Conventional Low Flow Oxygenation Versus High Flow Nasal Cannula in Hypercapnic Respiratory Failure

Current evidence suggests a mechanistic and physiological rationale for the use of high flow nasal cannula (HFNC) in acute respiratory hypoxemic failure (AHRF) based on physiological studies in airway models, healthy volunteers and patients with Chronic Obstructive Respiratory Disease (COPD). This is supported by observational studies in patients with AHRF with reductions in a range of respiratory and other physiological parameters. Observational studies also suggest similar intubation rates and lower failure rates with HFNC when compared to non-invasive ventilation (NIV) with improved patient acceptance and tolerance for HFNC. The role of HFNC is less clear in acute hypercapnic respiratory failure. Although non-invasive ventilation is the recommended treatment, it is associated with discomfort, and a significant proportion (up to 25% in some reports) cannot tolerate non-invasive ventilation. Observational reports and limited data from randomized controlled trials suggests that HFNC is effective in treating patients with hypercapnic respiratory failure. We designed this trial to assess whether early application of HFNC in patients with non-severe hypercapnic respiratory failure can correct barometric abnormalities, and prevent progression to non-invasive ventilation or tracheal intubation and mechanical ventilation.