Multiple coexisting forms of physiologic coupling
It is a challenge to determine interactions between complex systems where their coupling is not a-priory known, and where the only available information is contained in the output signals of the systems. For integrated physiological systems, such as the cardiac and respiratory system, this problem is further complicated by transient and nonlinear characteristics, and continuous fluctuations in the output signals. Both systems are under neuroautonomic control that regulates their complex dynamics and further influences their coupling through intrinsic feedback mechanisms at different time scales. The nature of cardio-respiratory interaction, its physiological and clinical relevance is not well understood.
Utilizing concepts and methods from nonlinear dynamics and statistical physics, we investigate dynamical aspects of the cardio-respiratory coupling. We focus on whether and how cardio-respiratory interaction changes in response to transitions across physiologic states. We hypothesize that cardio-respiratory interaction is carried not only by one form of coupling but instead is mediated through multiple forms acting at different time scales. Further, we hypothesize that different forms of coupling may simultaneously coexist, representing different aspects of neural regulation. Specifically, we hypothesize that at any given moment the cardiac and respiratory system interact through complementary forms of coupling with intermittent “on” and “off” periods, different strength and different stratification patterns across physiologic states.
We uncover that three distinct forms of coupling mediate cardio-respiratory interaction. In addition to the classic form of cardio-respiratory coupling, Respiratory sinus arrhythmia (RSA), we identified two other forms of nonlinear interaction, Cardio-respiratory phase synchronization (CRPS) and Time-delay stability (TDS). While RSA is a measure of amplitude modulation of the heart rate during the breathing cycle, CRPS and TDS characterize the temporal coordination between the cardiac and respiratory system. Specifically, the CRPS reflects the degree of clustering of heartbeats at specific relative phases within each breathing cycle (despite continuous fluctuations in heart rate and in breathing intervals), and the TDS quantifies the stability of the time-delay with which bursts in the activity in one system are consistently followed by corresponding bursts in the other system.
We find that all three forms of coupling undergo pronounced phase transitions across sleep stages characterized by different stratification patterns, indicating markedly different response to changes in neuroautonomic control. Our analyses show that all three forms of cardio-respiratory interaction are not of constant strength but are of transient and intermittent nature with “on” and “off” periods, and that these forms of coupling, representing different aspects of physiologic regulation, can simultaneously coexist.
Related Publications:
Peer-Reviewed Articles and Conference Proceedings:
Bartsch RP, Liu KKL, Ma QDY, and Ivanov PCh.
Three independent forms of cardio-respiratory coupling: transitions across sleep stages. [ PDF ]
Computing in Cardiology, 2014; 41:781-784
Bartsch RP, Schumann AY, Kantelhardt JW, Penzel T, Ivanov PCh.
Phase transitions in physiologic coupling. [ PDF ]
Proc Natl Acad Sci USA 2012; 109(26): 10181-10186.
Bartsch RP, Schumann AY, Kantelhardt JW, Penzel T, Ivanov, PCh.
Sleep-stage stratification pattern in cardio-respiratory phase synchronization.
Sleep 2012; 35 Supplement S: A52-A52
Bartsch RP, Schumann AY, Kantelhardt JW, Havlin S, and Ivanov PCh.
Sleep stage and age dependence of cardio-respiratory coupling in healthy subjects.
Proceedings of the 24th Annual Meeting of the Associated Professional Sleep Societies (APSS) 2010. Sleep 2010; 33 Supplement S: A16-A16.
Schumann AY, Bartsch RP, Penzel T, Ivanov PCh, Kantelhardt JW.
Aging effects on cardiac and respiratory dynamics in healthy subjects across sleep stages. [ PDF ]
Sleep 2010; 33(7):943-955.
Bartsch RP, Schumann AY, Kantelhardt JW, Havlin S, Ivanov PCh.
Sleep stage and age dependence of cardio-respiratory coupling in healthy subjects.
Sleep 2010; 33:A16-A16 0036 Suppl. S
Penzel T, Schumann AY, Bartsch RP, Ivanov PCh, Kantelhardt JW.
Aging effects in cardio respiratory variability in different sleep stages.
Sleep 2010; 33:A109-A109 0314 Suppl. S
Suki B, Alencar AM, Frey U, Ivanov PCh, Buldyrev SV, Majumdar A, Stanley HE, Dawson CA, Krenz GS, Mishima M.
Fluctuations, noise and scaling in the cardiopulmonary system.
Fluctuation and Noise Letters 2003;3(1):R1-R25.