Association Between Emergency Medical Services Crew Composition and Return of Spontaneous Circulation Following Out-of-Hospital Cardiac Arrest: A National Retrospective Cohort Study from Saudi Arabia

<title>Abstract</title> <p> Background The optimal composition of Emergency Medical Services (EMS) crews for out-of-hospital cardiac arrest (OHCA) remains uncertain. This study examined the association between EMS crew size, crew configuration, and return of spontaneous circulation (ROSC) in Saudi Arabia. Methods A retrospective cohort study was conducted using Saudi Red Crescent Authority registry data. Adult patients who underwent prehospital resuscitation with documented crew composition and ROSC status were included. Three multivariable logistic regression models evaluated the associations between crew size, crew configuration, and the number of Advanced Life Support (ALS) providers with ROSC after adjustment for age, sex, EMS response time, and initial cardiac rhythm. Results Among 1,511 patients, 446 (29.5%) achieved ROSC. Crew size was not independently associated with ROSC. Compared with two-provider crews, three-provider crews (adjusted OR 0.81, 95% CI 0.53–1.22; <italic>P</italic>  = 0.330) and crews with ≥ 4 providers (adjusted OR 1.34, 95% CI 0.78–2.25; <italic>P</italic>  = 0.274) showed no significant association. In contrast, ALS-only crews had significantly greater odds of ROSC than the BLS + BLS reference configuration (adjusted OR 1.87, 95% CI 1.13–3.05; <italic>P</italic>  = 0.014). Each additional ALS provider demonstrated a borderline positive association with ROSC (adjusted OR 1.20, 95% CI 1.00–1.44; <italic>P</italic>  = 0.054). Shockable initial rhythm remained the strongest predictor of ROSC. Conclusions Crew size alone was not independently associated with ROSC following OHCA. In contrast, ALS-only crew configuration was associated with significantly greater odds of ROSC, suggesting that provider qualifications may be more influential than crew size in prehospital resuscitation. Optimising ALS capability within EMS crews may represent a more effective staffing strategy than increasing crew size alone. </p>