Effect of Implementation of Cardiopulmonary Resuscitation-Targeted Multi-Tier Response System on Outcomes After Out-of-Hospital Cardiac Arrest: A Before-and-After Population-Based Study

Objective: A multi-tiered response (MTR) system has been controversial in terms of cost-effectiveness and outcome improvement. It remains uncertain whether a cardiopulmonary resuscitation (CPR)-targeted tiered response system is associated with better outcomes after out-of-hospital cardiac arrest (OHCA). This study aimed to investigate the effect of an MTR on OHCA outcomes. Methods: A natural experimental study was conducted for resuscitation-attempted adult OHCAs. The MTR system was implemented in Korea by the National Fire Agency in 2015 across the country where the single-tiered ambulance response system existed. The MTR program had the following 3 components: 1) detection of OHCA by dispatcher, 2) dispatch of ambulance or fire engine in addition to routine dispatch of ambulance, and 3) performance of team CPR. The study period of 2015–2016 was divided by 6 months (phases I [reference], II, III, and IV). The endpoints were prehospital defibrillation, prehospital return of spontaneous circulation (PROSC), survival to discharge and good neurological recovery. A multivariable logistic regression analysis was performed to evaluate the effect of the intervention, and adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were calculated, adjusting for potential confounders. Results: A total of 32,663 eligible OHCA cases were evaluated during the study period. As the intervention program spread, the MTR with ambulance increased (from 7.0% in phase I to 53.7% in phase IV, p for trend < 0.01). During the study period, prehospital defibrillation increased from 23.6% in phase I to 26.9% in phase IV and the study outcome was improved from 7.4 to 12.6% for PROSC, from 6.7 to 9.1% for survival to discharge, and from 4.5 to 5.8% for good neurological outcome (p for trend < 0.01 for all). Compared with phase I, the AORs (95% CI) of phase IV were 1.16 (1.08–1.25) for prehospital defibrillation, 1.82 (1.63–2.04) for PROSC, 1.37 (1.21–1.56) for survival to discharge, and 1.23 (1.06–1.43) for good neurological outcome. Conclusion: The nationwide implementation of a multi-tiered response system for OHCA was associated with increased prehospital defibrillation and improved outcomes of OHCA patients.