title: Effects of cardiopulmonary resuscitation on predictors of ventricular fibrillation defibrillation success during out-of-hospital cardiac arrest.
abstract: BACKGROUND
  Early defibrillation is considered the most important factor for restoring spontaneous circulation in cardiac arrest patients with ventricular fibrillation. Recent studies have shown that, after prolonged ventricular fibrillation, the rates of return of spontaneous circulation (ROSC) and survival are improved if defibrillation is delayed so that CPR can be given first. To examine whether CPR improves myocardial readiness for defibrillation, we analyzed whether CPR causes changes in predictors of defibrillation success calculated from the ventricular fibrillation waveform.
  
  
  RESULTS
  ECG recordings were retrieved for 105 patients from an original study of 200 patients receiving CPR or defibrillation first. Altogether, 267 CPR sequences from 77 patients were identified on which the effect of CPR could be evaluated. Five predictors of ROSC (spectral flatness measure, energy, centroid frequency, amplitude spectrum relationship, and estimated probability of ROSC) were determined from a spectral analysis of the ventricular fibrillation waveform immediately before and immediately after each of the 267 sequences. CPR increased spectral flatness measure, centroid frequency, and amplitude spectrum relationship (P<0.05, P<0.001, P<0.01). In an analysis of the effect of the duration of CPR, the probability of ROSC and amplitude spectrum relationship showed a positive change for CPR sequences lasting >3 minutes (P<0.001, P<0.05).
  
  
  CONCLUSIONS
  During resuscitation from ventricular fibrillation, changes in the predictors calculated from the ventricular fibrillation waveform indicated a positive effect of CPR on the myocardium.
authors.affiliation: Stavanger University College, Department of Electrical and Computer Engineering, PO Box 8002, 4068 Stavanger, Norway. trygve.eftestol@his.no
authors.forename: Trygve
authors.initials: T
authors.lastname: Eftestøl
authors.forename: Lars
authors.initials: L
authors.lastname: Wik
authors.forename: Kjetil
authors.initials: K
authors.lastname: Sunde
authors.forename: Petter Andreas
authors.initials: PA
authors.lastname: Steen
mesh_terms: D016887:Cardiopulmonary Resuscitation; D003131:Combined Modality Therapy; D004554:Electric Countershock; D004562:Electrocardiography; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000628:therapy*