Can I use the HRV module to calculate the variability in Systolic Blood Pressure?

The HRV module is designed to look at the variation in the R-R interval is a cardiac signal.  The most commonly used signal for this is an ECG due to its sharply defined R-wave.  A finger pulse or Arterial BP trace could be used as an alternative with a few customisations to the settings.  This does therefore mean that the HRV module is NOT suitable for other types of variability such as Systolic or Diastolic pressure.
A workaround for this would be to create a few extra channels of data from the Raw pressure signal and to use the Spectrum View in LabChart to display the Power density of the resulting signal.
The necessary steps are;
  • Measure the BP trace
  • Use the cyclic measurement option in a separate LabChart channel to calculate the changing systolic pressure measurements on a beat-to beat basis.
  • Downsample the calculated measurements to give a smoother trace using the Arithmetic option in another channel
  • Perform a spectral analysis on the resulting channel (highlight the data in the channel and choose spectrum from the window menu. It is wise to click on the settings in the top left of the spectrum view and change from Power attenuation to  Power density as this will give you a more familiar spectral trace).
A file is available here to demonstrate how this can be set up. For more details on applying this to your own data, please contact you nearest ADInstruments Distributor.