For patients on HFNO with persistent hypoxaemia or respiratory distress: • Check the equipment: inspect the exterior of the machine, the tubing (circuit), the prong for any sign of mechanical damage, confirm it fits and the filters are in place. Ensure the settings are appropriate and flow is maximized. • Check the oxygen source: there is sufficient oxygen available and flowing through the device. If FiO2 > 50% of oxygen is needed, the device must have a blender. • Check there is no obstruction with secretions: patients with COVID-19 may have very thick secretions which may block small and large airways and cause sudden respiratory deterioration.