Objective: To examine the independent relationship between effectiveness of bystander cardiopulmonary resuscitation (CPR) and survival following out-of-hospital cardiac arrest.
Design: Prospective observational cohort.
Setting: New York City.
Participants: A total of 2071 consecutive out-of-hospital cardiac arrests meeting Utstein criteria.
Intervention: Trained prehospital personnel assessed the quality of bystander CPR on arrival at the scene. Satisfactory execution of CPR required performance of both adequate compressions and ventilations in conformity with current American Heart Association guidelines.
Main outcome measure: Adjusted association between CPR effectiveness and survival. Survival was defined as discharge from hospital to home.
Results: Outcome was determined on all members of the inception cohort--none were lost to follow-up. When the association between bystander CPR and survival was adjusted for effectiveness of CPR in the parent data set (N = 2071), only effective CPR was retained in the logistic model (adjusted odds ratio [OR] = 5.7; 95% confidence interval [CI], 2.7 to 12.2; P < .001). Of the subset of 662 individuals (32%) who received bystander CPR, 305 (46%) had it performed effectively. Of these, 4.6% (14/305) survived vs 1.4% (5/357) of those with ineffective CPR (OR = 3.4; 95% CI, 1.1 to 12.1; P < .02). After adjustment for witness status, initial rhythm, interval from collapse to CPR, and interval from collapse to advanced life support, effective CPR remained independently associated with improved survival (adjusted OR = 3.9; 95% CI, 1.1 to 14.0; P < .04).
Conclusion: The association between bystander CPR and survival in out-of-hospital cardiac arrest appears to be confounded by CPR quality. Effective CPR is independently associated with a quantitatively and statistically significant improvement in survival.