Operating Instructions MI 34 / MI 34 H
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The normal range for compliance is 0.2 ml to approximately 1.8 ml. A
compliance peak within the range indicates normal mobility of the middle
ear system. A peak found outside of these limits may be indicative for one
of several pathologies.
Middle ear pressure should be equivalent to ambient air pressure (0 daPa
on an air pressure scale). Minor shifts of the peak compliance to the
negative may occur with congestion and are rarely to the positive side.
Establish criteria for abnormal negative pressure when you become more
familiar with using the equipment. It is generally accepted that negative
pressure of greater than -150 daPa indicates a referral for medical
evaluation.
9.3 Abnormal Values
It is the purpose of this section to provide samples of tympanograms which
reflect abnormal states of the middle ear mechanism. It is not the intention
of this section to provide you with a complete guide to interpreting results.
Complete information regarding pathologies and abnormal impedance
testing can be found in the literature referenced.
A perforation in the tympanic membrane will cause a high ear canal volume
measurement because the instrument will measure the volume of the entire
middle ear space. The MI 34 may refuse to run the test, with the probe
indicating a volume out of tolerance by illuminating the red light, or a flat
tympanogram will be recorded since no movement will occur with a change
in air pressure. Without a peak compliance of at least 0.1 ml, the reflex test
will not initiate.
An extremely flaccid tympanic membrane or an ossicular chain discontinuity
will yield a very high peak compliance in the presence of normal middle ear
pressure. Ear canal volume will be normal and the reflex will be absent.
A fixation of the ossicular chain, as in otosclerosis, will produce a
tympanogram with very low compliance in the presence of normal middle
ear air pressure. Ear canal volume is normal and the reflex is absent.
Middle ear fluid such as serious otitis media will yield a very flat
tympanogram with no definite peak and negative air pressure. A resolving
case or beginning case may produce a reduced peak in the presence of
