Non-linear Heart Rate and Blood Pressure Interaction in Response to Lower-Body Negative Pressure

Abstract

Early detection of hemorrhage remains an open problem. In this regard, blood pressure has been an ineffective measure of blood loss due to numerous compensatory mechanisms sustaining arterial blood pressure homeostasis. Here, we investigate the feasibility of causality detection in the heart rate and blood pressure interaction, a closed-loop control system, for early detection of hemorrhage. The hemorrhage was simulated via graded lower-body negative pressure (LBNP) from 0 to −40 mmHg. The research hypothesis was that a significant elevation of causal control in the direction of blood pressure to heart rate (i.e., baroreflex response) is an early indicator of central hypovolemia. Five minutes of continuous blood pressure and electrocardiogram (ECG) signals were acquired simultaneously from young, healthy participants (27 ± 1 years, N = 27) during each LBNP stage, from which heart rate (represented by RR interval), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were derived. The heart rate and blood pressure causal interaction (RR↔SBP and RR↔MAP) was studied during the last 3 min of each LBNP stage. At supine rest, the non-baroreflex arm (RR→SBP and RR→MAP) showed a significantly (p < 0.001) higher causal drive toward blood pressure regulation compared to the baroreflex arm (SBP→RR and MAP→RR). In response to moderate category hemorrhage (−30 mmHg LBNP), no change was observed in the traditional marker of blood loss i.e., pulse pressure (p = 0.10) along with the RR→SBP (p = 0.76), RR→MAP (p = 0.60), and SBP→RR (p = 0.07) causality compared to the resting stage. Contrarily, a significant elevation in the MAP→RR (p = 0.004) causality was observed. In accordance with our hypothesis, the outcomes of the research underscored the potential of compensatory baroreflex arm (MAP→RR) of the heart rate and blood pressure interaction toward differentiating a simulated moderate category hemorrhage from the resting stage. Therefore, monitoring baroreflex causality can have a clinical utility in making triage decisions to impede hemorrhage progression.

Effect of Aging on Muscle-Pump Baroreflex of Individual Leg Muscles During Standing

“…Prior to causality analysis, appropriate parameters to perform non-linear state space reconstruction of signals under consideration was determined according to a false nearest neighbor algorithm of the CRP toolbox in MATLAB (MathWorks Inc., MA, United States) (Marwan, 2017). The steps to obtain causal relationship between heart period and blood pressure, as well as skeletal muscle activation and blood pressure, are summarized in our previous work (Verma et al, 2017b; Xu et al, 2017).…”

“…The cardiac and muscle-pump baroreflexes were studied via convergent cross mapping (CCM) to gain insights regarding the directionality of the interaction (Sugihara et al, 2012; Schiecke et al, 2016; Verma et al, 2017a,b), while wavelet transform coherence was utilized to study the interdependency between the respective signals of the two systems (Garg et al, 2014b; Xu et al, 2017). The study outcome is expected to unravel the influence of aging on muscle-pump baroreflex of respective leg muscles, a pivotal mechanism which assures stable upright stance via continuous muscle activation in response to gravity-induced blood pooling to regulate blood pressure during standing.…”

Comparison of Autonomic Control of Blood Pressure During Standing and Artificial Gravity Induced via Short-Arm Human Centrifuge

“…The strength of closed loop heart rate-blood pressure interaction (RR↔SBP), signifying the feedforward (non-baroreflex) and feedback (baroreflex) controls of blood pressure was obtained using convergent cross mapping (CCM) similar to our previous work ( Verma et al, 2017b ; Xu et al, 2017 ). Prior to causality analysis, the evenly sampled continuous RR and SBP signals were resampled to 10 Hz.…”

Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization

“…We have developed a series of techniques to capture and segregate the cardiovascular and postural components associated with standing. Wavelet transform coherence (WTC) analysis 17 , 18 , 20 and convergent cross mapping (CCM) causality 19 , 31 , 32 methods have been adapted to extract indices characterizing the interaction time ( fraction time active, FTA ), response gain value ( gain ), and control directionality ( causality ) among cardiovascular and postural muscle measurements. Based on our previous evidence of an interactive system regulating blood pressure through cardio-postural interactions 18 – 20 , in this study we hypothesized that: (1) the cardio-postural interaction, in terms of FTA, gain, and causality, is reduced and associated with cardiovascular and postural deconditioning after HDBR ; (2) the cardio-postural impairment is reflex/neurally mediated and not due to changes in muscle-pump mechanics.…”