Maico Ero Scan Pro, Руководство по эксплуатации

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Operating Instructions
4
outside pressure by the ear tip. A manometer and a pump, which can produce both positive and
negative pressure, are connected with tube C. Less sound is reflected to the microphone when the
eardrum is stiff and the eardrum transmits the majority of the sound via the middle ear to the inner ear.
The highest compliance is normally reached with an air pressure corresponding to the outside pressure.
While performing tympanometry measurements,
a continuous change of positive and negative
pressure is produced by the pump of the
instrument in the outer auditory canal. The
compliance is measured simultaneously and
shown in a diagram (the tympanogram) which
illustrates the compliance in ml or mmho over the
pressure in daPa. The area for normal
tympanogram curves is hatched. Here you can
see that the highest compliance is reached with
normal pressure. When you create positive and
negative pressure the eardrum stiffens - the
compliance decreases. So you can draw
conclusions on the condition of the middle ear
from the form and the values of the
tympanogram.
NOTE: 1.02 mm H2O = 1.0 daPa.
1.4 Acoustic Reflex
Acoustic reflex refers to the reflexive contraction of the stapedius muscle in response to sound
stimulation (typically 70-100dB). This contraction causes reduced mobility of the ossicular chain and
reduces the compliance of the tympanic membrane which is measured by the probe as a change in
admittance. The Stapedial (acoustic) reflex is always bilateral in response to loud sound presented to
either ear, and the lowest level that causes a change in admittance is called the reflex threshold.
Typically the average threshold is around 85dB HL with normal limits falling between 70 and 95dB HL.