Estimation of Delay Times in Coupling Between Autonomic Regulatory Loops of Human Heart Rate and Blood Flow Using Phase Dynamics Analysis

Abstract

Objective: We assessed the delay times in the interaction between the autonomic regulatory loop of Heart Rate Variability (HRV) and autonomic regulatory loop of photoplethysmographic waveform variability (PPGV), showing low-frequency oscillations. Material and Methods: In eight healthy subjects aged 25–30 years (3 male, 5 female), we studied at rest (in a supine position) the simultaneously recorded two-hour signals of RR intervals (RRIs) chain and finger photoplethysmogram (PPG). To extract the low-frequency components of RRIs and PPG signal, associated with the low-frequency oscillations in HRV and PPGV with a frequency of about 0.1 Hz, we filtered RRIs and PPG with a bandpass 0.05-0.15 Hz filter. We used a method for the detection of coupling between oscillatory systems, based on the construction of predictive models of instantaneous phase dynamics, for the estimation of delay times in the interaction between the studied regulatory loops. Results: Averaged value of delay time in coupling from the regulatory loop of HRV to the loop of PPGV was 0.9±0.4 seconds (mean ± standard error of the means) and averaged value of delay time in coupling from PPGV to HRV was 4.1±1.1 seconds. Conclusion: Analysis of two-hour experimental time series of healthy subjects revealed the presence of delay times in the interaction between regulatory loops of HRV and PPGV. Estimated delay time in coupling regulatory loops from HRV to PPGV was about one second or even less, while the delay time in coupling from PPGV to HRV was about several seconds. The difference in delay times is explained by the fact that PPGV to HRV response is mediated through the autonomic nervous system (baroreflex), while the HRV to PPGV response is mediated mechanically via cardiac output.

Low-frequency variability in photoplethysmographic waveform and heart rate during on-pump cardiac surgery with or without cardioplegia

“…The obtained results agree with a conclusion that coupling from the heart to the peripheral vessels has a hemodynamic nature and the coupling from the vessels to the heart is carried out through the neural pathways 23 . In particular, for three out of five subjects, a significant impact of LF fluctuations in PPG on LF fluctuations in HR was detected.…”

Gender-related specificities of photoplethysmogram spectral assessment dynamics in healthy subjects during the passive tilt test

“…The study of interactions among various oscillatory processes in the human cardiovascular system has been attracting an attention of scientists for many years [1,2]. The study of the principles of regulatory processes interaction, manifested in the form of distal vascular bed oscillations, is of great fundamental and applied importance, allowing to indirectly evaluate the autonomic nervous system functioning.…”