Background and objective: According to international standards, autonomic function is assessed by heart rate variability (HRV) calculated from R-R intervals obtained with an electrocardiogram (ECG). However, intra-operative movement artefacts and electrical interference may complicate R-wave detection. Pulse rate variability (PRV) derived from continuous blood pressure measurements may provide a feasible alternative for HRV. We aimed to investigate the level of agreement between PRV and traditional HRV using a novel beat-to-beat non-invasive blood pressure monitoring device.
Methods: In this prospective observational study, R-R intervals and non-invasive blood pressure waveforms were recorded simultaneously from 20 healthy male individuals at rest. HRV and PRV were analysed offline by spectral analysis, which divides the signal into its composing frequencies. Spearman's correlation coefficient, intra-class correlation coefficients and Bland-Altman analysis were used to study the level of agreement between HRV and PRV.
Results: The correlation coefficient between HRV and PRV was 0.99 (P < 0.001). Level of agreement was excellent with a mean difference of 1% in the very low frequency and low-frequency band and 14% in the high-frequency band. Reliability of both HRV and PRV was moderate to high.
Conclusion: Our data show that PRV derived from non-invasive blood pressure waveforms corresponds well with traditional HRV derived from ECG. These results indicate that under standard conditions, blood pressure waveforms may replace HRV in healthy individuals and that the use of PRV in the peri-operative setting should be further evaluated.