Welch Allyn TM 262 Auto Tymp - User Manual - Manual (Page 49)

Revised 4/11/08 3-15
Operation
Tympanometry/Reflex Test Sequence
a. Tympanometry only mode
1. Select the Tymp only mode by pressing Tymp on the front panel. The display will
immediately show the format for the tympanogram along with the summary information
headers ECV, cm
3 , daPa, and GR. The default scale for compliance is 1.5 cm 3 . If a
compliance peak greater than 1.5 cm 3 is measured, the instrument automatically scales the
compliance axis to 3.0 cm 3 so that more of the tympanogram data can be seen.
2. Determine which ear is to be tested and select the appropriate ear (R or L) button so that
the test results will be labeled properly.
3. Examine the ear canal of the ear to be tested to determine the appropriate size eartip for the
test and position the eartip on the probe. Be certain that the eartip is pushed as far down
the probe tip as possible so that the eartip is flush with the tip of the probe. Position
yourself so that you are at eye level with the test ear.
4. Note that the green lamp is blinking, which indicates that the instrument is ready to begin
the test.
5. Place the probe up against the entrance of the ear Canal so that its opening is completely
covered with the eartip and no visible leaks are apparent.
6. The test sequence begins once the instrument determines that a volume between 0.2 cm 3
and 6.0 cm 3 is present. This is indicated by the green lamp changing from blinking to a
steady state. From this point on, hold the probe securely in this same position without any
hand motion. Keep your eyes on the probe and the individual’s ear.
At the start of the test, the pressure system establishes a pressure of +200 daPa within the
ear canal. When this pressure is achieved, the instrument makes a measurement of ear
canal volume. This information is valuable since it indicates whether a good seal has been
established and since it helps differentiate between two similar Tympanogram (i.e., a
fluid-filled middle-ear system and a perforated tympanic membrane). After the ear canal
volume (ECV) is obtained, this compliance value is subtracted from the remaining
compliance measurements so that a direct reading of the tympanogram compliance peak is
possible.
The pressure sweep begins at the starting pressure of +200 daPa and proceeds in the
negative direction at a rate of 600 daPa/second. Measurements of compliance are made
continuously as the pressure sweep continues in the negative direction. The slope of the
tympanogram increases as the measurement approaches the compliance peak. This signals
the instrument to slow down the rate of pressure sweep to 200 daPa/second to ensure a
more accurate reading of the compliance peak. After the peak compliance and pressure
values are detected and stored, the tympanogram dips downward toward the baseline (i.e.,
0 cm
3 ) and the pressure sweep rate increases back to 600 daPa/second. The tymp sweep
ends automatically when the compliance value returns to baseline and the pressure is at
least -100 daPa. Only when the middle-ear pressure is very negative is it necessary for the
pressure sweep to continue all the way down to -400 daPa. This automatic stop when the
tymp compliance returns to baseline eliminates unnecessary pressurization of the ear and
shortens the test time.