title: Joint symbolic analyses of heart rate, blood pressure, and respiratory dynamics.
abstract: BACKGROUND
  The dynamics of cardiovascular variables are modulated by respiration. The aim of this study was to assess baroreflex function in normal subjects based on the joint symbolic dynamics of heart rate, blood pressure and respiration.
  
  
  METHODS
  ECG, continuous blood pressure and respiration were recorded in ten healthy subjects during rest in the supine position and upon standing. Beat-to-beat time series of heart rate, systolic blood pressure and respiratory phase were extracted and transformed into binary symbol sequences. Words of length two that were reflective of baroreflex activity were statistically analysed with respect to the respiratory phase.
  
  
  RESULTS
  Symbolic analysis showed a significant influence of the respiratory phase on the occurrence of baroreflex patterns. Upon standing, the frequency of baroreflex words increased and the effect of respiration appeared to be reduced.
  
  
  CONCLUSIONS
  Symbolic dynamics provide a simple representation of cardiovascular dynamics and may be useful for assessing baroreflex function.
authors: School of Electrical and Electronic Engineering and Centre for Heart Rhythm Disorders, The University of Adelaide, Adelaide, Australia. Electronic address: mathias.baumert@adelaide.edu.au.
authors: Mathias
authors: M
authors: Baumert
authors: Michal
authors: M
authors: Javorka
authors: Muammar M
authors: MM
authors: Kabir
mesh_terms: D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003198:Computer Simulation; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D015656:Respiratory Mechanics / Q000502:physiology*; D013561:Symbolism
keywords: Baroreflex; Blood pressure variability; Heart rate variability; Symbolic dynamics