It is hypothesized that the use of Neurally Adjusted Ventilatory Assist (NAVA) compared to pressure support to provide noninvasive ventilation to children will result in a decrease in the number of children with moderate to severe respiratory failure failing noninvasive ventilation and requiring endotracheal intubation. It is further hypothesized that noninvasive ventilation with NAVA compared to pressure support will result in a decrease in the length of mechanical ventilation, and the length of PICU and hospital stay.