Influence of team size on the efficiency of time-critical ALS interventions in prehospital cardiac arrest - A prospective randomised multicentre simulation study.

Objective: To determine whether increasing emergency medical service (EMS) team size improves the efficiency of time-critical invasive procedures during advanced life support (ALS) for out-of-hospital cardiac arrest (OHCA). Design: Randomised prospective multicentre simulation study with a parallel-group comparison of four predefined team sizes. Setting: Three accredited EMS training centres in North Rhine-Westphalia, Germany. Participants: 210 ALS-trained paramedic students allocated to 59 teams of two to five members. Interventions: Teams managed a standardised adult ALS scenario (persistent ventricular fibrillation) requiring five invasive procedures: manual defibrillation, supraglottic airway insertion, intravenous access, preparation of amiodarone (300 mg), and preparation of epinephrine (1 mg). Measurements and main results: The primary endpoint was total scenario time from start to completion of the final procedure. Secondary endpoints were start and completion times for each intervention. Mean total times (mm:ss) decreased progressively with team size: two-person 6:33 ± 0:33 min, three-person 4:13 ± 0:40 min, four-person 2:54 ± 0:24 min, and five-person 2:14 ± 0:19 min (ANOVA, Conclusions: Larger EMS teams performed time-critical ALS procedures significantly faster, with optimal efficiency observed in four- to five-member crews. These findings highlight the operational importance of team composition for prehospital resuscitation performance and may inform staffing policies and simulation-based training.