The relationship between survival after out-of-hospital cardiac arrest and process measures for emergency medical service ambulance team performance.

Abstract

International institutes have developed their own clinical performance indicators for ambulance services. It is unknown whether these process measures are related to survival of patients after out-of-hospital cardiac arrest (OHCA). We aimed to determine whether Emergency Medical Service (EMS)-related ambulance team process measures correlate with patient survival. Four years of observational data were collected from an urban EMS OHCA registry. The two process measures were achieving an EMS response time ≤4 min and prehospital ROSC (return of spontaneous circulation). The outcome measure was survival to discharge. We used the GLMM (generalised linear mixed model) with stepwise selection to examine this process-outcome link at the patient and EMS team levels, respectively. We analyzed 3856 OHCA patients distributed across forty-three EMS ambulance teams. Survival to discharge was observed in 193 (5%) patients. The two EMS team process measures were positively associated with an improvement in survival at the patient level after case-mix adjustment. However, they were not associated with improvement in the risk-adjusted survival rate. The EMS team-level process measures proposed by international institutes may not predict the risk-adjusted survival rate. Using these measures to motivate EMS teams to improve their quality performance would be questionable. Increased efforts should be devoted to constructing more pivotal EMS team-level process measures that are tightly linked to survival.