Association between case volume of ambulance stations and clinical outcomes of out-of-hospital cardiac arrest: A nationwide multilevel analysis

Abstract Objectives The case volume effects of ambulance stations on the survival of out-of-hospital cardiac arrest (OHCA) patients are uncertain. This study was conducted to evaluate the association between the case volume of ambulance stations and clinical outcomes in OHCAs by the number of emergency medical services (EMS) providers at the scene. Methods Adult cardiac EMS-treated OHCAs between 2015 and 2018 were enrolled. The main exposure was the annual OHCA case volumes of 204 ambulance stations in Korea, which were categorized into three groups; low-volume ( Results A total of 92,534 patients were enrolled. OHCAs in the low-volume group tended to be arrest in a public place or a non-metropolitan area, less prehospital administration of an advanced airway and intravenous management. Significant differences were found the main analysis: AORs (95% CIs) compared to the low-volume group were 1.15 (1.03–1.29) and 1.14 (1.03–1.27) in the high-volume and moderate-volume groups for good neurological recovery and 1.19 (1.07–1.33) and 1.14 (1.04–1.25) in the high-volume and moderate-volume groups for survival to discharge. Significant interaction effects between the number of EMS providers at the scene and case volume on clinical outcomes were found. Conclusion OHCA case volumes of ambulance stations are associated with clinical outcomes after cardiac arrest.