Increased cardiorespiratory synchronization evoked by a breath controller based on heartbeat detection

Abstract

Background: The cardiovascular and respiratory systems are functionally related to each other, but the underlying physiologic mechanism of cardiorespiratory coupling (CRC) is unclear. Cardiopulmonary phase synchronization is a form of cardiorespiratory coupling. However, it is difficult to study in experimental data which are very often inherently nonstationary and thus contain only quasiperiodic oscillations. So how to enhance cardiopulmonary synchronization and quantify cardiopulmonary synchronization, the changes in cardiac function under the conditions of cardiopulmonary synchronization, and the physiological mechanisms behind them are the main issues to be discussed in this paper. Results: The results showed that the cardiorespiratory synchronization significantly increased when breathing was controlled by heartbeat detection (p < 0.001). And the respiratory sinus arrhythmia (RSA) obviously decreased (p < 0.01) in the 2/2 mode and increased (p < 0.001) in the 4/4 mode. During the 2/2 breathing pattern compared with spontaneous breathing, systolic blood pressure (SBP) decreased (p < 0.05), and diastolic blood pressure (DBP), mean arterial blood pressure (MBP), and SV decreased significantly (p < 0.01). During the 4/4 breathing pattern compared to 2/2 breathing patterns, DBP, MBP, and cardiac output (CO) increased (p < 0.05), and stroke volume (SV) increased significantly (p < 0.01). When analyzing the relationships among these parameters, the RSA was found to be associated with the respiration rate in all respiratory patterns. Conclusions: We demonstrated that voluntary cardiorespiratory synchronization (VCRS) can effectively enhance cardiopulmonary phase synchronization, but cardiopulmonary phase synchronization and RSA represent different aspects of the cardiorespiratory interaction. It is found that cardiac function parameters such as the blood pressure and output per stroke could be affected by the number of heartbeats contained in the exhalation and inspiratory phase regulated through VCRS. So we can study cardiopulmonary phase synchronization by VCRS. It can be used to study in experimental data for the physiological mechanism of cardiopulmonary coupling.

Resonance frequency is not always stable over time and could be related to the inter-beat interval

“…It is probable that RSA is mainly affected by breath frequency. And it may be possible to control the cardiovascular parameters by controlling respiratory rate and the number of heartbeats contained in the exhalation and inspiratory phase of the respiratory cycle 30 . But we have not analyzed this synchronization in our study, nor can we know if certain synchronization ratios may be influenced by the particular ages and genders of the participants, as noted in other study 31 .…”

Effect of Stress on Cardiorespiratory Synchronization of Ironman Athletes

“…It takes a participant a long time to recover from the physiological stress of completing an Ironman race. Such heavy exertion undoubtedly has a negative effect on the body's immune system with sustained inflammatory response to muscle fatigue, increased risk of respiratory tract infections, weight loss, and other medical conditions (Ren and Zhang, 2019 ). In this study we measured the effect of extreme physical stress on the cardiorespiratory system of athletes, while they performed a cognitive test to prevent them from cognitively controlling their breathing rates.…”

“…We studied the performance of the cardiorespiratory system by investigating the effects of the Ironman competition on cardiorespiratory synchronization. The cardiovascular and respiratory systems are coupled by several mechanisms (Berne et al, 1998 ; Ren and Zhang, 2019 ), where the interactions between these two systems involve a large number of feedback and feed-forward mechanisms. In healthy subjects, the heart rate increases during inspirations and decreases with expiration, which is the well-known, and well-studied phenomena (Anrep et al, 1936 ) respiratory sinus arrhythmia (RSA).…”

“…Earlier studies of cardiorespiratory synchronization support its existence (Pokrovskii et al, 1985 ; Rosenblum et al, 2004 ; Wu and Hu, 2006 ; Bartsch et al, 2007 ; Angelova et al, 2017 ) and as shown in Bartsch et al ( 2012 ) cardiorespiratory synchronization and RSA represent different aspects of the interaction between the cardiac and respiratory systems. Cardiorespiratory synchronizations were shown to exist in humans during rest (Schafer et al, 1998 ; Lotric and Stefanovska, 2000 ; Stefanovska et al, 2001 ; Ren and Zhang, 2019 ), Zen meditation (Cysarz and Bussing, 2005 ), Dharma-Chan meditation (Chang and Lo, 2013 ). Desynchronizations were reported following myocardial infarctions (Leder et al, 2000 ; Hoyer et al, 2002 ), as well as reduced cardiorespiratory coordination with obstructive sleep apnoea (Kabir et al, 2010 ) and acute insomnia (Angelova et al, 2020 ).…”

“…Cognitive stress is known to affect the physiological functioning of the cardiovascular system suppressing heart rate variability (HRV) (Wood et al, 2002 ; Hansen et al, 2003 ; Ren and Zhang, 2019 ). In physiology, HRV is the variation in time interval between heartbeats, measured by the variation in the beat-to-beat interval (Hon and Lee, 1965 ).…”