The impact of additional special emergency medical service units on non-traumatic adult out-of-hospital cardiac arrest outcomes in a high-resource metropolitan area

Background: Out-of-hospital cardiac arrest (OHCA) requires an effective cardiopulmonary resuscitation (CPR) and emergency medical service (EMS) response, yet survival rates remain low at 8.0–11.3 %. Factors such as team size, training and leadership influence outcomes, but optimal strategies are debated. The Vienna EMS routinely deploys field supervisors (FISU) to improve the quality of care. The aim of this study was to assess their impact on OHCA outcomes. Methods: This retrospective observational study analyzed all consecutive adult non-traumatic OHCA cases in Vienna between 01/2019 and 12/2023, focusing on the impact of additional specialised units (FISU or supervising senior emergency physician) on cardiac arrest outcomes (ROSC rates, survival to hospital discharge, neurological performance). Statistical analysis used descriptive statistics, group tests, and logistic regression. Results: A FISU was present in 45.7 % of cases, and its presence improved outcomes significantly including any ROSC (40.6 % vs 26.3 %; OR 1.963, CI 1.773–2.172, p < 0.001), survived event (sustained ROSC) (30.6 % vs 20.6 %; OR 1.720, CI 1.542–1.918, p < 0.001), survival to discharge (10.6 % vs 8.3 %; OR 1.263, 1.072–1.487, p = 0.005) and CPC 1/2 (7 % vs 6.4 %; OR 1.034, CI 1.152–1.253, p = 0.037). Multivariate analysis confirmed that the presence of FISU had an independently positive effect (any ROSC: OR 1.616, CI 1.440–1.813, p < 0.001; survived event: OR 1.335, CI 1.180–1.510, p < 0.001). Conclusions: The presence of additional EMS special units like field supervisors can improve outcomes of non-traumatic out-of-hospital cardiac arrest in a high-resource metropolitan area.