Flexible introducer sheath

1. An introducer apparatus, comprising:

an inner liner having a passageway extending longitudinally therethrough, said passageway having a substantially uniform diameter, said inner liner comprising a polyimide;

a coil in a stressed, expanded condition, said coil comprising a plurality of turns positioned longitudinally around said inner tube, said turns having a predetermined spacing therebetween; and

a polymeric outer tube positioned longitudinally around said coil and said inner liner and bonded to said inner liner through the spaces between said turns;

wherein the polymeric outer tube maintains the coil in said stressed radially expanded condition.

2. The introducer apparatus of claim 1 , wherein said outer tube comprises a polyimide.

3. The introducer apparatus of claim 2 , wherein said inner liner passageway has a substantially uniform diameter.

4. The introducer apparatus of claim 3 , wherein said inner liner has a thickness between about 0.001 and 0.004 inch (0.025 and 0.10 mm).

5. The introducer apparatus of claim 4 , wherein said inner liner has a thickness of about 0.001 inch (0.025 mm).

6. The introducer apparatus of claim 3 , wherein said coil turns are spaced apart a substantially uniform distance.

7. The introducer apparatus of claim 6 , wherein said coil turns are spaced from each other by about 0.008 inch (0.20 mm).

8. The introducer apparatus of claim 6 , wherein said coil comprises flat wire.

9. The introducer apparatus of claim 8 , wherein said flat wire has a thickness between about 0.001 and 0.003 inch (0.025 and 0.075 mm).

10. The introducer apparatus of claim 2 , wherein both the inner liner and the outer tube comprise the same polyimide composition.

11. The introducer apparatus of claim 2 , wherein at least the distal end of the outer surface of said introducer apparatus is coated with a hydrophilic compound.

12. The introducer apparatus of claim 2 , wherein said apparatus has a wall thickness of about 0.004 inch (0.10 mm).

13. A method of making an introducer apparatus, comprising the steps of:

positioning an inner liner over a mandrel;

positioning a coil over said inner liner;

radially stretching the coil into a stressed condition, and mounting the coil to one of said inner liner and said mandrel to maintain the coil in the radially stressed condition;

inserting a substrate comprising said mandrel, said inner liner and said stressed coil into a solution of a polymer, and maintaining said substrate in said polymer solution until a sufficient amount of said polymer adheres to an outer surface of said inner liner to form an outer tube, and to maintain the coil in the stressed condition;

curing said outer tube; and

removing said mandrel.

14. The method of claim 13 , wherein at least one of the inner liner and the outer tube comprises a polyimide.

15. The method of claim 13 , wherein both the inner liner and the outer tube comprise a polyimide.

16. The method of claim 13 , wherein said inner liner comprises a polyimide, and said polymer solution comprises a polyimide bath.

17. The method of claim 16 , wherein said coil is mounted to one of the inner liner and mandrel by clipping the axial ends of the stressed coil to said liner or mandrel.

18. The method of claim 13 , wherein said curing step takes place in an oven.

19. The method of claim 13 , wherein said inner liner has a thickness of about 0.001 inch (0.025 mm).

20. The method of claim 14 , wherein said apparatus has a wall thickness of about 0.004 inch (0.10 mm).