Study Comparing Two Ventilation Modes NAVA (Neurally Adjusted Ventilatory Assist) Mode and Spontaneous Breathing With Inspiratory Pressure Support (IPS) Mode in Consecutive Patients Hospitalized for Acute Respiratory Failure Requiring Mechanical Ventilation With Endotracheal Tube.

Inclusion Criteria: * Patient ventilated with endotracheal tube for more than 24 hours * Return for at least 30 minutes to spontaneous ventilation allowing IPS with a level of pressure support \<30 cm H2O; * Level of sedation =\< 4 on the Ramsay scale in the absence of medical decision to increase the level of sedation; * Fraction of inspired oxygen (FiO 2) =\< 50% with a positive end-expiratory pressure (PEEP) =\< 8 cm H2O; * Absence of administration of high-dose vasopressor therapy defined by: 1. norepinephrine \> 0.3 mcg / kg / min; 2. dopamine \> 10 mcg / kg / min; * Estimated duration of mechanical ventilation \> 48h00 Exclusion Criteria: * Contraindication to the implementation of the NAVA endotracheal tube, ie any contraindication to the implementation of a gastric tube or to the repositioning of a tube already in place: 1. Recent gastrointestinal suture ; 2. Esophageal varices rupture with gastrointestinal bleeding within 4 days prior to inclusion; * Therapeutic limitation or active treatment discontinuation; * Pregnant women; * Minors; * Protected adults; * Patient already included in the study;