Post on 21-Feb-2017
IMPEDANCE AUDIOMETRYAditya Ghosh RoyPGT2MS ENT
IMPEDANCE AUDIOMETRY
•USE
• TESTTYMPANOMETRY
EUSTACHIAN TUBE FUNCTIONSTAPEDIAL
REFLEX
SOUND WAVE
SOUND WAVESOLID
RELECTED SOUND
WAVE
AIR
AIR
ABSORBED SOUND
SOUNDAIR
SOLIDREFLECTED SOUND
IMPEDANCE
STIFFNES
S
MASS
FRICTION
IMPEDANCE
AIR
COCHLEA
SOUNDMIDDLE EAR IMPEDANCE MATCHING
DEVICE
COCHLEA
EAC
TM
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
• 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
• 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
• 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
• HENCE IF COMPLIANCE IS MEASURED USING LOW FREQUENCY TONE
• IMPEDANCE OF MIDDLE EAR SYSTEM
• MOST OF THE IMPEDANCE AUDIOMETERS MEASURE COMPLIANCE
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.
MIDDLE EAR PRESSURE
• PRESSURE AT WHICH COMPLIANCE VALUE IS MAXIMUM IS CALLED AS MIDDLE EAR PRESSURE IE PRESSURE OF AIR IN MIDDLE EAR CAVITY.
PHYSICAL VOLUME TEST VALUE
THE COMPLIANCE VALUE AT +200mM water IS THE VOLUME OF EAC .
TYMPANOMETRY
MEASUREMENT OF STATIC
COMPLIANCE
MEASUREMENT OF MIDDLE EAR PRESSURE
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
• 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
• 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
LARGE TM
OSSICULAR DISCONTINUITY
SCARED/HEALED TM
POST STAPEDECTOMY EAR
OTITIS MEDIA WITH EFFUSION
OSSICULAR FIXATION
TYMPANOSCLEROSIS
OTOSCLEROSIS
TUMOUR OF MIDDLE EAR
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
NORMAL MEP• SCARRED TM• OSICULLAR FIXATION• OSICULLAR DISCONTUINITY• STAPEDIAL OTOSCLEROSISNEGATIVE MEP• ET DYSFUNCTION• SECRETORY OTITIS
MEDIA/EFFUSION
ABSENCE OF PEAK• PERFORATED TM• ADHESIVE OTITIS MEDIA• ARTIFACT• PATENT GROMET IN TM• CERUMEN
POSITIVE MEP•EARLY ACUTE OTITIS MEDIA
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
TYPES AND SHAPES OF TYMPANOGRAMS
TYMPANOGRAMS
J. JERGER
A
B
A.S. FELDMAN
TYPE A
• SHARP MAXIMUM AT 0 mm WATER• NORMAL EAR AND SOME CASES OF
OTOSCLEROSIS
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
TYPE AS
• NORMAL MIDDLE EAR PRESSURE WITH LOW COMPLIANCE
• OTOSCLEROSIS AND THICKENED TM
TYPE B
• FLAT TYMPANOGRAM• LITTLE OR NO COMPLIANCE AND NO SHARP PEAK• SEEN IN ADHESIVE OTITIS MEDIA, OTITIS MEDIA
WITH EFFUSION, PERFORATION OF TM
TYPE C
• NEGATIVE MIDDLE EAR PRESSURE WITH NORMAL COMPLIANCE
• ET DYSFUNCTION WITHOUT EFFUSION
TYPE CS
• NEGATIVE MIDDLE EAR PRESSURE WITH LOW COMPLIANCE• ET DYSFUNCTION WITH OTITIS MEDIA WITH EFFUSION
CLASSIFICATION BY A.S. FELDMAN
PEAK PRESSURE
TYPE OF CONFIGURATION
OF TYMPANOGRAM
COMPLIANCE OR AMPLITUDE
1.NORMAL TYMPANO GRAM• GOOD COMPLIANCE AND PEAK PRESSURE AT 0
mm WATER• CORRESPONDS TO JAGER TYPE A
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
3.NORMAL MIDDLE EAR PRESSURE WITH LOW COMPLIANCE• OTOSCLEROSIS OR OSSICULAR FIXATION AND
THICKENED TM
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.
5.NEGATIVE MIDDLE EAR PRESSURE WITH LOW COMPLIANCE• ET DYSFUNCTION WITH OTITIS MEDIA WITH
EFFUSION• CORRESPONDS TO JAGER TYPE CS
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
7.NEGATIVE MIDDLE EAR PRESSURE WITH NORMAL COMPLIANCE• ET DYSFUNCTION WITHOUT EFFUSION
TO SUMMARISE
TO BE CONT..