Interacoustics AT235 Installation manual

D-0105061-D – 2017/05
Additional Information
AT235
Impedance Audiometer

Table of contents
1AT235 Tympanometry Module ........................................................................................................ 1
1.1 About the AT235 Tympanometry Module........................................................................... 1
1.2 Preparing for the Test......................................................................................................... 1
1.2.1 Tympanometry patient instruction.......................................................................... 1
1.2.2 Visual inspection of the ear canal.......................................................................... 1
1.2.1 Placement of the contralateral phones .................................................................. 2
2General Operation of the AT235 Tympano-metry Module.............................................................. 3
2.1 Tympanometry.................................................................................................................... 3
2.2 Reflex.................................................................................................................................. 5
2.3 Reflex Decay....................................................................................................................... 7
2.4 Reflex Latency.................................................................................................................... 8
2.5 Eustachian Tube Function – Non-perforated Eardrum....................................................... 9
2.6 Eustachian Tube Function – Perforated Eardrum ............................................................ 11
2.7 Eustachian Tube Function – Patulous Eustachian Tube.................................................. 12
3The Setup Menu ............................................................................................................................ 13
3.1 Common settings – IMP.................................................................................................... 13
3.2 Protocol Settings............................................................................................................... 14
3.2.1 Tymp settings....................................................................................................... 15
3.2.2 Reflex settings...................................................................................................... 17
3.2.3 Reflex decay ........................................................................................................ 20
3.2.4 Reflex latency....................................................................................................... 22
3.3 Eustachian Tube Function – Non-Perforated Eardrum .................................................... 24
3.4 Eustachian Tube Function – Perforated Eardrum ............................................................ 26
3.5 Eustachian Tube Function – Patulous Eustachian Tube.................................................. 27
3.6 Pause................................................................................................................................ 28
3.7 Manage Protocol Settings................................................................................................. 29
3.8 Instrument Settings........................................................................................................... 30
4AT235 Audiometry Module............................................................................................................ 33
4.1 About the AT235 Audiometry Module............................................................................... 33
5General Operation of the AT235 Tympano-metry Module............................................................ 35
5.1 Tone Test.......................................................................................................................... 35
5.2 Auto Test: Hughson-Westlake.......................................................................................... 36
6The Setup Menu ............................................................................................................................ 37
6.1 Common Settings - AUD................................................................................................... 37
6.2Tone Settings.................................................................................................................... 38
6.3 Auto Settings..................................................................................................................... 39
7Quick Guides ................................................................................................................................. 41
7.1 Selecting the Correct Ear Tip............................................................................................ 41

AT235 Additional Information Page 1
1AT235 Tympanometry Module
1.1 About the AT235 Tympanometry Module
The AT235, including Tympanometry Module, is an electro-acoustic test instrument that produces controlled
levels of test tones and signals intended for diagnostic hearing evaluations and assessment of possible
otologic disorders. It features tympanometry and acoustic reflex functions. It also measures various acoustic
properties of the ear, including complex acoustic impedance and admittance, and equivalent ear canal
volume. These measures enable evaluation of the functional condition of the middle and outer ear.
The target population for the AT235, including Tympanometry Module includes all ages.
The AT235 including Tympanometry Module is designed to be used only by skilled personnel such as
audiologists, ENT surgeons, doctors, hearing healthcare professionals or personnel with a similar level of
training and expertise. The device should not be used without the necessary knowledge and training in its
use and in how to interpret results.
The Tympanometry Module contains the following tests:
•Tympanometry 226, 678, 800 and 1000Hz
•Ipsilateral reflexes
•Contralateral reflexes
•Reflex decay
•Reflex latency
•Eustachian tube function – non-perforated
•Eustachian tube function – perforated
•Eustachian tube function – patulous
Availability of these tests or specific settings within these tests on the hardware or in the software will vary
depending on the license purchased.
1.2 Preparing for the Test
1.2.1 Tympanometry patient instruction
Place the patient on a comfortable chair or, if necessary, on an examination table. Younger children may feel
more comfortable sitting on a parent's or nurse's lap. Show the probe to the patient and then explain the
following:
•The aim of the test is to assess the mobility of the eardrum
•The tip of the probe will be inserted into the ear canal and has to make a perfect seal
•A small amount of air will flow through the probe to move the eardrum; it produces a sensation
similar to pressing a finger slightly into the ear canal
•One or more tones will be heard during the test
•No active participation is expected from the patient
•Coughing, talking and swallowing will disturb test results
1.2.2 Visual inspection of the ear canal
Check the external ear canal for wax with an otoscope and remove any excessive wax to prevent the probe
opening from clogging, as this would inhibit testing. Excessive hairs may have to be cut.

AT235 Additional Information Page 2
1.2.1 Placement of the contralateral phones
If the contra headphone is used, place the headband over the patient's head. The audiometric headphone is
placed over the non-test ear (or contralateral reflex ear).
If the insert phone is used, mount the proper foam tip on the end of the tubing before inserting into the non-
test ear.
.

AT235 Additional Information Page 3
2General Operation of the AT235 Tympano-
metry Module
2.1 Tympanometry
The default display of tympanometry tests shows graphs for both left and right ear. The following information
is found in the display:
A
The label above the graphs indicates which probe tone frequency was used while measuring the
recording that is plotted.
B
The normative box which shows where the peak of the audiogram is expected in normal middle ear
functioning. The size of the normative box can be customized in the protocol setup. Be aware that
the placement of the normative box is dependent on the ear canal volume. This means that when
the curves are shown in non-compensated view, the box will only be placed correctly after the ear
canal volume is determined.
C
The tympanometry curve(s). The numerical values of the curve should be read from the left Y-axis.
For tympanometry performed at 226 Hz the scaling is in ml. For all other probe frequencies, the unit
at the Y-axis is mmho.
D
The equivalent ear canal volume. In automated tympanometry, the acoustic admittance (Y) at the
start pressure is taken as the reference value. In manually performed tympanometry, it takes the
acoustic admittance at the highest recorded pressure as a reference. Be aware that at probe
frequencies other than 226 Hz, the equivalent ear canal volume is read from right Y.
E
The table with measurement values. Here you will find:
•Volume, the equivalent ear canal volume
•Compliance, the peak compensated static acoustic admittance. When the tympanogram is
shown compensated for the ear canal volume, it is the compliance value at the peak.
•Pressure, the tympanic peak pressure which is at the point of the curve where the highest
compliance value is detected
•Gradient,If it is chosen to show gradient as pressure, it gives the tympanogram width at
half the height of the peak compensated static acoustic admittance. If it is chosen to show
gradient as compliance, it gives the average of the two compensated admittance values
which are 50 daPa away from the peak pressure.
If the automated measurement for some reason does not reach the end pressure as set in the
protocol setup, the table will only show the equivalent ear canal volume.

AT235 Additional Information Page 4
Manual Tympanometry Testing
F
The dot represents the measurement of the (non-compensated) acoustic admittance. It is only
shown when not recording. During recording the display will always be non-compensated.
G
The empty triangle indicates actual pressure.
H
The full triangle is the pressure cursor showing the current target pressure. It is moved by turning the
wheel.

AT235 Additional Information Page 5
2.2 Reflex
Note that in case your protocol has no reflex test included, you can temporarily include a reflex test in your
protocol by pressing the I Reflex C button.
The default displays of reflex tests show a matrix of reflexes, which are measured in the order of appearance
on the screen. The following information is found in the display:
A
The reflex matrix shows graphs of equal stimulus types in the rows and equal stimulus levels in the
columns. Note that scroll bars appear when more stimuli are available than can fit on the screen.
B
Within the graph, the x-axis is the time scale on which the black bar indicates when the stimulus
was given.
C
A green square indicates that the reflex threshold is set (either automatically or manually)at the
chosen stimulus level.
D
The Deflection value is shown when this option is activated through the protocol settings.
E
A grey square indicates a stimulus level that is not available for that particular stimulus type.
F
The square outlined in black indicates which section of the matrix has been selected or is currently
being measured.
Note that the reflexes are indicated by the probe ear. This is shown as an example below.
In the first setup, the probe is placed on the right ear and the contra headphone is placed on the left ear.

AT235 Additional Information Page 6
In the second setup, the probe is placed in the left ear with the contra headphone placed on the right ear.

AT235 Additional Information Page 7
2.3 Reflex Decay
Note that in case your protocol has no reflex decay test included, you can temporarily include a reflex decay
test in your protocol by holding the Shift button while pressing the I Reflex C button. Pressing this
combination also allows including and excluding a reflex decay test from running automatically.
The decay test will be automatically performed with an activator intensity of 10 dB above the reflex threshold.
The test will show a pop-up and ask for the intensity of the activator in case:
•the reflex threshold cannot be found within the same protocol
•the required intensity is at or above the warning level as determined in the protocol settings
•the required intensity is above the maximum level that the transducer will permit allows playing for
this particular activator
The default display of the reflex decay tests shows the graphs of the decay measurements from the selected
ear. The following information is found in the display:
A
The tympanometric curve.
B
Within the graph, the x-axis is the time scale on which the black bar indicates when the stimulus was
given.
C
The table with measurement values which are only calculated if the measurement can be completed.
•Level, stimulus level
•Pressure, the pressure at which the decay reflex is measured. Usually the decay test will be
set up to use the peak pressure of a preceding tympanogram.
•Stimulus, stimulus frequency
•Decay Value, the percentage difference of the two reflex deflection values taken half a
second after the stimulus started and half a second before the stimulus stopped. If decay is
present, the percentage shows as a negative number. When the calculation results in
numbers larger than 125 % or smaller than -115 % the outcome is invalid and will not be
shown.

AT235 Additional Information Page 8
2.4 Reflex Latency
The reflex latency test will be automatically performed with an activator intensity of 10dB above the reflex
threshold. The test will show a pop up and ask for the intensity of the activator in case:
•the reflex threshold cannot be found within the same protocol
•the required intensity is at or above the warning level as determined in the protocol settings
•the required intensity is above the maximum intensity that the transducer will permit for this
particular activator
The default display of the reflex latency test shows the graphs of the latency measurements from the
selected ear. The following information is found in the display:
A
The first 300ms of the tympanometric curve.
B
The table with measurement values which are only calculated if the measurement can be
completed.
•Level, stimulus level
•Pressure, the pressure at which the decay reflex is measured. Usually the decay test will
be set up to use the peak pressure of a preceding tympanogram.
•Stimulus, stimulus frequency
•Latency Value, the time interval between onset of the stimulus and the point where 10% of
the reflex deflection value is reached. The reflex deflection value is measured as the
average of the deflection between 250 and 300ms after stimulus onset.

AT235 Additional Information Page 9
2.5 Eustachian Tube Function – Non-perforated Eardrum
The display of the Eustachian tube function test for the non-perforated eardrum shows graphs for the
selected ear in which the three tympanograms of the adapted Williams procedure are plotted. The Williams
procedure keeps the pressure between the first and second tympanogram at stop pressure, and between the
second and third tympanogram at the start pressure. In between all tympanograms, the original Williams
procedure involves asking the patient to swallow. In order to achieve a larger displacement in the
tympanograms, we advise asking the patient to perform a Valsalva maneuver after the first tympanogram,
then swallowing after the second tympanogram.
The following information is available during testing:

AT235 Additional Information Page 10
A
The non-compensated tympanometric curves.
B
The equivalent ear canal volume where the acoustic admittance (Y) at the starting pressure of the
first tympanogram is taken as the reference value.
C
The table shows the pressure values at which the three peaks are detected (or the highest
equivalent volume if there is no peak).
An instruction is displayed between the three tympanograms to tell you how to direct the patient. To
continue, either press Continue or Enter.

AT235 Additional Information Page 11
2.6 Eustachian Tube Function – Perforated Eardrum
The default display of the Eustachian tube function test for a perforated eardrum shows a graph for the
selected ear. The following information is available during testing:
A
The pressure curve showing that the pressure drops each time the patient swallows. Notice that an
exponential release of pressure means that the probe sealing might not be sufficient.
Before the measurement starts, an instruction is displayed to tell you how to direct the patient. To
continue, press either Continue or Enter.

AT235 Additional Information Page 12
2.7 Eustachian Tube Function – Patulous Eustachian Tube
The Patulous Eustachian Tube test is an impedance baseline test. It monitors changes in impedance over
time without applying pressure changes or acoustic stimuli. When a patulous Eustachian tube is present you
would typically expect to identify the breathing of the patient in the tympanometric curve. If the Eustachian
tube is closed and the tympanic membrane is intact, you would expect to measure small tympanometry
changes which can be caused by acoustical disturbances from around the patient, accidental displacements
of the probe, or by spontaneous movements of the eardrum. Additionally, it is possible to measure
movements due to the heart beat in, for example, a glomus tumor. Or the test can be used to measure
reflexes where the stimulus is presented through an external device such as a cochlear implant.
The default display of the Eustachian tube function test for the patulous Eustachian tube shows the graph for
the selected ear. Below is a real example of a measurement in which the breathing rhythm of the patient can
be recognized due to the presence of a patulous Eustachian tube.

AT235 Additional Information Page 13
3The Setup Menu
When holding the Setup button, a menu pops up from which you can select one of the options by rotating
the wheel and releasing the Setup button. By default, Protocol settings is selected in which you can
temporarily or permanently change the settings used during testing. Here you can also create new protocols.
In Instrument settings you can modify the license code, printer selection, time and date settings and the
brightness of the display.
In Common settings – IMP you can modify common functionalities for all impedance tests.
The Instrument protocol settings hold the default settings for when tests are added to a protocol. This is
also where you can, or example, define which reflex stimuli are used by default when adding contra reflexes
to a protocol that does not currently include contra reflexes.
In Manage protocols you can show/hide and delete protocols and set the region for factory protocols.
3.1 Common settings – IMP
For common setting imp you can toggle between Auto start (default) and Manual start. Enabling Manual
start forces the system to start each protocol paused. When Manual Start is enabled the light indicator on
the device will be flashing to indicate that the measure is paused. The measure is started by pressing Enter
or by pressing the button on the probe/shoulder box.

AT235 Additional Information Page 14
3.2 Protocol Settings
Press the Setup button to enter protocol settings.
Note that the protocol settings of a test can only be changed while there is no data stored for that test. In
instances where data is present at the top of the screen, it will say “Data is present, press ‘New session’ to
allow changing settings.
The following buttons are available while in protocol settings.
Note that all changes to the settings are stored immediately. Pressing Exit will
therefore result in the settings being temporarily in use. After saving or clearing a
session by the New session button, the original protocol settings are restored.
Press Save or SaveAs to permanently save protocol settings. Factory protocols
can be temporarily saved (by pressing Exitt) or saved with a new protocol name
by pressing SaveAs. To save customized protocols under a new name, hold the
Shift button and then press SaveAs.
Moves one test up in the current protocol
Pressing shift in addition will move the selected test upwards in the protocol.
Moves one test down in the current protocol
Pressing shift in addition will move the selected test downwards in the protocol.
Use the wheel while holding the Add button to select which test is added at the
bottom of the current protocol.
Note that each added test comes with the default settings as defined in the
Instrument protocol settings.
Pressing Remove deletes the current selected test from the protocol, without
warning.
Use the wheel to browse through the different settings in the menu and press
Toggle to change check boxes, or hold Change and rotate the wheel for
changing settings with more than two options. Touching the Enter button will also
toggle between check boxes or browse through setting options.

AT235 Additional Information Page 15
3.2.1 Tymp settings
Select a tymp test in your Protocol settings. By rotating the wheel, the following settings can be selected and
changed.
A
Auto run. Once enabled for a test auto run will cause this test to be automatically run as part of
the protocol.
B
Probe tone frequency. The frequencies which can be selected are 226 Hz (recommended for
normal testing), 678 Hz, 800 Hz, 1000 Hz (usually recommended for testing babies up to 6 months
old).
C
Start pressure. The start pressure for automated tympanometry is selected here. The start
pressure can vary between +400 and -600 daPa. For calculating the equivalent ear canal volume,
the measurement points at starting value are taken.
D
Stop pressure. The stop pressure for automated tympanometry is selected here. The stop
pressure can vary between +400 and -600 daPa.
E
Add reversed sweep. When the checkbox is marked, the automated tympanometry will add a
sweep from the stop pressure back to the start pressure.
F
Pump speed. The pump speed for automated tympanometry is selected here. The stated pump
speeds are dependent on the size of the ear canal or the cavity being used during the
measurement. The numbers below are therefore rough estimates.
•Automatic, is the high pump speed which automatically slows down to low pump speed
around the peak of the tympanogram. We recommend using this setting for screening and
normal tympanometry tests.
•Fast, which results in a constant speed of about 300 daPa/s

AT235 Additional Information Page 16
•Medium, which results in a constant speed of about 200 daPa/s
•Slow, which results in a constant speed of about 100 daPa/s
•Very slow, which results in a constant speed of about 50 daPa/s
G
Manual mode minimum pressure allows you to set the lower limit of the pressure range during
manual tympanometry.
H
Manual mode maximum pressure allows you to set the upper limit of the pressure range during
manual tympanometry.
I
Gradient. Gradient as either a measure of compliance (in ml) or as a measure of pressure (in
daPa). Select to display the gradient.
J
Show normative box can be selected to show a rectangle in which the compliance peak is that
expected under normal conditions of the middle ear.
K -
N
Normative box minimum and maximum pressure and compliance values are defined here.