 Patients with respiratory distress and an SpO2 below 90 in the prehospital setting will be randomized to receive either high-flow nasal oxygen therapy through a dedicated device or standard oxygen therapy through standard devices such as nasal cannula or face mask. Need of mechanical ventilation either invasive or noninvasive from enrollment to day 28 and time course of oxygenation between first SpO2 measured on scene and arrival to the hospital will be the main outcome measures. 