Conditions Which Artificially Flatten the Tympanogram
In order to measure the mechanical properties of the middle ear, a tympano-
metric device must be capable of changing the pressure differential across
the eardrum. Any occlusion of the ear canal, such as impacted cerumen,
foreign body, tumor, stenosis, atresia, or a pocket created by the incorrect
placement of the probe, can prevent this pressure differential from happening
and can artificially flatten the tympanogram.
The result is that the volume of air in front of the probe will be very small.
The MicroTymp2 Handle will display the occurrence of this condition with
the BLOCK message if the volume is less than 0.2 cc. However it is possible
to obtain a flat tympanogram with a smaller than expected ear canal volume
(less than 0.4 cc for children or less than 0.6 cc for adults), as shown in Figure 27.
Figure 27 – Ear Canal Occlusion
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