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Diagnostic Audiology > Tympanometry > Flashcards

Tympanometry Flashcards

1
Q

What is impedance?

A

The resistance or blockage of energy flow through a system

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2
Q

What is acoustic impedance?

A

The resistance or blockage of sound energy flow through a system

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3
Q

What is acoustic admittance?

A

The ease at which sound energy flows through a system

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4
Q

What would happen if the eardrum was connected directly to the cochlea (i.e. the middle ear didn’t exist)?

A

-99.9% of the sound would be reflected back into the ear canal
-This is because of the impedance mismatch between the air- filled ear canal and the fluid-filled cochlea

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5
Q

How does the middle ear help with impedance mismatch (three principles)?

A
  1. Surface area difference ratio
    -Forces collected at the larger tympanic membrane are concentrated at a smaller oval window which increases overall pressure
    -Surface area ratio gain is approximately 24.6 dB
  2. Curved tympanic membrane
    -The tympanic membrane is curved so the movement is greater at the edge rather than the centre
    -Pressure increase of 6 dB
  3. Lever ratio
    -The arm of the malleus is longer than the arm of the incus
    -Lever action increases the force but reduces velocity at the stapes
    -Pressure increase of 2 dB
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6
Q

What is the combined effect of the three middle ear principles?

A

24.6 + 6 + 2= 32.6 dB

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7
Q

How does stiffness of the tympanic membrane effect transfer of energy in the ear?

A

-If the tympanic membrane was too stiff it would reflect an even larger amount of energy back through the ear canal
-If it was too flaccid it would cause the membrane to absorb too much energy

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8
Q

What is the inverse of stiffness?

A

Compliance

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9
Q

What is the inverse of impedance?

A

Admittance

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10
Q

Fill in the blanks:
1. Stiffness opposes transmission of ____ Hz and passes ____ Hz
2. Mass opposes transmission of ____ Hz and passes ____ Hz

A
  1. Low, high
  2. High, low
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11
Q

What is tympanometry?

A

-Objective test to measure the function of the middle ear
-Measures the change of acoustic impedance/ admittance with changing applied pressure in the external ear

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12
Q

When is the middle ear most efficient in passing sound through?

A

When the air pressure is equal on both sides of the tympanic membrane- this creates the least stiffness of the ossicular chain

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13
Q

What equipment is used in tympanometry?

A

A probe is inserted into the patient’s ear which contains:
-Small loudspeaker generating a frequency of 226 Hz at 65 dB SPL
-Microphone to measure the SPL generated by the cochlea
-Air pump and manometer to generate and measure positive or negative pressure in the external ear canal

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14
Q

What happens to the sound as the tympanic membrane is hit by the 226 Hz tone?

A

-Some of the sound is absorbed and sent via the middle ear to the inner ear
-Some of the sound is reflected

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15
Q

What causes the transference of the sound to the middle to become less efficient?

A

Decreases or increases in pressure

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16
Q

What does the tympanogram show?

A

-The effect of varying external auditory canal pressure on the amount of low frequency tone that passes to the middle ear
-The sharp peak is showing where the most sound is being admitted into the middle ear

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17
Q

What is the ideal measurement for maximum admittance? Why?

A

Around 0 daPa because that is the measurement for atmospheric pressure which we are living at

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18
Q

What is the relationship between the ear canal volume and loudness?

A

-The smaller the ear canal the louder the sound will be
-Based on the loudness, the tympanometer can take a reading of the volume in cm^3 or ml

19
Q

What does the peak of the tympanogram signify?

A

The air pressure behind the tympanic membrane is the same as in the ear canal

20
Q

What are the three test cavities for tympanometry calibration checks and what are their accepted values for cavity volume?

A

-A calibration check in the test cavity should produce a horizontal line (if the line is not horizontal this might indicate a leak)
-0.5cm3: 0.5cm3
-2.0cm3: 1.9-2.1cm3
-5.0cm3: 4.8-5.2cm3

21
Q

What are the contraindications for tympanometry?

A

-Patients under general anaesthetic may have a positive peak pressure above 200 daPa
-Outer ear defects may require an umbrella0type probe
-Otorrhoea (ear discharge)
-Acute otitis media
-Tenderness/ soreness in the ear and otitis externa
-Foreign body in the ear canal
-Excessive wax- probe can push the wax further into the ear canal and soft wax in the cartilaginous portion of the ear canal can damage the probe
-Previous ear surgery (tympanometry should not be carried out within 2 months of ear surgery)

22
Q

What is the test procedure for tympanometry?

A
  1. Fit a clean tip of suitable size and shape to the probe and straighten the ear canal by pulling on the pinna
  2. Point the probe in the direction of the tympanic membrane
  3. Insert probe to obtain an airtight seal
  4. Press start to obtain tympanogram
23
Q

What is a normal shape for the tympanogram?

A

A single sharp peak

24
Q

What might double peaks on the tympanogram indicate?

A

Scarring on the eardrum

25
Q

What are the normal values for the tympanic peak pressure?

A

-50 to +50 daPa

26
Q

What are the normal values for middle ear admittance or compliance?

A

0.3 to 1.5 cm^3

27
Q

What are the normal values for ear canal volume (ECV)?

A

Between 0.6 and 2.5 cm^3

28
Q

What does an abnormally low ear canal volume indicate?

A

An occlusion in the ear canal

29
Q

What does an abnormally large ear canal volume indicate?

A

Open tympanic membrane perforation

30
Q

What is the onward referral criteria for tympanometry?

A

Unilateral flat tympanogram

31
Q

Describe this tympanometry result

A

-Single sharp peak
-ECV, pressure and compliance all within normal limits

32
Q

Describe this tympanometry result

A

-Flat tympanogram
-The ECV is very low- suggests occlusion of the probe
-Not able to obtain any measurements for compliance or pressure

33
Q

Describe this tympanometry result

A

-Flat tympanogram
-ECV within normal value
-Not able to obtain any measurements for compliance or pressure- change in compliance of the middle ear ossicular chain

34
Q

Describe this tympanometry result

A

-Flat tympanogram
-ECV within normal value
-Not able to obtain any measurements for compliance or pressure- change in compliance of the middle ear ossicular chain

35
Q

Describe this tympanometry result

A

-Sharp peak however it is shifted from 0 daPa
-Abnormal middle ear pressure (negative)
-Normal ear canal volume and compliance

36
Q

Describe this tympanometry result

A

-ECV, compliance and pressure within normal limits
-Single sharp peak

37
Q

Describe this tympanometry result. What condition could be associated with this result?

A

-Bilateral flat tympanogram
-Ear canal volume below normal
-Occlusion in the ear canal such as ear wax

38
Q

Describe this tympanometry result. What condition could be associated with this result?

A

-Very shallow peak
-ECV and pressure normal, compliance abnormal
-Suggests middle ear problem e.g. otosclerosis

39
Q

Describe this tympanometry result. What condition could be associated with this result?

A

-Flat tympanaograms bilaterally
-Increased ear canal volume
-Consistent with tympanic membrane perforation

40
Q

Describe this tympanometry result. What condition could be associated with this result?

A

-ECV, pressure and compliance all within normal limits
-Peak a bit more shallow than normal but probably not a middle ear problem

41
Q

Describe this tympanometry result. Which condition could be associated with this result?

A

-Normal right ear
-Flat tympanogram on the left
-ECV normal- suggests middle ear problem e.g. glomus tumour

42
Q

Describe this tympanometry result. Which condition could be associated with this result?

A

-Normal on the right
-Flat tympanogram on the left, no measurements for pressure or compliance but ECV within normal range
-Suggests middle ear problem e.g. otitis media with effusion

43
Q

Describe this tympanometry result. What condition could be associated with this result?

A

-Normal tympanogram on the right
-Unable to complete on the left due to some contraindication e.g. radical mastoidectomy

Diagnostic Audiology (12 decks)

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