Inclusion Criteria:  Intensive care unit admission (orders written) Age ≥18 years  Hypoxemic acute respiratory failure for at least 1 hour and still present at time of screening for eligibility (symptom onset during last 7 days) with the following:  Respiratory rate >21 or clinical evidence of increased work of breathing  and  b. Documented Hypoxemia defined as any one of: i. PaO2:FiO2 < 300 ii. If no arterial blood gas available, then SpO2:FiO2 < 315 iii. Oxygen saturation <98% on FiO2 >= 0.4 or higher by Venturi mask,TAVISH mask 10 litres / minute, or any non-invasive oxygenation strategy  Exclusion Criteria:  Patients who are intubated or with tracheostomy Already on HFNO or other non-invasive oxygenation strategy at FiO2>=0.4 for the last 18 hours Immediate need for intubation (e.g., inadequate airway protection or refractory hypoxemia or cardiopulmonary arrest, massive hemoptysis, etc) Extubated in the ICU within past 72 hours Clinician deems that face mask NIV is indicated to treat a primary diagnosis of acute exacerbation of chronic hypercapnic respiratory failure or acute congestive heart failure Known neuromuscular disease Patients being transitioned to Palliative care or unlikely to survive more than 24 hours ICU discharge is planned or anticipated on the day of screening Previously enrolled in this trial Trauma patients who remain in a cervical spine collar at the time of recruitment or who have upper limb/torso fractures.