Relationship between cardioventilatory coupling and respiratory sinus arrhythmia

Abstract

Recent studies have suggested a role for respiratory sinus arrhythmia in improving pulmonary gas transfer. However, the physiological role of cardioventilatory coupling is unknown. We have tested the hypothesis that cardioventilatory coupling aligns heart beats at positions of the ventilatory cycle where they are maximally affected by respiratory sinus arrhythmia (RSA). In 15 anaesthetized, spontaneously breathing subjects, we recorded continuously the timing of inspiration and the ECG. We then plotted the change in RR interval which occurred, as a result of RSA, after onset of inspiration (RSA plot). By comparing these RSA plots with the distribution of heart beats during the ventilatory cycle, we were able to examine the positioning of heart beats relative to acceleration of heart rate as a result of RSA. In all but two subjects we observed that during periods of strong cardioventilatory coupling, heart beats occurred at positions in the ventilatory cycle where they were maximally affected by RSA. In the presence of strong coupling, the shortest possible RR interval occurred during late inspiration, the longest possible RR interval occurred immediately before the start of inspiration. We suggest that cardioventilatory coupling may have a physiological role in optimizing RSA, perhaps to improve cardiopulmonary performance during sleep.

In vivo cardiac phase response curve elucidates human respiratory heart rate variability

“…It is well known [23][24][25][45][46][47][48]51,52 that the phase of respiration influences the peripheral autonomic nervous system's outflow to the heart. However, till now it has never been shown when exactly this happens inside the cardiac cycle.…”

“…Description of cardiorespiratory interaction in terms of coupling functions yields a new technique for the quantification of respiratory-related HRV. HRV is one of the central tools of psychophysiology and behavioural medicine 44 , and the respiratory component is a significant part of it [23][24][25][45][46][47][48] , representing mainly the vagal or parasympathetic part of the autonomic nervous system influences. Having introduced the time-continuous phase of the ECG, we obtain a continuous description of the HRV via the instantaneous frequency _ j e ðtÞ, instead of the commonly used discontinuous beat-to-beat description.…”

“…Human CRI has been studied for decades [23][24][25][30][31][32][33] . It has gained increased interest due to extensive application of ideas from nonlinear dynamics and information theory to medical problems, for example, to the use of heart rate variability (HRV) as an indicator of autonomic activity.…”

Cardioventilatory Coupling in Resting Human Subjects

“…We have previously demonstrated in anaesthetised subjects that during coupling, R waves are placed at discrete time intervals relative to inspiration to produce distinct clustering of heart beats on the RSA curve (Galletly & Larsen, 1998). In the current study, similar clustering of heart beats within the RSA curve was observed in pattern I and II epochs.…”

Quantification of Cardiorespiratory Interactions Based on Joint Symbolic Dynamics

“…Galletly and Larsen showed that during anesthesia CVC places the heart beats and inspiratory onsets such that they are maximally affected by vagal modulation of RSA implying common physiological roles and significant relationship between CVC and RSA. 18 Although the physiological significance of various aspects of cardiorespiratory interaction are not completely understood, it has been suggested that RSA enhances pulmonary gas exchange and thereby improves the energy efficiency of pulmonary circulation. 21 The quantification of cardiorespiratory interaction appears to have clinical merit for risk stratification of cardiac mortality, 24,32 and diagnosing obstructive sleep apnea.…”