Automated signal detection
Analysis → Locate Human ECG Complex Boundaries
This places markers on the QRS segments. We only really care about the “qrs” markers. They need to sit right on top of the R peaks.
Alternative automated signal detection
Instead of Analysis → Locate Human ECG Complex Boundaries, there are several other ways to get the peak detection.
Analysis → hemodynamics → ECG interval extraction
Analysis → HRV & RSA → this places markers on both respiratory and cardiac signal. However, this is often the least accurate
Inspect the signal for marker issues:
Markers missing
Duplicate markers
Incorrectly placed markers
Markers hiding behind other markers
If QRS markers are placed on the S dip
Biopac has detailed instructions here:
HOW CAN I MOVE QRS PEAK EVENT MARKS FROM THE BOTTOM OF S WAVES TO THE TOP OF R WAVES?
Missing markers
Manually add placeholder markers where systoles are missing
To add markers, select the flag tool and click above each R peak where the qrs marker is missing. Do all qrs markers at once. We have to place these placeholders roughly on the peaks, and subsequently use their locations to place qrs markers at the exact peaks of the signal.
Place qrs markers
Then go to Analysis → Find cycle
Under the Cycles/Peaks tab, select “Events”, then “Start event” → “Notes” → “Flag”
Under “End event”, also select the flag and under both “located on”, select CH9 ECG.
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 R peak.
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.
NEED TO REPLACE THIS IMAGE WITH AN ECG SIGNAL
Go to the Output tab → Events. Check the “Output events” box. Here we tell the software to output new markers (Events) onto our ECG signal. Select “Maximum”, i.e. top of the peak. The top dropdown channel is where the software will look for signal peaks. The Output type is “Hemodynamics → qrs”, i.e. we want to output qrs markers. The “Output channel” is where the qrs markers will be placed. If this seems confusing, you can technically find peaks on the ECG channel and output markers onto a different channel. Under “Event 2” on the bottom, select “None”.
Click “Find all cycles” on the bottom.
The software will ask where you want to start looking for markers. Click “Set to origin”.
Remove flags
The software now places qrs markers on the peaks on the peaks around each flag.
REPLACE IMAGE WITH ECG
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.
REPLACE IMAGE WITH CH9
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.