Improving Functional Capacity in Fontan Patients Through Inspiratory Muscle Training

Mechanisms that typically result in increased cardiac output, such as inotropic support, increased heart rate, and decreased afterload, have a blunted effect in Fontan circulation. The "thoracic pump" is a contributor to venous return that has been largely unexplored in patients with Fontan physiology. Inspiratory muscle training can improve the performance of competitive athletes across a range of sports and can improve quality of life and functional capacity in heart failure patients, presumably by reducing inspiratory muscle fatigue and possibly by improving peripheral blood flow during exercise. One could surmise that the effects of these changes would be particularly important in the Fontan population. The investigators propose to study the effects of inspiratory muscle training on exercise and pulmonary function parameters in a cohort of adult Fontan patients. The investigators hypothesize that a 12-week program of inspiratory muscle training with an inspiratory impedance threshold device will improve inspiratory muscle strength and endurance, and that this will translate into improved exercise performance in patients with Fontan physiology.

Subjects will be provided with noseclips and a threshold impedance device set to 40% of their measured maximal inspiratory pressure and will be trained on using the device. Specifically, subjects will be instructed to breathe through the inspiratory muscle training device while wearing noseclips at a rate of 12 to 16 breaths per minute for 30 minutes a day, 5 days a week for 12 consecutive weeks. Each subject will be provided a customized schedule for increasing resistance by 2 cm H2O every 2 weeks to a maximum resistance of 41 cm H2O.

The 36-Item Short Form (SF-36) Health Survey is a disease-generic survey of an individual's perceived health status and health-related quality of life. There are eight scaled scores, which are the weighted sums of the questions in their section. Each scale is transformed into a 0-100 scale on the assumption that each question carries equal weight. The lower the score the more disability. The higher the score the less disability. These eight scales are then used to calculate (using a proprietary formula) two summary scores: the physical component score (PCS), representing the four physical health scales (physical functioning, role physical, bodily pain, general health), and the mental component score (MCS), representing the four mental health scales (mental health, role emotional, vitality, social functioning). Component scores are norm-based with a mean of 50 (standardized to the US population) and a standard deviation of 10.

Inclusion Criteria: 18 years of age and older Fontan physiology Undergoing cardiopulmonary stress testing Able to complete a previous cardiopulmonary stress test in the preceding 24 months Ability to comply with the inspiratory muscle training protocol Ability to return for repeat stress testing and pulmonary function testing 12 weeks after enrollment Ability to provide informed consent Exclusion Criteria: Status post cardiac transplantation Current pregnancy or plans to become pregnant within the next 3 months (for females of childbearing potential) Active respiratory infection Active cigarette smoker Baseline oxygen saturation <90% at the previous clinic visit or exercise test Forced expired volume in 1 s and/or vital capacity <60% of predicted at the previous exercise test Cardiac surgery or catheter-based procedure in the preceding 18 months or planned surgery or catheter-based procedure within the next 3 months