Role of respiration in the cardiovascular response to orthostatic and mental stress

Abstract

The objective of this study was to determine the response of heart rate and blood pressure variability (respiratory sinus arrhythmia, baroreflex sensitivity) to orthostatic and mental stress, focusing on causality and the mediating effect of respiration. Seventy-seven healthy young volunteers (46 women, 31 men) aged 18.4 ± 2.7 yr underwent an experimental protocol comprising supine rest, 45° head-up tilt, recovery, and a mental arithmetic task. Heart rate variability and blood pressure variability were analyzed in the time and frequency domain and modeled as a multivariate autoregressive process where the respiratory volume signal acted as an external driver. During head-up tilt, tidal volume increased while respiratory rate decreased. During mental stress, breathing rate increased and tidal volume was elevated slightly. Respiratory sinus arrhythmia decreased during both interventions. Baroreflex function was preserved during orthostasis but was decreased during mental stress. While sex differences were not observed during baseline conditions, cardiovascular response to orthostatic stress and respiratory response to mental stress was more prominent in men compared with women. The respiratory response to the mental arithmetic tasks was more prominent in men despite a significantly higher subjectively perceived stress level in women. In conclusion, respiration shows a distinct response to orthostatic versus mental stress, mediating cardiovascular variability; it needs to be considered for correct interpretation of heart rate and blood pressure phenomena.

Slow 0.1 Hz Breathing and Body Posture Induced Perturbations of RRI and Respiratory Signal Complexity and Cardiorespiratory Coupling

“…In order to verify the reproducibility of an autonomic pattern characteristic for supin, stand, supin01, and stand01 we calculated the following linear parameters: absolute values, changes of mean, and standard deviation of RRI. The absolute values and their changes were in accordance with the literature (Javorka et al, 2018;Valente et al, 2018), where supin was characterized by slight parasympathetic dominance (Levy and Martin, 1996), stand by sympathetic dominance ( Table 1, decrease of mean RRI and SD with respect to supin, Table 2, Sobiech et al, 2017), supin01 with maximized parasympathetic dominance (Table 1, increase of SD with respect to supine, Shields, 2009) and stand01 with combined situation of higher sympathetic tone on mean RRI regulation (decrease of mRRI with respect to supin01, Table 1) with variability, most probably parasympathetically mediated, comparable to the supin values ( Table 1, supin-stand01, Table 2, p = 0.831).…”

“…Also, the research on the orthostasis effect on HRV has been well-documented (De Souza et al, 2014;Zaidi and Collins, 2016;Valente et al, 2018) and is routinely used as a sensitive test for the evaluation of "physiological adaptive mechanisms" generated by the autonomic nervous system (head up tilt, Zygmunt and Stanczyk, 2010;Hoshi et al, 2019). Most of the studies that evaluate HRV in these physiological conditions (supine position, standing, supine position with 0.1 Hz breathing and standing with 0.1 Hz) focused on linear properties of HRV (Kabir et al, 2011;de Paula Vidigal et al, 2016;Javorka et al, 2018;Jha et al, 2018). However, non-linear properties quantify and explain up to 80% of total RRI variability (Vandeput, 2010) and reflect physiological mechanisms of multiinteracting cardiovascular control, mostly exerted through sympatho-vagal effectors operating in nonlinear fashion (de Godoy, 2016).…”

“…As stated above, the actual evaluations of physiological RRI complexity measures were performed in the conditions of selective and total pharmacological blockade of sympathetic and parasympathetic system Silva et al, 2017a), posture change, mental stress (Castiglioni et al, 2009;Javorka et al, 2018), exercise and aging (Castiglioni et al, 2009). To the best of our knowledge, our approach is the first one to evaluate the physiologic background of RRI complexity measures in the conditions of physiological selective and joint enhancement of sympathetic (orthostasis) and parasympathetic (0.1 Hz breathing) activity on RRI regulation.…”

“…and pathological symptoms during the experimental procedures (high blood pressure, arrhythmias, headache, fatigue, etc.). For female participants, an additional criterium of exclusion was the second part of menstrual cycle (because of its substantial and diverse cardiovascular autonomic regulation in females, Bai et al, 2009;Javorka et al, 2018). All participants were advised to refrain from food and drink from about 4 h before the experiment, not to exercise (running, gym, yoga, other), to be restful and alert.…”

Information Domain Analysis of Respiratory Sinus Arrhythmia Mechanisms

“…During cognitive load, parasympathetic withdrawal and sympathetic activation are presumably initiated by projections from the amygdala and occur without major changes in venous return. Thus, mental stress is accompanied by a decrease of parasympathetic activity and/or an increase of the sympathetic activity (Kuipers et al 2008, Widjaja et al 2015; in this condition, RSA magnitude is usually decreased (Allen and Crowell 1989, Bernardi et al 2000, Herbert et al 2010, Wetzel et al 2006, Javorka et al 2018. In addition to these previous findings, we observed that the information flow from RESP to RR was amplified as regards the indirect connection during MA, but the degree of indirectionality was significantly lower than that during HUT (P=0.0255) (Fig.…”