title: Effects of interrupting precordial compressions on the calculated probability of defibrillation success during out-of-hospital cardiac arrest.
abstract: BACKGROUND
  Cardiopulmonary resuscitation (CPR) creates artifacts on the ECG and, with automated defibrillators, a pause in CPR is mandatory during rhythm analysis. The rate of return of spontaneous circulation (ROSC) is reduced with increased duration of this hands-off interval in rats. We analyzed whether similar hands-off intervals in humans with ventricular fibrillation causes changes in the ECG predicting a lower probability of ROSC.
  
  
  RESULTS
  The probability of ROSC after a shock was continually determined from ECG signal characteristics for up to 20 seconds of 634 such hands-off intervals in patients with ventricular fibrillation. In hands-off intervals with an initially high (40% to 100%) or median (25% to 40%) probability for ROSC, the probability was gradually reduced with time to a median of 8% to 11% after 20 seconds (P<0.001). In episodes with a low initial probability (0% to 25%; median, 5%), there was no further reduction with time.
  
  
  CONCLUSIONS
  The interval between discontinuation of chest compressions and delivery of a shock should be kept as short as possible.
authors: Stavanger University College, Department of Electrical and Computer Engineering, Stavanger, Norway. trygve.eftestol@tn.his.no
authors: Trygve
authors: T
authors: Eftestøl
authors: Kjetil
authors: K
authors: Sunde
authors: Petter Andreas
authors: PA
authors: Steen
mesh_terms: D016477:Artifacts; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D003661:Decision Support Techniques; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D004632:Emergency Medical Services / Q000379:methods*; D005583:Fourier Analysis; D006801:Humans; D009664:Norway; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy*