Association Between Emergency Medical Services Intervention Volume and Out-of-Hospital Cardiac Arrest Survival: A Propensity Score Matching Analysis.

Background: Out of hospital cardiac arrest (OHCA) survival rates are very low. An association between institutional OHCA case volume and patient outcomes has been documented. However, whether this applies to prehospital emergency medicine services (EMS) is unknown.

Objectives: To investigate the association between the volume of interventions by mobile intensive care units (MICU) and outcomes of patients experiencing an OHCA.

Methods: A retrospective cohort study including adult patients with OHCA managed by medical EMS in five French centers between 2013 and 2020. Two groups were defined depending on the overall annual numbers of MICU interventions: low and high-volume MICU. Primary endpoint was 30-day survival. Secondary endpoints were prehospital return of spontaneous circulation (ROSC), ROSC at hospital admission and favorable neurological outcome. Patients were matched 1:1 using a propensity score. Conditional logistic regression was then used.

Results: 2,014 adult patients (69% male, median age 68 [57-79] years) were analyzed, 50.5% (n = 1,017) were managed by low-volume MICU and 49.5% (n = 997) by high-volume MICU. Survival on day 30 was 3.6% in the low-volume group compared to 5.1% in the high-volume group. There was no significant association between MICU volume of intervention and survival on day 30 (OR = 0.92, 95%CI [0.55;1.53]), prehospital ROSC (OR = 1.01[0.78;1.3]), ROSC at hospital admission (OR = 0.92 [0.69;1.21]), or favorable neurologic prognosis on day 30 (OR = 0.92 [0.53;1.62]).