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.