The intervention will last until one of the following conditions: 1) physician in charge decide to interrupt NIV and perform endotracheal intubation and invasive mechanical ventilation because patient shows one or more of these conditions: respiratory arrest, respiratory pauses with loss of consciousness, psychomotor agitation making nursing care impossible, heart rate < 50 with loss of alertness, hemodynamic instability with systolic arterial blood pressure <70 mmHg, development of conditions requiring intubation either to protect the airway or to manage copious tracheal secretions, inability to tolerate the devices; 2) clinical improvement defined as all these conditions: normal mental status, hemodynamic stability, respiratory rate below 25 per minute, absence of activation of accessory respiratory muscles and paradoxical abdominal motion, no dyspnoea arterial pH > 7.35, Arterial partial pressure of carbon dioxide (PaCO2) < 70 mmHg and Arterial partial pressure of oxygen (PaO2) > 55 mmHg with an inspired oxygen fraction (FiO2) < 0.35.