Calibration
If you see flat-line periods as those below, these are calibrations and can’t be used for analysis. It is possible that these fall in a task of interest, e.g. when the participants move their feet or arm, we might lose the signal and the CNAP machine starts to recalibrate to regain the signal. Make sure you inspect your signal carefully before you begin your analysis.
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Automated signal detection
To place markers for systole and diastole on the signal, click Analysis → hemodynamics → ABP classifier
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Use the Zoom tool to zoom in close enough so you can accurately select a systole, then click the “Systole is selected” button:
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Signal inspection
You now have to manually inspect the signal markers from beginning to end. The asterisks on top of the blood pressure peaks are systole markers, the D’s on the lowest dips before each new systole is the diastole marker. You may find individually markers or periods of markers missing as you see below. You may also find duplicates which need to be removed.
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A period of markers missing:
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Manually add placeholder markers where systoles are missing
To add markers, select the flag tool and click above each systole where the marker is missing. Do all systoles at once. We have to place these placeholders roughly on the peaks, and subsequently use their locations to place systole markers at the exact peaks of the signal.
DO NOT add flags for both systoles and diastoles, the software can only change one at a time correctly.
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Place systolic markers
Then go to Analysis → Find cycle
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Under the Cycles/Peaks tab, select “Events”, then “Start event” → “Notes” → “Flag”
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Under “End event”, also select the flag and under both “located on”, select the BP channel 5.
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Go to the selection tab. Since we used eye balling to place the flag markers, we now want to select an area around the flag in which we can tell the software to place the correct markers exactly on the maximum signal of each systole.
We have to provide a range to the left of the flag (“Left edge”) and to the right of the flag (“Right edge”).
The left requires you to add a “-” in the “seconds” box, followed by a number. Try something like -0.2 and under right edge, try 0.2. On the bottom of the window, you will see the selection range appear in blue. Make sure all peaks are included by the selection.
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Go to the Output tab → Events. Check the “Output events” box. Here we tell the software to output new markers (Events) onto our BP signal. Select “Maximum”, i.e. top of the peak (for diastole, we would select “Minimum”). The top dropdown channel is where the software will look for signal peaks. The Output type is “Hemodynamics → Systole”, i.e. we want to output systole markers. The “Output channel” is where the systole markers will be placed. If this seems confusing, you can technically find peaks on the blood pressure channel and output markers onto a different channel. Under “Event 2” on the bottom, select “None”.
Click “Find all cycles” on the bottom.
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The software will ask where you want to start looking for markers. Click “Set to origin”.
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Remove flags
The software now places systoles on the peaks on the peaks around each flag.
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We now have to remove all flags. Right-click on any marker and click “Edit event”. In the new window, check the first two boxes. Select “Flag” under type and select the blood pressure channel. Be careful here, this action cannot be undone. If you have flags saved in other channels, they will be removed if you don’t check the second box. In the “Events” window on the right, click “Clear” towards the bottom.
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In the next box, the warning says “this action cannot be undone”. Click ok. The flags are now removed.
Repeat the Find cycle steps as briefly summarized below.
Manually removing duplicate event place markers
To remove extra systole and diastole events, use the tool by right clicking on the extra event markers. Systole and diastole events should only be at the peak and lowest points of each cycle respectively.
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Click on “Clear Event” to remove the event. You should have to do this twice since the extra events automatically come in pairs. Check to make sure you delete both the systole and diastole events. You can also click on “Edit Event” to see the selected event and the event for all events.
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Manually adding systole or diastole events
To add systolic or diastolic events, use the event marker set to add a hemodynamics “Systole” or “Diastole'' marker. Left click and hold down on the flag icon, then select “Hemodynamics” => “Blood Pressure” => “Systole” or “Diastole”
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Once you have selected what you want to add, simply click on areas where event markers were missed. It is easiest to do all the systole markers first and then all the diastole markers.
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Diastoles
Automated signal detection
Place flags into the dip before each systolic peak, wherever missing.
Analysis → find cycle
Peaks/Events:
Select Event
Start event: Flag; CH5, CNAP Blood Pressure
End event: Flag; CH5, CNAP Blood Pressure
Selection:
Select are around flags where the dips are included
Output:
Output events check
Event 1: Minimum
Input and output channel: CH5 CNAP Blood Pressure
Output type: Hemodynamics → Diastole
Clear flag events
Right-click on any event → edit event → clear → are of type flag → on CH5 CNAP Blood Pressure → ok → cannot be undone ok
Inspect the entire signal again
Check for markers that are
Missing
Duplicates
In the wrong place
Sitting on top of each other: you can toggle through the Event list under right-click → edit event to check for this