Expandable sheath
A delivery sheath includes an outer tubular layer and an initially folded inner tubular layer. When an implant passes therethrough, the outer tubular layer expands and the inner tubular layer unfolds into an expanded lumen diameter. The sheath may also include selectively placed longitudinal support rods that mediate friction between the inner and outer tubular layers to facilitate easy expansion, thereby reducing the push force needed to advance the implant through the sheath's lumen.
1. A sheath comprising:
an expandable outer member including a lumen extending therethrough;
an inner member extending longitudinally within the lumen of the outer member, the inner member defining a central lumen of the sheath and including a folded portion comprising one or more folds, each of the one or more folds comprising portions of the inner member arranged in an overlapping configuration that move to a less overlapping configuration increasing a diameter of the central lumen of the sheath;
a second folded portion circumferentially spaced around the inner member from the folded portion;
a third folded portion circumferentially spaced around the inner member from the folded portion and the second folded portion, wherein the folded portion, second folded portion and third folded portion are equally spaced circumferentially around the inner member; and
at least two reinforcing members extending longitudinally along a length of the sheath and located radially outward of the folded portion and the second folded portion;
wherein the inner and outer members are configured to expand; and
wherein expansion of the sheath causes a circumferential distance between the at least two reinforcing members to increase from a first circumferential distance to a second circumferential distance.
2. The sheath of claim 1 , wherein when the sheath is in an unexpanded configuration, the folded portion of the inner member is located radially inward of and is at least partially radially aligned with the first circumferential distance between the at least two reinforcing members.
3. The sheath of claim 1 , wherein when the sheath is in an unexpanded configuration, the folded portion of the inner member is located radially inward of and is at least partially radially aligned with one of the at least two reinforcing members.
4. The sheath of claim 1 , wherein the folded portion is configured to at least partially unfold during expansion of the inner member,
wherein the at least partially unfolded portion of the folded portion is at least partially radially aligned with the second circumferential distance between the two reinforcing members.
5. The sheath of claim 1 , wherein the folded portion is configured to at least partially unfold during expansion of the inner member,
wherein the at least partially unfolded portion of the folded portion is at least partially radially aligned with one of the at least two reinforcing members.
6. The sheath of claim 1 , wherein the one or more folds wrap along an inner surface of the inner member.
7. The sheath of claim 1 , wherein when the sheath is in an unexpanded configuration, overlapping portions of the one or more folds extend longitudinally along a length of the inner member, and the overlapping portions extending generally parallel to and partially around a central longitudinal axis of the sheath.
8. The sheath of claim 1 , wherein, the one or more folds form an S-shape, wave-shape, Z-shape, or T-shape in cross-section.
9. The sheath of claim 1 , wherein the folded portion and the second folded portion at least partially unfold during expansion of the inner member,
wherein the at least partially unfolded portions of the folded portion and the second folded portion are at least partially radially aligned with the second circumferential distance between the two reinforcing members.
10. The sheath of claim 1 , wherein the at least two reinforcing members include a first, second and third reinforcing member each extending longitudinally along a length of the sheath, the first, second and third reinforcing members oriented generally parallel to each other and extending in a direction generally parallel to a central longitudinal axis of the sheath,
wherein the folded portion, second folded portion and third folded portion each at least partially unfold during expansion of the inner member,
wherein the at least partially unfolded portions of the folded portion, second folded portion and the third folded portion are at least partially radially aligned with a corresponding portion of the second circumferential distance between the first, second and third reinforcing members.
11. The sheath of claim 1 , wherein the at least two reinforcing members are oriented generally parallel to the other, and the at least two reinforcing members extend in a direction generally parallel to a central longitudinal axis of the sheath.
12. The sheath of claim 1 , wherein the at least two reinforcing members are embedded within a wall of the outer member.
13. The sheath of claim 12 , wherein the at least two reinforcing members and the outer member form a unitary member,
wherein the at least two reinforcing members are manufactured by at least one of coextrusion with the outer member, melting with the outer member, and reflowing with the outer member.
14. The sheath of claim 1 , wherein the at least two reinforcing members are embedded within a wall of the inner member.
15. The sheath of claim 1 , wherein the at least two reinforcing members have a substantially constant width along the length of the at least two reinforcing members.
16. The sheath of claim 1 , wherein the at least two reinforcing members have a width that varies along the length of the at least two reinforcing members.
17. The sheath of claim 1 , wherein the at least two reinforcing members include a thickness that varies along the length of the reinforcing member.