Dual valve, flexible expandable sheath and method

This invention relates to an expandable sheath and more particularly to a dual valve, reinforced, large-diameter expandable sheath and method of use. A sheath for use in introducing a catheter or other medical instrument into a vessel in the body of a patient. The sheath includes an elongate sheath tube formed of a flexible material which has proximal and distal extremities and a passage extending therethrough A backflow adapter is secured to the proximal extremity of the elongate sheath tube. The backflow adapter has a central opening therein in registration with the passage in the sheath tube. A normally closed primary valve is disposed in the central opening of the backflow adapter and is movable le to an open position. A normally open secondary valve, movable to a closed position, may be configured in the backflow adapter proximal the sheath tube and distal the primary valve. The primary and secondary valves when open permit a catheter or other medical instrument to be inserted into the sheath.