Continuous improvements in "chain of survival" increased survival after out-of-hospital cardiac arrests: a large-scale population-based study.

Background: The impact of ongoing efforts to improve the "chain of survival" for out-of-hospital cardiac arrest (OHCA) is unclear. The objective of this study was to evaluate the incremental effect of changes in prehospital emergency care on survival after OHCA.

Methods And Results: This prospective, population-based observational study involved consecutive patients with OHCA from May 1998 through December 2006. The primary outcome measure was 1-month survival with favorable neurological outcome. Multiple logistic regression analysis was used to assess factors that were potentially associated with better neurological outcome. Among 42,873 resuscitation-attempted adult OHCAs, 8782 bystander-witnessed arrests of presumed cardiac origin were analyzed. The median time interval from collapse to call for medical help, first cardiopulmonary resuscitation, and first shock shortened from 4 (interquartile range [IQR] 2 to 11) to 2 (IQR 1 to 5) minutes, from 9 (IQR 5 to 13) to 7 (IQR 3 to 11) minutes, and from 19 (IQR 13 to 22) to 9 (IQR 7 to 12) minutes, respectively. Neurologically intact 1-month survival after witnessed ventricular fibrillation increased from 6% (6/96) to 16% (49/297; P<0.001). Among all witnessed OHCAs, earlier cardiopulmonary resuscitation (odds ratio per minute 0.89, 95% confidence interval 0.85 to 0.93) and earlier intubation (odds ratio per minute 0.96, 95% confidence interval 0.94 to 0.99) were associated with better neurological outcome. For ventricular fibrillation, only earlier shock was associated with better outcome (odds ratio 0.84, 95% confidence interval 0.80 to 0.88).

Conclusions: Data from a large, population-based cohort demonstrate a continuous increase in OHCA survival with improvement in the chain of survival. The incremental benefit of early advanced care on OHCA survival is also suggested.