Purpose

In patients with Fontan circulation blood is not pumped to the lungs from a ventricle. Instead the superior vena cava and inferior vena cava is connected to the pulmonary artery and blood flow to the lungs occurs passively along this Fontan pathway. This passive blood flow to the lungs occurs best when the patient is breathing on their own (spontaneous ventilation). However for certain surgeries and procedures patients need to have an endotracheal tube inserted and need to be muscle relaxed and receive positive pressure ventilation. Prior studies have shown that positive pressure ventilation can reduce blood flow to the lungs and consequently blood returning to the heart resulting in less blood pumped out to the rest of the body (cardiac output). The purpose of this study is to investigate if changing the volume of the positive pressure ventilation (tidal volume) affects blood flow to the lungs and cardiac output in patients with Fontan circulation.