NeuroMetrix ASCEND User manual

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NeuroMetrix
ASCEND
User’s Manual

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Copyright © 2009 NeuroMetrix, Inc. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means,
electronic or mechanical, for any purpose without the express written permission of NeuroMetrix,
Inc.
ASCEND™ and NeuroMetrix® are trademarks of NeuroMetrix, Inc. Waltham, MA 02451 USA
The Bluetooth®word mark and logos are owned by the Bluetooth SIG, Inc. and any use of such
marks by NeuroMetrix, Inc. is under license.
Part Number: PN 2202661 Rev. X16
Protected by US and international patents pending.
CAUTION: Federal law restricts the use of output of ASCEND to a physician
or other properly licensed practitioner.
.

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Table of Contents
Chapter One – Indications for Use, Principles of Operation, ASCEND Description 4
Indications for use 4
Contraindications 4
Nerve Stimulation: Overview 4
Nerve Stimulation: Principles of Operation 5
ASCENDDescription 5
Chapter Two – Preparing ASCEND for Use 8
Overview 8
CradleSetup 8
StimulatorSetup 8
Registration 9
Chapter Three – User Interface and Controls 10
Overview 10
ControlButton 10
Chapter Four – Device Description 14
Overview 14
Connecting Cables 14
PowerOn 14
PowerOff 14
Stimulation Current 14
Stimulation Duration 15
Stimulation Frequency 15
Chapter Five – Device Checks 16
Overview 16
Powerupselftest 16
Stimulation Electrodes Connection Check 16
Check Stimulation High Voltage 16
Stimulation Circuitry check 16
Appendix A – Warranty, Service, Care and Device Registration 17
Cleaning 17
Warranty 17
Device Registration 19
Service 20
Appendix B – Error Messages, Warnings and Cautions 23
Appendix C – Specifications 27
Appendix D – Symbols and Acronyms 29
Appendix E – Accessories 31
Appendix F – Electromagnetic Compatibility Declaration 32

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CHAPTER ONE
Indications for Use, Principle of Operations, ASCEND
Description
This manual is intended for users of the NeuroMetrix ASCEND Peripheral Nerve Stimulator
(“ASCEND”).
Indications For Use
NeuroMetrix ASCEND is a peripheral nerve stimulator used for localization and verification of
needle placement for perineural application of pharmacological agents.
Contraindications
Absolute and relative contraindications for using a peripheral nerve stimulator for percutaneous
nerve localization procedures using insulated hypodermic needles include:
•Refusal of regional anesthesia by the patient
•Infection at the puncture site
•Preoperatively known neurological dysfunctions
•Anatomical abnormalities
•Severe coagulation disorders
•Insufficient liver function
Nerve Stimulation: Overview
Peripheral nerve stimulation (PNS) facilitates the performance of peripheral nerve and plexus
blocks. Using nerve stimulation (NS), the physician does not need to rely on feedback from the
patient about paresthetic sensations. As a result, the danger of mechanical nerve lesions is
significantly diminished. When the stimulation needle is placed sufficiently close to the target
nerve, predefined electrical pulses evoke compound muscle action potentials (CMAP) and
consequent muscle contractions. During this procedure, direct contact of the injection needle with
the nerve is intentionally avoided.
NS is not a substitute for the anatomical knowledge required to perform regional anesthesia.
Therefore an accurate knowledge of the topography and nerve distribution area is essential.
The advantages of NS include:
•Muscle response is obtained without the user having to rely on information or
cooperation from the patient
•Reduction in probability of direct needle-nerve contact, painful paresthesias, mechanical
nerve lesions, and intraneural injections.
Nerve Stimulation: Principle of Operation
The resting potential at the nerve membrane is around 80 mV. The cell’s interior is negatively
charged compared to the surrounding medium. Sufficiently large ion movement reduces the

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membrane potential to about 55 mV, making the membrane freely permeable and generating an
action potential.
The various types of nerve fiber differ with regard to their sensitivity to electrical stimulation.
The Aαmotor fibers have the shortest chronaxia (50–100 μs). The afferent fibers that transmit
pain sensation (Aδand C-fibers) require a longer pulse (150 and/or 400) at a minimum current.
Mixed peripheral nerves can be localized using short pulses (100 μs) without triggering pain
sensations. For pure sensory nerves, a longer pulse is recommended (200 μs, 500 μs or 1000 μs).
When unipolar needles (insulated and with conductive tip) are used, the current necessary to
trigger muscle responses correlates with the distance from the tip of the needle to the nerve. The
lower the current, the more accurately the target nerve can be localized. This allows quicker onset
and ensures a more reliable success of the blockade.
Nevertheless, it is important to observe and stay within the predefined threshold currents so as to
avoid a too close proximity to the nerve and prevent nerve damage. The shorter the electrical
pulse (i.e., stimulus duration), the faster is the rise in current to the nerve. This allows better
discrimination by the physician as to whether the needle tip is sufficiently close to the nerve. The
stimulation needle should always be connected to the negative pole. If the needle is connected to
the positive pole, higher currents are required. The conductive tip of the stimulation needle
affects the geometry of the electrical field. The smaller the emission site of the electrons at the tip
of the needle, the higher is the current density at this point and the lower the threshold level once
the nerve has been localized exactly.

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ASCEND Description
ASCEND is a battery powered nerve stimulator for localization of peripheral nerves. It is
comprised of the following components.
1. Stimulator
The Stimulator includes the electronic circuits that provide
electrical nerve stimulation, user controls which include a
stimulation current magnitude control and function buttons that
control stimulation parameters such as duration and frequency,
and a 320 by 240 color LCD touch screen for user input and
display of the target current, impedance and other important
parameters. The Stimulator includes a permanent 3.7V Li-
Polymer battery. The stimulator has a connector to a needle
and electrode interface cable as well as a micro USB port.
2. Needle and Electrode Interface Cable (“Cable”)
The Cable provides an interface between the Stimulator and the
insulated hypodermic needles and surface electrodes used in
nerve localization procedures. One end of the Cable plugs into
connector on the top of Stimulator. The other end of the
connector ends in yoke with two connectors: one into which a
needle with a pre-attached leads is connected and one into
which a cable terminating in an alligator clip is connected (the
alligator clip is then attached to a disposable surface electrode).
3. Charging Cradle (“Cradle”)
The Cradle is connected to an AC outlet via a medical grade
AC/DC adapter. The Cradle has LEDs that indicate its on/off
status and the charging/charge status of Stimulator (see Chapter
2 for a description of the Cradle LED indicator).
4. USB port
The USB port is for programming and communication.
Stimulation is disabled and cannot be performed when the USB
port is connected
Figure 1
Figure 2
Fi
g
ure 3

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ASCEND may be used with the following accessories.
1. Hypodermic Insulated Needles (“Needles”)
ASCEND is optimized for nerve localization procedures using
disposable hypodermic needle electrodes distributed by
NeuroMetrix. These needles typically serve as the stimulation
cathode.
2. Surface Electrodes (“Electrodes”)
ASCEND utilizes a disposable tab surface electrode as the
stimulation anode. ASCEND can be used with any suitable
disposable surface electrode.
Figure 4

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CHAPTER TWO
Preparing ASCEND for Use
Overview
Prior to use, the ASCEND Stimulator, Cradle, and other packaged components should be
inspected to ensure that they have not been damaged in shipping. If damage is encountered, or if
any component fails to operate as described in this manual, contact NeuroMetrix Customer
Service immediately. Within the USA, customers should contact NeuroMetrix via:
Phone: [phone]
Fax: [phone]
Email: [email protected]
International customers should contact the nearest authorized NeuroMetrix representative. If the
shipping container is damaged, customers should also notify the shipping carrier.
The ASCEND system package should contain the following components:
Installation Card
User’s Manual
Stimulator
Cable
Cradle
Power Supply for Cradle
Operating software is pre-installed in the device before it is shipped from the factory.
Cradle Setup
Before use, visually inspect the Cradle. Make sure that the Cradle’s plastic housing is
undamaged. The Cradle should then be plugged into a power outlet using the medical grade
power supply provided.
Stimulator Setup
Before use, visually inspect the Stimulator. Make sure wire insulation is intact and that the
plastic housing of the device is undamaged. Place the Stimulator in the Cradle to charge its
internal battery. Charge the battery for a minimum of 6 hours. When an incompletely charged
Stimulator is placed in the Cradle, the Stimulator charge status LED will display an amber light; a
green light signifies a fully charged battery.
Once the Stimulator battery is charged, power up the Stimulator by pressing the POWER button.
After the Stimulator powers up, it will conduct a self test. Once completed, the LCD will display
the START screen. If the device fails the self test, the device will disable the stimulator circuit, and
the LCD will display the message STIMULATOR ERROR . If the Stimulator fails to power up when
the power button is pressed, confirm that the battery is fully charged and try again. If the
Stimulator fails to power up again, please contact Customer Service.

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Registration
NeuroMetrix Customer Service will register your system at the time of installation.

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CHAPTER THREE
User Interface and Controls
Overview
This section describes the Stimulator User Interface. Physical buttons are indicated in bold blue.
On screen buttons, which are activated by tapping the touch screen with the stylus, are indicated
in bold green. On screen messages are indicated in orange.
Control Buttons
POWER – powers Stimulator on and off.
FUNCTION – the Stimulator has four context sensitive function buttons along the left side of the
device (Chapter 1, Figure 1). The button’s current function is indicated on the screen to the right
of the button. (Figure 6, red rectangle). The function of these buttons varies depending upon the
Stimulator’s operating mode and can change within an operating mode.
DIAL – regulates the target stimulation current.
RESET – resets Stimulator.
Screens
The Stimulator has one screen from which the operator controls the device. In this screen
the operator controls nerve stimulation.
Figure 6 – Stimulation Control Screen
In the Stimulation Control Screen, (Figure 6), the four function buttons described above have the
following functions. The top button controls stimulation frequency. Values of Single, 1Hz or 2
Hz may be selected. The second button controls stimulus duration. Values of 50, 100, 200, 500,