High Flow Nasal Oxygen Therapy: From Physiology to Clinic

High-flow nasal oxygen (HFNO) therapy has several physiological advantages over traditional oxygen therapy devices, including decreased nasopharyngeal resistance, washing out of the nasopharyngeal dead space, generation of positive pressure in the pharynx, increasing alveolar recruitment in the lungs, humidification of the airways, increased fraction of inspired oxygen and improved mucociliary clearance. Recently, the use of HFNO in treating adult critical illness patients has significantly increased, and it is now being used in many patients with a range of different disease conditions. However, there are no established guidelines to direct the safe and effective use of HFNO for critical patients. This review summarizes the positive physiological effects, mechanisms of action, and the clinical applications of HFNO with available published literatures.