Immitance Intro Flashcards
What type of testing does immittance testing encompass?
Tympanometry
Ear canal volume measurement
Acoustic reflex testing
Acoustic reflex threshold
Acoustic reflex decay
Tests of Eustachian tube function
What structures are assessed using immittance measures?
tymp middle ear
reflexes - effect on middle ear, auditory nerve, cochlea, b.s., facial nerve
What are the components of an immittance meter?
probe signal (tone)
air pressure
microphone
How is immittance testing conducted?
based on changing the pressure in the ear canal and measuring sound levels in the ear canal
describes the flow of sound energy
immittance
how much sound doesn’t get through the middle ear -
acoustic impedance
how much sound does get through the middle ear -
acoustic admittance (height of the peak)/ compliance
3 tubes (probe) = tymp
air pressure generator
microphone
tone generator
how do you prepare the pt for a tymp?
Otoscopy first
Ask about ear-related symptoms
Discomfort, pain, drainage
Previous surgeries
Seat patient comfortably, instruct to remain still
Child may need to be gently restrained
what is the probe tip
part that comes off - finding right size for patient - gets tight seal and couples to ear canal
black only tube only generates just the tone
acoustic reflexes
probe itself has 3 components
tone that is played when tymp is ran
microphone picks up sound in me space while running it
air pressure - changes air pressure
explain the process of a tymp
sound goes into the ear, changes the pressure and measure the sound in the ear as the pressure changes by the microphone
what is plotted on a tymp axis
x is pressure and y is admittance
what can evaluate the middle ear function and identify middle ear disorders?
tympanometry
volume measures
Eustachian tube function measures
what differentiates cochlear from retrocochlear
site-of-lesion testing
acoustic reflex thresholds
acoustic reflex decay
do we expect a middle ear disorder with purely snhl?
no
abg shows it is conductve = middle ear
snhl = cochlear vs retrocochlear and no middle ear abnormalities
what are tymp contradictions?
Complete stenosis or atresia
Otorrhea
Acute otitis media with red and bulging tm
Tenderness/soreness, otitis externa
In this case, test healthy ear and allow patient to judge
If proceed, let pt. know how to signal to stop test
Foreign bodies should be removed prior
what is the right side of a tymp plot?
positive
middle line on tymp?
line represents 0 (same atmosphere pressure as the room)
left side of tymp plot?
left is negative
gives measurement in dcpascals
relative to the room
what is the pressure in the ear canal the same as?
environment
how can you manipulate pressure in the ear canal?
seal it off with probe tip
explain what the peak of a tymp means
middle ear system operates the most effectively and letting the most sound through is the peak
other sides of peak is that sound is being opposed
higher admittance
more sound is going through the middle ear
floppy
lower admittance
less sound
stiffness in the system
when does middle ear operate most efficiently?
ear canal and middle ear should be equal, when those are equal, middle ear operates the most efficiently
peak means no neg middle ear pressure - et is working properly
what tymp would we see if et is not ventilating the middle ear?
it is more negative
peak shifts to the left - negative middle ear pressure, leading to fluid
when would excessive cerumen contradict tymps?
Do not test if probe insertion will push against impacted cerumen
Soft wax can damage probe
Remove cerumen prior to tympanometry
In some cases, tympanometry is performed when view of tm is obscured
Do this only if deemed safe to do so!
when should tymps be done with previous ear surgery
Not within 2 months of ear surgery unless formally approved and documented
Reconstruction of ossicles or tm
Only if given medical advice that it is safe
If in doubt, ask medical advice
P.E. tubes- to test or not to test?
This will vary depending on placement
No sooner than within two weeks of placement, otherwise generally ok
Pressure is continuously changed in the ear canal from _____ pressure to ______ pressure, relative to ambient pressure
negative, positive
he most common probe tone
220/226 Hz
probe tone for under 6 months
1,000 Hz
pressure expressed in
daPa
admittance expressed in
mmho or ml
are mmho or ml equivalent?
yes refers to admittance
how are tymps classified previouslY?
by shapes
vary far negative peak
type c
flat tymp
type b
has the peak and falls within the box (norms)
not to far high or low or left or right
type a
very high peak (ossicular disarticulation)
a sub d
shallow (stiffness/shallow)
a sub s
point where middle ear system is operating most efficiently
peak pressure
how close the peak is to 0
peak pressure
what is the peak pressure norm for adults
+50 to -100 daPa
what gives us an indication if there is neg pressure or not in the me
peak pressure
approximates but does not measure middle ear pressure
peak
what do we see if ET is not functioning (ETD)
Possible positive peak early stages of acute OM
Negative peak
Measures stiffness or “floppiness” of the ossicular chain/middle ear system
static admittance
Frequently referred to as compliance or peak compliance
static admittance
Ytm
static admittance
0.3 – 1.7 mL
static admittance
what is considered floppy ossicular chain
above 1.7
what is considered stiff in ossicular chain
lower than .3
what part of me is being measured by static admittance
ossicular chain plus ™ or middle ear system
Static admittance lower in middle ear conditions with increased stiffness
OME
Cholesteotoma
Ossicular adhesions
Space occupying lesions that contact TM or ossicular chain
otosclerosis
Static admittance higher in middle ear conditions with decreased stiffness
Ossicular chain discontinuity
AKA ossicular chain disarticulation
TM atrophy
What is tympanometric peak pressure measuring? Will this shift along the x or the y axis? What are adult norms for TPP? Which physical structure(s) will affect this measurement if not functioning properly?
ET, shifts right or left on the x axis, +50 to -100 in adults, ET and it is actually measuring the pressure point where the me system is the most efficient
What is static admittance measuring? Will this shift along the x or the y axis? What are adult norms for static admittance? Which physical structure(s) will affect this measurement if not functioning properly?
it measures how efficient sound transmission is, measuring stiffness vs floppiness, it will shift along the y axis up and down, .3 to 1.7 is norm, ossicular chain and the tm (middle ear system)
ECV
ear canal volume
Vea
ear canal volume
Noted as Vea or Vec or Veq
ear canal volume
ear canal volume tells us
status of the ™ (if it is intact or not, if PE tubes are open or not)
if there is something significant in the ear canal that we couldnt see
Reported in cc or mL
ear canal volume
Increases with age (developmentally)
ear canal volume
Clinic norms for adults: 0.9 – 2.0 ml
ear canal volume
on average, volume is 2.0
ear canal volume
if somebody lost a dome, bug, hair, etc. in the ear from a ha, will it effect canal volume?
will not give an abnormal volume
refer to the width of the tympanogram
gradient and width
measurement at the halfway point
width
ratio of the peak to the halfway point divided by the whole thing
gradient
very large width tells us
we have a flat tympanogram
why is replicability important
anytime you have a physiologic measure we have to replicate the response
make sure the response didnt come by chance
run again and make sure you got an unusual result again and it wasn’t your mistake
reflexes always replicate
