Information Domain Analysis of Respiratory Sinus Arrhythmia Mechanisms

Abstract

Ventilation related heart rate oscillations -respiratory sinus arrhythmia (RSA) -originate in human from several mechanisms. Two most important of them -the central mechanism (direct communication between respiratory and cardiomotor centers), and the peripheral mechanism (ventilation-associated blood pressure changes transferred to heart rate via baroreflex) have been described in previous studies. The major aim of this study was to compare the importance of these mechanisms in the generation of RSA non-invasively during various states by quantifying the strength of the directed interactions between heart rate, systolic blood pressure and respiratory volume signals. Seventy-eight healthy volunteers (32 male, age range: 16.02-25.77 years, median age: 18.57 years) participated in this study. The strength of mutual interconnections among the spontaneous beat-to-beat oscillations of systolic blood pressure (SBP), R-R interval (RR signal) and respiration (volume changes -RESP signal) was quantified during supine rest, orthostatic challenge (head-up tilt, HUT) and cognitive load (mental arithmetics, MA) using bivariate and trivariate measures of cardio-respiratory information transfer to separate baroreflex and nonbaroreflex (central) mechanisms. Our results indicate that both basic mechanisms take part in RSA generation in the intact cardiorespiratory control of human subjects. During orthostatic and mental challenges baroreflex based peripheral mechanism becomes more important.

Information decomposition in the frequency domain: a new framework to study cardiovascular and cardiorespiratory oscillations

“…The little relevance within the LF band of the measures of multivariate interaction involving the respiratory volume is due to the known fact that the variability of respiration and its effects on the variability of HP and arterial pressure are almost exclusively confined in the HF band of the spectrum [2]. The significant decrease with tilt of the information shared between respiration and HP (measures F [SR];H , F R;H , U R;H ) confirms a number of previous investigations based on entropy analysis [10,11,16,25] that documented a reduction of cardiorespiratory interactions during orthostatic stress. Physiologically, these findings reflect the vagal withdrawal and the dampening of respiratory sinus arrhythmia occurring with tilt [39].…”

“…This section reports the application of the framework for the analysis of multivariate interactions in the frequency domain to an historical database of short-term cardiovascular variability series previously studied in the context of information decomposition [13,16,25,26]. The present analysis is performed on the beat-to-beat time series of HP, SAP and DAP to study cardiovascular interactions, and on the series of HP, systolic pressure and respiration to study cardiorespiratory interactions.…”

“…In particular, two sources are redundant if each carries individually information about the same aspects of the target, while synergy arises from independent mechanisms of interaction between each source and the target. These concepts, implemented in the measures of interaction information [18,21] and partial information decomposition (PID) [22,23], have been successfully used to investigate the mechanisms of cardiovascular and cardiorespiratory interaction in a variety of pathophysiological states [6,11,16,[24][25][26]. A drawback of information dynamic measures is that they are not frequency-specific, meaning that they evaluate the 'overall' interaction among multiple time series without focusing on specific rhythms.…”

Effect of Acute Hypoxia on Cardiorespiratory Coherence in Male Runners

“…However, while moderate hypoxia does not change RSA, hypercapnic stress increases RSA amplitude in line with heart rate (HR) (Tzeng et al, 2007;Brown et al, 2014) and declines with increasing hypoxia in dogs (Yasuma and Hayano, 2000). Other work suggests that orthostatic challenge and cognitive load enhance the role of the baroreflex-mediated cardiorespiratory interaction (Krohova et al, 2018). Since the effect of baroreflex is demonstrated in the low-frequency (LF) band, it seems reasonable to suspect that stress induces a rise in cardiorespiratory coupling in a lower frequency range rather than in the range characterizing vagal tone.…”