Pediatric patients often require prolonged mechanical ventilation after cardiac surgery which comes with many undesirable effects. As a result, neurally-adjusted ventilatory assist (NAVA) and biphasic positive airway pressure support (BiPAP) have been developed as non-invasive alternatives to providing respiratory support post-operatively. The investigators hypothesize that providing synchronized biphasic support with NAVA will be associated with shorter duration of non-invasive respiratory support, less sedation requirements, and reduced length of hospital stay. This is a prospective, randomized study. Subjects are randomized to receive either NAVA or BiPAP following their cardiothoracic surgery.