WIN Ratio Analysis to Determine a Strategy of Non- Invasive SUpport for Respiratory Failure in the EmeRgency Department

The purpose of this clinical trial is to determine the best initial non-invasive respiratory support (NIRS) strategy for adults who present to the emergency department with acute hypoxemic respiratory failure, a condition in which blood oxygen levels are dangerously low and require urgent treatment. This study compares two commonly used non-invasive respiratory support strategies to evaluate their effectiveness and safety, based on important patient outcomes during hospitalization, including survival, the need for invasive mechanical ventilation, and the duration of respiratory support. Participants will be randomly assigned (with an equal chance) to receive one of the following treatments: * Non-Invasive Positive Pressure Ventilation (NIPPV): Oxygen delivered under pressure through a face mask. * High-Flow Nasal Oxygen (HFNO): Oxygen delivered at high-flow through a specially designed nasal cannula placed in the nostrils. Researchers will compare the two treatment strategies using a hierarchical assessment of major pulmonary outcomes, including: * Hospital survival * Days on mechanical ventilation * Duration of non-invasive respiratory support As part of the study, researchers will collect: * Blood and urine samples * Physiologic measurements (such as chest movement measured through sensors placed on the skin) * Information from participants' medical records