Users Manual Part 1

17
Nerve Integrity Monitor
a. Original Rejection Period setting.
b. Stimulus Artifact.
c. Move Rejection Period line to here to avoid artifact.
d. EMG Response.
Understanding and recognizing other artifacts
The NIM Vital system features sophisticated artifact rejection technology designed to provide highly sensitive and accurate
monitoring. However, there may be electrically generated signals in the range of true response that the NIM Vital system cannot
dierentiate. Refer to the “Troubleshooting” topic for more information.
Examples:
• A transcutaneous stimulator used by the anesthesiologist might generate an audible signal.
• Any external nerve locator/stimulator may not provide automatic synchronized muting with the NIM Vital system.
• Electrical leakage from faulty thermal cautery units. You can identify the spurious signals by their lack of surgical context (there
was nothing the surgeon was doing at that moment that could have caused a true EMG response).
• If the recording electrodes and the stimulator (+) or (-) cables become tangled the resulting stimulus artifact might be spuriously
detected as an EMG event. Be careful to route the recording electrodes away from stimulator cables.
• If/when wires must cross, they should cross at right angles. Never run other operating room cords/cables parallel to any of the
NIM Vital system wires.
• The pace pulse generated by pacemakers may be detected and displayed by the NIM Vital system as a rhythmic artifact signal.
This is caused by the electrode ground or stimulus return electrodes being in close proximity to the pacemaker or its lead wire(s).
The artifact caused by the pacemaker may be reduced by repositioning the Electrode Ground and Stimulus Return electrodes to
the top of the patient’s shoulder (the Acromion) (use shoulder opposite operated side). The Electrode Ground (green plug green
wire) and Stimulus Return (red plug white wire) electrodes should be positioned about 5 cm apart, green Proximal, red Distal.
Once the electrodes are repositioned, verify that the Stimulus Return and Ground Impedances are within tolerance (review Setup
Mode/Electrode Check ).
• There may also be interference-generated signals in the range of true response that the NIM Vital system cannot dierentiate. An
example of this type of artifact signal could occur when the surgeon strikes two metal instruments together within the surgical
eld, such as a metal suction tube with a dissecting tool. Such signals are typically monophasic with fast onset and oset. That is,
the signals appear on the screen as sharply peaked responses in one direction only.
• While these artifacts are signicantly dierent in waveform appearance from true EMG events (which have a biphasic waveform),
the magnitudes of these signals can reach several hundred microvolts causing the event tone to sound. However, the surgeon is
usually aware when two instruments have been struck together and can, therefore, relate such “false positive” responses to the
surgical context.
MONITORING tab right panel
STIM 1
The STIM1 panel displays the following settings:
• Stimulation setting (large numbers in mA units)
• Measured value (small numbers)
• Adjustment buttons for the STIM1 current settings.
• You can adjust the current of the stimulator plugged into the STIM 1 port using or , or the knobs located on the side of the
monitor. Refer to the “Stimulation panel” topic for more information.
STIM 2
If the STIM2 panel is inactive, it displays the Activate button. If active as a second stimulator, its display is the same as STIM1.
You can adjust the current of the stimulator plugged into the STIM 2 port using
or , or the knobs located on the side of the
monitor. Refer to the “Stimulation panel” topic for additional information.
Threshold
Use threshold to dene where EMG activity becomes signicant. EMG activity exceeding the threshold is dened as an event and
results in event tones. Any activity below this threshold does not trigger an audible event.
FCC use only, not for Medical use