A method for the recursive identification of physiological models of the cardiovascular baroreflex is proposed and applied to the time-varying analysis of vagal and sympathetic activities. The proposed method was evaluated with data from five newborn lambs, which were acquired during injection of vasodilator and vasoconstrictors and the results show a close match between experimental and simulated signals. The model-based estimation of vagal and sympathetic contributions were consistent with physiological knowledge and the obtained estimators of vagal and sympathetic activities were (...) compared to traditional markers associated with baroreflex sensitivity. High correlations were observed between traditional markers and model-based indices. (shrink)

This renin‐angiotensin system (RAS) interpretation is focused on differences in tissue dependence on RAS and on the topological hierarchy that allows mediators to act only on downstream tissues.Dependence of tissues on RAS: Tested by expectation maximization clustering of the RNA human tissue expression (https://biogps.org/). ACE and vasoconstrictive AT1R clustered with the prorenin receptor. ACE2 and dilatory MAS1 clustered with nine RAS‐related genes, highly expressed in: Liver; Cardiac_Myocytes; Skeletal_Muscle; Uterus; Kidney; Lung; Small_Intestine; Smooth_Muscle.RAS and stress accumulation: While prorenin is active after (...) binding to its receptor, binding of soluble renin increases its enzymatic activity several times. Increased renin secretion multiplies the overall capacity for producing Ang I, leading to hypertension and increased vascular resistance.Coronavirus infection and comorbidities: Cardiorespiratory failure during infection is linked to the previously altered RAS role in lungs and myocardium. Reduced vasodilation by ACE2 lead to vasoconstriction and suboptimal tissue perfusion patterns. Also see the video abstract here https://www.youtube.com/watch?v=Jf0Iped-Mws. (shrink)