Apparatus and methods for sealing a vascular puncture

An apparatus for sealing a puncture extending through tissue, comprising:

• a cartridge comprising a proximal end, a distal end sized for insertion into a puncture through tissue, and a lumen extending between the proximal and distal ends;
• a plug disposed within the cartridge lumen, the plug comprising a lumen extending between proximal and distal ends thereof;
• a pusher member disposed within the cartridge lumen for deploying the plug from the cartridge when the cartridge is retracted relative to the pusher member;
• a positioning member comprising an elongate member and an expandable positioning element carried on a distal end of the elongate member, the elongate member received though the lumens of the plug and the cartridge such that the cartridge, plug, and pusher member are advanceable from a proximal position on the positioning member to a distal position wherein the plug is disposed adjacent the positioning element;
• and
• cooperating elements on the pusher member and the positioning member that limit subsequent movement of the pusher member relative to the positioning member when the pusher member is advanced to the distal position,
• wherein the positioning member is removable through the pusher member with the positioning element collapsed, thereby allowing the positioning member to be withdrawn from a puncture before the pusher member is withdrawn such that pusher member prevents the plug from moving proximally while the positioning member is withdrawn.