Objective: To describe changes in out-of-hospital cardiac arrest (OOHCA) survival before and after the release of the 2005 American Heart Association (AHA) guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC).
Methods: Data were extracted from an OOHCA registry for 1,681 adult cases of cardiac arrest treated by one emergency medical services (EMS) system between April 1, 2004, and December 31, 2007, in a large city (2005 population 730,657). The primary endpoint was survival to hospital discharge. A convenience sample of 69 electronic electrocardiogram (ECG) recordings was reviewed to assess CPR quality parameters using impedance waveform analysis during corresponding time periods. Intervention. Implementation of the 2005 AHA guidelines for CPR and ECC in spring 2006.
Results: The annual treated OOHCA incidence rate was 68/100,000; and the treated ventricular fibrillation (VF) incidence rate was 15/100,000. Bystanders performed CPR in 28% of cases. Public automated external defibrillator (AED) use was < 2% over the entire study, and few patients received hypothermia therapy. Unadjusted OOHCA survival rates were significantly higher in the postguidelines period at 9.4% (n = 1,021) than in the preguidelines period at 6.1% (n = 660), despite similarities in all major predictors of outcome (odds ratio [OR] 1.6; 95% confidence interval [CI] 1.1 to 2.4). Bystander-witnessed OOHCA survival for victims in VF on EMS arrival was 19 of 78 (24%) in the preguidelines period versus 34 of 112 (30%) in the postguidelines period (OR 1.4; 95% CI 0.7 to 2.6). CPR quality measures showed significant improvement in the postguidelines period. The mean no-flow fraction in the preguidelines group was 0.46 and dropped to 0.34 in the postguidelines group, a difference of 0.12 (95% CI 0.05 to 0.19). Multivariate regression analysis adjusting for significant predictors of survival showed that OOHCA in the postguidelines period was associated with 1.8 greater odds of survival than in the preguidelines period (95% CI 1.2 to 2.7).
Conclusion: In this large city, substantial improvement occurred in overall OOHCA survival rates following the implementation of the 2005 AHA guidelines for CPR and ECC. These changes were associated with improvements in the quality of CPR.