Tympanometry Flashcards
What is tympanometry
a test of integrity of the TM and middle ear function
what are the three main measures of tympanometry?
- tympanogram
- acoustic reflexes
- other: reflex delay, ET function
What is immitance?
a measure of how readily a system can be set into motion by a driving force
What is admittance/ compliance?
the ease with which energy will flow through a vibrating system
What is impedance?
the extent to which a system resists the flow of energy though it
What three factors determine the impedance of system? which one is the most important?
- stiffness **most important
- resistance
- mass
If the ear has high compliance this means that there is _______ sound bouncing back to the ear
minimal
T or F the ear drum vibrates most efficiently when pressure is equal on both sides
true
As pressure displaces the TM from rest what three things happen?
- decrease in vibratory efficiency
- decrease in energy flow
- increase in sound bouncing back
What does a tympanogram measure
it measures changes in compliance as a function of air pressure changes in the ear canal
On a tympanogram, as compliance increases, sound ______
decreases
Describe a Type A tympanogram
point of greatest compliance is at 0 daPa (-100 to 100 daPa) and compliance is normal
Describe a Type As tympanogram
pressure is normal, but compliance is low so the peak is not as big
Describe a Type AD tympanogram
pressure is normal, but compliance is high so the peak is larger
Who has a Type A tympanogram
- people with normal hearing
- people with sensorineural hearing loss
Describe a Type B tympanogram
there is no point of greatest compliance, it is a flat tympanogram
Who has a Type B tympanogram
- People with conductive hearing loss
- People with advanced otosclerosis
- People with fluid in their middle ear
- People with perforated ear drum or PE tubes
- Could also be caused from a blocked probe
Describe a Type C tympanogram
the point of maximum compliance occurs when negative pressure is in the ear canal, so pressure in the middle ear must be negative (less than -100 daPa)
We don’t normally see hearing loss until the negative middle ear pressure reaches _____ daPa
-150
Who would have a Type C tympanogram?
- People with ET dysfunction
- If you have a cold
- If you just got off of an airplane
- Pressure from large adenoids or tonsils
Kids with negative middle ear pressure will often return with ______ in middle ear space due to effusion
fluid
What are the two important things to look at when reading a tympanogram?
- pressure at the peak
- height of the peak (compliance)
What is the range of normal compliance values?
.30 - 1.70 cm3
If you have a compliance value smaller than the normal range, it means that the ear has ________ than normal mobility
less
If you have a compliance value larger than the normal range, it means that the ear has ________ than normal mobility
greater
The first step in a tympanogram is figuring out the compliance of the outer ear. How do we do this?
- Immobilize the eardrum with positive pressure (+200 daPa)
- There is a large amount of sound returned to the probe, this helps us determine the volume of the outer ear in cm3 which represents the compliance of the outer ear
The second step in a tympanogram is figuring out the compliance of the outer ear and middle ear together. How do we do this?
- Decrease the pressure in the EAM until the TM reaches maximum compliance
- Increased mobility allows more energy to be admitted by middle ear, there is decreased sound coming back to the probe
What is involved in the third step of a tympanogram?
-We take the measurement of the outer ear + the middle ear and we subtract out the outer ear to find the compliance of the middle ear only
What is typical ear canal volume?
between 0.6 - 2.0cm3 with ear difference less than or equal to 2cm
With a Type B temp and a normal ECV the lesion is likely where?
middle ear space
With a Type B temp and a high ECV the lesion is likely where?
tympanic membrane (perforation)
With a Type B temp and a low ECV the lesion is likely where?
- outer ear canal
- clogged probe
- probe against wall
Predict the tymp type for someone with microtia
Type A
Predict the tymp type for someone with a middle ear tumour
Type B
Predict the tymp type for someone with an incompletely formed cochlea
Type A - there is no impairment in the outer or middle ear
Predict the tymp type for someone with a marble stuck in the EAM
Type B
Predict the tymp type for someone with inflamed tonsils and adenoids
Type C
Predict the tymp type for someone with a large TM perforation
Type B
Predict the tymp type for someone with noise-induced hearing loss
Type A (noise-induced HL is typically sensorineural)
What is the acoustic reflex?
a stiffening of the middle ear in response to intense sounds
The acoustic reflex is frequency specific, to what frequencies?
500-4000Hz
The acoustic reflect may be absent if there is damage in the auditory pathway below the _______
superior olive
What is an ipsilateral acoustic reflex?
present a signal to one ear and detect a decrease in TM compliance (increase in stiffness and sound bouncing of TM) in that ear
What is a contralateral acoustic reflex?
present a signal to one ear and detect a decrease in TM
compliance in the opposite ear
T or F the acoustic reflex typically occurs unilaterally
F - it occurs bilaterally
What level of dB HL elicits the acoustic reflex?
less than or equal to 100 dB HL
People with what type of temps demonstrate a acoustic reflex?
- measured with Type A
- never with type B
- seldom with type c
What are the 3 small tubes within the metal probe on the tympanometer?
1) air pump
2) tone generator
3) mic
