Guidance procedures require a quality hypodermic needle electrode and two surface electrodes. The needle electrode plugs into the black connector. One surface electrode is connected to the green connector and is for the ground, and the other connects to the red connector and is for the reference. We would like to present the following guidelines to ensure you have the best possible situation for measuring great EMG signals from the hypodermic needle electrode to support your injection guidance procedures. The hallmark we all need to embrace is that we need “Fresh Surface Electrodes!” “oldies are not goodies”. Avoid using surface electrodes that have been sitting in an open package laying around without any knowledge of when the package was opened. Surface electrodes will keep for a 2-3 weeks once the foil package has been opened. Please don’t use old electrodes, as they will affect the quality of the EMG signal and the ability to deliver stimulation. Let’s address the placement of the surface electrodes to help us collect the best possible signals. Some simple pre-planning will gain best results for the entire procedure if one area is being treated. These simple principles will help you create the best opportunities to collect great signals:

•  No real need to move the reference and ground electrodes if all the injection sites are close by.
•  Most times only the reference electrode needs to be moved if there are bilateral injections.
•  Avoid placing electrodes in areas that will see ultrasound goop! This will avoid short circuits and peeling surface electrodes.

Finer Points

Myoguide’s EMG bandwidth is tuned to record from the highest density of EMG spectral elements.  Myoguide can measure a range of 10-700Hz and the audio section can produce high fidelity sounds that range from 20-700Hz.   This is creates the best possible EMG audio within a the range of the most important EMG spectral elements  needed for aural identification of EMG.  This provides the clinician with EMG audio similar to what is heard on full size EMG systems.   Exclusive feature  “Audio Mute” allows the clinician to easily  silence the EMG audio.  Audio will be returned to the pre-muted level with a touch of any button

Myoguide is equipped with what is essentially a single channel EMG machine with a full featured, built in stimulator.

Myoguide’s stimulator presents 5 stimulation frequency choices, four pulse width choices, and 1- 20 mA of stimulation current available in both  1 mA and 0.1 mA steps.

0.1 mA steps are helpful and necessary for nerve location procedures  allow evoking responses at lower, more comfortable stimulation levels.  This capability is the latest update for Myoguide and available as an upgrade for any Myoguide device currently only capable of 1.0 mA steps. Please contact us for details about our upgrade program.

Pulse widths of up to 500 microseconds allow evoking muscle twitches at lower currents, yielding a more comfortable clinical experience for patients undergoing stimulation location procedures.

Wider stimulation choices allow evoking twitch at lower, more comfortable stimulation levels. 

Exclusive feature, “Stimulation Pause” allows clinicians to easily halt the stimulation process.  This is especially useful when repositioning the injection needle electrode in order to fine tune its location for a more accurate injection point.  Stimulation can easily be returned to the pre-paused current level with the touch of any button.

Feel free to browse our website, or view YouTube videos on the “intronixtech” channel, to see Myoguide in action in both clinical and animated videos.

EMG may, or may not, be present when the hypodermic needle is inserted.  Here are a few  possible scenarios:

1. Needle insertion may result in transient insertional activity, resulting in a transient EMG signal that will disappear. 
2. Needle insertion may result in spontaneous continuous EMG 
3. Needle insertion may result in no spontaneous EMG signals. (If this is the case, confirmation of the muscle target must be confirmed and isolated, by patient initiated movement and/or specific manual manipulation to activate the muscle, using patient engagement and resistance to movement to initiate EMG signals)

Myoguide Power:  Alkaline Versus NiMH Rechargeable Batteries

Even though the NiMH rechargeable batteries have a lower specified capacity (2300mAH) and lower voltage (1.2V) compared to a typical Duracell ProCell Alkaline AA battery (2850mAH, 1.5V), they tend to provide more capacity in a higher current draw situation.

NiMH rechargeable batteries provide a more steady discharge than an alkaline battery.  i.e. Alkaline batteries have a steeper discharge curve as the load current requirements increase.

The downside to using a NiMH rechargeable in the Myoguide is that the battery display icon is calibrated for a 1.5V (Alkaline) battery and hence when using NiMH rechargeables, the battery icon will only display ¾ full when the NiMH are at full charge and will show empty when batteries are 50% discharged.  i.e. The unit will run for quite a considerable time when the battery icon shows empty

Note: Due to the fact that battery discharge is not linear (logrhythmic) and the battery detection circuit is designed to linearly display the current battery voltage, the display is not a truly accurate rendition of the state of charge.  i.e. when the display shows one bar, there still may be considerable battery capacity remaining.  The batteries should be replaced when the display indicates “ Battery Low!”

Battery test comparison

Test 1:

80% EMG mode with 200Hz, 1mVp-p signal in, Vol:4.

20% Stimulation @ 1mA, 500uS pulse width, 1 Hz frequency into a 10 KOhm load

Alkaline batteries (Duracell MN1500): 8 Hr. 20 min.

Alkaline batteries (Duracell ProCell PC1500): 8 Hr. 10 min.

NiMH Rechargeable (Energizer NH15): 14 Hr. 39 min.

Test 2:

Constant Stimulation @ 4mA, 500uS pulse width, 1 Hz frequency into a 10 KOhm load

Alkaline batteries (Duracell MN1500): 3 Hr. 5 min.

Alkaline batteries (Duracell ProCell PC1500): 2 Hr. 15 min

NiMH Rechargeable (Energizer NH15): 4 Hr. 35 min

Test 3:

Constant Stimulation @ 1mA, 500uS pulse width, 1 Hz frequency into a 10 KOhm load

Alkaline batteries (Duracell MN1500): 3 Hr. 33 min

Alkaline batteries (Duracell ProCell PC1500): 3 Hr. 6 min

NiMH Rechargeable (Energizer NH15): 5 Hr. 17 min

Test 4:

80% EMG mode with 200Hz, 1mVp-p signal in, Vol:4.

20% Stimulation @ 4mA, 500uS pulse width, 1 Hz frequency into a 10 KOhm load

Alkaline batteries (Duracell MN1500): 7 Hr. 47 min.

Alkaline batteries (Duracell ProCell PC1500):  7 Hr. 35min.

NiMH Rechargeable (Energizer NH15): 9 Hr. 33 min.

Conclusion:

NiMh rechargeable battery use in the Myoguide unit provides considerably more run time compared to disposable alkaline batteries.  This is especially true when the unit heavily used in Stimulation Mode.

Myoguide Loaner Programs

Ambu USA offers a Myoguide loaner program to customer as part of their ongoing support of their customers. Simply contact your inside sales representative to arrange for a demo unit. These loaner units are available for up to 2 weeks to qualified clinicians. Ambu backs up their commitment by supporting both their own and Allergan’s loaner program, by making sample electrode kits available upon request.
Email: sales@ambuusa.com

Allergan USA offers a Myoguide loaner program to customers as part of its commitment to injection training and support.  Physicians can have an opportunity to demo the Myoguide™ system in their clinic, and use it to practice muscle localization for injection.  Systems are available free of charge for 1 month.  Contact your Allergan Representative about Myoguide™ unit availability.  The Intronix website and iNFOcard  provide comprehensive training resources including how to operate Myoguide, however, we are available at our toll-free number, or by Email, should anyone have any questions about Myoguide operation or best practices.

Benefits to Using the Loaner Program

• Practice using EMG for muscle selection and injection in your own clinic
• Demo an EMG unit without large capital commitment
• Ability to purchase a Myoguide™ system with Allergan preferred pricing

At the end of Allergan’s 30 day period, the Myoguide™ system must be returned to MedForce via a pre-paid FedEx Label which your Allergan Representative will provide during delivery.  Intronix and Ambu USA are providing special purchase pricing for program participants.  Participants can request a sample electrode package from Intronix, which will be provided by Ambu USA, for your convenience, during the loaner period.

For more information, click here to read the brochure (PDF format).

Need more training?  Please contact us for a WebEx based training session to review Myoguide operation and live Q & A.

Hands- On: Learning to Use Myoguide

The following steps can be used to learn and verify functionality of the Myoguide device.

For first time users, it is a good idea to play with Myoguide on your own, before engaging patients.  These exercises will help you learn about measuring EMG and delivering stimulation on your own hand, using surface electrodes.  It’s a simple way to learn to use Myoguide without a patient.

This procedure can also be used when experiencing perceived issues related to excess noise or stimulator performance.  If perceived issues have been eliminated using the following procedure, the functionality of the Myoguide device can be confirmed and sources of perceived issues can be focussed on electrode quality, electrode placement or proper skin preparation.

Myoguide Set-up Procedure

1.0 Application and setup of electrodes

Using the photo as a guide, place electrodes on the thumb. Feel free to use leaded, snap or tab electrodes.  For snap or tab electrodes, you must use the alligator adaptors. 

If using leaded surface electrodes, the surface electrode leads can be plugged directly into the Myoguide Input Cable (Model 8008-CT) with red surface electrode connector plugged into red connector on Myoguide input cable, black surface electrode plugged into black connector on Myoguide input cable and green surface electrode connector plugged into green connector on Myoguide input cable.

Tab or Snap type surface electrodes can alternately be used by using the supplied colour coded Myoguide cable adapters (Model 8008-CA, Model 8008-CA-R and Model 8008-CA-G). Simply connect the cable adapters to the corresponding coloured jacks on the Myoguide Input Cable and clip the alligator connector end to the surface electrode tab or snap.

Leaded electrodes should be as short as possible, to avoid extraneous noise pick up from the unshielded high impedance lines.  This is true for both this learning exercise, as well as clinically.

When long lines are unavoidable in the clinic, you can reduce noise by eliminating noise sources like fluorescent lights.  Noise can also be reduced by twisting the leads, that will wrap the ground wire around the input and reference inputs.  This will act as a makeshift shield.

Please clean the skin area where surface electrodes are to be applied using proper skin preparation techniques and apply the electrodes as shown.

NOTE:  Surface electrodes must be from an un-opened, non-expired package.  As surface electrodes have a shelf life, use of expired or dried out/stale electrodes can cause noise and performance issues which will be seen as excessive noise or failure to display EMG correctly or degraded stimulator performance.

2.0 EMG Mode Verification

Turn on the Myoguide and set the Vol: parameter to 4 (default setting) and the V: parameter to 2.

The volume setting is actual the amplifier’s gain control.  The “V” parameter is simply a visual display control.

Myoguide should now display EMG with minimal display deflection when the thumb is at rest and clean larger EMG deflection when thumb is flexed. If this is observed, the device is functioning correctly in EMG Mode.

3.0 Stimulation Mode Verification

To verify Stimulation Mode functionality, press and hold the Mode button on the device until the Stimulation screen is displayed.  Set F: parameter (Frequency) to 1 Hz and PW: parameter (Pulse Width) to 500uS.  Position the cursor over to the leftmost digit of the mA parameter (adjusts stimulation current by 1mA per step).

Slowly increase the Stimulation current until stimulation is felt in the thumb. Typically, stimulation becomes quite pronounced by 5 or 6 mA.  If Stimulation is felt, the device is functioning correctly in Stimulation Mode.

Please play around with the stimulation pulse widths, and you should notice that wider pulse widths can evoke a twitch at a lower current setting.  This should be more comfortable for you and subsequently for your patients.

If correct functionality is determined using the above procedure, issues related to noise, movement artifact and stimulation performance are most likely related to electrode quality, sub-optimal electrode placement or skin preparation.

Feel free to contact us if there are any questions.  We will be happy to respond and help you with learning to use Myoguide, or solving any performance issues.