Neonates, infants and children from birth through 5 years of age undergoing mechanical ventilation following cardiac surgery for congenital heart disease. Congenital heart lesions include "two ventricle repairs", including tetralogy of Fallot, transposition of the great arteries, "unobstructed" total anomalous pulmonary venous return, truncus arteriosus, atrioventricular canal defect and ventricular septal defect.