Heart Rate Variability (HRV) analysis using simultaneous handgrip electrocardiogram and fingertip photoplethysmogram

The integration of sympathetic and parasympathetic activity with afferent signals from the baroreceptors produces beat-to-beat changes in heart rate and heart rate variability (HRV), which reflects autonomic nervous system (ANS) function. Research has indicated that HRV data should be obtained using an electrocardiogram (ECG) signal rather than a photoplethysmogram (PPG) signal. This study presents statistical validation for the interchangeability of two heart rate detection methods for assessing ANS function. Simultaneous ECG and PPG signals were acquired from six healthy volunteers using handgrip Lead II type ECG and fingertip PPG methods while measuring HRV for 5 min. Statistical tests were performed to compare 5-min ECG-PPG data pairs and HRV indices (Ln_VLF, Ln_LF, Ln_HF) after the spectral analysis. In the frequency domain, the concordance correlation coefficient (CCC) was 0.9996, 0.9998, and 0.9863 in Ln_VLF, Ln_LF, and Ln_HF, respectively. In the time domain, the CCC was 0.8741 to 0.9907 for the six data pairs. The correlation coefficient, r, was calculated with a 0.9917 maximum for ECG-PPG pair6 and with a 0.8751 minimum for ECG-PPG pair3. The results suggest that ECG and PPG signal recordings could be interchanged for HRV analysis, including the time and frequency domains.