Tube with reverse necking properties

ES 2 575 244 T3

DESCRIPTION

Tube with reverse necking properties

Field of the invention

The present invention relates to an improved tubular structure with unique properties suitable for a wide range of applications, including use in manufacturing, as an apparatus for positioning and deployment of medical diagnosis and treatment devices on a body, and in other uses.

Description of Related Art

A known property of many tubular constructions, such as those made of flexible plastic materials, is that the tube will contract in diameter, if the tube is elongated longitudinally. This property is commonly referred to as "stricture". Such tightening can be problematic in many applications.

For example, if a plastic wrap is applied on a mandrel in a manufacturing process, stretching on the end of the plastic wrap to pull the wrap out of the mandrel will result in pinching of the wrap on the mandrel. This sometimes makes it difficult or impossible to slide the plastic coil out of the mandrel, necessitating cutting of the coil or distorting the mandrel to separate the coil.

Similarly, constriction can likewise be a factor if a plastic tube is used to contain or constrict a device. For example, in self-expanding medical devices for remote deployment to a patient, such as an endoprosthesis or blood filter, the designer of the device can adapt the constriction of the plastic tube if it must be separated from the medical device through relative sliding of the tube. device and constriction tube. Typically, this requires the use of plastic tubes that resist constriction, such as thicker and / or more rigid materials that can add undesirable profiles to the device and / or reduce its flexibility and maneuverability within the body. Optimizing compactness and flexibility are highly desirable, as clinicians try to achieve tighter treatment sites through narrower and more tortuous blood vessels.

Alternatively, a medical device designer may employ other deployment methods to separate the tube from the implantable device. For example, a constriction sleeve can be designed to be cut or slit from the implant device, as described in US Patent 6,352,561 to Leopold et al. Others have suggested extending the sleeve to reduce the force required to slide the sleeve out of the implantable device. Variations on this concept are described, for example, in US patent 4,732,152 to Wallsten, in US patent 5,571,135 to Fraser et al., In US patent 6,942,682 to Vrba et al. , and in US application 2006/0025844 in the name of Majercak et al., and US patent application 2006/0030923 in the name of Grunderson.

US 2008/0312733 A1 describes a radially compliant, implantable stent that includes a plurality of coiled elongated members.

Although the extension of the sleeves may reduce the stress that must be applied to the constriction sleeve, they may still require considerable tension in order to stretch the sleeve on themselves and on the self-expanding device during deployment, which is primarily from friction of the extended portion of the sleeve rolling against the unextended portion of the sleeve while the sleeve is being removed. To some degree, the sleeve material tapers onto the device during deployment, further complicating device design. These issues are combined with longer device lengths and tightly compact self-expanding devices that exert greater outward pressures. The greater the tension required to extend and remove the sheath, the greater the strain on the medical team removing the sheath while trying to retain the apparatus in its exact position during deployment. Increased deployment stresses also require more substantial sleeve constructions, to prevent the sleeve and deployment line from breaking during deployment. These sheath extension deficiencies are believed to have limited practical applications for such deployment methods.

In published United States application SN 12 / 014,536 to Irwin et al. (MP / 263) a deployment sleeve has been proposed that includes diametrically stored material to assist in removal of the sleeve during deployment of the implantable device. For example, by constructing a constriction sleeve with one or more pleats or "folds", it is much easier to extend the sleeve on itself during deployment by allowing the pleats to open as the sleeve extends over itself. This essentially produces an inverse effect of the constriction - as the folds open, the tubular sleeve appears to grow diametrically, while extending on itself. This has been found to help greatly in the deployment process. As a result, such folded display sheaths are believed to be useful in a wide range of medical diagnostic and treatment devices, including stents, stent grafts,

ES 2 575 244 T3 balloons, blood filters, occluders, probes, valves, electronic conductors, orthopedic devices, etc.

Clearly bent tubes can be used not only to address the problem of constriction, but can actually allow the tube to increase in effective diameter as axial force is applied to the tube. This is an important advance over prior medical device deployment apparatuses. Regardless, the application of folded sheaths with strictly controlled "growth" properties, as required for medical device deployment, requires careful design and quality control controls. Folded sleeves also work well when deployed in extended tube configurations.

The use of a folded sheath to constrict and unfold a medical device such as when used as described above may be desirable, but it is recognized that a single layer of material would be preferable for such applications, since the profile is further reduced. Of the device.

US 2008/0312733 describes a polymeric shape memory stent.

WO 03/045284 describes an endovascular graft and a graft trimmer.

Accordingly, it would be desirable to develop a tubular apparatus that is capable of increasing diametrically as axial tension is applied to it.

Furthermore, it would be desirable to develop a tubular construction that increases in diameter when axially elongated, which can be used in single or multiple layers, both cone and without pleats.

Summary of the invention

The present invention relates to an improved tubular structure that is adapted to increase the diameter when axial force is applied to the structure. This increase in diameter can be accomplished by constructing the tube from multiple layers of material that move relatively relative to each other during axial elongation of the tube. The tube of the present invention can be used to avoid "pinching" problems found in many prior tube devices, and to provide additional benefits that tube diameter increases during axial elongation can provide. As such, the tube of the present invention can be used as a manufacturing aid, as a deployment sheath (eg, for dispensing medical devices), and in other applications that can benefit from easier removal of the tubular sheath.

In an embodiment of the present invention, a tubular structure is provided according to claim 1. A tubular structure comprises a first helical winding at a first winding angle and a second helical winding at a second winding angle, having the tubular structure a first diameter and a first axial length. When the tubular structure is increased from the first axial length to a second alarmed axial length, the first diameter increases to a second enlarged diameter.

A tubular structure has a longitudinal axis comprising a winding of at least one tape at a first winding angle of x, and a winding of at least one tape at a second winding angle of y, both windings being in the same relative direction. . The two winding angles x and y are both formed at an angle of 0 to 90 degrees with respect to the axis of the tubular structure, the angle x being different from the angle y, and the angles x and y being oriented at an acute included angle one with respect to the other. When an axial force is applied to the tubular structure, both x and y angles are reduced relative to the longitudinal axis, and the acute included angle between x and y is increased. Preferably, one or both tapes are anisotropic, being relatively non-compliant in the direction of winding. Constructed in this way, when the tubular structure increases from the first axial length to a second elongated axial length, the first diameter increases to a second enlarged diameter.

Another defined structure comprises a tubular structure having a first axial length and a first diameter, in which an off-axis strain forms in the tubular structure under stress. When stress is applied to the tubular structure, the tubular structure assumes a second elongated axial length and a second enlarged diameter.

Furthermore, a tubular device is defined having a tubular structure with at least one helically oriented element and a diameter. The application of axial force to the tubular device causes the helically oriented element to unwind at least partially, increasing the diameter of the tubular device.

One of the advantages of the present invention is that it can be used as a single layer of uniform thickness. When used, for example, to deploy medical devices, these properties are believed to provide important benefits over extended and / or folded tubes of the prior art. However, it should be appreciated that the present invention can be incorporated with extended or folded constructions (or both) to provide additional improved properties. In all of these iterations, the present invention provides the

ES 2 575 244 T3 advantage of providing a remotely deliverable medical device with narrower profile and more adaptable, and device deployment with better tension and more exact placement.

As a medical device display apparatus, the present invention can be used to display a wide variety of devices for diagnosing and / or treating patients. Such devices can include stents, stent grafts, balloons, blood filters, occluders, probes, valves, electronic conductors (eg, stimulation or defibrillator conductors), orthopedic devices, and the like. The deployment apparatus can be modified to meet many different device delivery and deployment needs. For example, the winding number, winding angles, types of winding materials, the use of grooves or other means of deflection, the use of pleats, the orientation of the pleats, the use of eversion of the function, etc. . can be adjusted to allow devices to be deployed in different ways. Additionally, sheaths can be mounted in a variety of ways on devices to meet different deployment requirements, such as allowing a device to deploy a catheter from hub to tip or from tip to hub, or from a midpoint of one device out in both directions.

Additional features and advantages of the invention will be set forth in the description that follows and in part will be apparent from the description, or may be learned by practice of the invention. The objects and other advantages of the invention will be realized and achieved by the structure indicated particularly in the written description and in the claims thereto as well as in the accompanying drawings.

It will be understood that both the following general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the claimed invention.

Brief description of the drawings

The incorporated drawings, which are included to provide a better understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

Figure 1 is an elevation view of a schematic model demonstrating the concept of the present invention, in a constrained configuration.

Figure 2 is an elevation view of the schematic model of Figure 1 with the model subjected to axial load, demonstrating an increase in the diameter of the model as the model elongates.

Figure 3 is a diagram illustrating the relative orientations of the components of the present invention in a first unconstrained configuration.

Figure 4 is a diagram illustrating the relative orientations of the components of the present invention in a second constrained configuration under axial load.

Figure 5 is a schematic representation of a first embodiment of a tube of the present invention.

Figure 6 is a schematic representation of a second embodiment of a tube of the present invention.

Figure 7 is a schematic representation of a third embodiment of a tube of the present invention.

Figure 8 is a schematic representation of one embodiment of a tube of the present invention.

Figure 9 is a plan view of a tube of the present invention mounted on a mandrel.

Figure 10 is a plan view of one embodiment of a tube of the present invention used in a medical device deployment system mounted near a distal end of a delivery catheter.

Figure 11 is an enlarged perspective view of a distal end of a delivery catheter showing the tube of the present invention as it is unwound, progressively releasing a self-expanding stent contained therein.

Detailed description of the illustrated embodiments

Reference will now be made in detail to an embodiment of the present invention, the example of which is illustrated in

ES 2 575 244 T3 the accompanying drawings.

The present invention relates to an improved tubular structure that is adapted to increase in diameter when axial force is applied to the structure. This increase in diameter is preferably accomplished by constructing the tube from multiple layers of material that move relatively relative to each other during axial elongation of the tube.

In its simplest form, the tubular structure of the present invention comprises a first helical coil at a first coil angle and a second helical coil at a second coil angle, the tubular frame having a first diameter and a first axial length. When the tubular structure increases from the first axial length to a second elongated axial length, the first diameter increases to a second enlarged diameter. This concept is best illustrated in the model shown in Figures 1 and 2.

Figure 1 shows a model 10 comprising a first helical structure 12, in the form of a permanently elongated SLINKY® spring toy, exhibiting a first angle of winding from axis 14. A winding of a second helical structure 16, in the form of of three sections 18aa, 18b, 18c, it is fixed at approximately equidistant points around the first helical structure 12. In this first unconstrained configuration, the model comprises a first diameter x.

Figure 2 shows the same model 10 with axial force applied to the structure, causing its elongation. The effect of this elongation is that the angle of the second helical structure 16 is reduced relative to axis 14. This has the effect of essentially "unscrewing" the first helical structure 12. This relative movement of the first helical structure causes the model 10 grow radially to a second enlarged diameter and.

This phenomenon can be further understood by reference to the diagrams of Figures 3 and 4. Figure 3 is a diagram illustrating in two dimensions a parallelogram-shaped element that defines the orientations of the components of the present invention in a first unconstrained configuration. The axis of the tubular structure is defined by line 14. A winding angle of first component 12 is defined by angle ángulo from axis 14. A winding angle of the second component 16 is defined by the angle γ from axis 14. As indicated in Figure 3, it is desirable that the first and second components 12, 16 have minimal flexibility along their winding angles Θ , γ respective. Oriented in this way, the direction of primary strain in this structure is along line 20. The circumference (diameter) of this tube is defined by the distance between points AA.

When axial load is applied along line 14 to the structure of Figure 3, the resulting reorientation of the structure is illustrated in Figure 4. As the tube elongates, the angle γ will decrease. The circumference as defined by the line A'-A 'will increase accordingly until the angle eventually reaches zero (0).

By constructing a tube in this way, it has been determined that tubes can be designed that can provide increases in diameter during elongation of 5, 10, 15, 20, 25% or more. Even larger diameter changes are possible, with increments of 30, 35, 40, 45, 50% or more easily achievable. Theoretically, even more substantial diameter changes from 100% to 500% to 1000% or more can be achieved, constrained by practical material and application limitations such as true shaft oriented deformation, wall thinning, axial elongation , lack of targeted resistance, etc. as the angles converge and approach the axis.

There are numerous options for creating a tube of the present invention. Preferably, the tube comprises two or more unidirectional deflection windings of material at different angles about the intended axis. Preferably, the angle Θ of the first component is between about 0 and 90 degrees from the axis of the tube, with about 45 to 85 degrees being more preferred, and about 60 to 80 degrees being still more preferable. In the same way, the angle γ of the second component is between about 0 and 90 degrees from the axis of the tube, and about 10 to 80 degrees being more preferable, and still more preferably about 20 to 60 degrees. In general, the component 12 with a small pitch and a large winding angle resistencia provides resistance from the ring to the tube; the large pitch / small winding angle component 16 provides axial strength and limits axial deformation.

For some applications, it may be desirable to include additional coils of three, four, five, or more layers of material to provide additional strength, increased thickness or cushioning, modified permeability, or other desirable application-specific properties.

The components of the tube of the present invention can take a number of forms. For most applications, it is preferred to employ tapes of material that provide oriented strength and minimal flexibility in the direction of their respective winding angles. The first component should be attached to the second component such that a change in the angle of the first component produces a resulting change in the angle of the

ES 2 575 244 T3 second component in relation to the longitudinal axis of the tube. Outside of their wrap angles, for many applications it is preferable to have a more compliant material that allows the orientation of the two active components to be changed relative to each other to provide maximum diameter growth during axial elongation. Suitable materials for use in the present invention may include, without limitation, fluoropolymers (especially polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP)), polyethylenes, polyethylene terephthalate (PET), nylon, polyurethane, polypropylene, polyester, polyimide, etc. . as well as composite materials that combine these and / or other materials to achieve the desired characteristics of resistance and elasticity. PTFe (ePTFE) is considered to be more preferred for many applications, as it provides excellent axial strength in the direction of expansion, it is easily adaptable in a direction perpendicular to the direction of expansion.

Depending on the applications, the tubes of the present invention can be constructed from a continuous material, such as continuous films, tapes, or sheets of materials. Alternatively, the tubes of the invention may include discontinuous structures, such as sheets or tapes that include holes or slots in them, or even materials formed from fabrics, knitwear, or other open structures.

Without intending to limit the scope of the present invention, Figures 5 to 8 illustrate various embodiments that may be useful in practicing the present invention.

Figure 5 illustrates an embodiment of the present invention comprising a fully open mesh tube 10. In this embodiment, the first component 12 and the second component 16 each comprise a fiber or wire material. Open spaces 22 are provided between the two components 12, 16 which can be left unfilled or covered with a layer of another material (eg, a continuous or discontinuous film). Such materials can be used, as one or the other or both components 12, 16 can include metals such as steel, nitrinol, etc., polymers such as nylon, ePTFE, etc. As noted, with the correct selection of components 12, 16 and with gaps 22 left free, this construction is believed to provide optimal growth characteristics in accordance with the present invention.

Figure 6 illustrates an embodiment of a tube 10 of the present invention, comprising an offset wound tube of two film components (or "tape") 12, 16. Preferably, the two tape components are uniaxially oriented materials with minimal shear and transverse strength. As described above, ePTFE is particularly desirable for use as one or both of these components.

Figure 7 illustrates yet another embodiment of a tube 10 of the present invention. This embodiment employs a full density, high modulus film 24 fine pitch angle helix, such as a polyimide, and a uniaxial film 26 low angle pitch, such as ePTFE.

Figure 8 illustrates yet another embodiment of the present invention. In this embodiment, tube 10 comprises a homogeneous material with high and low angular orientations defined by grooves 28 oriented in the homogeneous material. Low angle component slots are oriented in helical rows 30 around the circumference of the tube, while high angle component grooves are defined by diagonal lines 32 through low angle rows 30.

The above examples are just a few of the many different orientations of the present invention that are conceivable. For example, it should be appreciated that many of the properties of the various embodiments of Figures 5 to 8 can be combined, such as by constructing a tube with the continuous material of Figure 6 combined with selected open spaces from Figure 5 or by combining the high modulus film of Figure 7 with any of the other three constructions, or employing oriented grooves of Figure 8 on part or all of any one of the other three constructions, etc.

The tube of the present invention can be used both to avoid "pinching" problems found in many prior art tube devices as well as to provide additional benefits that tube diameter increases during axial elongation can provide. As such, the tube of the present invention may be useful as a manufacturing aid, as a deployment sleeve (for example, for dispensing medical devices), and in other applications that can benefit from easier removal of the tubular sleeve. .

Figure 9 illustrates one such application, where tube 10 is mounted on a fabrication mandrel 34, such as those commonly used to construct various tubular structures (eg, taped vascular graft components). Heating or other processing steps can retract the tube around the mandrel making it difficult or impossible to slide the tube out of the mandrel once the manufactured article is removed. With the tube of the present invention, the axial movement of tube 10 causes it to grow diametrically, greatly facilitating its removal from the mandrel. This property can be highly beneficial in assisting in the removal of an article manufactured out of a mandrel.

Figure 10 shows an embodiment of a tube 10 of the present invention mounted on a

ES 2 575 244 T3 containment sheath near the end of a medical device deployment system 36. The deployment system comprises a catheter shaft 38 extending from a distant olive 40 to a control hub 42. A medical device, such as a stent, stent graft, balloon, blood filter, occluder, probe, valves, etc. It may be contained in the sleeve 10 that is to be deployed at a treatment site, within the body of a patient. The sleeve 10 can be stretched over itself to form two layers, an outer segment partially or fully covering an inner segment. Tube 10 is attached to a deployment line 44 which is fed to a catheter shaft through port 46. Deployment line 46 is operatively connected to a deployment button 48 on hub 42.

Tube 10 manufactured in accordance with the present invention can be formed from any material that is robust enough to constrain the device to be delivered and to withstand the stress of the removal process. It is desirable that the sleeve 10 be as thin and lubricating as possible to maintain a small profile of the device delivery and to facilitate the removal process. Since tube 10 is temporarily positioned deep within a patient during delivery and deployment, it is in the same way desirable that the sheath be formed of a biocompatible material. As explained in more detail below, suitable sheath materials may include: Polytetrafluoroethylene (PTFE), Expanded PTFE (ePTFE), Fluorinated Ethylene Propylene (FEP), Polyethylene Terephthalate (PET), Nylon, Polyurethane, Polypropylene, Polyester , etc.

To activate the deployment line 44, medical personnel will unscrew the deployment button 48 and pull the button and the attached deployment line to cause the tube 10 to be progressively withdrawn out of the contained device. If the tube 10 extends on itself, as the outer segment of the tube is withdrawn, the tube of the present invention will progressively increase in diameter, continuously extending the inner segment, to become the outer segment of the tube. . The diametrical growth of tube 10 of the present invention assists in the extension process, since the outer segment of tube 10 will form a larger diameter than the unconstrained inner segment. As a result, the larger diameter outer segment easily slides over the inner segment and is easily removed with minimal friction between the two layers.

The device delivery process can best be seen in FIG. 11. In this embodiment, an outer segment 50 is shown folding over an inner segment 52, shown exposed in section. As the larger diameter outer segment 50 is removed, the axial force opens the tube 10 of the present invention. As tube 10 is withdrawn in this manner, a constricted self-expanding stent 54 is progressively deployed from this embodiment.

It should be appreciated that deployment of the medical device using the present invention can be performed as a single layer or in an extended manner as described above. When an extended embodiment is employed, in the final construction, the outer segment should have an inner diameter that is sufficiently larger than the outer diameter of the inner segment in order to minimize friction between the two segments. That is, in order to minimize interference between the inner segment and the outer segment, the axially elongated outer segment should be elongated sufficiently so that its inner diameter comfortably releases the outer diameter of the unconstrained inner segment. It is preferred that the inner diameter of the outer segment is 0.1 to 50% larger than the outer diameter of the inner segment, and more preferably 10 to 20% larger.

For example, to achieve these dimensions, typically a tube with a wall thickness of about 0.08mm and an outer segment inner diameter of about 2.1mm will be provided with an unconstrained inner segment having an outer diameter of about 1.9 mm.

The tube of the present invention is believed to greatly reduce the amount of tension required to deploy a device.

It is believed that the advantages of the tube of the present invention can be easily adapted to improve many other devices and processes. An example of such an improved combination is to employ the tube of the present invention with the folded tube deployment constructions described in published US patent application SN 12 / 014,538 to Irwin et al. filed on January 15, 2008. In this regard, the tube of the present invention can be used with one or more pleats to aid in device delivery and to provide other beneficial results.

The invention of the present invention is believed to have many other useful applications, including angioplasty devices, retrieval devices, implantable filters, stents, adaptive grafts, etc. It should be noted that the present invention can be scaled to virtually any dimension.

EXAMPLES

Without intending to limit the scope of the present invention, the following examples illustrate various forms of

ES 2 575 244 T3 embodiment of how the present invention can be practiced.

Example 1 - Uniaxially Oriented ePTFE Film

This example describes mounting an ePTFE tube that can be easily removed from a mounting mandrel. A 1 "wide expanded polytetrafluoroethylene (ePTFE) film (having minimum longitudinal oriented strength, minimal transverse and shear strength, and with FEP on one side that functions as an adhesive) at a 40 ° pitch relative to the mandrel axis in a right hand helical orientation with the FEP facing outward from the mandrel. Next, a 6.35mm (0.25 ") wide ePTFE film was wound at a pitch of 74 ° in a right hand helical orientation over the first film with the FEP facing the mandrel. The assembly was then thermally processed on the mandrel at a temperature of 320 ° C for 13 minutes. The tube was easily pulled out of the mandrel and no necking was observed with loads below the limiting strength of the material.

Example 2 - Uniaxially Oriented ePTFE Film with Polyimide Film

This example describes the assembly of an ePTFE tube comprising a non-compliant polyimide film (Kapton®) between the ePTFE layers. A 1.0 "wide expanded polytetrafluoroethylene (ePTFE) film was wound on a 6 mm cm (0.236") steel mandrel in a 56 ° pitch relative to the axis of the mandrel in a right hand helical orientation with the FEP facing toward the mandrel. out from the chuck. Next, a 1.27mm x 0.025mm (0.050 "x 0.001") polyimide film was wound at a pitch of 82 ° relative to the mandrel axis in a right hand helical orientation on the first film. A 1 "wide ePTFE film was then wound in a 56 ° pitch relative to the mandrel axis in a right hand helical orientation on top of the polyimide film with the FEP facing the mandrel. The assembly was then thermally processed on the mandrel at a temperature of 320 ° C for 13 minutes, after which the tube was withdrawn from the mandrel.

The non-compliant polyimide film used for high angle wrapping limits axial deformation and allows the use of a higher angle ePTFE wrap. Higher angle ePTFE winding increases the "unwind" effect for a given axial load. The diameter defined by the polyimide coil increases with axial stress, but necking can be observed on the ePTFE between the polyimide.

Example 3 - Uniaxially Oriented ePTFE Film with Polyimide Film

To see if the tube made in Example 2 can be modified to reduce necking, grooves were created with a blade in the ePTFE in an orientation parallel to that of the film structure (56 ° pitch relative to the axis of the mandrel ), with a spacing of approximately 0.050 ”between the grooves. These grooves eliminate the "off-axis" resistance of the ePTFE film allowing diametral growth of the polyimide helix under tension without constriction of the ePTFE. Therefore, the introduction of these grooves eliminates the constriction.

Example 4 - Uniaxially Oriented ePTFE Film

This example describes the assembly of the ePTFE tube as described in Example 1, but in a reduced-scale version. On a 1.905 mm (0.075 ") steel mandrel, a 6.35 mm (0.25") wide ePTFE film was wound in a pitch of 25 ° relative to the axis of the mandrel in a right hand helical orientation with the FEP looking out of the chuck. A 3.175mm (0.125 ") wide type ePTFE film was then wound at a pitch of 75 ° relative to the mandrel axis in a right hand helical orientation with the FEP facing the mandrel. The assembly was then thermally processed on the mandrel at a temperature of 320 ° C for 13 minutes. This construction was removed from the mandrel and was used as a limitation of the device that was extended for deployment.

Example 5 - Uniaxially Oriented ePTFE Film with Polyimide Film

This example describes the assembly of a tube that is quasi-continuous polyimide that responds well to axial stress and returns to the initial diameter with little relative force. On a 2.1082 mm (0.083 ") steel mandrel a 6.35 mm (0.25") wide ePTFE film was wound at a pitch angle of 28 ° relative to the mandrel in a right helical orientation. with the FEP looking out of the chuck. Next, a 1.0922mm x 0.0254mm (0.043 "x 0.001") polyimide film was wound at a pitch angle of 68 ° relative to the mandrel axis in a right hand helical orientation on the first film. A 6.35mm (0.25 ") wide EPTFE film was then wound at a pitch angle of 28 ° relative to the axis of the mandrel in a right hand helical orientation on the polyimide film with the FEP facing the chuck. The assembly was then thermally processed on the mandrel at a temperature of 320 ° C for 13 minutes.

The tube was then transferred to a 1.905 mm (.075 ") steel mandrel and the polyimide helix was either" turned down "or" wound "to eliminate the slack between the tube and the mandrel, effectively increasing the angles. of passage for all windings. The tube was then compressed wound with a film of

ES 2 575 244 T3 ePTFE to immobilize it on the mandrel and was thermally processed for 7 minutes at 320 ° C, after which the compression wrap was removed. The resulting tube is nearly continuous polyamide and responds well to axial stress, returning to the initial diameter with little relative force.

Although particular embodiments of the present invention have been illustrated and described, the present invention should not be limited to such illustrations and descriptions. It should be apparent that changes and modifications can be incorporated and included as part of the present invention within the scope of the following claims.