TYMPANOMETRY
1) Tympanometer
Definition:
A tympanometer is an instrument, which provides information on the functioning and status of the middle ear.
2) Tympanometry:
Definition:
Tympanometry is an objective test and as it requires little cooperation, it can be carried out at any age and with any degree of deafness. It always for the measurement of the elasticity or compliance of the introduced into the middle ear system.
Tympanometry is one of three principal subtests of immittance audiometry. Immittance audiometry is an objective procedure that assesses, in an individual ear, the relative impedance (resistance offered to the flow of energy in acoustics signals) and admittance or compliance (the reciprocal of impedance, and the case with which the ear accepts the flow of energy in an acoustic signal). The other two subtests of immittance audiometry are static admittance/ compliance and the acoustic reflex test. The general term ‘immittance’ is used to indicate the principle of evaluating energy flow. Particular test equipment may measure either impedance or admittance.
Explanation:
Tympanometry assesses the ability of the tympanic membrane to accept sound, and is therefore a test of the conductive mechanism of the ear. It is a dynamic measure, meaning that the tympanic membrane is in motion during the test. The basic approach in tympanometry is to introduce a pure-tone (usually 220 Hz or 660 Hz) into the external auditory meatus and to measure how much of that sound wave is accepted (admitted) or rejected (impeded) by the tympanic membrane. In a normal ear the tympanic membrane will accept most of the sound and will do this when the air in the external auditory meatus is at or very close to normal atmospheric pressure.
During tympanometry, air pressure, expressed in decapascals (daPa) or millimeters of water (mm water), is varied continuously in the external auditory meatus from values greater than normal atmospheric pressure (usually + 200daPa/mm water), through normal atmospheric pressure (0 daPa/mm water), to values less than atmospheric pressure (usually- 200 daPa/mm water). This causes the tympanic membrane to move in the response to the positive and negative pressure allied to it.
3) Tympanogram-
Tympanometry results are plotted, either automatically or manually, on a tympanogram, a graph of impedance/admittance values against air pressure values.
By using handtymp we can get the tympanogram. It is very important to hold the handtymp properly. We have to set the tip in right position. Other wise it would be difficult for anyone to get the tympanogram. Then we can press the button until the pick showing. Thus we can have the result of the tympanogram. From this we can know air pressure, canal position, eardrum mobility etc. If the pick is in the range of 0.35-1.4 the compliance is normal. If the pick is in the range of –100-+50 the middle ear pressure is normal. And for other range it is not normal.
4) Instructions for the tympanometry
We should follow these instructions for the tympanometry-
a) Tympanometry may be carried out in almost any reasonably quiet room.
b) As very low levels of ambient noise are not required, although the British society of Audiology recommends that the ambient room noise be less than 50 dB A SPL, if possible (BSA, 1992).
c) The range of equipment available is considerable.
d) Glove should be used during middle ear testing.
e) An auroscope or otoscope is required for inspection of the external auditory meatus.
f) The tympanometer should be hold in proper way
g) The button of the tympanometer should be pressed until the pick showing.
h) The tip of the tympanometer should be set correctly in the ear.
i) Tip size will be well fitted for the client
j) Different tip for different client
k) All of the equipment will be neat and clean
l) Before starting test we have to check all of the equipments.
m) Set up the room and equipment to ensure satisfactory hygiene and client co-operation.
n) Washing hands and follow other hygiene protocols as appropriate
5) Instructions for testing the client
We have to always follow the instruction for testing the client-
a) Explain the test and instruct the client.
b) Inspect the pinna visually and the external auditory canal with an otoscope to determine the size and angle of lateral portion and to check for any contraindications to tympanometry.
c) Contraindications include discharge from the ear, wax occlusion, tenderness of the ear, foreign bodies and obvious perforation or inflammation of the tympanic membrane (ASHA< 1990c; BSA, 1992)
d) Select an appropriate sized probe tip for the client.
e) For all the things we have to get permission from the client.
f) Asking the client to open their mouth, and pull the pinna upwards and backwards
g) These actions will straighten the lateral, cartilaginous portion of the external auditory canal and make insertion easier.
h) If using an automatic tympanometer, the instrument will indicate whether or not an airtight seal has been obtained.
i) Inform the client of the result, taking care not to interpret beyond the available data.
j) Keep appropriate records, ensuring that the date of tympanometry screening is recorded.
References
a) Doyle, J., (2002), Practical audiology for Speech-language therapy, Whurr Publishers, London.
b) Bess, F.H.; Humes, L.E.; (1990), Audiology the Fundamentals, Wiliams & Wilkins, Baltimore.
c) Tucker, I.; Powell, C. (1991), The Hearing Impaired Child and School, A condor book, London
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