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, p ' 0.001). All pairwise differences were statistically significant (Bonferroni-corrected p ₐdj ' 0.01). Earlier initiation of intravenous access and drug preparation accounted for most time savings. All teams completed every task successfully. 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.