AmpliVox Otowave 302, Руководство по эксплуатации

Страница: 20 / 64

PRINCIPLES OF OPERATION
15
D-0115696-C (OM038)
– Otowave 302 Operating Manual
3. PRINCIPLES OF OPERATION
3.1. OTOSCOPIC EXAMINATION
A suitably-qualified health care professional should perform a thorough otoscopic examination to establish that
the condition of the ear is suitable for the test options selected and that no contraindications are present. The
latter would include obstruction of the external ear canal due to excessive wax and/or hairs, both of which
would need to be removed. This is required to ensure that the probe tone delivered by the probe are able to
reach the ear drum and are not reflected by cerumen or debris and thereby alter the test result.
3.2. PRINCIPALS OF ADMITTANCE MEASUREMENT
The Otowave 302 measures the admittance of the tympanic membrane and middle ear by playing a continuous
tone into the ear canal at either 226 Hz or 1000 Hz. The level of this tone is calibrated to give 85 dB SPL (226
Hz) or 79 dB SPL (1000 Hz) into a 2 ml cavity. The sound level this produces in the ear canal is measured
using a microphone and the admittance calculated from the result.
In line with normal audiometric practice admittance is displayed as an equivalent volume of air in ml (for 226
Hz) or mmho/mƱ (for 1000 Hz). The residual ear canal volume between the probe and the tympanic membrane
is always displayed in ml; when using a 1000 Hz probe tone the measured value in mmho is converted to ml
using a conversion factor of 226/1000.
3.3. TYMPANOGRAM
Tympanometry is part of the objective impedance test battery and provides information about the middle ear
mobility and pressure in the middle ear system.
To record the tympanogram, the admittance is measured while the air
pressure in the ear canal is varied from +200 daPa to -400 daPa by means
of a small pump. The admittance peaks when the air pressure is the same
on both sides of the tympanic membrane. The change of admittance with
pressure is displayed graphically.