Methods are disclosed for the formation of arterio-venous fistula creation. Embodiments include a femoral access approach to the creation of an Aorta-caval fistula at the bifurcation of the Aorta and the Inferior Vena Cava; an apparatus for the creation, modification and maintenance of a fistula; and a method of supplying oxygenated blood to the venous circulation of a patient. The devices, systems and methods can be used to treat patients with one or more numerous ailments including chronic obstructive pulmonary disease, congestive heart failure, hypertension, hypotension, respiratory failure, pulmonary arterial hypertension, lung fibrosis and adult respiratory distress syndrome.