Maico MI 24, MI 24h Operating Instructions Manual

MI 24, MI 24h

Operating Instructions

MAICO Diagnostics | 10393 West 70th Street | Eden Prairie, MN 55344, USA | Toll Free 888.941.4201

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Operating Instructions MI 24, MI 24h

Table of Contents Page

1. Introduction 1

2. Description 2

3. Getting started 4

4. How to create a tympanogram 12

5. How to create a tympanogram with high probe tone (MI 24h) 17

6. How to measure the Stapedius reflex 18

7. Interpreting test results 23

8. How to test children 26

9. Additional Reading 27

10. Individual setup of the MI 24 28

11. Care and maintenance of the instrument 33

12. How to change the printer paper 34

13. Warranty, maintenance and after-sales service 35

14. Safety regulations 38

15. Subjective checklist 39

16. Technical data 40

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Operating Instructions MI 24, MI 24h

1 Introduction

Thank you very much for purchasing a quality product from the family. This
automatic Tympanometer MI 24 is manufactured to meet all quality and safety
requirements.

This user manual should make it as easy as possible for you to become familiar

with the functions of the MI 24. The description of the position (e.g., ) of

controls, displays and connections, found again in the text, will make it easier
for you to learn how to operate the MI 24.

If you have problems or have ideas for further improvements, please get in
touch with us. Simply call.

Your MAICO team

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hearing
nerve

ear canal

middle
ear
bones

ear drum

middle ear

eustachian tube

cochlea

musculus
stapedius

Figure 1

The middle ear

Operating Instructions MI 24, MI 24h

2 Description

The MI 24 is an automatic instrument that is designed for tympanometric screening.
Tests done in the tympanometric screening mode measure middle ear mobility and
ipsilateral acoustic reflex. Contralateral acoustic reflex is available as an option. Test
results are displayed on the front panel LCD (liquid crystal display) screen and may be
printed.

The design of the MI 24 allows rapid and reliable measurements. This equipment is
designed for middle ear function screening.

PC-Interface:

A USB interface for data transfer to a connected computer is built in.

2.1 Tympanometry

Tympanometry is the objective
measurement of middle ear
mobility (compliance) and pressure
within the middle ear system.
During the test, a low-pitched
probe tone (226 Hz) is presented to
the ear canal by means of the
hand-held probe. This tone is used
to measure the change in
compliance in the middle ear
system while the air pressure is
varied automatically from a positive
value (+200 daPa) to a negative
value (-400 daPa max.).

Maximum compliance of the middle ear system occurs when the pressure in the
middle ear cavity is equal to the pressure in the external auditory canal. This is the
highest peak of the curve as it is recorded on the chart. The position of the peak on
the horizontal axis and on the vertical axis of the chart will provide diagnostic
information regarding the function of the middle ear system. Examples of normal and
abnormal tympanograms can be found in a later section of this manual.

Gradient calculations are reported as the tympanogram width at half of peak
compliance expressed in daPa. A “limits” box is available on both the display and
printout to aid in diagnosis.

Compliance is measured with respect to an equivalent volume of air, with the
scientific quantity milliliter (ml). Air pressure is measured in deca-Pascals (daPa).

Operating Instructions MI 24, MI 24h

3

NOTE: 1.02 mm H2O = 1.0 daPa.

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Operating Instructions MI 24, MI 24h

2.2 Acoustic Reflex

An acoustic reflex, or contraction of the Stapedial muscle, occurs under normal
conditions when a sufficiently intense sound is presented to the auditory pathway.
This contraction of the muscle causes a stiffening of the ossicular chain which
changes the compliance of the middle ear system. As in tympanometry, a probe tone
is used to measure this change in compliance.

When the stimulus presentation and measurement are made in the same ear by
means of the probe, this acoustical reflex is referred to as an ipsilateral acoustic
reflex. When the stimulus presentation and measurement are made in opposite ears,
the reflex is referred to as a contralateral acoustic reflex.

For best results, this reflex measurement is automatically conducted at the air
pressure value where the compliance peak occurred during the tympanometric test.
Stimulus tones of varying intensities at 500, 1000, 2000 or 4000 Hz are presented as
short bursts. If a change in compliance greater than 0.05 ml is detected, a reflex is
considered present. Because this is an extremely small compliance change, any
movement of the probe during the test may produce an artifact (false response). The
test result is recorded as Pass/No Response, and in graphical form.

If the tympanometric results display any abnormal findings, the results of the acoustic
reflex testing may be inconclusive and should be interpreted with care. Theoretically,
a compliance peak is necessary to observe a reflex at peak pressure.

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Operating Instructions MI 24, MI 24h

3 Getting started

Your MI 24 was carefully inspected and packed for shipping. However, it is good
practice to thoroughly inspect the outside of the shipping container for signs of
damage. If any damage is noted, please notify the carrier immediately.

3.1 Unpacking

Remove the accessories. Carefully remove the instrument from the shipping carton.
Remove the instrument from the plastic bag and inspect the case for any damage.
Notify the carrier immediately if any mechanical damage is noted. This will assure that
a proper claim is made. Save all packing material so the claim adjuster can inspect it

as well. When the adjuster has completed the inspection, notify the MAICO Special

Instrument Distributor you purchased this unit from.

Save all the original packing material and the shipping container so the
instrument can be properly packaged if it needs to be returned for service or
calibration.

3.1.1 Accessories Supplied

Please check that all accessories listed below are received in good condition. If any

accessories are missing or damaged, immediately notify your MAICO Special

Instrument Distributor.

Description Part No.
Hand-held probe 570G-14
24-count eartips kit: 6613
(4) yellow, 7 mm 6643

(4) green, 9 mm 6644
(4) white, 11 mm 6645
(4) yellow, 13 mm 6646
(4) green, 15 mm 6647
(4) blue, 18 mm 6648

Thermal printer paper 5529
Calibration test cavity 5533

Operating Instructions 1162-0321

Optional Accessories:

Soft-sided carrying case 1035-3002
Contra button phone and cable 4796

Contra TDH 39 phone and cable 4682

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Operating Instructions MI 24, MI 24h

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Figure 2

The probe of the MI 24

C

B

A

Operating Instructions MI 24, MI 24h

3.2 Environmental conditions for the MI 24

The MI 24 should be operated in a quiet room.

The test room must be at normal temperature, usually 15° C / 59° F to 35° C / 95° F,
and the instrument should be switched on about 10 minutes before the first
measurement to guarantee precise measuring results. If the device has been cooled
down (e.g. during transport), please wait until it has warmed up to room
temperature

3.3 Preparing the MI 24 for use

3.3.1 Connect probe and accessories

- Connect the probe cable to socket on the rear of
the instrument.

- Insert the plug into the socket and secure the
connection by fastening the two screws of the
connector.

- Insert the pressure tube into the socket  and press
it until it is secure on the socket.

- Put the enclosed power cable into the power
connection socket and then plug it into a power
outlet. The instrument is now operational.

Operating Instructions MI 24, MI 24h

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Figure 3

The controls of the MI 24

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3.4 Getting familiar with the MI 24

3.4.1 The MI 24 Front Panel Controls

See the following keys:

1. PRINT = Printout

2. L/R = Switch over left/right ear

3. REFLEX = Reflex measure off/ipsi/contra

4. MENU

5. LEFT = Left (cursor control)

6. DOWN = Down (cursor control)

7. RIGHT = Right (cursor control)

8. UP = Up (cursor control)

9. ENTER = Enter

10. POWER = Power switch

How to use the extended functions is described in chapter 9: “Individual Setup of the MI

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Operating Instructions MI 24, MI 24h

24."

Operating Instructions MI 24, MI 24h

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10

B

E

C A D

Figure 4

Connectors on the rear of the MI 24

3.4.2 The MI 24 Rear Panel Connections

A. Power connection socket
B. Probe tube connection
C. Probe connection socket
D. PC interface
E. Contra receiver socket

3.4.3 Switch the instrument on

Turn the power switch on. The LCD will show the type of instrument and
software version for a moment. Then the basic measuring figure appears.

The MI 24 should be switched on about 10 minutes before the first measurement to
guarantee precise measuring results. If the device has been cooled down (e.g. during
transport), please wait until it has warmed up to room temperature.

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Status

READY

Ear Volume

Compliance

Pressure

Gradient

Impedance IpsiRight

ml

3

2

1

0

-600 -300 300 daPa

1

80

500 Hz I

4

80

4000 Hz I

3

80

2000 Hz I

2

80

1000 Hz I

AUTO dB

Figure 5

The measurement screen of the MI 24

Operating Instructions MI 24, MI 24h

3.4.4 The display of the MI 24

The test result is shown during the measurement on the LCD. The measurements are
saved automatically and can be printed out in a fast and quiet way with the
integrated printer.

In figure 5 the initial empty
measurement screen is shown.
The measurement screen shows
actual settings, test results and
the graphical display of the
tympanogram and reflexes.

From left to right the top line
shows the type of test
(impedance is shown in Figure 5)
the selected test ear (left or right)
and the selected reflex test (

contra
tympanogram

(optional) or

if no reflex test is

selected).

ipsi

,

At the left center, the graph of
the tympanogram is shown. At the right, five boxes show the status and test values.

The upper box shows the actual status of the instrument:

READY - means that the instrument is ready for testing
IN EAR - shows that the probe is inserted in the ear
TESTING - means that the test is in progress
BLOCKED - means that probe is blocked in the ear
LEAKING - indicates that the ear tip does not have a proper seal

The boxes below Status show the volume of the ear canal, the compliance, the
pressure at maximum compliance and the gradient of the tympanogram when the
test has been completed.

The four boxes at the bottom of the screen, marked 1 to 4, show the graphical reflex
curves after the test. Below each box the test level (Figure 5: 80 dB), and the test
frequencies (Figure 5: 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz) are displayed. After
the frequency an “I” shows that ipsilateral testing is selected.

Finally, at the very bottom in (Figure 5) the word Auto and 80 dB scale is shown. This
means that the reflex test level will increase automatically until a reflex is found or the
maximum level is reached. With the arrow keys, the test levels can be changed to a
fixed level. The dB values below the boxes change accordingly. It is possible to have
fixed levels from 70 dB to 100 dB or Auto.

Operating Instructions MI 24, MI 24h

12

Main Menu
Tympanometry :

Calibration :
Setup :

Change item
ENTER Select item

Figure 6

The MI 24 main menu

Figure 7

The calibration screen

Calibration

Place the probe in the .5 ml cavity.

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S

3.5 Calibrate the probe

Adjust the impedance measuring instrument
every day to the actual atmospheric
pressure by means of the enclosed
calibration volume. The calibration is very
easy and takes only 20 seconds.

Press the menu key and the main menu
(Figure 6) appears on the LCD. Select the
menu option Calibration with the arrow
keys and press Enter.Follow the instructions
on the LCD as shown in figure 7.

Put the probe tip without ear tip into
the hole of the test cavity labeled 0.5 ml.
The text on the display will request that the
probe tip be inserted for the 2 ml
calibration. Put the probe tip in the 2 ml
cavity. Do this again for the 5 ml volume.
The MI 24 will automatically change into
the tympanometry mode. The basic menu
for the impedance measurement appears
again and you are ready for measurements.

If the error information Cavity Calibration
Out of Range appears during the
calibration, please check if the opening of
the probe tip is clean and try to recalibrate
the probe. If the error information appears
again, the probe or the instrument are
probably in need of service. Inform your
Maico Special Instrument Distributor to get
immediate help.

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T P M

O

Q

R

B D

C

E G

M O

N R SEQEPEL

Figure 8

The probe of the MI 24

D

C E G

T

N R SEPEL

Operating Instructions MI 24, MI 24h

3.6 Getting familiar with the probe

The probe of the MI 24 is shown in figure 8. The probe head is adjustable to three
angles (0°, 60° and 80°). It is adjusted by turning the locking screw at the bottom
of the probe using a coin or a screw driver.

Adjust the probe head by pulling it into the required position until it rests. After
it is set to the required position tighten the fixation screw again.

The probe button can be
used to select the required
test ear.

The color of the control
light changes accordingly to
red (right ear) or blue (left
ear).

The color of the control light
on the probe indicates your
current operation.

A red control light indicates
that the right ear is selected.
The system is ready for
measurements. As soon as
you have put the probe into
the auditory canal the control light turns green. Now the test is in progress. Do not
change the position of the probe until the green control light goes out indicating the
end of the measurement.

A blue control light indicates that the left ear is selected. The system is ready for
measurements. As soon as you have put the probe into the auditory canal the control
light turns green. Now the test is in progress. Do not change the position of the
probe until the green control light goes out indicating the end of the measurement.

A yellow control light indicates an error. The kind of the error is indicated on the LCD
under status:

LEAKING: The ear tip is not sealed in the auditory canal. Change the position of the

probe until the control light turns green. If you are not successful use a
bigger ear tip.

BLOCKED: Indicates blockage in the probe opening. Change the position of the

probe so that it points straight into the auditory canal until the control
light turns green. If you are not successful, check that the probe is not
blocked with ear wax.

The complete probe insert can be changed by pressing the release button . and removing the probe insert.

Operating Instructions MI 24, MI 24h

14

min 0 mm
max 1 mm

Figure 9

Proper placement

of ear tip

If the probe tip is clogged, you can remove it by opening the fixation ring . After
cleaning the probe tip or attaching a new one, the tip must be fixed again by
fastening the fixation ring.

3.7 Choose an appropriate ear tip

Choose an ear tip of the appropriate size from the ear tip set. Put the ear tip tightly
on the probe tip. The probe tip should end near the end of the ear tip. It should not
be inserted more than about 1 mm inside the ear tip or just protrude out of the ear
tip (see Figure 9).

By choosing an appropriate ear tip and placing it correctly on the probe you create
the basic conditions for measurements without problems and mistakes.

Now all preparations are concluded and you can start the impedance and reflex
measurement. Please read the following chapters.