Effects of Different Tidal Volume Ventilation Strategies on Fontan Flow and Hemodynamics

Overview

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.

If it can be shown that changing the tidal volume does affect the blood flow to the lungs and cardiac output in patients with Fontan circulation the information can be used to learn from this study to optimize the tidal volume ventilation, and therefore pulmonary blood flow and cardiac output when Fontan patients come for general anesthesia. This is important because the population of patients with Fontan circulation is increasing and an increasing number will present for cardiac and non cardiac surgery when positive pressure ventilation will be required. They may also spend time on the cardiac intensive care unit on a ventilator and improving our knowledge on how best to ventilate them may help improve their overall hospital outcomes.