Datex-Ohmeda S-5 Service Manual M-NMT

Datex-Ohmeda

S/5TM NeuroMuscular Transmission Module, M-NMT (Rev. 02)

Technical Reference Manual Slot

Datex-Ohmeda Inc.
3030 Ohmeda Drive
53707-7550 MADISON, WIS

USA
Tel. [phone], Fax [phone]

www.us.datex-ohmeda.com

All specifications are subject to change without notice.

Document No. 800 1018-1

June 2001

Datex-Ohmeda Division,

Instrumentarium Corp.

P.O. Box 900, FIN-00031

DATEX-OHMEDA, FINLAND

Tel. [phone] Fax [phone]

www.datex-ohmeda.com

 Instrumentarium Corp. All rights reserved.

Table of contents

TABLE OF CONTENTS

NeuroMuscular Transmission Module, M-NMT

TABLE OF CONTENTS i

TABLE OF FIGURES ii

Introduction 1

1 Specifications 2

1.1 General specifications ..............................................................................................................................2

1.2 Technical specifications............................................................................................................................2

1.2.1 NMT.................................................................................................................................................2

1.2.2 Stimulator........................................................................................................................................2

1.2.3 Regional block mode........................................................................................................................2

2 Functional description 3

2.1 Measurement principle .............................................................................................................................3

2.1.1 Nerve stimulation.............................................................................................................................3

2.1.2 Response.........................................................................................................................................4

2.1.3 Regional block .................................................................................................................................4

2.2 Main components.....................................................................................................................................4

2.2.1 NMT board.......................................................................................................................................4

2.3 Connectors and signals.............................................................................................................................6

2.3.1 Module bus connector......................................................................................................................6

2.3.2 Front panel connector.......................................................................................................................7

3 Service procedures 8

3.1 General service information.......................................................................................................................8

3.2 Service check ...........................................................................................................................................9

3.2.1 Recommended tools ........................................................................................................................9

3.3 Disassembly and reassembly..................................................................................................................13

4 Troubleshooting 14

4.1 Troubleshooting chart .............................................................................................................................14

4.2 Troubleshooting flowchart .......................................................................................................................15

5Service Menu 16

5.1 NMT menu..............................................................................................................................................17

6 Spare parts 19

6.1 Spare part list.........................................................................................................................................19

6.1.1 NMT Module, M-NMT rev. 00...........................................................................................................19

6.1.2 NMT Module, M-NMT rev. 01...........................................................................................................19

6.1.3 NMT Module, M-NMT rev. 02...........................................................................................................19

6.1.4 Front panel stickers for AS/3 modules (square buttons) ...................................................................20

6.1.5 Front panel stickers for S/5 modules (round buttons).......................................................................20

7 Earlier revisions 21

APPENDIX A 23

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i

Datex-Ohmeda S/5 monitors

Service check form A-1

TABLE OF FIGURES

Figure 1 NeuroMuscular Transmission Module, M-NMT ....................................................................................... 1

Figure 2 Principle of response measurement ......................................................................................................4

Figure 3 Serial communication and opto isolation...............................................................................................5

Figure 4 Stimulator block diagram......................................................................................................................5

Figure 5 Module troubleshooting flowchart .......................................................................................................15

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Document No. 800 1018-1

INTRODUCTION

This section provides information for the maintenance and service of the NeuroMuscular
Transmission Module, M-NMT. The M-NMT module is a single width plug-in module designed for
use with the S/5 Anesthesia and Compact Anesthesia Monitors. The module contains peripheral
nerve stimulation and response measurement which supports electromyography EMG. The module
can also be used as a nerve locator for regional nerve blocking with a regional block cable.
However, in this case there is no response measurement.

NeuroMuscular Transmission Module, M-NMT

Figure 1 NeuroMuscular Transmission Module, M-NMT

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Datex-Ohmeda S/5 monitors

1 SPECIFICATIONS

1.1 General specifications

Module size, W × D × H 37 × 180 × 112 mm / 1.5 × 7.1 × 4.4 in
Module weight 0.37 kg /0.8 lbs
Power consumption 3.3 W

1.2 Technical specifications

1.2.1 NMT

Stimulation modes Train of four (TOF)

Measurement intervals for TOF and DBS

Measurement intervals for ST Manual; 1 s, 10 s, 20 s

Double burst (3.3) (DBS)
Single twitch (ST)
50 Hz tetanus + post tetanic count (PTC)

Manual; 10 s, 12 s, 15 s, 20 s, 1 min, 5 min, 15 min

1.2.2 Stimulator

Stimulus pulse Square wave, constant current
Pulse width 100, 200 or 300 µs
Stimulus current range 10...70 mA with 5 mA steps
Stimulus current accuracy 10 % or ±3 mA whichever is the greater
Max. load 3 kΩ
Max. voltage 300 V

1.2.3 Regional block mode

Stimulation modes Single twitch
Intervals 1 s, 2 s, 3 s
Stimulus pulse Square wave, constant current
Pulse width 40 µs
Stimulus current range 0...5.0 mA with 0.1 mA steps
Stimulus current accuracy 20 % or 0.3 mA whichever is the greater

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2 FUNCTIONAL DESCRIPTION

2.1 Measurement principle

2.1.1 Nerve stimulation

There are three stimulus modes in the NeuroMuscular Transmission Module: Train of Four (TOF),
Double Burst 3,3 (DBS) and Single Twitch (ST).

In the Train of Four stimulus mode, four stimulation pulses are generated at 0.5 second intervals.
The response is measured after each stimulus and the ratio of the fourth and first response of the
TOF sequence is calculated (TOF%).

NOTE: If the first response does not exceed a certain signal level, TOF% is not calculated due to
poor accuracy.

Double burst (3,3) stimulation includes two bursts with a 750 ms interval. Both bursts consist of
three pulses separated by 20 ms intervals. The responses of both bursts are measured, and the
ratio of the second and first response is calculated (DBS%). EMG responses are measured
immediately after the first stimulus pulse of both bursts.

NeuroMuscular Transmission Module, M-NMT

Tetanic/PTC

In Single Twitch stimulation, one stimulation pulse is generated. The response is measured after
the stimulus. In order to prevent decurarization of the stimulated area, the measurement is
automatically stopped after 5 minutes stimulation in 1 sec cycle time.

Tetanic/PTC (Post Tetanic Count) can measure deeper relaxation than TOF. The tetanic stimulation
is produced when Start is chosen under Tetanic/PTC. The length of stimulation is 5 seconds. The
stimulation generates pulses with a frequency of 50 Hz and with a selected pulse width and
current. After tetanic stimulation and a three second delay, Single Twitch stimulation is produced
to detect the post tetanic count (PTC). PTC describes the number of responses detected after
tetanic stimulation. If there is no response, the measurement will be stopped. If responses will not
fade away, a maximum of 20 responses will be calculated. If more can be detected, the PTC value
is displayed only as '> 20' and measurement will be stopped. If the TOF, DBS or ST measurement
cycle was on when tetanic stimulation started, the cycle will continue after the PTC. After
completing the PTC measurement during 1 minute TOF, DBS or another PTC measurement is not
possible. This is to avoid erroneous readings due to post tetanic potentiation.

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A

µ

2.1.2 Response

Before each stimulation, the sequence offset, noise and threshold for the response detection is
measured. Offset is a baseline of the noise measurement. Noise is calculated by the same
algorithm as the response signal itself. The response detection threshold is calculated based on
the noise, and if the response is not greater than the threshold then it is interpreted as no response.

EMG

Mechano

Sensor

Measurement

/D & P

Timing control

EMG leads off

Figure 2 Principle of response measurement

EMG measurement

The EMG response is measured as integrated muscle activity. The EMG measurement starts 3 ms
after the stimulation and lasts 15 ms. The 3 ms delay helps to prevent the effect of stimulation
artifact.

Mechano sensor measurement

Response is measured as movement of the thumb, which is the area of positive signal.

2.1.3 Regional block

A regional block cable can be used as a nerve locator in local anesthesia. A maximum current of

5.0 mA is given every, every other or every 3rd second. The response measurement is ocular.

2.2 Main components

2.2.1 NMT board

The NMT Circuit Board consists of the following functional sections:

• constant current stimulator

• measuring electronics for the EMG signals

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• microprocessor for the stimulation and measuring control, and for counting the measuring

• serial communication

The serial bus speed is 500 kbps and the bus itself is half duplex, i.e. data can be transferred in
both directions but only one way at a time.

Serial communication

NeuroMuscular Transmission Module, M-NMT

results

Stimulator

Figure 3 Serial communication and opto isolation

The constant current stimulator generates pulses whose amplitude is independent of the load. The
main components of the stimulator are a transformer, a capacitor and a transistor. The transformer
produces a high voltage which charges the capacitor and the transistor adjusts the pulse width and
amplitude of the current.

Power supply

Current

80C196KD

PWM

HSO

Patient

Constant current
generator

adjustment

Current
control

Continuous
stimulation
congestion

Figure 4 Stimulator block diagram

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Document No. 800 1018-1