RR Intervals
From ACLab Wiki
To calculate R-R Intervals post-processing in Acqknowledge or BSL Pro:
- Select the ECG channel.
- Click Transform -> Find Rate.
- Set Function: Interval (sec).
If you select "Put result in a new graph" you will obtain a graph that has beat number on the horizontal axis and R-R interval on the vertical axis. By default the data will be displayed in X/Y mode. You can switch back to Chart Mode by clicking the chart mode button.
There will be one data point per R-R interval. If you want to extract the R-R tachogram as a text file where there is one column of R-R intervals for every beat you can start by removing the time channel. Delete the Time channel by selecting it and going to Edit->Remove Waveform. Now you can save as a text file.
Go to File->Save As
Set Save as type to Text (*.TXT)
Click on the Options button on the right side of the dialogue box
The Include header option will paste information about the recording in the beginning of the text file.
The Selected section only option will allow you to save only the data that is currently highlighted.
The Horizontal scale values option will insert an extra column of data with the horizontal axis (which is usually time).
If you notice in your ECG file that the signal drifts, apply a Band Pass filter at 2-35Hz. The attached file has the result of applying Transform->Digital Filters->FIR->Band Pass with 2-35Hz setting and 500 coefficients.
Finally, your waveform sample rate is 250Hz and the recommended sample rate for ECG for HRV is 1000Hz.
