Dual valve, flexible expandable sheath and method

摘要

A sheath assembly for use in introducing a catheter or other medical instrument into a vessel in the body of a patient. The sheath assembly includes an outer tubular member and an inner tubular member with a conically shaped cap at its distal end. A locking mechanism prevents advancement of the inner tubular member and associated cap in a distal direction of the vessel of the patient independent of the outer tubular member, but allows free movement of the inner tubular member in the proximal direction independent of the outer tubular member.