title: Changes of heart and respiratory rate dynamics during weaning from mechanical ventilation: a study of physiologic complexity in surgical critically ill patients.
abstract: OBJECTIVE
  The aim of the study was to investigate heart rate (HR) and respiratory rate (RR) complexity in patients with weaning failure or success, using both linear and nonlinear techniques.
  
  
  METHODS
  Forty-two surgical patients were enrolled in the study. There were 24 who passed and 18 who failed a weaning trial. Signals were analyzed for 10 minutes during 2 phases: (1) pressure support (PS) ventilation (15-20 cm H(2)O) and (2) weaning trials with PS (5 cm H(2)O). Low- and high-frequency (LF, HF) components of HR signals, HR multiscale entropy (MSE), RR sample entropy, cross-sample entropy between cardiorespiratory signals, Poincaré plots, and α1 exponent were computed in all patients and during the 2 phases of PS.
  
  
  RESULTS
  Weaning failure patients exhibited significantly decreased RR sample entropy, LF, HF, and α1 exponent, compared with weaning success subjects (P < .001). Their changes were opposite between the 2 phases, except for MSE that increased between and within groups (P < .001). A new model including rapid shallow breathing index (RSBI), α1 exponent, RR, and cross-sample entropies predicted better weaning outcome compared with RSBI, airway occlusion pressure at 0.1 second (P(0.1)), and RSBI × P(0.1) (conventional model, R(2) = 0.887 vs 0.463; P < .001). Areas under the curve were 0.92 vs 0.86, respectively (P < .005).
  
  
  CONCLUSIONS
  We suggest that nonlinear analysis of cardiorespiratory dynamics has increased prognostic impact upon weaning outcome in surgical patients.
authors.affiliation: Democritus University of Thrace, Alexandroupolis University Hospital, Department of Intensive Care Medicine, Dragana 68100, Greece. papabil69@vodafone.net.gr
authors.forename: Vasilios E
authors.initials: VE
authors.lastname: Papaioannou
authors.forename: Ioanna
authors.initials: I
authors.lastname: Chouvarda
authors.forename: Nikos
authors.initials: N
authors.lastname: Maglaveras
authors.forename: Christos
authors.initials: C
authors.lastname: Dragoumanis
authors.forename: Ioannis
authors.initials: I
authors.lastname: Pneumatikos
mesh_terms: D000005:Abdomen / Q000601:surgery; D000368:Aged; D016638:Critical Illness; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care; D011379:Prognosis; D056152:Respiratory Rate / Q000502:physiology*; D015300:Ventilator Weaning