Tympanometry Flashcards
List three factors that influence the magnitude of the compliance reading at +200daPa?
- Size of the ear canal
- Insertion depth of probe tip
- Whether or not the TM is intact
WHat are the normal ranges for Ctotal (+200) for adults and children?
Adults: 0.6-1.5
Children: 0.2-1.0
What is the normal range of Cme?
0.3 – 1.6
List at least three contraindications for performing impedance audiometry.
Recent middle ear surgery (not grommets)
Discharging ear
Painful /bleeding ear
Active otitis externa
List at least 3 reasons why we examine the ear prior to performing tympanometry.
To check size and shape of ear canal to help with tip size selection
To check direction of ear canal to help with direction of insertion
To check for wax occlusion
To show conditions which may affect tympanogram and so help with interpretation of results (eg. Perforation, tympanosclerosis)
To show conditions that may contraindicate tympanometry
List at least three things we should try if we are unable to get a seal
Reposition tip
Try different size tip
Put small amount of gel on outside of tip
Adjust headset placement (make sure it is not pulling tip upwards out of ear or dragging it down)
Try foam or air-filled tip
Check equipment is not faulty
Why do we use a 226Hz probe tone?
Using a low frequency probe tone we can measure a middle ear system that is stiffness dominated (in an adult ear). The total compliance is the sum of the ear canal compliance and the middle ear compliance. Since the Ear Canal is a hard walled cavity the changes in compliance that we see as a result of pressure changes in the ear canal are due to the middle ear only. At +200daPa we are effectively measuring the compliance of the ear canal. When we measure the compliance of the ear we are measuring the compliance of the ear canal + the compliance of the middle ear. At +200daPa, the eardrum will be stretched tightly and will hardly move in response to sound. The middle ear compliance will thus be negligible and the compliance reading at +200daPa will just be the compliance of the ear canal (the equivalent volume)
What does tympanometry measure?
It measures acoustic admittance/compliance of the ear as a function of varying pressure in the ear canal. This enables us to derive a measurement of middle ear compliance, middle ear pressure and get a measure of ear canal volume
What does the compliance reading at +200mmH2O effectively measure? Why?
This effectively measures the compliance of the ear canal. When we measure the compliance of the ear we are measuring the compliance of the ear canal + the compliance of the middle ear. At +200daPa, the eardrum will be stretched tightly and will hardly move in response to sound. The middle ear compliance will thus be negligible and the compliance reading at +200daPa will just be the compliance of the ear canal (the equivalent volume).
What does the result of a Type B (high volume) tell us?
TM is not intact
>2.0 Equivalent volume
What does the result of a Type B (high volume) tell us?
TM is not intact Patent ventilation tubes/grommets TM perforation Previous surgery or pathology eroding the middle ear &/or ear canal space >2.0 Equivalent volume
What are the possible pathologies of a Type B (low volume) tympanogram?
Serous Otitis Media
Wax occlusion (especially if very low volume).
Otitis externa
Otosclerosis
What are the possible pathologies of a Type A tympanogram?
Nothing that fills the ME space
Otosclerosis
What are the possible pathologies of a Type C tympanogram?
Eustachian Tube dysfunction
How could you differentiate between the different possible pathologies causing the type of Tymp you see? (i.e. what other information you would have obtained at this point in the appointment that could help you discern between the pathologies?)
Otoscopy, history, audiogram shape/configuration.
