week 4 Flashcards
low frequencies encounter high impedance due to
stiffness
high frequencies encounter high impedance due to
mass
why is use of single probe tympanometry not beneficial
it may not be as sensitive to middle ear pathologies
Patient has a build up of fluid in ME causing increasing mass and stiffness. What hearing loss and tymp configuration might we expect
FLAT CONDUCTIVE HEARING LOSS
type b
patient has increase in stiffness in ME due to otosclerosis. What hearing loss and tymp configuration might we expect
low frequency conductive loss
type A, AS or B (in late stages)
what is different in children’s ears to adults that make 226Hz not as sensitive
- bony portion not fully formed, more soft tissue (increasing compliance)
-smaller canals - change in TM orientation (more horizontal when first born)
- tightening of ossicular joints
An infant has a more compliant ear canal. What frequencies are impeded? What hearing loss and tymp configuration might we expect?
- all frequencies (maybe more likely high freq. BC mass dominated)
- flat conductive
Possible A (for adults we expect B but bc less bony can see type A even if fluid)
issues of 226 tympanometry
its hard to tell the difference between 2 very different pathologies causing conductive HL
ex., infant with ME effusion (type A) or Normal hearing vs early otosclerosis (type A)
Multi-frequency tympanometry
used to assess ME disorders by looking at resonant frequencies of middle ear
What is 1B1G
its a tympanogram that is peaked like a normal Type A we expect to see
What is B in a type 1B1G
B refers to suceptance
What is a G in a type 1B1G
G refers to conductance
How do we interpret multi-peak tymps in children
challenging
higher proportion of infants with multiple peaks using 226HZ
why is 1000Hz used
tight variation among children which is helpful when you are trying to indicate deviations, easier to interpret when someone falls outside of the norm
how does area of ear canal change
the relative area increases over time
- length increases (increased bony tissue and becomes more stiff over time)
immitance
impedance+admittance
Admittance
Conductance (Ba) + Susceptance (Ga)
Conductance
frictional commonents in ME
- how much friction is present at these points
- driven by how things are connected ex., ossicles
susceptance
mass and compliance components
impedance
inverse of admittance (1/admittance)
- vector sum of mass compliance and friction elements
- ease at which it can move
multicomponent tympanometry
- simultaneously measure admittance components of susceptance and conductance
- change frequency beyond 226Hz
-look at #of peaks when we tease apart (1B1G) - frequency and pressure specific
resonant frequency
where mass and stiffness are equal
this is where succeptance =0
at 45 degrees what do we see on a BA GA graph
1B1G
what is the name of the model for multicomponent tympanometry
Vanhuyse model
what are we looking for when we use multiple frequencies to assess tymps
changes in the patterns
things to consider with Vanhuyse model
- # of peaks for B should not exceed 5 and G should not exceed 3
- Distance b/w outermost G must not exceed distance between the 8 maxima- G peak should be within b peak in terms of height
- distance b/w outermost maxima must not exceed 75daPA for tymps with 3 peaks and 100dapa for tymps with 5 peaks
what is a system that is more mass dominated
5B3G
-cholesteatoma forming
resonant frequency increases when
stiffness increases
resonant frequency decreases when
mass increases
whats a system thats more stifness dominated
3B1G
otosclerosis
what is an abnormal Vanhuyse
anything bigger than 5B3G
resonant frequency averages for adults vs infants
adults 1000Hz
infants 250Hz
72-84 days 385Hz
objective of MFT or WT
obtain resonance frequencies of middle ear
Multifrequency Tympanometry steps
4 Steps
1. set to +200daPa sweep through frequencies
2. measure tymp at 226HZ obtain TPP
3. Keep pressure at Tympanic peak pressure sweep frequencies
4. conduct several tympanograms around RF (where suceptance crosses 0)
Wideband Tympanometry
1 step
simultaneously records tympanometry across pressure and frequency using broad band stimulus click
wideband energy reflectance
measures ratio of energy reflected back by middle ear system.
advantages of wideband energy reflectance over MFT
- location of probe not crucial
- can test up to 10KHz (compared to 2KHz in MFT)
- greater sensitivity to various pathologies
3D typanometry
absorbance across pressures and frequencies
-as we increase frequencies, peak in middle of graph corresponding to resonant, more accoustical energy around ambient or peak pressure
Benefits of 3D Tymp
faster
higher resolution
wider bandwith
more sensitive to ME pathologies
how does an ear with otosclerosis differ form normal ear with absorbance
stiffness dominated system so more energy in low frequencies reflected back
- less energy absorbed
how does a conductive hearing loss in a child (presence of airbone gap) change their absorbance
- shifts lower (particularly in mid-high frequencies and becomes flat) as most of energy reflected back
- as gap shrinks it trends towards normative
GSI tympstar V2.0
Multicomponent/Multifrequency tymp
titan
wideband tymp, OAE
mimosa
wideband energy reflectance, OAE
GSI tympstar pro
MFT and wideband Tymp
