otometrics Madsen ZODIAC 901, Руководство пользователя

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artificially-created pressure differential, and this will be indicated by the
absence of a “staircase”.
Impaired Eustachian
Tube Function Steady pressure, on the other hand, indicates a blockage in the Eusta-
chian Tube. Impaired Eustachian Tube function will be indicated by re-
duced pressure drops.
L/R Shift When starting to test the patient’s other ear, remember to register the
change-over on the ZODIAC 901, otherwise the data for the first ear will
be overwritten. To change to the other ear, press
Alt. Select and then
Softkey 4 .
4.2 REFLEX TESTING
“Reflex testing” in audiology refers to the Stapedius Reflex, a mechanism
which automatically tensions both eardrums after the onset of particularly
loud sounds, in order to prevent overload and possible damage to the hear-
ing mechanism. The ZODIAC 901 allows a very wide range of measure-
ments of patients’ Reflexes to be performed by applying a controlled
acoustic stimulus and measuring the change in acoustic impedance which
will be observed if the ear is healthy.
The change in Compliance which results from the functioning of the re-
flex mechanism is very small, and will be further diminished if the ear-
drum is tensioned by a static pressure differential between the ear canal
and the middle ear. If there is any doubt about whether the Middle-Ear
Pressure is close to atmospheric pressure, this should be checked first of
all by means of a tymp. measurement. The Setup facility for reflex and
threshold testing allows the ZODIAC 901 to set the static pressure in the
ear canal automatically to a level related to a previously measured value
of Middle Ear Pressure.
In automatic reflex testing, the Status lamp on the front panel flashes
green until a compliance is detected, whereupon it lights steady green.
The Stimulus lamp then lights during the application of the stimulus. If
there
is too much noise, the Status lamp lights red and
Operation Manual 39
GN Otometrics MANUAL MODE Chap. 4
ZODIAC 901 Middle-Ear Analyzer
REFLEX TESTING
4.2
Fig.4.13
Eustachian Tube Function,
Perforated Eardrum