All the patients were continuous monitored of vital signs.whereas arterial blood gases were analyzed before NIV and 1h after NIV, before and after FBO, and once a day and in the case of any change either in the ventilatory settings or in the FIO2; duration of noninvasive ventilation, the rate and cause of endotracheal intubation, ICU and hospital mortality and length of stay in the ICU and in hospital, study procedure related complications.