Neurally adjusted ventilatory assist (NAVA) and Proportional Assist Ventilatory Plus (PAV +) are new modes of mechanical ventilation that delivers ventilatory assist in proportion to the electrical activity of the diaphragm for NAVA and to patients efforts for PAV +. The goal of this trial is to compare oxygenation,ventilator comfort, patients -ventilator asynchronies, and sleep pattern between NAVA and PAV+.

Twenty patients will be enrolled. They will be ventilated with PAV+ and NAVA for one day, each in a randomized crossover order. The oxygenation,ventilator comfort, patients -ventilator asynchronies, and sleep pattern will be compared.

Inclusion Criteria:

• Estimated remaining duration of mechanical ventilation for more than two days
• patient alert and calm
• Surrogate decision maker's consent

Exclusion Criteria:

• Clinical contraindication for the use of NAVA: contraindications for an EAdi catheter placement (e.g., esophageal varices, upper gastrointestinal bleeding, gastroesophageal surgery)
• Clinical instability for any reason
• Contraindications for continuing intensive care treatment
• Patient under tutelage
• Age < 18 years
• Pregnancy
• No French health insurance