Fontan Physiology Ventilation Strategy

Inclusion Criteria: * Patients of UPMC Children's Hospital of Pittsburgh that have Fontan physiology (single heart ventricle) that are presenting as outpatients to undergo a cardiac catheterization with general endotracheal anesthesia for purpose of diagnosis or interventional cath. * Parents and/or guardians willing to provide informed consent. Exclusion Criteria: * Those unwilling to give consent and those patients who do not have Fontan physiology. * Any urgent/emergent catheterization procedure will be excluded. * Any Fontan patient having a cardiac catheterization under monitored anesthesia care (as opposed to general endotracheal anesthesia) will not be eligible. * Inability to undergo cardiac catheterization. * Pregnant women will be excluded. * \< 6 weeks post-op from Fontan completion surgery * Same hospitalization as Fontan completion surgery * Intrinsic pulmonary disease which would be anticipated to impact study protocol / findings * Fontan completion surgery performed at age \> 7 years