JAGER TYPE B.
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5.NEGATIVE MIDDLE EAR PRESSURE WITH LOW COMPLIANCE• ET DYSFUNCTION WITH OTITIS MEDIA WITH
EFFUSION• CORRESPONDS TO JAGER TYPE CS
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6. POSITIVE MIDDLE EAR PRESSURE NORMAL COMPLIANCE• RARELY SEEN• IN EARLY AOM
IN EARLY AOM PUS FORMED IN MEC AND ET DYSFUNCTION
DECREASE VOLUME + INCREASE PRESSURE OF MEC
POSITIVE PRESSURE PEAK
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7.NEGATIVE MIDDLE EAR PRESSURE WITH NORMAL COMPLIANCE• ET DYSFUNCTION WITHOUT EFFUSION
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TO SUMMARISE
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TO BE CONT..