title: Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest.
abstract: BACKGROUND
  Cardiopulmonary resuscitation (CPR) and electrical defibrillation are the primary treatment options for ventricular fibrillation (VF). While recent studies have shown that providing CPR prior to defibrillation may improve outcomes, the effects of CPR quality remain unclear. Specifically, the clinical effects of compression depth and pauses in chest compression prior to defibrillation (pre-shock pauses) are unknown.
  
  
  METHODS
  A prospective, multi-center, observational study of adult in-hospital and out-of-hospital cardiac resuscitations was conducted between March 2002 and December 2005. An investigational monitor/defibrillator equipped to measure compression characteristics during CPR was used.
  
  
  RESULTS
  Data were analyzed from 60 consecutive resuscitations in which a first shock was administered for VF. The primary outcome was first shock success defined as removal of VF for at least 5s following defibrillation. A logistic regression analysis demonstrated that successful defibrillation was associated with shorter pre-shock pauses (adjusted odds ratio 1.86 for every 5s decrease; 95% confidence interval 1.10-3.15) and higher mean compression depth during the 30s of CPR preceding the pre-shock pause (adjusted odds ratio 1.99 for every 5mm increase; 95% confidence interval 1.08-3.66).
  
  
  CONCLUSIONS
  The quality of CPR prior to defibrillation directly affects clinical outcomes. Specifically, longer pre-shock pauses and shallow chest compressions are associated with defibrillation failure. Strategies to correct these deficiencies should be developed and consideration should be made to replacing current-generation automated external defibrillators that require long pre-shock pauses for rhythm analysis.
authors.affiliation: Section of General Internal Medicine, University of Chicago Hospitals, Chicago, IL 60637, United States.
authors.forename: Dana P
authors.initials: DP
authors.lastname: Edelson
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Abella
authors.forename: Jo
authors.initials: J
authors.lastname: Kramer-Johansen
authors.forename: Lars
authors.initials: L
authors.lastname: Wik
authors.forename: Helge
authors.initials: H
authors.lastname: Myklebust
authors.forename: Anne M
authors.initials: AM
authors.lastname: Barry
authors.forename: Raina M
authors.initials: RM
authors.lastname: Merchant
authors.forename: Terry L Vanden
authors.initials: TL
authors.lastname: Hoek
authors.forename: Petter A
authors.initials: PA
authors.lastname: Steen
authors.forename: Lance B
authors.initials: LB
authors.lastname: Becker
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004554:Electric Countershock / Q000379:methods*; D005260:Female; D006323:Heart Arrest / Q000401:mortality / Q000628:therapy*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D011785:Quality Assurance, Health Care; D014693:Ventricular Fibrillation / Q000401:mortality / Q000628:therapy*