Performing Evoked Potentials on the Sierra II
(A) Start the Sierra Program, Login if necessary.
Double click the mouse on the Sierra Icon to start the program. If necessary,
select the appropriate login name.
(B) Enter a New Patient or select an existing patient.
To enter a New Patient press the F1-New Patient key. The patient information
window will be displayed. Use Knob 1 to move through the displayed fields and
use Knob 2 to switch between the three available tabs in this window. The
Lastname, Firstname and ID# are required before you can begin testing. Click
on the Start Test button when finished. You can re-display and edit/add to this
information at any time during the testing process, simply press the Patient key
on the base unit.
To select a Patient that has already been entered into the Quickmed system, press
the F2-Select Patient key. A list of available patient names will be displayed.
Use Knob 1 or the mouse to select the appropriate patient name.
(C) Select the Evoked Potential Test from the Test Protocols Menu.
If you selected the Start Test button from the patient information window the Test
Protocols menu is automatically displayed. Use Knob 1 or the mouse to select
the Evoked Potential test.
If the Test Protocols menu is not displayed, press the ALL key on the custom
base or use the mouse to click on the Test Protocols menu at the top of the
screen.
(D) Configuring the Recording and Stimulating Parameters.
Most of the recording and stimulating parameters are located on special toolbars
which are located at the top of the screen. These toolbars contain fields or buttons for
Amplifier, Stimulus and Averager settings.
Amplifier Settings
All channels that are turned On are displayed as a white line across the grid area.
The current display gain (uV/div) for each of these channels is displayed in the
toolbar at the top of the screen. If a channel is turned Off its corresponding
display gain field will be “greyed out” on the toolbar. The Sweep Speed
(msec/div) is also included on this toolbar.
Amplifier toolbar showing each channels Display Gain value, channel 4 is turned Off.
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To select which channels are On or Off, change Filter settings, and the check the
status of the Common Reference Input (4 channel amplifiers only) use Knob 1
or the mouse to click on the Amplifier Settings
button at the top of the
screen. A window titled “EP Secondary” will pop up displaying a row of
settings for each channel. Channels which are turned On will be displayed in
white (channel number button is also pushed in) and channels that are turned Off
are all grey (channel number button is not pushed in). The current display gain,
hicut and locut filter settings, as well as the status of the Common Reference
Input (On or Off) are displayed for each channel. To change the filter settings,
click on the up/down arrows next to the filter you want to change.
EP Secondary Window
The Common Reference input is On for the corresponding channel when the
button is depressed. It is Off for that channel when the Common reference button
is not depressed. In the above example, the Common Reference input is turned
On for channels 1, 2, and 3.
To close the Amplifier Settings window use Knob 1 or the mouse to click a
second time on the Amplifier Settings toolbar button. You can also use the mouse
to click on the “X” in the upper right hand corner of the EP Secondary window.
Stimulus Settings
Every evoked potential protocol has a unique Stimulus toolbar. This toolbar is
usually positioned at the top of the screen just below the Amplifier toolbar. The
first thing you should do on the Stimulus toolbar is to select the SIDE you are
going to stimulate first.
SEP stimulus toolbar:
Side – use to select the side of stimulation. Left, Right or Both.
mA – displays the electrical stimulus intensity in milliamps.
PW – displays the electrical stimulus pulse duration in microseconds.
RR – indicates the stimulus repetition rate in pulses per second.
Stim – this indicator flashes “yellow” while the stimulator is turned On.
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VEP stimulus toolbar:
Side – use to select the side of stimulation. Left, Right or Both.
Vid Chk – use to select the type of visual stimulus. Video Checks, LED,
Goggles, Flash or Ganzfeld.
Full – use to select the visual field when Video Checks is selected for the
stimulus type. Full, Half, Quarter.
CheckSz – use to select the number of checks displayed across a row on the
video monitor. Only available when Video Checks are selected
for the stimulus type. (2, 3, 4, 5, 6, 8, 10, 16, 32, 64, 128)
Target
– when this button is pushed in a visual target is centered on the
video monitor. This control is only available when Video Checks
are selected as the stimulus type.
RR – displays the stimulus repetition rate in stimuli per second.
Stim – this indicator flashes “yellow” while the stimulator is turned On.
ABR stimulus toolbar:
Side – use to select the side of stimulation. Left, Right or Both.
Phones – use to indicate either Phones or Inserts. **When using Inserts the
program will automatically subtract 1.0 ms from the cursor values
to compensate for the stimulus delay induced by the plastic tubes.
Rare – use to select the click stimulus polarity. Rarefaction, Condensation,
or Alternating.
IntenL – set the stimulus intensity for the Left ear. Units are normalized
hearing level, nHL.
IntenR – set the stimulus intensity for the Right ear. Units are normalized
hearing level, nHL.
ThreshL – set the patient’s threshold level for the Left ear.
ThreshR – set the patient’s threshold level for the Right ear.
Mask – set the level of differential masking noise in the contralateral ear.
For example, with a stimulus intensity of 70 and a differential setting
of 30 the masking noise would be 40 dB. 70 – 30 = 40.
Mask On/Off
– when this button is pushed in the masking noise is
turned On.
– when this button is pushed in the Clicks will continue
Clicks On/Off
to be delivered when the averager is stopped. Same function as the
F2 -Stim Avg/ Stim On key. This button goes on and off
automatically during Threshold level adjustment.
Stim - this indicator flashes “yellow” while the stimulator is turned On.
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How to Set Auditory Threshold Levels.
There are two specially designated knobs for setting the threshold levels.
Knob-2 (Lt Thr/Off,On) and Knob-3 (Rt Thr/Off,On). To set the threshold
level follow these steps.
1. Make sure the Masking noise is turned Off.
2. Turn Knob-2 or Knob-3. The threshold level for that ear will turn
“yellow” and the threshold level will increase as the knob is turned.
The clicks are also automatically started in the corresponding ear.
3. Continue to turn the knob until the patient can definitely hear the
clicks.
4. Now, slowly turn the knob in the reverse direction to decrease the
threshold level. Keep decreasing the level until the patient signals that
they can no longer hear or can just barely hear the clicks.
5. Press the knob to stop delivery of the clicks and set the threshold
value for that ear. Repeat these steps for the other ear.
The threshold value is added to the intensity value for output to the
headphones/inserts. For example, if the Left Intensity was set to 70 and
the Left Threshold was determined to be 12. The actual intensity from the
Left headphones/inserts will be 82.
Auditory EP Knobs.
Averager Settings
The Averager toolbar displays the running average count, the shutoff average
count and the artifact rejection status.
BAEP protocol Averager toolbar.
Average Count – to adjust click on the up/down arrows with the mouse or use
Knob-1 to select and modify this field.
Artifact Reject – this parameter is turned On when the Artifact Reject
button is depressed. When it is turned On it will display the percentage of sweeps
that are being “rejected” from the running average. If this parameter indicates
100% all the sweeps are being rejected. (see step #1 of Acquiring the Evoked
Potential on page 9) When this parameter is turned Off, the percentage is not
displayed and the word “Off” is displayed in its place.
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(E) Display Settings
Every EP protocol has controls that can be used to split the screen into right and left
halves and has options for changing the labels displayed on the screen for each
channel. To check these settings, use the mouse to select Test Setup from the Edit
pull-down menu.
Split Screen – the trace area of the display can be divided into left and right
halves. This allows traces from both sides to be organized on the screen in an
easy to manage fashion. Typically, the screen is split Vertically by Side. Traces
acquired for the left side will be placed on the left half of the screen while traces
acquired for the right side will be placed on the right half of the screen.
Split Screen controls.
Trace Labels – there are three fields comprising the trace labels. The factory
default settings put the channel # in the first field, the trial# in the second field,
and the side of stimulation in the third field. You can change the order and type
of information contained in these fields by clicking the down arrow next to each
of the fields.
Trace Label options.
The preset choices are: Trial#, Channel#, Side, Gain, Sweep, Intensity, Rep Rate,
Time of Day, and CustomCh.
Custom labels – if CustomCh is selected for any of the three fields the
bottom portion of the display will be activated. This area allows the input of
custom trace labels. In the above example, custom trace labels have been
entered for a three channel SEP protocol. When the side of stimulation is
changed the trace labels will automatically be changed as well.
Display mode – sometimes the screen can get very cluttered, especially
when all the traces have their labels turned On. This control provides a way
to select which traces will have their labels activated. The possible choices
for this control are: All Trials, No Trials, First Trial, and Active Only.
Note – the First Trial only selection will label the first trial acquired for each
side.
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(F) AutoCursor Setup
Every EP protocol has an AutoCursor setup table. This table is used to pre-program
the cursors that will be used to mark the peaks and troughs of the collected responses.
To access this setup table, use the mouse to select Test Setup from the Edit pulldown menu. Then, click on the Cursor Table tab.
Cursor Table for a BAEP-Click protocol.
Auto Cursors Section
Name – enter the label for the cursor.
Feature – click on this button to identify the cursor as a Peak or a Trough.
Start Lat. & End Lat. – enter a time window for the cursor. The program
will initially place the cursor on the highest point (peak) or lowest point
(trough) within this time window.
Ch. – this field is only available for SEP protocols. Use it to specify the
channel number for the cursor. For example, if channel #1 will be
recording the cortical response and channel #2 the cervical response, for
an upper SEP, you would specify that the N20 and P22 cursors be placed
on the channel 1 traces, and the N13 cursor be placed on the channel 2
traces.
Latency Section
Name – use the down arrow to select the cursor names for which you want
latency measurements displayed on-screen and in printed reports. Up to 5
latency measurements can be selected.
Norm – enter a normal value for the cursor in this field. This value will be
displayed in the TabData View and on printed reports.
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L-R – use this field to enter a normal value for the Left minus Right latency
difference. This value will be displayed in the TabData View and on
printed reports.
Inter Latency Section
Cursor 1 – use the down arrow to select the first cursor to use for interlatency measurements.
Cursor 2 – use the down arrow to select the second cursor to use for interlatency measurements.
Norm – enter a normal value for the inter-latency in this field. This value will
be displayed in the TabData View and on printed reports.
L-R – use this field to enter a normal value for the Left minus Right interlatency difference. This value will be displayed in the TabData View and
on printed reports.
Amplitude Section
Cursor 1 – use the down arrow to select the first cursor to use for amplitude
measurements.
Cursor 2 – use the down arrow to select the second cursor to use for
amplitude measurements.
Norm – enter a normal value for the amplitude in this field. This value will
be displayed in the TabData View and on printed reports.
L-R – use this field to enter a normal value for the Left minus Right
amplitude difference. This value will be displayed in the TabData View
and on printed reports.
Inter Amplitude – if two amplitude measurements have been specified you
can use this field to calculate the Ratio between the two amplitudes or the
Difference between the two amplitudes.
(G) Apply electrodes to patient and connect to amplifier.
Some example montages:
BAEP-Click: 2 Channel recording
Channel #
Active Input:
Reference Input:
Channel 1
Act 1 = A1 (left earlobe)
Ref 1 = Cz
Channel 2
Act 2 = A2 (right earlobe)
Ref 2 = Cz
Ground on forehead.
Note : With a 2 Channel amplifier a jumper will be needed in order to connect the
Cz electrode to both the Ref 1 and Ref 2 inputs. With a 4 Channel amplifier you
have the option of connecting the Cz electrode to the CREF input, then turn On the
CREF input for both channel 1 and 2.
When the Left ear is stimulated the ipsilateral response will be recorded in channel
1. When the Right ear is stimulated the ipsilateral response will be recorded in
channel 2.
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SEP Upper: 3 Channel recording
Channel #
Active Input:
Reference Input:
Channel 1
Act 1 = C3’ or C4’
Ref 1 = Fz
Channel 2
Act 2 = C7 spine
Ref 2 = Fz
Channel 3
Act 3 = Ipsi Erbs Point
Ref 3 = Fz
Ground on forehead or stimulated limb.
Note: Connect the Fz electrode to the CREF input and turn On the CREF input for
all three channels.
SEP Lower: 3 Channel recording
Channel #
Active Input:
Reference Input:
Channel 1
Act 1 = Cz’
Ref 1 = Fz
Channel 2
Act 2 = T12 spine
Ref 2 = Iliac Crest
Channel 3
Act 3 = Ipsi Pop. Fossa
Ref 3 = Ipsi Medial Knee
Ground on forehead or stimulated limb.
Note: CREF is turned Off when using this montage.
VEP: 1 Channel recording
Channel #
Active Input:
Channel 1
Act 1 = Oz
Ground on forehead.
Reference Input:
Ref 1 = Cz
(H) Check Electrode Impedance (<5.0 is reccommended)
To check the electrode impedances, press the Impedance key. The impedance
window displays two circles for each channel, the top circle is for the active input
and the bottom circle is for the reference input. At the bottom of the impedance
window is a single circle representing the CREF input (operational on 4 Ch. systems
only).
Impedance Window (channels 3 & 4 are turned
Off, the CREF input is turned Off for channels 1
& 2.)
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If a channel is turned Off, there will be no circles displayed for that channel. When
the CREF input is turned On for a channel, that channel’s reference input will not be
displayed and the CREF will be activated.
Impedance Window (the CREF input is turned
On for channels 2, 3, and 4.)
(I) Acquiring the Evoked Potential
1. Start Data Acquisition
Press the Run/Stop key to begin stimulus presentation and data acquisition. If
you are running an SEP test you can also pull back on the black knob on the hand
held electrical stimulator. The average count should start incrementing and the
traces will begin to take shape.
Display Gain - you can adjust the display gain of all channels by turning Knob 4.
To change the gain of a single channel, change the corresponding control in the
amplifier toolbar at the top of the screen (use the mouse or Knob 1 to do this).
Reject % - if the artifact reject is turned On and goes right to 100% then no
averaging will take place. Basically, every sweep is being rejected from the
running average. You need to stop and determine what is causing so much
rejection to take place.
Some possible reasons for high reject percentage include:
- High electrode impedances or bad electrode.
- Patient is not relaxed.
- Common Reference input is not setup correctly. For example, it could be
turned On for a channel when it shouldn’t be.
- Environmental noise. Turn off flourescent lights, turn off other equipment
in the room.
- Stimulator cables wrapped around electrode lead wires or amplifier cable.
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Avgerage/Live – press the F1-Avg/Live key to toggle the display between
viewing the running average traces and the “live” non-averaged traces.
Sometimes the Live view is useful for determining how much noise is present in
the recording. Normally the Live view should be fairly quiet without any large
artifacts or spikes in the traces.
Smooth – you can press the F3-Smooth key during acquisition to remove high
frequency noise from the active traces. To smooth stored traces you must first
press the Position key (see positioning traces, step #7 below).
Store key – pressing the Store key during acquisition will cause the currently
active traces to be stored, the average count will be reset to zero and stimulation
will continue on a new set of traces.
Clear key – you can press the Clear key to reset the average count back to zero
without stopping stimulation.
2. Press the Store key
When the average count is reached, stimulation will stop automatically. Press the
Store key to store the active traces. A copy of the active traces will appear on the
screen and are displayed in a purple color.
3. Clear the Averager
Clear the averager by pressing the Clear key. The active “white” traces will be
reset to flat lines and the average count will be reset to zero.
4. Press the Run/Stop key again.
To collect another set (trial) of traces, press the Run/Stop key. Once the average
count is reached press the Store key to keep the traces.
5. Change the Side of Stimulation.
To acquire traces for the other side, change the Side control on the stimulus
toolbar. If you are using the Split Screen feature the active (white) traces will
automatically move to the appropriate side of the display. If you haven’t done so
already, reset the averager to zero by pressing the Clear key.
Repeat steps 1-4 to acquire traces for this side.
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6. Place AutoCursors
To Place Autocursors - press the Cursors key on the base unit. The function
key and knob labels will change to reflect the cursor mode.
Cursor mode function keys.
Cursor mode knobs.
Use the Trace Sel knob to select the trace (or the Trial Sel knob if performing an
SEP test), the selected trace/trial will be displayed in a yellow color. Now press
the F3-Auto Cursors key. The cursors, which were setup in the Cursor Table
(step F. above), will be displayed on the selected trace/trial. The corresponding
measurements for the cursors are displayed in the table to the right of the traces.
Cursor measurement table, located to the right of the traces.
To Adjust/Move a cursor – while in the Cursor mode use the Cursor Sel/Move
knob. Turn this knob until a circle appears around the cursor you want to move
(see example on next page). Now press the knob to select this cursor, turn the
knob to move the cursor along the trace. To lock the cursor in its new position,
press the knob a second time. Repeat this procedure for any cursors that you
need to move. An alternate method for moving cursors is to click on the cursor
with the mouse and while holding down the left mouse button, drag the cursor to a
new position, then let up on the mouse button.
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Cursor I is selected and can be moved with the Cursor Sel/Move knob.
To Clear Cursors – while in the Cursor mode press the F2-Clear Cursors key
and the cursors will be removed from the selected trace/trial.
When you are finished placing cursors, press the OK key on the base unit to reset
the function key and knob labels back to the normal acquisition mode labels.
7. Positioning Traces, Deleting Traces, and Smoothing stored traces.
To Position traces – press the Position key on the base unit. The function key
and knob labels will change to reflect the position mode.
Position mode function keys.
Position mode knobs.
Use the Select/Move knob and turn to select the trace you want to move, the
selected trace will turn a yellow color. Press the knob and then turn the knob to
position the selected trace. To lock the trace into its new position, press the knob
a second time. Repeat this procedure for any traces that you need to move. An
alternate method for positioning traces is to click on the trace with the mouse and
while holding down the left mouse button, drag the trace to a new position, then
let up on the mouse button.
To Delete traces – while in the Position mode use the Select/Delete knob. Turn
this knob to select the trace you want to delete, press the knob to delete the trace.
***Be careful, this is a permanent action, you cannot undelete a trace.***
To Smooth traces – while in the Position mode use the Select/Move knob to
select the trace/trial you want to smooth. The selected trace/trail will turn a
yellow color. Press the F3-Smooth key to smooth the selected trace/trial. Each
time you press the F3-Smooth key the smoothing filter will be applied. Be careful
not to over-smooth, this is a non-reversible filter.
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When you are finished positioning traces, press the OK key on the base unit to
reset the function key and knob labels back to the normal acquisition mode labels.
8. Changing to another EP test.
To switch from one evoked potential test to another, press the All key and use
Knob 1 to select a new test. Or use the mouse to select a test protocol from the
Test Protocols pull down menu.
When a different test is selected the data for the current test is automatically
added to the TabData View.
9. Printing the Results
Evoked potential tests can be printed individually or as a group.
To Print An Individual EP – from the test protocol screen press the Report 2
key. The Report 2 key is programmed from the factory to automatically generate
a report using a report template called “QuickPrint”. This template includes the
report header, patient information, traces, cursor table, stimulus table, and
comments. Another way to start a report is to select Print Report 2 from the File
pull-down menu. You can also select any report template on the system by
selecting Display Report Menu from the File pull-down menu. For more
information on the Report Generator see the document titled “Report Generation
and the Template Editor”.
To Print all the EP’s as a Group – After all the EP’s have been acquired go to
the TabData View by pressing the F4-TabData key. From the TabData View
press the Report 1 key. The Report 1 key is programmed from the factory to
automatically display the menu of all report templates in the system. Select the
template titled “TabData (with traces)”. The TabData report template includes the
report header, patient information, all EP traces, all EP cursor tables, and
comments. For more information on the Report Generator see the document titled
“Report Generation and the Template Editor”.
10. Close the Patient File.
When all testing and printing is complete close the patient file by selecting
Close from the File pull-down menu.
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(J) Reviewing Stored Evoked Potiential Tests and Reports.
Reviewing Evoked Potential Tests:
To recall a patient record you must either select Review from the File Menu or
you can press the F3-Review key if you are in the initial startup screen. After
selecting Review a menu will pop up displaying a list of patient files. By using
Knob 1 or the mouse you may select the patient to be recalled. Press the knob or
click the left mouse button twice to select the appropriate patient. The patient’s
Tabular Data and Traces are re-displayed. If a particular patient name is not
visible in the Review menu, use the search tools on the left side of the review
screen or scroll down through the list of records using the scroll bar controls.
Reviewing Stored Reports:
From the Review screen change the file type of “Sierra”, on the left side of the
Review screen, to “Report”. A list of stored reports will be displayed. Use
Knob 1 or the mouse to select the report of interest. The stored report will be
displayed. **If the report is not visible within a few seconds place the mouse
anywhere on the screen and click once and the report should appear. You may
now edit or re-print the report.
(K) Changing and Saving Default Test Parameters
After making changes to parameter settings, select Save Parameters from the Test
Protocols pull-down menu to save the current settings as the new defaults for the
protocol.
(L) Creating New Evoked Potential Tests
To create a new evoked potential protocol, follow these steps.
1. Go to an existing EP protocol that is of the same type as the new one you are
about to create. For example, to create a new test protocol for ABR-Screening
you would need to start out in the BAEP-Click protocol.
2. Select Save New from the Test Protocols menu. The “Create New Protocol”
window will be displayed.
Create New Protocol window.
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3. Enter a name for the new protocol. The name must be unique, you cannot have
two test protocols with the same name. Click the OK button.
4. The Sierra will automatically load the new protocol.
5. Change the amplifier, stimulus and averager settings as needed for this protocol.
Also, setup the Auto Cursor table.
6. To save the parameter settings, select Save Parameters from the Test Protocols
menu.
(M) Changing the order of Test Protocols and Deleting Test Protocols.
To Change the Order of the tests, follow these steps.
1. Select System Setup from the Edit pull-down menu. The “System Setup”
window will be displayed.
System Setup window.
2. Click on the Test Menu tab.
3. To move a test, click on the left column to highlight the row.
4. Now, click on the left column again but this time hold down the left mouse
button.
5. While holding down the left mouse button, drag the selected row to its new
position. The red line that appears indicates that the test will be positioned
above this line.
6. Release the left mouse button and the row will be dropped into its new position.
To Delete tests, follow these steps.
1. Select System Setup from the Edit pull-down menu. The “System Setup”
window will be displayed.
2. Click on the Test Menu tab.
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3. To delete a test, click on the left column to highlight the row.
4. Now, click on the Delete button.
Note: the factory default tests cannot be deleted from the test protocols menu,
they can only be moved to new positions. The factory default tests are, EMG,
EMG2, NCV/F/H, RNS, BLINK, BAEP-CLICK, VEP, SEPU, SEPL, SFEMG,
and SSFEMG.
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