Arteriovenous graft

Abstract

A cannulation chamber for use with an arteriovenous graft including a flexible conduit is provided. The cannulation chamber includes an elongate body defining an annular passage having a longitudinal axis extending between a first end and a second end. The body receives and surrounds the conduit within the passage. The body includes a self-sealing material and a cannulation port exposing the self-sealing material. A flexible, resilient, elongate backplate is embedded in the body of the cannulation chamber such that the backplate extends generally parallel to the passage and can partially surround the passage. The backplate is formed from a substantially rigid material such that when a needle is inserted through the cannulation port and the self-sealing material, the backplate inhibits or prevents a needle from extending through the backplate.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 166,790 and U.S. Provisional Patent Application No. 63 / 166,794, both filed March 26, 2021, the contents of both of which are incorporated herein by reference in their entireties.

[0002] background DETAILED DESCRIPTION OF THE INVENTION Vascular grafts, more specifically arteriovenous grafts used in hemodialysis, are described. [Background technology]

[0003] A common technique for providing vascular access for hemodialysis is to connect an artificial graft or shunt between an artery and a vein, for example, in the upper or lower limbs. Occasionally, patient complexity may justify access placement on the chest or abdominal wall. Conventional artificial arteriovenous grafts (AVGs) are often constructed from polymeric materials such as expanded polytetrafluoroethylene (ePTFE) or polyetherurethane.

[0004] A significant mode of failure of arteriovenous grafts is associated with traumatic cannulation with a dialysis needle. This can occur when the needle traverses the anterior wall of the arteriovenous graft and then continues through the posterior or side wall of the graft. This type of trauma can cause a defect in the posterior or side wall of the graft, often resulting in hematoma formation, and ultimately graft thrombosis (i.e., formation of a blood clot within the graft, obstructing blood flow through the graft) due to external compression of the graft and ultimately graft failure.

[0005] The cannulation-related complications mentioned above can also be exacerbated when the vascular access is difficult to locate under the skin, which can be a common problem associated with vascular access in hemodialysis. Difficulty locating the vascular access can cause significant anxiety for both the cannulator and the patient, as both the dialysis technician / nurse and the patient are well aware that cannulation errors can lead to serious morbidity (e.g., hematoma, bleeding, pain, or swelling) and missed dialysis sessions.

[0006] Furthermore, repeated puncture of graft materials such as ePTFE promotes coring and degeneration of the graft material, often leading to graft rupture, pseudoaneurysm formation, and graft thrombosis. This degeneration process can be significantly accelerated when used in a home hemodialysis (HHD) setting. This is because, to achieve some of the most important benefits of HHD, treatments are typically performed four to six times per week, generally doubling the number of graft punctures per week compared to traditional in-center hemodialysis. Furthermore, ePTFE grafts generally do not self-seal upon puncture and typically require implantation three to four weeks or more before the initial puncture to allow for graft integration, which involves the attachment of a layer of fibrous tissue to the outer surface of the graft.

[0007] Some of these problems have been solved by incorporating rigid or semi-rigid structures into the AVG to prevent needles from passing inside the AVG. For example, a self-sealing vascular access graft is described in U.S. Pat. No. 5,192,310, and the problem of posterior or sidewall perforation of the graft is discussed in U.S. Pat. Nos. 6,261,257 and 9,585,998, all of which are incorporated herein by reference in their entireties. However, because the tight bending required to deploy the AVG into a subject's limb, such as the upper or lower arm, can cause the rigidity of the AVG to kink in areas of the rigid structure, or the clinician may simply not be able to sufficiently bend the chamber during the implantation procedure. As a result, puncture-resistant chambers that are substantially straight or do not bend to an appropriate degree may not be used or may fail in certain applications. Furthermore, bending of a graft using a semi-rigid shield can weaken or kink the graft, or even if the graft is not kinked, can disrupt the flow characteristics of blood through the graft.

[0008] For the foregoing reasons, there is a need for an arteriovenous graft configured to be implanted in a patient's upper or lower extremity that is more kink resistant, easily identifiable, more tolerant to increased frequency of needle punctures, and configured to prevent complications associated with needle cannulation. Ideally, the new graft would be self-sealing, resistant to inadvertent needle penetration, and able to bend or flex without kinking or otherwise affecting fluid flow through the graft. Summary of the Invention

[0009] Abstract A cannulation chamber for use with an arteriovenous graft including a flexible conduit is provided. The cannulation chamber includes an elongated body having a first end and a second end and defining an annular passageway having a longitudinal axis extending between the first end and the second end. The body is adapted to receive and surround at least a portion of the conduit within the passageway. The body includes a flexible, non-porous, elastomeric, self-sealing material and a cannulation port exposing the self-sealing material. A flexible, resilient, elongated backplate having a first end and a second end is embedded in the body of the cannulation chamber. The first and second ends of the backplate are adjacent the first and second ends of the body, respectively, such that the backplate extends generally parallel to the passageway. The backplate is formed from a substantially rigid material such that when a needle is inserted through the cannulation port and the self-sealing material, the backplate is inhibited or prevented from extending therethrough.

[0010] An arteriovenous access graft is also provided, configured to be subcutaneously implanted between a first blood vessel and a second blood vessel of a subject such that blood flows from the first blood vessel to the second blood vessel through the graft. The arteriovenous graft includes a flexible conduit having a first end and a second end and defining a longitudinal flow path between the first end and the second end. The first end is adapted to connect to an artery of the subject, and the second end is adapted to connect to a vein of the subject, such that blood flows through the conduit flow path from the first end to the second end. The cannulation chamber includes an elongate body having a first end and a second end and defining an annular passage having a longitudinal axis extending between the first end and the second end. The body is configured to receive and surround at least a portion of the conduit within the passage. The body includes a flexible, non-porous, elastomeric, self-sealing material and a cannulation port exposing the self-sealing material. A flexible, resilient elongate backplate having a first end and a second end is embedded in the body of the cannulation chamber, the first end and second end of the backplate being adjacent the first end and second end of the body, respectively, such that the backplate extends generally parallel to the passageway. The backplate is formed from a substantially rigid material such that when a needle is inserted through the cannulation port and the self-sealing material, the backplate is inhibited or prevented from extending through the cannulation port backplate.

[0011] In one embodiment, the body of the cannulation chamber includes an outer layer surrounding the cannulation chamber. The outer layer can include ePTFE.

[0012] In one embodiment, the backplate can be planar. In another embodiment, the backplate has a C-shaped cross section and includes a rear wall and a pair of side walls extending from the rear wall and partially enclosing a passageway, defining an open forward portion facing the cannulation port of the body.

[0013] In yet another embodiment, the backplate comprises multiple individual pieces of the same shape embedded within the body, the pieces being unconnected and separated from adjacent pieces with spacing between the pieces sufficient to prevent passage of a needle, or adjacent pieces partially overlapping each other.

[0014] In another embodiment, the pieces are connected at their midpoints by a longitudinal spine that runs parallel to the backplate, or the pieces are connected by a flexible material that spans the space between adjacent pieces.

[0015] The backplate can have a plurality of openings that are small enough to prevent passage of a needle. The openings can be hexagonal.

[0016] In one embodiment, the backplate has opposed longitudinal side edges extending between first and second ends, and spaced linear blind slots extend inwardly at right angles from the edges to define a zigzag pattern that zigzags transversely to the longitudinal axis between the side edges of the backplate.

[0017] The body of the cannulated chamber can be curved to accommodate placement in the subject's limb, with an arc angle of 10 to 30 degrees formed by the longitudinal axis at one end of the curved chamber and an axis parallel to the longitudinal axis of the straight chamber.

[0018] In a further aspect, the body has an exterior surface that includes a continuous raised perimeter portion adjacent the cannulation port to provide tactile or visual identification of the cannulation port. Alternatively, the exterior surface can include a pair of spaced parallel flanges adjacent the cannulation port to provide tactile or visual identification of the cannulation port and to allow for manipulation of the cannulation chamber after the implant procedure.

[0019] There may be a bead of material disposed around at least a portion of the length of the conduit. [Brief explanation of the drawings]

[0020] BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the vascular arteriovenous graft, reference should be made to the embodiments illustrated in the accompanying drawings and described below.

[0021] [Figure 1] FIG. 1 is a perspective view of one embodiment of a vascular arteriovenous graft.

[0022] [Figure 2] FIG. 2 is a top view of the arteriovenous graft as shown in FIG.

[0023] [Figure 3] FIG. 3 is a side view of the arteriovenous graft as shown in FIG.

[0024] [Figure 4] FIG. 4 is a longitudinal cross-sectional view of the arteriovenous graft as shown in FIG. 1 taken along line 4-4 of FIG.

[0025] [Figure 5] FIG. 5 is a transverse cross-sectional view of the arteriovenous graft as shown in FIG. 1 taken along line 5-5 of FIG.

[0026] [Figure 6] FIG. 6 is a top view of one embodiment of a flexible conduit for use in an arteriovenous graft as shown in FIG.

[0027] [Figure 7] FIG. 7 is a top perspective view of one embodiment of a flexible backplate used in the arteriovenous graft as shown in FIG.

[0028] [Figure 8]FIG. 8 is a perspective view of one embodiment of a cannulation chamber for use with the arteriovenous graft as shown in FIG. 1 , shown in dashed lines, excluding the backplate as shown in FIG. 7 , which is shown in solid lines.

[0029] [Figure 9] FIG. 9 is another embodiment of an arteriovenous graft that includes two spaced apart cannulated chambers.

[0030] [Figure 10] FIG. 10 is an enlarged front perspective view of the cannulation chamber as shown in FIG.

[0031] [Figure 11] FIG. 11 is a perspective view of another embodiment of a flexible backplate for use in the arteriovenous graft as shown in FIG.

[0032] [Figure 12] FIG. 12 is a perspective view of a third embodiment of a flexible backplate for use in the arteriovenous graft as shown in FIG.

[0033] [Figure 13] FIG. 13 is a perspective view of a fourth embodiment of a flexible backplate for use in an arteriovenous graft as shown in FIG.

[0034] [Figure 14] FIG. 14 is a perspective view of a fifth embodiment of a flexible backplate for use in an arteriovenous graft as shown in FIG.

[0035] [Figure 15] FIG. 15 is a perspective view of a portion of a sixth embodiment of a flexible backplate for use in the arteriovenous graft as shown in FIG.

[0036] [Figure 16]16 is a perspective view of a portion of a fifth embodiment of a flexible backplate for use in the arteriovenous graft shown in FIG. 1. FIG.

[0037] [Figure 17] 17A-17C are a top perspective view, a top view, and a side view, respectively, of another embodiment of a cannulation chamber for use with the arteriovenous graft as shown in FIG.

[0038] [Figure 18] 18A and 18B are a perspective view and a cross-sectional view, respectively, taken along line 18B-18B of FIG. 18A, illustrating a third embodiment of a cannulation chamber for use with the arteriovenous graft shown in FIG.

[0039] [Figure 19] 19A and 19B are a perspective view and a cross-sectional view, respectively, taken along line 19B-19B of FIG. 19A, illustrating a fourth embodiment of a cannulation chamber for use with the arteriovenous graft shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0040] explanation The present invention will now be described in more detail with reference to the accompanying drawings, in which embodiments of the invention are shown. However, the present invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. The thickness and dimensions of some components may be exaggerated for clarity.

[0041] Additionally, spatially relative terms such as "under," "below," "lower," "over," "upper," "downward," "upward," "inward," and "outward" may be used herein for ease of description to describe the relationship of one element or feature to another element or feature as shown in the figures. It is understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures were turned over, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus, the exemplary term "under" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptions used herein would be interpreted accordingly.

[0042] An embodiment of an arteriovenous graft is shown in FIG. 1 and is generally designated 30. The arteriovenous graft 30 is configured to be implanted into a subject. The AVG 30 includes a conduit 32 having a first end 34 and a second end 36. The conduit 32 may be formed of an inert, biocompatible material, such as ePTFE, polyurethane, or Dacron. The conduit 32 may also be formed from other biological materials, such as animal or human conduits or biologically engineered tissue conduits. The first end 34 is configured to connect at its end to a first blood vessel of the subject, such as an artery. The second end 36 is configured to connect at its end to a second blood vessel of the subject, such as a vein. In this regard, blood flows through the conduit 32 from the first end 34 to the second end 36. The arteriovenous graft 30 can be used as an arterio-arterial graft, for example, when the vein can instead be an artery. A beading material 38 can be included on the outer periphery of the conduit 32. Such beading material may be in the form of PTFE wrapped around the exterior surface in a spiral or helical configuration, which provides some resistance to kinking or kink resistance. One or both of the ends 34, 36 of the conduit 32 may be corrugated. Other examples of external support or localized strain relief may be used, particularly at the intersection of the conduit 32 and the cannulation chamber 40, including rings, bushings, or other means for mitigating kinking of the arteriovenous graft 30 at the transition from the chamber body 46 to the conduit 32.

[0043] The cannulation chamber 40 is disposed between the first end 34 and the second end 36 of the conduit 32. The chamber 40 includes an inlet end 42 and an outlet end 44. The conduit 32 extends through the chamber 40 from the inlet end 42 to the outlet end 44. The chamber 40 includes an elongated chamber body 46 that surrounds the conduit 32. The chamber body 46 defines the chamber inlet 42 and the chamber outlet 44. The chamber 40 further includes a flexible elongated backplate 50 embedded in the chamber body 46.

[0044] Cross-sectional views of the cannulated chamber 40 are shown in FIGS. 4 and 5. As shown, the chamber body 46 has an inner surface 52 and an outer surface 54. An outer layer of material, such as ePTFE, can be added to the chamber 40 to promote tissue ingrowth and minimize foreign body reaction adjacent to the chamber. The inner surface 52 can define an annular fluid flow path having a longitudinal axis coaxial with the longitudinal axis of the chamber 40. The longitudinal passage extends from the inlet end 42 to the outlet end 44 of the chamber body 46. The longitudinal passage defines a longitudinal fluid flow path through which blood flows. The longitudinal passage has a circular or substantially circular cross-section. This configuration accommodates a conduit 32 having a similarly shaped flow path to minimize disruption of laminar flow. The conduit 32 is shown in the drawings extending through the chamber body 46. This configuration allows the conduit 32 to maintain a circular or substantially circular cross-section or shape, reducing disruption of flow therethrough.

[0045] The backplate 50 can be disposed between the inner surface 52 and the outer surface 54 of the cannulation chamber 40. In particular, the chamber body 46 can be molded around the backplate 50. Alternatively, the backplate 50 can be glued or otherwise attached to the inner surface 52. The inner surface 52 can then be glued or otherwise attached to the conduit 32. The chamber body 46 is formed from a flexible self-sealing material, such as, but not limited to, silicone, which is a stretchable material suitable for repeated punctures. When a needle N is inserted through the self-sealing material, the self-sealing material can self-seal after removal of the needle N. In various embodiments, the self-sealing material 80 can have a thickness of about 0.5 mm to about 10 mm, or about 1 mm to about 5 mm.

[0046] In some embodiments, the arteriovenous graft 30 can have a total extended length of about 30 cm to about 80 cm. The ends 34, 36 of the conduit 32 can each have a length of about 5 cm to about 15 cm. The ends of the conduit can be trimmed or shaped to create an anastomosis. The ends of the conduit can also have a hooded configuration to provide additional options for anastomosis creation.

[0047] The backplate 50 is formed from a substantially rigid biocompatible material, such as a biocompatible metal, including, for example, nitinol and titanium, or a substantially rigid polymer or composite, including thermoplastic polyurethane and silicone. Mesh or woven materials, such as Kevlar, chainmail, or other puncture-resistant fabrics, can also be used. Hard biomaterials, such as connective tissue, are also possible. When a dialysis needle is inserted through the cannulation port 66 of the chamber 40, the needle is prevented or substantially prevented by the backplate 50 from extending through the rear wall 60 or one of the side walls 62 of the chamber body 46. The plate 50 can be any shape, such as flat ( FIG. 13 ), C-shaped, or U-shaped in the form of a half-cylindrical opening at both ends, to prevent the needle N from penetrating the backplate. In this C-shaped or U-shaped configuration, the backplate 50 includes a rear wall 60 and opposing side walls 62 that define a cavity 64. The conduit 32 may be received within a cavity or recess 64 defined by the backplate 50. The backplate 50 therefore surrounds the chamber body 46 and the conduit 32 approximately 180 degrees around the periphery. The backplate 50 has a length that is at least a substantial portion of the length of the chamber 40. In some embodiments, the lengths of the backplate 50 and the chamber 40 are substantially the same. The backplate 50, the conduit 32, and the chamber body 46 may be provided as an integrated cannulation chamber 40. The cannulation chamber 40 may be molded and then fitted over the graft conduit 32.

[0048] The cannulation chamber 40 has an open forward portion that includes an aperture that defines a cannulation port 66 configured to receive a dialysis needle. As mentioned above, in some embodiments, the exterior surface 54 can include an additional layer of material, such as ePTFE or a self-sealing material, that traverses the cannulation port 66. The chamber body 46 can include a raised perimeter or rim 68 that defines the port 66, thereby providing tactile or visual identification of the cannulation port when the AVG is implanted in a subject. That is, the raised perimeter can be seen through the subject's skin or felt through the skin by medical personnel as a port-locating feature.

[0049] When a dialysis needle is inserted through the cannulation port 66, the needle may be inhibited or prevented from extending through the rear wall 60 or side wall 62 of the backplate 50. Referring to the backplate 50 as shown in FIGS. 7 and 8 , the backplate 50 is an elongated, flexible, resilient member configured to provide structural support to the cannulation chamber 40 while preventing the needle from passing through the body. The backplate 50 includes two opposing major longitudinal edges 70 that are substantially equidistant from one another along the length of the backplate. The end edges 72 of the backplate 50 are much shorter and extend between and interconnect the longitudinal edges 70 of the backplate 50. The backplate 50 has blind linear slots 74 extending perpendicularly from the longitudinal edges 70 of the backplate 50. The slots 74 extend alternately from one edge and then the opposite edge. The backplate 50 is curved so that the width of the slots 74, starting from the outer curved edge 70 of the backplate, is approximately 2.7 mm. The width of slot 74, which begins at the inner curved edge of backplate 50, is approximately 0.8 mm. Thus, slot 74 is small enough to prevent needle penetration, yet still allows backplate 50 great flexibility.

[0050] Another embodiment of a flexible, resilient backplate is shown in FIG. 11 and is generally designated 80. The backplate 80 includes multiple identical U-shaped pieces 82 joined at their midpoints by spines 84 extending along the length of the backplate. Other than the connections at the spines 84, the pieces 82 do not include any other connections, allowing free movement of each piece and the backplate 80. Other backplate embodiments can be configured as a solid C- or U-shaped backplate 90 (FIG. 12) or a substantially planar backplate 92 (FIG. 13). In yet another embodiment, a concave solid backplate 94 (FIG. 14) can be drilled with multiple openings 96. The openings 96 in the backplate 94 are small enough to prevent needle penetration. In the illustrated embodiment, the openings 96 are hexagonal, thereby creating a honeycomb-like appearance for the multiple openings 66 along the backplate 94.

[0051] 15, yet another embodiment of a backplate is shown and generally designated 100. In this embodiment, the backplate 100 includes individual C-shaped pieces 102 that overlap, but are not directly connected to, one another when molded into the cannulation chamber 40. This configuration allows each piece 102 to move freely, providing the desired overall flexibility for the cannulation chamber 40. FIG. 16 shows a similar configuration, except that the individual pieces 102 are connected by a flexible material 104 that does not restrict the relative movement of the pieces 102 and the flexibility of the chamber 40.

[0052] As described above and shown in the drawings, the cannulated chamber 40 and associated backplate 50 can be curved to varying degrees to accommodate implantation procedures in various locations throughout the body. The cannulated chamber is shown with a longitudinal passageway extending from the inlet end 42 through the outlet end 44. The curvature angle, or arc angle, is defined by the angle between the passageway extending from the inlet or outlet 42, 44 and an axis parallel to the longitudinal axis defined by a "straight" cannulated chamber 40. The cannulated chamber 40 may be generally symmetrical, i.e., the arc angle at each end may be equal. For purposes of this application, a chamber generally referred to as having an "arc angle" or "curvature angle" or "curved" to a particular value (e.g., number of degrees) is a chamber having equal or substantially equal angles A1 and A2. The chamber may initially be curved between about 0 degrees and about 60 degrees. In other words, each of the arc or curve angles A1 and A2 can be from about 0 degrees to about 60 degrees. The curved chamber forms a curved longitudinal passageway or flow path therethrough. The curved chamber can be configured to provide a surface area of ​​the cannulation port 30 on the front exterior surface of the housing of about 10 degrees to about 30 degrees, for example, to be configured for implantation in a subject's arm, so that a large "target" cannulation area can be advantageously provided. It will be appreciated that because the cannulation chamber 40 is flexible, the angle of curvature can be changed or customized during the implantation procedure to accommodate the anatomical location and position of the graft 30. Furthermore, the cannulation chamber 40 as described herein is sufficiently flexible to allow the ends 42, 44 to come together so that the cannulation chamber 40 forms a closed loop. While this arrangement may not be necessary for the application, it demonstrates the degree of flexibility of the cannulation chamber 40.

[0053] Referring to FIGS. 17A-17C, another embodiment of the cannulation chamber 40 is shown, including multiple domes spaced longitudinally along the front of the chamber body 46. The domes 106 replace the cannulation port 66 and provide tactile feedback to the user in determining the cannulation target. FIGS. 18A and 18B show a third embodiment of the cannulation chamber 40, including circumferentially spaced ears 108 that replace the cannulation port 66. The ears 108 allow the cannulation chamber 40 to be manipulated across the skin boundary when in a subcutaneous position for implantation and to aid in cannulation. Also, in FIGS. 19A and 19B, the ears 108 are replaced by rails 110, which are smaller and spaced further circumferentially apart than the ears 108. The rails 110 provide rotational position information for the cannulation chamber 40 along with transcutaneous tactile feedback.

[0054] It is contemplated that the cannulation chamber 40 as described herein can be prepared separately from the conduit 32. It is also contemplated that the various components described above can be supplied as a medical kit. For example, the chamber may be supplied with the conduit for later assembly and use. Each arteriovenous graft 30 can include two or more cannulation chambers (FIG. 9). The chambers may be identical or substantially identical. An intermediate portion of the conduit 32 is typically disposed between the chambers.

[0055] The arteriovenous graft 30 as described herein has many advantages, including a self-sealing, ready-to-use graft that is flexible when the graft is implanted and maintained in a subject. The AVG can be bent or otherwise manipulated to accommodate a particular implantation site or geometry as the patient moves through daily activities. The graft is versatile enough to be implanted in different or specific configurations within a subject's body, depending on the implantation location selected based on the appropriate vascular anatomy. The arteriovenous graft is flexible due to the backplate, which allows the cannulation chamber to flex while resisting needle puncture of the posterior or lateral wall. Because the arteriovenous graft is flexible, the cannulation chamber can be larger to conform to the underlying patient anatomy. This allows for longer and larger cannulation areas, facilitating more frequent cannulation, such as during home hemodialysis. Other embodiments as described herein create an improved tactile interface to more easily locate the location for cannulating the graft. Additionally, embodiments of the arteriovenous graft are compatible with any ePTFE graft, biological graft, and fistula. The arteriovenous graft can help prevent traumatic cannulation or graft degeneration that leads to higher arteriovenous graft patency rates, reduce the risk of bleeding or infection in hemodialysis patients, and reduce overall vascular access-related medical costs.

Claims

1. 1. A cannulation chamber for use with an arteriovenous graft including a flexible conduit, said cannulation chamber comprising: an elongated body having a first end, a second end, an inner surface, an outer surface, and an annular passage defined by said inner surface and having a longitudinal axis extending between said first end and said second end, wherein said body is adapted to receive and surround at least a portion of a conduit within said passage; a flexible, non-porous, elastomeric, self-sealing material; and a cannulation port exposing said self-sealing material; and a flexible, resilient elongate backplate having a first end and a second end, wherein the backplate is embedded in the body of the cannulation chamber such that the flexible, resilient elongate backplate is disposed between the inner and outer surfaces of the elongate body with the first and second ends of the backplate adjacent the first and second ends of the body, respectively, such that the backplate extends generally parallel to the passageway; Including, the backplate is formed from a substantially rigid material such that when a needle is inserted through the cannulation port and the self-sealing material, the needle is inhibited or prevented from extending through the backplate.

2. The cannulation chamber of claim 1 , wherein the body includes an outer layer surrounding the cannulation chamber.

3. The cannulation chamber of claim 2 , wherein the outer layer comprises ePTFE.

4. The cannulation chamber of claim 1 , wherein the backplate is flat.

5. 2. The cannulation chamber of claim 1, wherein the backplate has a C-shaped transverse cross section, the backplate including a rear wall and a pair of side walls extending from the rear wall, partially enclosing the passageway and defining an open front facing the cannulation port of the body.

6. 2. The cannulation chamber of claim 1, wherein the backplate comprises a plurality of separate, identical pieces that are not connected to adjacent pieces but are separate and embedded within the body with spacing between pieces sufficiently close to prevent passage of a needle.

7. 2. The cannulation chamber of claim 1, wherein the backplate comprises a plurality of separate, identical pieces that are embedded in the body without being connected to adjacent pieces such that adjacent pieces partially overlap one another.

8. The cannulation chamber of claim 6 , wherein the pieces are connected at their midpoints by a longitudinal spine that extends parallel to the backplate.

9. The cannulation chamber of claim 6 , wherein the pieces are connected by a flexible material spanning the spaces between the pieces.

10. The cannulation chamber of claim 5 , wherein the backplate has a plurality of openings small enough to prevent passage of a needle.

11. The cannulation chamber of claim 10, wherein the opening is hexagonal.

12. 6. The cannulation chamber of claim 5, wherein the backplate has opposed longitudinal side edges extending between the first end and the second end, and spaced apart linear blind slots extending inwardly perpendicularly from the edges defining a zigzag pattern that zigzags transversely to the longitudinal axis between the side edges of the backplate.

13. 2. The cannulation chamber of claim 1, wherein the body is curved to accommodate placement on a subject's limb such that the arc angle formed by the longitudinal axis at one or other end of the curved chamber and an axis parallel to the longitudinal axis of the straight chamber is between 10 and 30 degrees.

14. The cannulation chamber of claim 1 , wherein the body has an exterior surface including a continuous raised perimeter portion adjacent the cannulation port such that the cannulation port is tactilely or visually identifiable.

15. 2. The cannulation chamber of claim 1, wherein the chamber body has an outer surface including a pair of spaced parallel flanges adjacent the cannulation port to allow tactile or visual identification of the cannulation port and to allow manipulation of the cannulation chamber after an implant procedure.

16. 1. An arteriovenous access graft configured to be subcutaneously implanted in a subject between a first blood vessel and a second blood vessel of the subject such that blood flows through the graft from the first blood vessel to the second blood vessel, the arteriovenous graft comprising: a flexible conduit having a first end, a second end, an interior surface, an exterior surface, and a longitudinal flow path defined by the interior surface between the first end and the second end, wherein the first end is adapted to connect to an artery of a subject and the second end is adapted to connect to a vein of a subject, whereby blood flows through the flow path of the conduit from the first end to the second end; a cannulation chamber, wherein said cannulation chamber comprises: an elongated body having a first end and a second end and defining an annular passage having a longitudinal axis extending between the first end and the second end, the body being configured to receive and surround at least a portion of a conduit within the passage; a flexible, non-porous, elastomeric, self-sealing material; and a cannulation port exposing said self-sealing material; and a flexible, resilient elongate backplate having a first end and a second end, wherein the backplate is embedded in the body of the cannulation chamber such that the backplate is disposed between the inner and outer surfaces of the flexible conduit with the first and second ends of the backplate adjacent the first and second ends of the body, respectively, such that the backplate extends generally parallel to the passageway; Contains, It contains an arteriovenous access graft, wherein the backplate is formed from a substantially rigid material such that when a needle is inserted through the cannulation port and the self-sealing material, the needle is inhibited or prevented from extending through the backplate.

17. The arteriovenous access graft of claim 16, further comprising a bead of material disposed around at least a portion of the length of the conduit.

18. The arteriovenous access graft of claim 16 , wherein the body includes an outer layer surrounding the cannulation chamber.

19. The arteriovenous access graft of claim 18 , wherein the outer layer comprises ePTFE.

20. The arteriovenous access graft of claim 16 , wherein the backplate is flat.

21. 17. The arteriovenous access graft of claim 16, wherein the backplate has a C-shaped transverse cross section, the backplate including a posterior wall and a pair of side walls extending from the posterior wall, partially enclosing the passageway and defining an open front facing the cannulation port of the body.

22. 17. The arteriovenous access graft of claim 16, wherein the backplate comprises a plurality of separate, identical pieces that are not connected to adjacent pieces but are separate and embedded within the body with spacing between pieces close enough to prevent passage of a needle.

23. 17. The arteriovenous access graft of claim 16, wherein the backplate comprises a plurality of separate, identical pieces that are embedded in the body without being connected to adjacent pieces such that adjacent pieces partially overlap each other.

24. 23. The arteriovenous access graft of claim 22, wherein the pieces are connected at their midpoints by longitudinal spines that extend parallel to the backplate.

25. The arteriovenous access graft of claim 22 , wherein the pieces are connected by a flexible material spanning the spaces between the pieces.

26. The arteriovenous access graft of claim 21 , wherein the backplate has a plurality of openings small enough to prevent passage of a needle.

27. 27. The arteriovenous access graft of claim 26, wherein the opening is hexagonal.

28. 22. The arteriovenous access graft of claim 21, wherein the backplate has opposed longitudinal side edges extending between the first end and the second end and spaced apart linear blind slots extending inwardly perpendicularly from the edges defining a zigzag pattern that zigzags transversely to the longitudinal axis between the side edges of the backplate.

29. 17. The arteriovenous access graft of claim 16, wherein the body is curved to accommodate placement in a subject's limb such that the arc angle formed by the longitudinal axis at one or other end of the curved chamber and an axis parallel to the longitudinal axis of the straight chamber is between 10 and 30 degrees.

30. The arteriovenous access graft of claim 16, wherein the body has an exterior surface including a continuous raised perimeter portion adjacent the cannulation port such that the cannulation port is tactilely or visually identifiable.

31. 17. The arteriovenous access graft of claim 16, wherein the chamber body has an outer surface including a pair of spaced parallel flanges adjacent the cannulation port to allow tactile or visual identification of the cannulation port and to allow manipulation of the cannulation chamber after the implant procedure.

32. The cannulation chamber of claim 1 , wherein the cannulation port is defined such that an aperture exposes a front side of the self-sealing material.

33. 33. The cannulation chamber of claim 32, wherein the backplate is disposed behind the self-sealing material.

34. The cannulation chamber of claim 1 , wherein the backplate is positioned opposite the cannulation port.

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