High Flow Nasal Cannula Oxygen Therapy: Physiological Effects and Clinical Data
In patients with mild to moderate acute respiratory failure the commonly used techniques to ameliorate gas exchange are oxygen therapy and non invasive ventilation (NIV) However due to mask intolerance, hypercapnia, respiratory acidosis, muscle fatigue and hypoxemia, intubation and invasive mechanical ventilation are frequently required. High flow nasal cannulas, originally developed to improve gas exchange in neonatal and pediatric settings, have recently been evaluated in various groups of adult critically ill patients. High flow nasal cannulas deliver a high humidified air/oxygen gas flow (up to 60 l/min) via a nasal cannula. The main advantages of high flow nasal cannulas are the ability to deliver a very high flow of humidified gas, exceeding, in the majority of patients, the peak inspiratory flow, with a constant oxygen fraction and the use, as interface, of a nasal cannula which can insure patient comfort. Several studies have shown that use of high flow nasal cannulas was able to improve gas exchange and reduce the respiratory rate and, in selected patients, also to improve outcomes.