title: Dynamics and state transitions during resuscitation in out-of-hospital cardiac arrest.
abstract: BACKGROUND
  The state or rhythm during resuscitation, i.e. ventricular fibrillation/tachycardia (VF/VT), asystole (ASY), pulseless electrical activity (PEA), or return of spontaneous circulation (ROSC) determines management. The state is unstable and will change either spontaneously (e.g. PEA-->ASY) or by intervention (e.g. VF-->ASY after DC shock); temporary ROSC may also occur. To gain insight into the dynamics of this process, we analyzed the state transitions over time using real-life data.
  
  
  METHODS
  Detailed recordings from 304 episodes of attempted resuscitation from out-of-hospital cardiac arrests of presumed cardiac etiology were obtained from modified Heartstart 4000 defibrillators. State transitions were visualized and described, and analyzed in terms of a Markov probability model.
  
  
  RESULTS
  The median number of state transitions was 5 (range 1-39), and more transitions were observed with VF than PEA or asystole as the initial rhythm. Of 105 patients (35%) who regained ROSC at some point during CPR, only 65 (21%) achieved sustained ROSC; suggesting an unrealized survival potential. A 3-min transition probability matrix was estimated: for example, a patient early in VF has a probability of 31% to be in ASY, 32% of still being in VF, 5% to have temporary ROSC, and 2% to have sustained ROSC after 3 min.
  
  
  CONCLUSIONS
  The dynamics of resuscitation can be described in terms of state transitions and a Markov probability model. This framework enables prediction of short-term clinical development, supports informed decisions during CPR, and suggests a novel area for research.
authors.affiliation: Unit for Applied Clinical Research, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Norway. eirik.skogvoll@ntnu.no
authors.forename: Eirik
authors.initials: E
authors.lastname: Skogvoll
authors.forename: Trygve
authors.initials: T
authors.lastname: Eftestøl
authors.forename: Kenneth
authors.initials: K
authors.lastname: Gundersen
authors.forename: Jan Terje
authors.initials: JT
authors.lastname: Kvaløy
authors.forename: Jo
authors.initials: J
authors.lastname: Kramer-Johansen
authors.forename: Theresa Mariero
authors.initials: TM
authors.lastname: Olasveengen
authors.forename: Petter Andreas
authors.initials: PA
authors.lastname: Steen
mesh_terms: D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004562:Electrocardiography; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008390:Markov Chains; D011446:Prospective Studies; D015996:Survival Rate