Immittance Measures: Tests of Middle Ear Functions

Question 1

Impedence

Answer 1

Opposition to flow of energy through a system

Question 2

Impedence is greatest when ME is _________, such as in:

Answer 2

Stiff/immobile, otitis media or otosclerosis

Question 3

_______ ME system reflects less energy and can be caused by:

Answer 3

Flaccid, ossicular chain disruption

Question 4

Admittance

Answer 4

Relative ease w/ which energy flows through a system (if high, low impedance)

Question 5

Acoustic immittance sensitive/objective tool to:

Answer 5

• fluid in middle ear
• evaluate eustachian tube function
• facial nerve function
• predict audiometric findings
• determine nature of HL
• assist in diagnosing site of lesion
• assess difficult to test PTs

Question 6

Immittance Test Battery

Answer 6

Tympanometry
Static Acoustic Immittance
Acoustic Reflex Threshold

Question 7

Tympanometry

Answer 7

measurement of mobility of ME when air pressure varies from -200 to +400 daPa in ear canal
Tells us: ME peak pressure, compliance

Question 8

Static Acoustic Immittance

Answer 8

1. Determine immittance @ 200 daPa (little energy flow)
2. Measure eardrum @ most compliant point
   * Can difference = “equivalent ear canal volume” in cm3

Question 9

Equivalent Ear Canal Volume Norms

Answer 9

Children: 0.25 - 0.9 cm3
Adults: 0.9 - 2.0 cm3

Question 10

Middle Ear Peak Pressure

Answer 10

Normal -150 to +50 daPa

Question 11

Compliance norms

Answer 11

Normal: 0.3-1.6 mL
Stiff: 1.6

Question 12

Type A Tympanogram

Answer 12

Normal ears
Peak b/t -150 mm and +50 mm H20
Curve large inverted “V”

Question 13

Type As Tympanogram

Answer 13

Spike ~0 mmH20 = normal pressure but shallower

Stiff ME system (ex: stapes immobilization)

Question 14

Type Ad Tympanogram

Answer 14

Type A pattern preserved but peak off the chart
Flaccid eardrum (ossicles disarticulated)

Question 15

Type B Tympanogram

Answer 15

Increased impedance
No peak (very stiff)
ME filled w/ fluid, wax blocks canal or hole in eardrum flat

Question 16

Type C Tympanogram

Answer 16

Increased negative ME pressure (-150-400 mmH20)
ME pathology (possible eustachian tube dysfunction)
Found before Type B (fluid)
*Not necessarily clinically significant

Question 17

Acoustic Reflex Threshold

Answer 17

Lowest possible intensity required to elicit ME muscle contraction of stapedius muscle
(Will temp ^ impedance)
Stimulating one ear (ear under test) will travel up brainstem to elicit BOTH reflexes

Question 18

AR Thresholds help determine cochlear or retrocochlear pathology.
If cochlear loss

Answer 18

Cochlear: AR should be increased but present
Retrocochlear: No AR

Question 19

AR Elicited in Normal Ears At:

Answer 19

Pure tones of 500, 1000, 2000 Hz

~ 65-95 dB