High flow nasal cannula (HFNC) oxygen therapy devices are used on a daily-basis in many intensive care units and postoperative wards. Such a device deliver a mixture of air and oxygen, warmed, humidifi ed, with gas flow between 20-60 L/min, and inspired oxygen fraction between 0.21-1. Therefore, it improves oxygenation, decreases dead space, washes out the carbon dioxide (CO2) from patients’ airways, improves thoraco-abdominal synchrony and decreases the work of breathing. Studies have shown effi cacy of HFNC oxygen therapy use for acute hypoxemic respiratory failure, for patients with exacerbations of chronic pulmonary diseases, after extubation in order reduce the need for mechanical ventilation, in perioperative period to prevent atelectasis and in palliative care, in order to reduce breathlessness. It isn`t feasible for patients with severe altered neurological status, facial trauma, basal skull fracture, complete airway obstruction or epistaxis. There are no standardized recommendation for the use or contraindication of HFCN oxygen therapy. The weaning is realised according with patients’ tolerance, oxygen saturation, respiratory and heart rates.