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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.