Validity of Venous Waveform Signal for Heart Rate Variability Monitoring

Heart rate variability (HRV) at rest is widely accepted as a non-invasive measure of autonomic nervous system regulation of the heart. A novel technology has been developed by VoluMetrix®that captures venous waveforms via sensors on the volar aspect of the wrist, called NIVAband. In this study, we aim to assess its validity to determine pulse rate variability as a surrogate of HRV. Seven volunteers were recorded while breathing both spontaneously and at a fixed slow pace. Subjects wore a NIVAband and the ECG was recorded simultaneously. Pulses in the NIVA signal were detected using an adaptive threshold on the output of a matched filter. From both beat (ECG) and pulse (NIVA) detections, we derived the power associated to main spectral components of their variability in the low frequency (LF) and high frequency (HF) bands. Good reliability (>0.75) was achieved in average. Mean heart rate and LF power derived from NIVAband and ECG showed no significant differences. HF power, however, was significantly higher in the NIVA measures.