Dynamic Phase Extraction: Applications in Pulse Rate Variability

• Published in: Applied psychophysiology and biofeedback 2022-09, Vol.47 (3), p.213-222
• Main Authors: Li, Christopher H., Ly, Franklin S., Woodhouse, Kegan, Chen, John, Cheng, Zhuowei, Santander, Tyler, Ashar, Nirmit, Turki, Elyes, Yang, Henry T., Miller, Michael, Petzold, Linda, Hansma, Paul K.
• Format: Article
• Language: English
• Subjects: Arrhythmia; Behavioral Science and Psychology; Fourier transforms; Health Psychology; Psychology; Psychotherapy and Counseling; Public Health; Respiration; Sensors; Ventricle
• ISSN: 1090-0586; 1573-3270
• DOI: 10.1007/s10484-022-09549-z

Pulse rate variability is a physiological parameter that has been extensively studied and correlated with many physical ailments. However, the phase relationship between inter-beat interval, IBI, and breathing has very rarely been studied. Develop a technique by which the phase relationship between IBI and breathing can be accurately and efficiently extracted from photoplethysmography (PPG) data. A program based on Lock-in Amplifier technology was written in Python to implement a novel technique, Dynamic Phase Extraction. It was tested using a breath pacer and a PPG sensor on 6 subjects who followed a breath pacer at varied breathing rates. The data were then analyzed using both traditional methods and the novel technique (Dynamic Phase Extraction) utilizing a breath pacer. Pulse data was extracted using a PPG sensor. Dynamic Phase Extraction (DPE) gave the magnitudes of the variation in IBI associated with breathing ( Δ I B I ) measured with photoplethysmography during paced breathing (with premature ventricular contractions, abnormal arrhythmias, and other artifacts edited out). Δ I B I correlated well with two standard measures of pulse rate variability: the Standard Deviation of the inter-beat interval (SDNN) (ρ = 0.911) and with the integrated value of the Power Spectral Density between 0.04 and 0.15 Hz (Low Frequency Power or LF Power) (ρ = 0.885). These correlations were comparable to the correlation between the SDNN and the LF Power (ρ = 0.877). In addition to the magnitude Δ I B I , Dynamic Phase Extraction also gave the phase between the breath pacer and the changes in the inter-beat interval (IBI) due to respiratory sinus arrythmia (RSA), and correlated well with the phase extracted using a Fourier transform (ρ = 0.857). Dynamic Phase Extraction can extract both the phase between the breath pacer and the changes in IBI due to the respiratory sinus arrhythmia component of pulse rate variability ( Δ I B I ) , but is limited by needing a breath pacer.