title: Nonlinear methods of biosignal analysis in assessing terbutaline-induced heart rate and blood pressure changes.
abstract: The aim of this study was to characterize how different nonlinear methods characterize heart rate and blood pressure dynamics in healthy subjects at rest. The randomized, placebo-controlled crossover study with intravenous terbutaline was designed to induce four different stationary states of cardiovascular regulation system. The R-R interval, systolic arterial blood pressure, and heart rate time series were analyzed with a set of methods including approximate entropy, sample entropy, Lempel-Ziv entropy, symbol dynamic entropy, cross-entropy, correlation dimension, fractal dimensions, and stationarity test. Results indicate that R-R interval and systolic arterial pressure subsystems are mutually connected but have different dynamic properties. In the drug-free state the subsystems share many common features. When the strength of the baroreflex feedback loop is modified with terbutaline, R-R interval and systolic blood pressure lose mutual synchrony and drift toward their inherent state of operation. In this state the R-R interval system is rather complex and irregular, but the blood pressure system is much simpler than in the drug-free state.
authors.affiliation: Department of Physics, University of Turku, 20014 Turku, Finland. tom.kuusela@utu.fi
authors.forename: Tom A
authors.initials: TA
authors.lastname: Kuusela
authors.forename: Tuomas T
authors.initials: TT
authors.lastname: Jartti
authors.forename: Kari U O
authors.initials: KU
authors.lastname: Tahvanainen
authors.forename: Timo J
authors.initials: TJ
authors.lastname: Kaila
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D018592:Cross-Over Studies; D019277:Entropy; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D017711:Nonlinear Dynamics; D013566:Sympathomimetics / Q000008:administration & dosage*; D013726:Terbutaline / Q000008:administration & dosage*
chemical_list: D013566:Sympathomimetics; D013726:Terbutaline