Introduction: Advanced airways are used to optimize oxygen delivery during cardiac arrest. However, the effectiveness of advanced airways (endotracheal intubation: ETI or laryngeal tube: LT) over bag-valve-mask (BVM) ventilation on out-of-hospital cardiac arrest (OHCA) remains unclear with few controlled trials. In Okayama City, all OHCA patients are transported to hospitals by Okayama City Emergency Medical Services (EMS). Paramedics require medical direction approval for the use of advanced airway device. Direction alternates between two different hospitals on odd and even days.Hypothesis: We tested whether different prehospital medical direction for airway management affects outcome for OHCA patients.Methods: We conducted a retrospective study of patients transported from 2013 to 2016 in Okayama City. Physicians in two different hospitals provided medical direction with differing philosophies for airway management between the two hospitals. We compared two OHCA patient groups. Group A: patients with medical direction by hospital A which does not permit ETI except for cases with asphyxia. Group B: patients with medical direction by hospital B which allows ETI for other cases such as difficult BVM ventilation. Both hospitals permit LT use if needed. We compared prehospital procedures (airway management) and outcomes (rate of return of spontaneous circulation [ROSC]/1-month survival/Cerebral Performance Category [CPC] 1 or 2) of the two groups.Results: Included were 2449 OHCA patients with 1230 in Group A and 1219 in Group B. Patient age (74.1±18.4 years), sex (56% male), rate of VF (6%), rate of witnessed collapse (45%), and time from EMS call to hospital arrival (30.3±11.9 min), did not differ between the two groups. Use of BVM (Group A vs B: 46.2% vs 45.4%. p = 0.69) was not different, however, there was difference in use of LT (52.8% vs 42.6%, p < 0.001) and use of ETI (1.1% vs 12.1%, p < 0.001) between groups. There was no difference in rate of ROSC (25.0% vs 24.9%, p = 0.97), 1-month survival (6.7% vs 7.6%, p = 0.41), or CPC 1/2 (3.4% vs 3.5%, p = 0.81), between groups.Conclusions: Although there were two different medical direction policies for advanced airway in a single city in a same period, impact on outcomes for OHCA patients was small.