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Compliance Peak
NORMAL
The range of normals for compliance is 0.2 cm
3
to approximately 1.4 cm
3
. Some protocols use a larger
range up to 1.8 cm
3
. A measured compliance peak within this range indicates normal mobility within
the middle-ear system.
ABNORMAL
A compliance value of less than 0.2 cm
3
indicates a pathological condition as the middle-ear system is
stiffer than normal. To distinguish the probable cause of the stiffening, the pressure value where this
stiffened compliance peak occurs needs to be considered. For example, normal pressure along with a
stiff middle ear system is indicative of otosclerosis, a severely scarred tympanic membrane or a layer
of plaque across the tympanic membrane. On the other hand, abnormal pressure along with a
stiffened middle-ear system is consistent with a poorly functioning eustachian tube with possible
effusion (serous otitis media)
or “glue ear.”
NOTE:
If the measured compliance value is less than 0.1 cm
3
, the letters NP will be printed next to the
heading cm
3
on the screen and printout. The letters NP indicate a poorly defined or flat Tympanogram.
The Tympanogram may depict a very shallow peak.
A compliance value greater than 1.4 cm
3
(or 1.8 cm
3
) indicates a hyperflaccid tympanic membrane or
a possible disarticulation depending upon how far above the normal range the value is. Generally
speaking, a compliance value of greater than 3.0 cm
3
is indicative of a disarticulated ossicular chain.
Further testing is necessary to confirm this suspicion.
NOTE:
If a compliance value is measured to be greater than 1.5 cm
3
, the instrument automatically
changes the range assigned to the graph to 3.0 cm
3
.
The validity of tympanometry and acoustic reflex testing is dependent upon a healthy tympanic
membrane. A pathological condition at this membrane can mask the true condition of the middle ear.