title: Conditional symbolic analysis detects nonlinear influences of respiration on cardiovascular control in humans.
abstract: We propose a symbolic analysis framework for the quantitative characterization of complex dynamical systems. It allows the description of the time course of a single variable, the assessment of joint interactions and an analysis triggered by a conditioning input. The framework was applied to spontaneous variability of heart period (HP), systolic arterial pressure (SAP) and integrated muscle sympathetic nerve activity (MSNA) with the aim of characterizing cardiovascular control and nonlinear influences of respiration at rest in supine position, during orthostatic challenge induced by 80° head-up tilt (TILT) and about 3 min before evoked pre-syncope signs (PRESY). The approach detected (i) the exaggerated sympathetic modulation and vagal withdrawal from HP variability and the increased presence of fast MSNA variability components during PRESY compared with TILT; (ii) the increase of the SAP-HP coordination occurring at slow temporal scales and a decrease of that occurring at faster time scales during PRESY compared with TILT; (iii) the reduction of the coordination between fast MSNA and SAP patterns during TILT and PRESY; (iv) the nonlinear influences of respiration leading to an increased likelihood to observe the abovementioned findings during expiration compared with inspiration one. The framework provided simple, quantitative indexes able to distinguish experimental conditions characterized by different states of the autonomic nervous system and to detect the early signs of a life threatening situation such as postural syncope.
authors.affiliation: Department of Biomedical Sciences for Health, University of Milan, Milan, Italy IRCCS Galeazzi Orthopedic Institute, Milan, Italy alberto.porta@unimi.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Porta
authors.affiliation: Department of Anesthesia and Intensive Care Unit, Rozzano, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Marchi
authors.affiliation: Department of Cardiothoracic-Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy.
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bari
authors.affiliation: Institut für Klinische Pharmakologie, Medizinische Hochschule Hannover, Hannover, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Heusser
authors.affiliation: Institut für Klinische Pharmakologie, Medizinische Hochschule Hannover, Hannover, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Tank
authors.affiliation: Institut für Klinische Pharmakologie, Medizinische Hochschule Hannover, Hannover, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Jordan
authors.affiliation: Department of Internal Medicine, Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Barbic
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy Department of Internal Medicine, Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
authors.forename: Raffaello
authors.initials: R
authors.lastname: Furlan
mesh_terms: D000328:Adult; D000465:Algorithms; D001341:Autonomic Nervous System; D017704:Baroreflex; D002319:Cardiovascular System; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D015233:Models, Statistical; D056888:Patient Positioning; D015203:Reproducibility of Results; D012119:Respiration; D012815:Signal Processing, Computer-Assisted; D013575:Syncope; D013997:Time Factors; D055815:Young Adult
keywords: autonomic nervous system; baroreflex; head-up tilt; heart rate variability; muscle sympathetic nerve activity; postural syncope