Welch Allyn TM 262 Auto Tymp - User Manual - Manual (Page 61)

Revised 4/11/08 4-3
Test Results
Ear Canal Volume
Normal
As a general rule, values for ear canal volume should be between 0.2 and 2.0 cm 3 . However, the
normal values will vary with age and bone structure.
Abnormal
An ear canal value of less than 0.2 cm 3 indicates an abnormal condition. If the probe is partially
plugged with cerumen or if the probe is positioned up against the ear canal wall, a smaller than
expected value will be measured. Also, if an individual has a relatively large bone structure for
his/her age group and a smaller than expected value is measured, the probe could also be
partially occluded or up against the canal wall. It is also possible to collapse the canal if the
probe is held too firmly against it. Examine the Tympanogram and the reflex results to confirm
your suspicions. If they are abnormal as well, it is good practice to repeat the test.
An ear canal volume greater than 2.0 cm 3 also may indicate an abnormal condition. An
important application of the ear canal volume measurement is to determine if there is a
perforation of the tympanic membrane. If there is a perforation due to trauma or due to the
presence of a pressure-equalization (P-E) tube, the measured ear canal volume will be much
larger than normal since the combined volume of the ear canal and the middle-ear space is
being measured.
Compliance Peak
Normal
The range of normals for compliance is 0.2 cm 3 to approximately 1.4 cm 3 . Some groups 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 a “glue-ear”, 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).
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.