Welch Allyn TM286 Auto Tymp - User Manual - Manual (Page 28)

24 Operation Welch Allyn TM286 Auto Tymp
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 decrease 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 tympanogram 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 to -400 daPa. The automatic stop when the tympanogram
compliance returns to baseline eliminates unnecessary pressurization of the ear and
shortens the test time.
When the tympanogram is completed and the test is finished, the steady green lamp
turns off and the test results are displayed.
The test results are stored automatically in memory. The actual memory location number
is determined by the number of tests that are stored. For example, if this is the first test
to be stored in memory, it will be assigned the number M1. If it is the third test to be
stored in memory, it will be numbered M3, etc.
In addition to the tympanogram tracing, the screen displays the test summary
information. This data includes the ear canal volume (ECV), the compliance peak in cm
3
,
the pressure at the peak of the tympanogram in daPa, and the gradient (GR) as a peak
width value. This test result can be printed out immediately as a single test by selecting
the Print Screen Only
button or other tests can be performed and saved before all
tests in memory are printed via the Print All button.
Tympanometry and Ipsilateral Reflex
The default parameters for this test are tympanometry followed by an ipsilateral acoustic
reflex test at 1000 Hz.
When a seal is obtained, the tympanometry sequence is initiated. (See “Tympanometry
only mode” on page 23 for details). As long as no large leak is encountered during
tympanometry (orange lamp illuminated) and no occlusion is detected (yellow lamp
illuminated), the test automatically transitions to the reflex portion of the test as follows:
1. For 226 Hz probe tones, the pressure from the tympanogram peak compliance is re-
established within the ear canal and is offset by -20 daPa so as to avoid any problems
with extremely sharp tympanogram slopes (+20 daPa for positive peak pressure).
2. With the air pressure held constant throughout the reflex test sequence, the lowest
intensity level for the starting frequency is presented and a measurement of
compliance change is made. If the compliance change of at least 0.05 cm
3
for the 226
Hz probe tone is measured, this reflex intensity level is stored in memory, as a
response.
3. If no other frequencies were selected for the test, the Tymp Reflex sequence ends
here. The green lamp is no longer illuminated indicating that it is appropriate to
remove the probe from the ear. The display will indicate the reflex test result as a Yes,
as an HL value, or as an HL value plus a tracing of the reflex response curve. The
Note If a second tympanogram needs to be performed, remove and reinsert the probe.