Does physiological testing require behavioral responses from patients
no
What is acoustic immittance
combination of ease of flow and restriction of flow of energy
All determinations of middle ear function are indirectly made in the plane of the
tympanic membrane
what device is used to obtain acoustic immittance
tympanometer
What are the two main measurements of acoustic immittance
tympanometry and acoustic reflexes
What specifically does tympanometry measure
middle ear pressure, tympanic membrane/middle ear compliance, ear canal volume
What are the three main parts of the tympanometer
body, probe, insert earbud
Explain the tympanometers body
a monitor that shows value and tracing (compliance on y-axis and pressure on x-axis)
Explain the tympanometers probe
-3 rubber tubes combined together that connected from the body to the probe
-one loud speaker that is emitting 226 Hz tone (1000Hz for infants)
-one microphone to detect how the 226 Hz tone is deflected off tympanic membrane
-a pressure pump to change air pressure within ear canal (positive to negative sweep)
Explain the tympanometers ear insert
emits loud tones used for acoustic reflexes
How does tympanometry measure middle ear pressure
-based on the idea that the TM vibrates most efficiently when the pressure on both sides of the TM are equal.
-pressure in the ear canal is changed from +200 to -200, with atmospheric pressure being 0
-whatever pressure point TM moves the best at is considered to be the same pressure within the middle ear
Explain the results of tympanometry when measuring middle ear pressure
-close to 0 daPa is considered normal
<-150 is considered to be diagnostically significant negative middle ear pressure (could be closed Eustachian tube)
>150 daPa is rarely seen
How does tympanometry measure middle ear compliance
measures how much the TM is moving during point where there is equalized pressure
Explain the results of tympanometry when measuring middle ear compliance
-normal compliance 0.3-2.0
-reduced could be middle ear dysfunction like fluid in ear space, stiff ossicles, a lot of ear wax, scar tissue
-too much compliance could be indication of scar tissue
How does tympanometry measure ear canal volume
measure how much air is required to generate specific pressure changes
Explain the results of tympanometry when measuring ear canal volume
-normal volume values 0.3-2.0
-reduced volume could be too much waxed
-large volume could be TM perforation or PE tubes
Explain tympanograms type A_d
seen in patients with normal pressure and volume, but abnormally HIGH COMPLIANCE
tracing is inverted V with large amplitude of peak.
could be because of broken ossicles, or scar tissues on TM
Explain tympanograms type A:
seen in patients with normal middle ear functions.
normal pressure, compliance, volume
tracing is large inverted V
Explain tympanograms type A_s
seen in patients with normal pressure and volume, but reduced COMPLIANCE
tracing is shallow inverted V.
stiff ossicles or scar tissue on TM
Explain tympanograms type B
normal volume but absent pressure and compliance.
because of high impedance, point of greatest compliance cannot be found so pressure cannot be determined either.
appears as a flat tracing.
seen in patients with middle ear effusion (fluid)
Explain tympanograms type B open
large volume but absent pressure and compliance.
also seen as a flat tracing
either because of TM perforation or PE tubes.
the measurement includes volume of outer and middle ear
Explain tympanograms type C
normal volume and compliance with negative middle ear pressure.
tracing is large inverted V towards the left due to the negative pressure
(closed Eustachian tube)
when do most normal hearing adults demonstrate a bilateral intra-aural muscle reflex when pure tones are introduced
85 to 100 dB SPL
what is acoustic reflex
contraction of the middle ear muscles., this stiffens the ossicular chain which stiffens that TM
