Sildenafil Exercise: role of PDE5 Inhibition

Cystic Fibrosis (CF) is the most common fatal genetic disease in Caucasians. The predicted median life expectancy age for patients with CF is 47.7 years compared to 78.8 years in the general U.S. population. Exercise intolerance, evaluated as a reduction in exercise capacity (VO2 peak), has been shown to predict mortality in patients with CF independent of lung function. A critical barrier to improving exercise tolerance in CF is the lack of knowledge regarding the different physiological mechanisms which contribute to decreased exercise capacity. The present investigation will not only evaluate the impact that sildenafil has on clinically relevant and patient oriented outcomes, it will also provide mechanistic insight. Phosphodiesterase type 5 (PDE5) inhibitors reduce inflammation, improve vascular health, increase microvascular O2 delivery and improve skeletal muscle function. Accordingly, the central hypothesis of the study is that treatment with the PDE5 inhibitor, sildenafil, can improve exercise capacity, vascular and cardiac function, and overall quality of life, all of which may contribute to improvement in exercise tolerance in people with CF