ECG and blood pressure signals contain identifiable frequencies that contain physiologic information. Frequency domain techniques are performed on the inter-beat-interval signal, a plot of the R-R intervals (ms) versus time or beat number. It is very important with frequency domain techniques that the data points be equidistant. Therefore, the inter-beat-interval data must be interpolated.
There are typically three main frequency components of HRV. Ranges for each of the frequency components vary based on species being studied.
- Very Low Frequency (VLF)
- Low Frequency (LF)
- High Frequency (HF)
Parameters derived from frequency components*
- Total Power (TP)
- VLF, LF, HF
- Normalized LF and HF (removes VLF component)
- LF/HF ratio
*Custom Frequency Domain analysis can be accomplished by user defined bin criteria