Cardiorespiratory interactions in humans and animals: rhythms for life

Abstract

The cardiorespiratory system exhibits oscillations from a range of sources. One of the most studied oscillations is heart rate variability, which is thought to be beneficial and can serve as an index of a healthy cardiovascular system. Heart rate variability is dampened in many diseases including depression, autoimmune diseases, hypertension, and heart failure. Thus, understanding the interactions that lead to heart rate variability, and its physiological role, could help with prevention, diagnosis, and treatment of cardiovascular diseases. In this review, we consider three types of cardiorespiratory interactions: respiratory sinus arrhythmia (variability in heart rate at the frequency of breathing), cardioventilatory coupling (synchronization between the heart beat and the onset of inspiration), and respiratory stroke volume synchronization (the constant phase difference between the right and the left stroke volumes over one respiratory cycle). While the exact physiological role of these oscillations continues to be debated, the redundancies in the mechanisms responsible for its generation and its strong evolutionary conservation point to the importance of cardiorespiratory interactions. The putative mechanisms driving cardiorespiratory oscillations as well as the physiological significance of these oscillations will be reviewed. We suggest that cardiorespiratory interactions have the capacity to both dampen the variability in systemic blood flow as well as improve the efficiency of work done by the heart while maintaining physiological levels of arterial CO. Given that reduction in variability is a prognostic indicator of disease, we argue that restoration of this variability via pharmaceutical or device-based approaches may be beneficial in prolonging life.

Enhancing respiratory sinus arrhythmia increases cardiac output in rats with left ventricular dysfunction

“…Instead, Ben-Tal and colleagues proposed that RSA reduced cardiac work while maintaining physiological levels of arterial carbon dioxide (Ben-Tal et al 2014). We suggest that through these mechanisms RSA serves to optimize oxygen delivery to the heart with increasing workload (Elstad et al 2018). In contrast, RSA is lost in cardiovascular and pulmonary diseases (e.g.…”

“…We suggest that through these mechanisms RSA serves to optimize oxygen delivery to the heart with increasing workload (Elstad et al . ). In contrast, RSA is lost in cardiovascular and pulmonary diseases (e.g.…”

“…Certainly, a loss of RSA is a well-described prognostic indicator for cardiovascular disease and sudden cardiac death (Binkley et al 1991;Mortara et al 1994;La Rovere et al 1998). Thus, in heart failure where there is already reduced coronary blood flow and oxygen supply, the absence of RSA may further compromise adequate tissue perfusion enhancing susceptibility to episodes of hypoxia triggered by increased metabolic demand (Elstad et al 2018), thereby promoting cardiac remodelling (Mulder et al 2004). The robust observation of a loss of RSA in cardiorespiratory diseases in addition to the predicted role of RSA in enhancing cardiac work efficiency has led to the specific question of whether there would be any therapeutic gain from its reinstatement in an animal model of heart failure.…”

Influence of inspiratory threshold load on cardiovascular responses to controlled breathing at 0.1 Hz

“…Slow, deep breathing increases the amplitude of blood pressure swings during respiratory cycle. This is largely due to the mechanical effects of respiration on the left and right ventricle stroke volume (Elstad, O'Callaghan, Smith, Ben-Tal, & Ramchandra, 2018). The increase in blood pressure swing leads to increased baroreceptor stimulation, reflected by the increase in RSA, and other HRV indexes (Horsman et al, 2015;Stankovski et al, 2013).…”

The Resting-State Pulse-Respiration Quotient of Humans: Lognormally Distributed and Centered Around a Value of Four

“…Two intrinsic oscillatory processes accompany each moment of a living human being: cardiac activity and respiration. Both oscillations are locally triggered but regulated in a complex way as best represented by a nonlinear dynamical system based on two weakly coupled oscillators that are coupled by several structural and functional types of cardiorespiratory interactions, leading to emergent cardiorespiratory coupling phenomena (Benarroch 2018, Dick et al 2014, Elstad et al 2018, Krause et al 2017, Lotrič and Stefanovska 2000, Moser et al 2008, Schulz et al 2013, Valenza et al 2016. Such a cardiorespiratory coupling phenomenon is that the heart rate (HR) and the respiration rate (RR) have a specific frequency relationship.…”