HNFO With or Without Helmet NIV for Oxygenation Support in Acute Respiratory Failure Pilot RCT

Inclusion Criteria: 1. Intensive care unit admission (orders written) 2. Age ≥18 years 3. Hypoxemic acute respiratory failure for at least 1 hour and still present at time of screening for eligibility (symptom onset during last 14 days) with the following: 1. Respiratory rate \>21bpm or clinical evidence of increased work of breathing and 2. 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 4. Not already intubated or with tracheostomy Exclusion Criteria: 1. Already on HFNO or other non-invasive ventilation strategy at FiO2\>=0.4 for the last 24 hours in the ICU. 2. Immediate need for intubation (e.g., inadequate airway protection or refractory hypoxemia or cardiopulmonary arrest, massive hemoptysis, etc) 3. Extubated in the ICU within past 72 hours 4. Clinician deems that face mask NIV is indicated to treat a primary diagnosis of hypercapnic respiratory failure or acute congestive heart failure 5. Known neuromuscular disease 6. Patients being transitioned to Palliative care or unlikely to survive more than 24 hours 7. ICU discharge is planned or anticipated on the day of screening 8. Previously enrolled in this trial 9. Trauma patients who remain in a cervical spine collar at the time of recruitment or who have upper limb/torso fractures that would preclude them from safe application of the helmet 10. Clinician decision that positive pressure to face and/or nasal pharynx is a contraindication (eg. Transphenoidal surgery, basal skull fracture etc.)