Many scores derived from Early Warning Scores have been developed to detect patients at risk of poor outcome. Few of these scores incorporate the oxygen flow rate while this is a major marker in patients with respiratory complaint. We developed and evaluated a new automatable monitoring tool (Early Warning ScoreO: EWS.O) that incorporates cardio-respiratory parameters (Respiratory rate, Heart rate, SpO, and FiO derived from oxygen flow rate), aiming to achieve early detection of poor outcome among patients with dyspnea.All patients presenting at an emergency department for dyspnea from June 2011 to June 2018 with available initial value (nurse triage) of respiratory parameters were included. Our primary endpoint was a composite criterion including the use of non-invasive ventilation, ICU admission and death. The Area under the Receiver Operating Characteristic curve (AUROC) of the SpO/FiO index, NEWS, NEWS2, and the EWS.O were compared, including in subgroup analysis by final diagnosis or oxygen supplementation.Among the 1729 patients retrieved, the composite outcome was observed in 288 (16.7%). The EWS.O displayed better or comparable predictive accuracy at triage (AUROC: 0.704, 95%CI 0.672-0.736) compared to NEWS (0.662, p < 0.01), NEWS2 (0.672, p = 0.02) and SpO/FiO (0.695, p = 0.46).This new ScoreO is equivalent or superior to common early warning scores and index to predict poor outcome at first medical contact. This score may be automatically and continuously recorded with new closed-loop devices to titrate oxygen flow. Further prospective studies will allow to verify its accuracy at multiple time points of the patient's journey.