Immittance Measures: Tests of Middle Ear Functions Flashcards Preview

Audiology > Immittance Measures: Tests of Middle Ear Functions > Flashcards

Flashcards in Immittance Measures: Tests of Middle Ear Functions Deck (19):
1

Impedence

Opposition to flow of energy through a system

2

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

Stiff/immobile, otitis media or otosclerosis

3

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

Flaccid, ossicular chain disruption

4

Admittance

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

5

Acoustic immittance sensitive/objective tool to:

-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

6

Immittance Test Battery

Tympanometry
Static Acoustic Immittance
Acoustic Reflex Threshold

7

Tympanometry

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

8

Static Acoustic Immittance

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

9

Equivalent Ear Canal Volume Norms

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

10

Middle Ear Peak Pressure

Normal -150 to +50 daPa

11

Compliance norms

Normal: 0.3-1.6 mL
Stiff: 1.6

12

Type A Tympanogram

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

13

Type As Tympanogram

Spike ~0 mmH20 = normal pressure but shallower
Stiff ME system (ex: stapes immobilization)

14

Type Ad Tympanogram

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

15

Type B Tympanogram

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

16

Type C Tympanogram

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

17

Acoustic Reflex Threshold

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

18

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

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

19

AR Elicited in Normal Ears At:

Pure tones of 500, 1000, 2000 Hz
~ 65-95 dB