Association between EMS response time and return of spontaneous circulation in out-of-hospital cardiac arrest patients in Busan, South Korea

Abstract

Objectives: This study evaluated the impact of response time on prehospital return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA) patients in Busan, South Korea. Methods: We analyzed OHCA cases from Busan Fire and Disaster Headquarters (January–December 2022). A total of 2388 patients aged ≥18 years with complete EMS records were included. After excluding response time groups with <30 observations, 2268 cases were analyzed using SAS 9.4 for multiple logistic regression. Results: Among 2388 OHCA patients in Busan, 179 (7.5 %) achieved ROSC. Only 2.5 % of cases met the 4-min response time benchmark. Multiple logistic regression identified key factors associated with higher ROSC: younger age (OR = 3.650 for 18–60 years vs. oldest group), witnessed arrest (OR = 2.788), shockable rhythm (OR = 3.105), bystander CPR (OR = 1.881), and EMS defibrillation (OR = 4.554). Response time showed the strongest association at <4 min (OR = 2.812), declining progressively at 5 min (OR = 1.748), 6 min (OR = 1.339), and 7 min (OR = 1.146). Conclusions: Shorter response times were associated with increased ROSC rates in OHCA patients. This highlights the need for policy measures to reduce response times, including community-based early recognition systems and optimized emergency resource allocation.