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Tympanometry
Audiology PowerPoint 5
| Question | Answer |
|---|---|
| The main principles of tympanometry are to: | Test the condition of the tympanic membrane and to test the transmission properties of the middle ear |
| Transmission through the tympanic membrane is best when: | the pressure in the environment / external auditory meatus is the same as in the middle-ear cavity / Eustachian tube |
| If there is a difference of pressure: | there is reduced transmission of the sound through the tympanic membrane / middle-ear space |
| Impedance | resistance to sound transmission |
| compliance | ease with which the sound is carried through the TM/middle-ear |
| When doing a tympanometry, you are assessing... | the amount of compliance and impedance |
| Tympanometer | device delivers a tone to a sealed volume (EAM) and detect the sound level changes as the pressure is varied |
| The pressure pump (function)... | varies air pressure against the tympanic membrane |
| The speaker (function)... | introduces a pure tone (220 Hz) |
| The microphone (function)... | measures the loudness in the external auditory meatus (how much sound is reflecting back) |
| If the tympanic membrane is hit by a sound... | part of the sound is absorbed and sent via middle ear to the inner ear while part of the sound is reflected. The stiffer the tympanic membrane the more sound is reflected. |
| The steps of performing a tympanometry | 1) The probe tip is inserted into the external auditory canal to make a tight seal, 2)A pure tone is delivered to the external auditory meatus, 3) The pump decreases the ear canal pressure to ~ -200 daPa, then increases the pressure to ~ +200 daPa, |
| If the TM is stiff, the peak of compliance... | goes down. |
| If hyper flaccid, the peak of compliance... | goes up. |
| Tympanogram | a graphic representation of the relationship between pressure within the external auditory meatus vs. compliance of the middle ear |
| Compliance is maximal when... | when there is no difference of pressure between the EAM and the middle-ear cavity / ET |
| Pressure in the external auditory meatus is varied from _________________ while monitoring compliance | -200 daPa through +200daPa |
| + pressure variation means you are... | blowing air into the EAM |
| - pressure variation means you are... | sucking air out of the EAM |
| maximal compliance of the middle ear = | maximal mobility |
| normal range of compliance | 0.2 through 1.4 ml |
| If peak is < .02 ... | small compliance --> high resistance --> system is stiff |
| If peak is > 1.4 ... | high compliance --> low resistance --> system is hyperflaccid |
| Pressure Peak indicates | the pressure at which pressure equalization occurs on both sides of the tympanic membrane. It also indicates the pressure at which peak compliance or maximum mobility is attained. |
| normal range of pressure | -150 to 100 daPa |
| If pressure peaks more negative than –150 daPa | indicative of poorly functioning Eustachian tube or possibly some fluid. |
| Extreme positive pressures | often associated with onset of otitis media |
| Normal Box | indicates the range of pressure peak and compliance peak values associated with normal middle-ear function |
| Tympanograms can be classified into 3 basic groups on the basis of their shape: | A, B, and C |
| Type A | represents normal ME function |
| Type A-s | Represents a stiff ME: shallow curve w/ normal ME air pressure but reduced mobility-->suggests limited mobility of the TM and ME structure, commonly seen in fixation of the ossicular chain (e.g., otosclerosis). |
| Type A-d | Represents hypermobile or hyperflaccid ME: deep curve with normal ME pressure but tall peak of abnormally compliant ME ->indicative of a flaccid TM due to disarticulation of the ossicular chain, loss of elastic fibers in the TM, thin TM |
| Type B | represents a restricted tympanic membrane mobility: no sharp peak, with little or no variation in impedance over a wide range of pressure. This curve is usually typical of a stiff ME secondary to non-compressible fluid in the ME (otitis media) |
| Type C | represents significant negative pressure in the middle ear cavity: normal compliance but the peak compliance is significantly below zero, indicating negative pressure in the ME space. This curve is usually typical of Eustachian tube dysfunctions. |
| Normal adult range of EAM volume | 0.6-2 ml |
| If the EAM volume is abnormal... | you cannot accurately measure the compliancy or pressure |
| If EAM volume is > 2ml, due to... | Pressure Equalizer (PE) tubes or perforation |
| If EAM volume is <0.6, due to... | Something blocking the EAM, e.g., impacted cerumen; exostosis; foreign object |
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100000299709410
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