<qa>  What is the clinical efficacy of noninvasive positive pressure ventilation?The clinical efficacy of noninvasive positive pressure ventilation NPPV has been demonstrated. Interest has emerged in using NPPV to facilitate earlier removal of an endotracheal tube and decrease complications associated with prolonged intubation. Studies assessing NPPV in weaning are not enough and generally are performed with face masks as device for NPPV. This study assesses the efficacy of helmet as device for NPPV during weaning from mechanical ventilation in an ICU and compares this procedure with invasive mechanical complication IMV by analyzing respiratory parameters, clinical course and complications. 