After the patient has been successfully intubated at the beginning of the procedure, a trained nurse, using standard technique for placement of a oro/nasogastric tube, will place an appropriately sized NAVA catheter in the patient. The lumen of the NAVA tube can be used as a conventional oro/nasogastric tube and the electrodes will be connected to the Servo-I ventilator. Although the Servo-I is a ventilator, it will be used only as a monitor for this study. The position of the nasogastric tube will then be refined using the catheter positioning screen as needed.