title: Modifiable factors associated with improved cardiac arrest survival in a multicenter basic life support/defibrillation system: OPALS Study Phase I results. Ontario Prehospital Advanced Life Support.
abstract: OBJECTIVE
  This study was conducted to identify modifiable factors associated with survival for prehospital cardiac arrest in a large, multicenter EMS system with basic life support/defibrillation (BLS-D) level of care.
  
  
  METHODS
  This observational cohort study constitutes Phase I of the 3-phase Ontario Prehospital Advanced Life Support (OPALS) Study. Included were all adults who had cardiac arrest before EMS arrival in 21 urban/suburban communities that operate under the jurisdiction of 1 ambulance services branch, have 911 telephone service, and provide ambulance defibrillation but no prehospital advanced life support (ALS). Central dispatch and ambulance records were reviewed according to the Utstein guidelines. Associations between multiple patient and EMS factors and survival to discharge were assessed by univariate then stepwise logistic regression analyses.
  
  
  RESULTS
  From January 1, 1991, to January 31, 1995, 5,335 eligible patients were treated. Of these, 46.8% of cardiac arrests were witnessed by citizens, 14.5% received bystander CPR, 25.6% received CPR by fire or police, and 38.2% had an initial rhythm of ventricular fibrillation/ventricular tachycardia (VF/VT). The mean interval from call received to vehicle stopped was 6.7 minutes. Survival was 3.5% overall and 8.8% for VF/VT. Multivariate analysis found the following factors to be independently associated with survival (odds ratio with 95% confidence intervals): age.81 (. 73,.89), bystander-witnessed arrest 4.05 (2.78, 5.90), bystander CPR 2.98 (2.07, 4.29), CPR by fire or police 2.20 (1.46, 3.31), and response interval call received to vehicle stopped.76 (.71,.82).
  
  
  CONCLUSIONS
  This represents the largest multicenter BLS-D study of prehospital cardiac arrest yet conducted and clearly indicates that patient survival may be improved by optimization of EMS response intervals, bystander CPR, as well as first-responder CPR by fire or police.
authors.affiliation: Division of Emergency Medicine, Department of Medicine, and Ottawa Hospital Loeb Research Institute, University of Ottawa, Ontario, Canada.
authors.forename: I G
authors.initials: IG
authors.lastname: Stiell
authors.forename: G A
authors.initials: GA
authors.lastname: Wells
authors.forename: V J
authors.initials: VJ
authors.lastname: DeMaio
authors.forename: D W
authors.initials: DW
authors.lastname: Spaite
authors.forename: B J
authors.initials: BJ
authors.lastname: Field
authors.forename: D P
authors.initials: DP
authors.lastname: Munkley
authors.forename: M B
authors.initials: MB
authors.lastname: Lyver
authors.forename: L G
authors.initials: LG
authors.lastname: Luinstra
authors.forename: R
authors.initials: R
authors.lastname: Ward
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016887:Cardiopulmonary Resuscitation / Q000706:statistics & numerical data*; D004554:Electric Countershock / Q000706:statistics & numerical data*; D004632:Emergency Medical Services; D005260:Female; D006323:Heart Arrest / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008020:Life Support Care; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D009864:Ontario; D016019:Survival Analysis; D013997:Time Factors