The purpose of this study is to compare a specific mode of artificial ventilation (help from a breathing machine) with other modes. This specific mode is called Neurally Adjusted Ventilatory Assist (NAVA) and is different from other modes as it uses direct signals from the diaphragm (breathing muscle) to help patients breathe. The investigators believe that using these signals, NAVA can determine the exact timing for patients' spontaneous breathing effort and delivers the artificial breath at the same time (in synchrony) with their own breath. Other modes (breathing methods) may cause asynchrony between the patient and the ventilator while delivering artificial breaths because of the way they operate. Asyncrony between patient and ventilator is a risk factor for increasing the length of artificial ventilation and number of related complications. The investigators would like to find out if NAVA performs better in establishing synchrony between patient and ventilator and as a result decreasing time for artificial ventilation and increasing better outcomes.

Study Goal To compare the ability of NAVA vs. conventional lung protective ventilation in a multicenter, unblinded, randomized, controlled fashion to provide invasive ventilatory support during acute respiratory failure in adults who are expected to require ventilatory support for greater than 72 hours.

Hypothesis It is hypothesized that the use of NAVA compared to conventional lung protective ventilation will result in a decrease in the number of days of mechanical ventilation. It is further hypothesized that NAVA compared to conventional lung protective ventilation will result in a decrease in the length of weaning, the length of ICU and hospital stay, and mortality.

Primary Outcome

• Number of invasive ventilator free days.

Secondary Outcome

• Mortality
• Length of Invasive Ventilation in survivors
• Length of ICU and hospital stay
• Incidence of barotrauma (defined as the presence of any extra-pulmonary air that was not present at study enrollment).
• Ventilator associated pneumonia (development of a pneumonia 48 hrs after entry into the study).
• Development of ARDS (after enrollment into the study; defined as a rapid onset, a P/F<200 mmHg, and bilateral pulmonary infiltrates that are not of cardiac origin).

Inclusion Criteria:

• Age greater than or equal to 18 years
• Hypoxemic or hypercapnic acute respiratory failure
• Intubation and mechanical ventilation
• Anticipated mechanical ventilation equal or longer than 72 hrs
• Mechanically ventilated less or equal to 5 days
• Able to spontaneously trigger the ventilator

Exclusion Criteria:

• moderate-to-severe acute respiratory distress syndrome
• Post-operative patient's normally requiring a short course of mechanical ventilation (for example most cardiac surgical patients)
• Unable to spontaneously breathe
• Need to provide controlled ventilation
• Poor short term prognosis (defined as a high risk of death in the next 3 months)
• Neuromuscular or neurologic disease
• Age < 18 years
• Patients with major esophageal, gastric and oral surgery
• Acute brain injury or elevated intracranial pressure (> 18 mmHg)
• Severe cardiac disease: New York Heart Association class 3 or 4 or acute coronary syndrome or persistent ventricular tachyarrhythmias.
• Pregnancy, must be confirmed by laboratory analysis.