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Operating Instructions
5.3 Interpreting the Tympanometric test result
As a general rule, values for ear canal volume should be between 0.2 and 2.0 ml (children and adults).
A variance will be seen within this range depending on the age and ear structure of the person. For
example, a 2.0 ml or larger reading in a small child could indicate a perforation in the tympanic
membrane, while it may be a normal reading in an adult. You will become more familiar with the
normal ranges when you use the instrument.
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 indicate
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.
5.4 Abnormal Tympanometric 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 published audiology literature.
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 EROSCAN Pro may refuse to
run the test, with the instrument indicating a seal problem, or a flat tympanogram will be recorded
since no movement will occur with a change in air pressure.
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