Evaluation of Coherence Between ECG and PPG Derived Parameters on Heart Rate Variability and Respiration in Healthy Volunteers With/Without Controlled Breathing

Abstract

Introduction Photoplethysmography (PPG) is used as a surrogate of electrocardiograms (ECG) for heart rate variability (HRV) analysis or respiratory rate monitoring. PPG is a more convenient way to measure HRV than ECG at rest, since respiration could be a confounding factor in HRV evaluation. However, it remains unclear whether or not controlled breathing affects breath-volume and breathing rate when HRV and pulse rate variability (PRV) are measured in different situations. Consciously controlled breathing was performed to alter the autonomic nervous states of subjects caused by respiratory sinus arrhythmia (RSA). The aim of this study was to investigate the coherence between parameters derived from ECG and PPG on healthy subjects with/without controlled breathing. Method With 30 healthy volunteers, we measured their respiratory frequency and recorded their ECG and PPG signals during spontaneous breathing and controlled breathing, including natural paced breathing, rapid and deep breathing, slow and deep breathing, rapid and shallow breathing, and slow and shallow breathing. Results Obvious coherence was observed between pulse rate and heart rate in both spontaneous breathing and controlled breathing tasks. However, a comparison of PRV and HRV indices demonstrated significant differences during controlled breathing. The results based on time domain and nonlinear method analysis showed that the frequency-dependent changes have more of an impact. The results also indicated that breathing corresponded well in ECG-derived parameters comparing with PPG-derived ones. Conclusion We concluded that PPG-based devices cannot be applied as a precision screening tool to detect HRV, particularly during the cardiopulmonary analysis for the controlled breathing maneuver.

A Critical Review of Ultra-Short-Term Heart Rate Variability Norms Research

“…ECG sensors detect the R-spike and PPG sensors identify the peak of the pulse wave to determine when a heartbeat has occurred (Shaffer et al, 2014). The ECG method is more accurate than PPG during paced breathing (Jan et al, 2019) and when increased sympathetic tone results in vasoconstriction in monitored fingers (Giardino et al, 2002;Schafer and Vagedes, 2013). UST measurements are ideal for these ambulatory fitness and wellness applications if investigators can demonstrate their accuracy Credit: Center for Applied Psychophysiology.…”

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“…It has been hypothesized that factors such as stress (Giardino et al, 2002 ), respiratory patterns (Jan et al, 2019 ), exercise (Lin et al, 2014 ), orthostatic changes (Pernice et al, 2018 ), and ambient temperature (Shin, 2016 ) may have different effects on PRV, when compared to HRV, and therefore affecting their relationship. However, the origin of these differences is still not clear, and may be related to changes in hemodynamics, blood pressure or pulse transit time (PTT) (Charlot et al, 2009 ; Gil et al, 2010 ; Chen et al, 2015 ).…”

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“…There is bilateral symmetry in phase delay between homologous recording sites ( Allen, 2019 ). During resting conditions following 1 min of deep breathing, PPG recordings from the ear lobe achieve good agreement with ECG measurements ( Weinschenk et al, 2016 ); however, the PPG method may measure HRV less accurately during slow paced breathing ( Jan et al, 2019 ). In addition, ECG values are more accurate than PPG values when there is marked sympathetic activation – typically occurring in disorders such as anxiety – as peripheral vasoconstriction affects detection of the peak of the blood pressure wave from the digits but not R-spike detection from the chest, torso, or wrists ( Giardino et al, 2002 ; Schafer and Vagedes, 2013 ; Shaffer and Combatalade, 2013 ).…”