Title: Mechanical ventilation and acute respiratory distress syndrome in the emergency department: a multicenter, observational, prospect ive, crosssectional study Short title/running head: Mechanical ventilation and ARDS in the ED

Abstract Background: There is little data regarding mechanical ventilation and acute respiratory distress syndrome (ARDS) in the emergency department (ED). This could be a vital arena for prevention and treatment. Methods: Multi-center, observational, prospective, cohort study aimed at analyzing ventilation practices in the ED. The primary outcome was the incidence of ARDS after admission. Multivariable logistic regression was used to determine predictors of ARDS. Results: We analyzed 219 mechanically ventilated patients to assess ED ventilation practices. Median tidal volume was 7.6 mL/kg predicted body weight [PBW] (IQR, 6.9 - 8.9), with a range of 4.3 - 12.2 mL/kg PBW. Lung-protective ventilation was used in 122 (55.7%) patients. The incidence of ARDS after admission from the ED was 14.7%, with a mean onset of 2.3 days. Progression to ARDS was associated with higher illness severity and intubation in the prehospital environment or transferring facility. Of the fifteen (6.8%) patients with ARDS in the ED, lung-protective ventilation was used in 7 (46.7%) patients. Patients that progressed to ARDS experienced greater duration in organ failure, ICU length of stay, and mortality.