Patent Publication Number: US-2023148169-A1

Title: Introducer with expandable capabilities

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. application Ser. No. 16/730,467, filed Dec. 30, 2019, which is a continuation of U.S. application Ser. No. 15/439,998, filed Feb. 23, 2017, which claims benefit of U.S. Provisional Application Ser. No. 62/303,774, filed Mar. 4, 2016, the entire disclosure of which hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure relates generally to medical devices and more particularly to medical devices that are adapted for use in percutaneous medical procedures. 
     BACKGROUND 
     In some instances, performing percutaneous medical procedures may require the insertion and/or maneuvering of relatively large medical devices through a patient&#39;s vasculature. However, inserting the medical device into the vasculature may result in undesirable forces being applied to the vessel walls. For example, as the medical device passes into the vasculature, it may make undesirable contact with one or more vessel walls. This interference may cause injury to the vessel as the medical device is navigated into calcified or diseased vessels. Therefore, in some instances an introducer is utilize to facilitate the insertion of medical devices into the vessel. Further, vessel trauma resulting from forces applied to the vessel wall by a medical device may be lessened by minimizing the size of an introducer used to access the vessel. Therefore, it may be desirable to design an introducer having a reduced insertion profile, yet capable of expansion when necessary (e.g., during the passage of a medical device therethrough). 
     SUMMARY 
     This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. An example introducer includes an inner liner including a lumen, a distal region and at least one folded portion extending along the distal region. The introducer also includes a reinforcing member having a length and including at least one spine extending along the length of the reinforcing member. The introducer also includes a sheath disposed along at least a portion of the introducer, wherein the sheath includes at least one perforation, wherein material adjacent to the at least one folded portion is removed from a distal portion of the introducer to form a tip region. The introducer also includes a tip member disposed along the tip region. 
     Alternatively or additionally to any of the examples above, wherein the at least one folded portion allows the liner to radially expand. 
     Alternatively or additionally to any of the examples above, wherein the folded portions wrap along an inner surface of the inner liner. 
     Alternatively or additionally to any of the examples above, wherein the at least one spine of the reinforcing member has a substantially constant width along the length the reinforcing member. 
     Alternatively or additionally to any of the examples above, wherein the at least one spine of the reinforcing member includes a proximal end, a distal end and a width, wherein the width of the spine varies from the distal end of the spine to the proximal end of the spine. 
     Alternatively or additionally to any of the examples above, wherein the at least one spine of the reinforcing member includes a thickness, wherein the thickness of the spine varies along the length of the reinforcing member. 
     Alternatively or additionally to any of the examples above, wherein the at least one perforation of the sheath includes an opening, and wherein the opening is configured to tear apart as the at least one folded portion radially expands. 
     Alternatively or additionally to any of the examples above, wherein the sheath includes a length and a plurality of perforations, and wherein the plurality of perforations are longitudinally aligned along the length of the sheath. 
     Alternatively or additionally to any of the examples above, wherein the sheath further includes a proximal end, a distal end and a length extending therebetween, and wherein each of plurality of perforations are separated by a distance, and wherein the distance between each of the plurality of perforations varies along the length of the sheath from the distal end to the proximal end. 
     Alternatively or additionally to any of the examples above, wherein each of the perforations define a surface area, and wherein the surface area of each of the perforations varies along the length of the sheath from the distal end to the proximal end. 
     Alternatively or additionally to any of the examples above, wherein the at least one perforation is substantially radially aligned with the at least one folded portion. 
     Alternatively or additionally to any of the examples above, wherein the tip member is designed to tear as the at least one folded portion radially expands. 
     Alternatively or additionally to any of the examples above, wherein the tip member is radiopaque. 
     Alternatively or additionally to any of the examples above, wherein the tip member includes a tapered portion. 
     Alternatively or additionally to any of the examples above, wherein the at least one spine is substantially radially aligned with the at least one folded portion. 
     Another example introducer comprises: 
     an inner liner including a lumen, a distal region and a plurality of folds disposed along an inner surface of the liner; 
     a spine member having a length and a plurality of longitudinally extending support members; 
     a sheath disposed along at least a portion of the liner, wherein the sheath includes a plurality of openings extending at least partially through the sheath; 
     wherein material adjacent to the plurality of folds is removed from a distal portion of the introducer to form a tip region; and 
     a tip member disposed along the tip region. 
     Alternatively or additionally to any of the examples above, wherein the plurality of folds are configured to radially expand. 
     Alternatively or additionally to any of the examples above, wherein each of the plurality of reinforcing members includes a proximal end, a distal end and a width, wherein the width of each of the reinforcing members decreases from the distal end of the reinforcing member to the proximal end of the reinforcing member. 
     Alternatively or additionally to any of the examples above, wherein the plurality of openings on the sheath are configured to tear apart as the plurality of folds radially expand. 
     Alternatively or additionally to any of the examples above, wherein the sheath further includes a proximal end, a distal end and a length extending therebetween, and wherein each of plurality of openings are separated by a distance, and wherein the distance between each of the plurality of openings increases along the length of the sheath from the distal end to the proximal end. 
     Alternatively or additionally to any of the examples above, wherein each of the openings define a surface area, and wherein the surface area of each of the openings decreases along the length of the sheath from the distal end to the proximal end. 
     Another example introducer comprises: 
     an inner liner including a lumen, a distal region and a plurality of folds extending along an inner surface of the liner, the inner liner including a first configuration and an expanded configuration; 
     a spine member including at least one reinforcing member; 
     a sheath disposed along at least a portion of the liner, wherein the sheath includes at least one opening extending at least partially through the sheath; 
     wherein material adjacent to the at least one folded portion is removed from a distal portion of the introducer to form a tip region; and 
     a tip member disposed along the tip region; 
     wherein the folds along an expandable region are configured to shift between a first configuration and an expanded configuration. 
     The above summary of some examples is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these examples. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG.  1    is a perspective view of an example introducer; 
         FIG.  2    is a cross-sectional view of an example introducer taken along the line  2 - 2  of  FIG.  1   ; 
         FIG.  3    is a cross-sectional view of an example introducer; 
         FIG.  4    is a perspective view of an example liner; 
         FIG.  5    is a perspective view of an example outer sheath; 
         FIG.  6    is a perspective view of an example spine member; 
         FIG.  7    is a perspective view of an example spine member; 
         FIG.  8    is a perspective view of an example introducer; 
         FIG.  9    is a side view of an example introducer; 
         FIG.  10    is a perspective view of an example introducer including tip member. 
     
    
    
     While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular examples described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
     DETAILED DESCRIPTION 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure. 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     It is noted that references in the specification to “an embodiment”, “some examples”, “other examples”, etc., indicate that the embodiment described may include one or more particular features, structures, and/or characteristics. However, such recitations do not necessarily mean that all examples include the particular features, structures, and/or characteristics. Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used connection with other examples whether or not explicitly described unless clearly stated to the contrary. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative examples and are not intended to limit the scope of the disclosure. 
     In some instances, performing percutaneous medical procedures may require the insertion and/or maneuvering of relatively large medical devices through a patient&#39;s vasculature. However, inserting the medical device into the vasculature may result in undesirable forces being applied to the vessel walls. For example, as the medical device passes into the vasculature, it may make undesirable contact with one or more vessel walls. This interference may cause injury to the vessel as the medical device is navigated into calcified or diseased vessels. Therefore, in some instances an introducer is utilize to facilitate the insertion of medical devices into the vessel. Further, vessel trauma resulting from forces applied to the vessel wall by a medical device may be lessened by minimizing the size of an introducer used to access the vessel. Therefore, it may be desirable to design an introducer having a reduced insertion profile, yet capable of expansion when necessary (e.g., during the passage of a medical device therethrough). The following examples disclose an intravascular medical device including an expandable introducer, whereby the introducer is designed to expand from a reduced profile, unexpanded configuration to an expanded configuration. 
       FIG.  1    illustrates an example expandable introducer (e.g., delivery sheath, access sheath, etc.)  10  including an elongated compliant liner (e.g., tubular membrane, etc.)  20  having a lumen  22 , proximal portion  24  and a distal portion  26 . The introducer  10  may also include an outer sheath  30  and a spine member  40 . Spine member  40  may include reinforcement members  38 . 
     Introducer  10  may include a tapered region  78 . In some examples, the tapered region  78  may be positioned proximal to the distal portion  26  of introducer  10 . In some examples at least a portion of distal portion  26  of introducer  10  may have a substantially constant outer diameter which transitions into tapered portion  78 . At least a portion of tapered portion  78  may have an outer diameter which is greater than the outer diameter of at least a portion of distal region  26 . However, this is not intended to be limiting. It is contemplated that any portion of the introducer  10  may include any number of tapers, constant diameter regions or combinations thereof. 
     The proximal portion  24  of the liner  20  and/or sheath  30  may be attached to a spring member  50 . In some examples, liner  20  and/or sheath  30  may cover either the outer surface, inner surface or both the inner and outer surfaces of spring member  50 . For example, in some instances, spring member  50  may be positioned between (e.g., laminated) liner  20  and/or sheath  30 . 
     Additionally, in some instances the spring member  50 , sheath  30  and/or liner (e.g., a combination of spring member  50 , sheath  30  and liner  20 ) may be attached to a hub  12 . The hub  12  may include a hemostatic valve or seal disposed therein. The hemostatic valve or seal may prevent blood or other bodily fluid(s) from flowing proximally through the lumen  22  of liner  20 . In at least some examples, the hub  12  may include a port in fluid communication with the lumen  22  of liner  20 . 
       FIG.  1    illustrates an outer sheath (e.g., perforated covering)  30  and a spine member (e.g., support member)  40  fixedly attached to liner  20 . As will be described in greater detail below, both outer sheath  30  and spine  40  may be disposed (e.g., attached) along liner  20  from distal portion  26  to proximal portion  24 . Outer sheath  30  may include one or more apertures (e.g., openings)  32  extending through at least a portion of the wall thickness of sheath  30 . As shown in  FIG.  1   , the one or more apertures  32  may be aligned with one another along the central longitudinal axis  35  of introducer  10 . Additionally, apertures  32  may be positioned between adjacent reinforcement members  38 . For example,  FIG.  1    shows apertures  32  positioned between two reinforcement members  38 . As will be described in greater detail below, the distal portion  26  of introducer  10  may include an atraumatic tip member  28 . 
       FIG.  2    shows a cross-sectional view along line  2 - 2  of  FIG.  1   .  FIG.  2    illustrates liner  20  including three folded sections  34  extending along the inner surface of liner  20 . While  FIG.  2    shows three folded sections  34 , it is contemplated that liner  20  may include greater or less than three folded sections  34 . For example, liner  20  may include 1, 2, 4, 5, 6, 7, 8, 9, 10 or more folded sections  34 . 
     Additionally, it can be appreciated that  FIG.  2    represents the cross-section of introducer  10  after manufacturing. For example,  FIG.  2    illustrates that spine  40  is incorporated into the tubular wall of outer sheath  30 . In other words,  FIG.  2    illustrates that in some examples, outer sheath  30  and spine member  40  may be manufactured (e.g., melted/reflowed together) such that they form a unitary member. Similarly to that discussed with respect to folded members  34 , it can be appreciated that while  FIG.  2    shows spine member  40  including three support members  38 , spine  40  may include greater or less than three support members  38 . For example, spine  40  may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more support members  38 . 
     As discussed above, in some instances outer sheath  30  may include one or more apertures  32  extending at least partially through the wall thickness of outer sheath  30 . The detailed view in  FIG.  2    shows one example of an aperture  32  having extending partially through the tubular wall of outer sheath  30 . The reduced wall thickness of aperture  32  is depicted as thickness “X.” Further, a portion of the tubular wall of outer sheath  30  adjacent to aperture  32  is depicted as “Y.” It can be seen that the thickness “X” of aperture  32  is less than the thickness “Y.” As will be described in greater detail below, it can be appreciated that the reduced wall thickness “X” (as compared to wall thickness “Y”) may create a preferential “tear point” within outer sheath  30 . In other words, aperture(s)  32  may define a perforated tear line extending along introducer  10 . 
     Additionally, in at least some examples, the apertures  32  (e.g., openings, cutouts, perforations, notches, holes) or other weakening features formed in the wall of the sheath  30  may be positioned adjacent to, radially outward of, in communication with, and/or directly over the one or more folds  34  formed in liner  20 . For example,  FIG.  2    shows apertures  32  positioned directly over the one or more folds  34  in liner  20 . More particularly, in some instances apertures  32  may be aligned at a point along outer sheath  30  in which fold  34  begins to wrap underneath outer sheath  30 . It can be appreciated that the point at which aperture  32  is aligned with fold  34  may be the point at which fold  34  initially begins to separate when liner  20  shifts from the configuration shown in  FIG.  2    to an expanded configuration. 
     One example methodology to construct the introducer  10  (shown in  FIG.  1   ) may include configuring spine  40 , outer sheath  30  and liner  20  as shown in  FIG.  3    followed by applying heat such that outer sheath member melts (e.g., reflows) and encapsulates spine member  40  as shown in  FIG.  2   . It can be appreciated that liner  20  may be constructed from a material that has a higher melting point than either outer sheath  30  or spine member  40 , and therefore, will not melt upon the application of heat sufficient to melt outer sheath  30  and/or spine member  40  together. In other examples, liner  20  may be constructed from a non-thermoplastic material designed to resist melting while heat is applied to reflow outer sheath  30  and spine  40  together. Additionally, it is contemplated that arrangement of liner  20 , outer sheath  30  and spine member  40  may include a variety of configurations throughout the manufacturing steps. For example, examples contemplated herein may include different positions, alignment, spacing, sizes, dimensions, etc. of spine  40 , liner  20  and/or sheath  30  relative to one another during the manufacturing process and/or final design. 
       FIG.  4    shows liner  20  having a substantially annular shape and a lumen  22  extending at least partially therethrough. In some examples, the lumen  22  may extend from a proximal end  24  of liner  20  to a distal end  26  of liner  20 . Additionally, the lumen  22  may extend completely through an entire length of liner  20 . It is contemplated that other shapes and/or configurations are possible within the scope of the present disclosure, as will be apparent from the discussion below, and other shapes or configurations discussed herein may be used in the configuration(s) schematically shown in the figures. 
     As stated, liner  20  may be described as having a compliant elongated tubular structure having a lumen  22  extending therethrough from proximal end  24  to a distal end  26 . Liner  20  may include a wall having an inner surface and an outer surface. In some examples, a thickness of the wall may be defined by the inner surface and the outer surface. 
     In some examples, liner  20  and/or lumen  22  may be configured to radially expand from a delivery configuration to an expanded configuration when subjected to a radially outward force from within the lumen  22  and/or liner  20 . In at least some examples, liner  20  may be substantially or completely compliant and/or liner  20  may have no radial self-bias—that is, no radially inward self-bias and/or no radially outward self-bias. In other words, liner  20  may be non-self-supporting and may not include a mechanism to radially expand and/or open on its own (i.e., absent a radially outward force exerted upon liner  20 ). Instead, liner  20  may require a device or object that has a greater outer diameter than an inner diameter of lumen  22  and/or liner  20  to be disposed within lumen  22  to push and/or force liner  20  radially outward toward the expanded configuration. 
     Additionally, liner  20  may not require a radially inward force be applied upon itself to collapse itself inward when there is no device, object, etc. disposed within lumen  22 . In other words, liner  20  may not be held open or maintain a particular expanded size on its own, or liner  20  may be non-self-supporting as mentioned above. Similarly, liner  20  may not be biased to collapse inwardly on its own. In other words, liner  20  may take the shape and/or form of surrounding tissue(s) after being expanded. For example, a constriction in or of a vessel or body lumen in which liner  20  is disposed may urge liner  20  radially inward, but liner  20  is not self-biased inwardly on its own (i.e., liner  20  may have zero return force after expanding/opening). 
     In the delivery configuration, lumen  22  may have a first inner diameter defined by the inner surface of the wall of liner  20 . In some examples, as will be apparent herein, the first inner diameter may be defined as a first inner radial extent and/or distance from a central longitudinal axis  35  of liner  20  and/or the expandable introducer  10 . In the expanded configuration, lumen  22  may have a second inner diameter defined by the inner surface of the wall. In some examples, as will be apparent herein, the second inner diameter may instead be defined as a second inner radial extent and/or distance from a central longitudinal axis  35  of liner  20  and/or the expandable introducer  10 . In some examples, the second inner diameter may be greater than the first inner diameter. Similarly, the second inner radial extent may be greater than the first inner radial extent. 
     Similarly, liner  20  may have an outer diameter and/or outer radial extent defined by the outer surface of the wall of liner  20 . In the delivery configuration, liner  20  may have a first outer diameter and/or first outer radial extent defined by the outer surface of the wall. In the expanded configuration, liner  20  may have a second outer diameter and/or a second outer radial extent defined by the outer surface of the wall. In some examples, the second outer diameter may be greater than the first outer diameter. Similarly, the second outer radial extent may be greater than the first outer radial extent. 
     As discussed above, liner  20  may include one or more folds  34  formed therein in the delivery configuration. In some examples, the one or more folds  34  may include two folds, three folds, four folds, five folds, six folds, seven folds, eight folds, nine folds, ten folds, or another desirable number or quantity of folds. In at least some examples, liner  20  may be disposed radially inward of outer sheath  30 . In some examples, the one or more folds  34  may each fold back on themselves to form, for example, a wave shape, an S-shape, T-shape and/or a Z-shape when viewed in cross-section. In some examples, each of the one or more folds forming a T-shape may include two or more distinct waves, S-shaped, or Z-shaped secondary folds within and thus forming each of the one or more T-shaped folds. Other shapes and configurations, while not expressly illustrated, are also contemplated. 
     Additionally, in some examples, liner  20  may be configured to permit the lumen  22  to radially expand from the first inner diameter and/or the first inner radial extent to the second inner diameter and/or the second inner radial extent. In some examples, liner  20  is configured to substantially prevent axial stretching along the lumen  22 . In other words, liner  20  may permit the lumen  22  to expand radially outward from a central longitudinal axis  35  of liner  20  and/or the expandable introducer  10  without stretching or expanding in an axial or longitudinal direction. In some examples, the second inner diameter and/or the second inner radial extent may be greater than the first outer diameter and/or the first outer radial extent. Because liner  20  may be made from an inelastic material, it may be configured to expand radially outward to a predetermined maximum second inner diameter and/or second inner radial extent, but may not stretch or expand radially outward beyond the predetermined maximum second inner diameter and/or second inner radial extent. 
     In some examples, the inner surface of the wall of liner  20  may include one or more layers or coatings, such as a lubricious coating, a hydrophilic coating, a hydrophobic coating, or other suitable coatings, and the like, or liner  20  may include a lubricant disposed within the lumen  22 . In some examples, an outer surface of the expandable introducer  10  and/or outer sheath  30  may include one or more layers or coatings, such as a lubricious coating, a hydrophilic coating, a hydrophobic coating, or other suitable coating, and the like, or the expandable introducer  10  and/or outer sheath  30  may include a lubricant disposed upon the outer surface thereof. 
     Additionally,  FIG.  4    shows spine member  40  positioned along the outer surface of liner  20 . Spine member  40  may have one or more reinforcement member  38  extending along an outer surface of liner  20 . In some instances, spine member  40  may be positioned (e.g., attached, glued, tacked, adhered, etc.) to the outer surface of liner  20  during the manufacturing process. For example, in some examples spine member  40  may be positioned on the outer surface of liner  20  prior to outer sheath  30  being positioned over the combination of liner  20  and outer sheath  30 . 
       FIG.  5    shows an example outer sheath  30 . In some examples, outer sheath  30  may be fixedly attached to the outer surface of liner  20  and/or spine  40 . In some examples, outer sheath  30  may be bonded, laminated, fused, glued, co-molded, melted, welded, or other suitable means, to liner  20  and/or spine  40 . In other words, in some examples, outer sheath  30  may be permanently attached to the outer surface of liner  20 . 
     In some examples, outer sheath  30  may be formed from a polymeric material, which may form at least a portion of a wall of outer sheath  30 . In some examples, outer sheath  30  may be formed from the same material as liner  20 . In some examples, outer sheath  30  may be formed from a different material than liner  20 . In some examples, some or all of outer sheath  30  may be fixedly attached to the outer surface of the wall of liner  20 . In some examples, the entire outer sheath  30  may be fixedly attached to the outer surface of the wall of liner  20  and/or spine  40 . 
     In some examples, at least a portion of outer sheath  30  may extend continuously around a circumference of liner  20  in a first configuration. In some examples, at least a portion of outer sheath  30  may be discontinuous. In other words, and as described above, in some examples outer sheath  30  may include a plurality of apertures  32  (e.g., openings, cutouts, perforations, notches, holes, apertures, or other weakening features) formed in the wall of outer sheath  30  which effectively remove at least (or in some cases, only) a portion of the wall of outer sheath  30 . While apertures  32  shown in  FIG.  5    are substantially hexagonal, it is contemplated that apertures  32  may be any shape. For example, apertures  32  may be circular, square, rectangular, ovular, triangular, diamond shaped, or the like. 
     In some examples, the plurality of apertures  32  formed in the wall of outer sheath  30  may be arranged in one or more longitudinal lines along the length of the expandable introducer  10 , liner  20 , and/or outer sheath  30 . In some examples, the plurality of apertures  32 , or other weakening features formed in the wall of outer sheath  30  may extend laterally and/or transversely through the wall of outer sheath  30  relative to the central longitudinal axis  35 . In some examples, a wall thickness of the outer sheath may be tapered about the circumference of liner  20  such that a reduced thickness region of outer sheath  30  is disposed adjacent to, radially outward of, in communication with, and/or directly over the one or more folds  34  of liner  20 . 
     Further, in some examples the apertures  32  included in outer sheath  30  may be spaced apart from one another. For example,  FIG.  5    shows adjacent apertures  32  located near the distal end  26  of outer sheath  30  spaced apart from one another a distance “W”. Similarly,  FIG.  5    shows two other adjacent apertures  32  located near the proximal end  24  of outer sheath  30  spaced apart from one another a distance “Z”. It can be appreciated that in some examples, distance “W” and distance “Z” may be equal. In other words, in some examples all the apertures  32  positioned along outer sheath  30  may be spaced equidistant from one another. However, in other examples, it can be appreciated that distances “W” and “Z” may be different. In other words, in some examples apertures  32  may include variable spacing between one another. For example, it can be appreciated that the spacing between apertures  32  may gradually increase from the distal portion  26  to the proximal portion  24  of outer sheath  30 . 
     Similarly,  FIG.  5    illustrates the apertures  32  having a surface area. While the term surface area may be used to herein, the “surface area,” of a given aperture  32  as described herein may be defined as the “area” bounded by the shape of a given aperture  32 . For example, in  FIG.  5   , the surface area of a given aperture  32  may be defined as the area bounded by an individual hexagon. Further,  FIG.  5    shows two different individual apertures  42  and  44 . Aperture  42  may be positioned near the distal end  26  of outer sheath  30  while aperture  44  may be positioned near the proximal end  24  of outer sheath  30 . In some examples, the surface area of the apertures  32  of outer sheath  30  may be equal. In other examples, such as that shown in  FIG.  5   , the surface area of apertures  32  may be different. For example, the surface area of aperture  42  may be larger than that of aperture  44 . Further, the area of apertures  32  may decrease along outer sheath  30  from the distal portion  26  to the proximal portion  24 . Additionally, during the manufacturing process, it is contemplated that the size, shape and/or spacing between apertures  32  may change. For example, smaller apertures (e.g., aperture  44 ) may expand as the proximal portion  24  of the outer sheath  30  may be pulled and/or stretched over the tapered portion  78  of introducer  10 , for example. It is further contemplated that various different arrangements, spacing, areas, surface areas and/or alignments of apertures  32  may be utilized in the design of outer sheath  30 . 
     Additionally, as described above with respect to  FIG.  2   , it can be appreciated that outer sheath  30  may include a given wall thickness at various locations along its length. It can further be appreciated that the wall thickness of outer sheath  30  may vary along its length. For example, while some examples contemplated herein may include apertures  32  being defined as “holes” through the wall of outer sheath  30 , in other examples, apertures  32  may be defined as substantially “thinner” sections of the wall of outer sheath  30 . 
     In some examples, outer sheath  30  may be configured to separate, split, or tear as liner  20  is expanded from a first configuration to a second, expanded configuration. The expansion may be due to a radially outward force applied from within liner  20 . In some examples, outer sheath  30  may be configured to separate, split, perforate and/or tear along and/or through the plurality of apertures  32 , or other weakening features formed in the wall of outer sheath  30 . In other words, outer sheath  30  may separate, split, or tear where outer sheath  30  is discontinuous and/or constructed of a thinner material. In other words, as liner  20  radially expands outward toward an expanded configuration, outer sheath  30  may tear along preferential tear points corresponding to apertures  32 . Further, the expansion of sheath  30  may correlate with the expansion of the lumen  22 . Lumen  22  may expand from a first inner diameter and/or the first inner radial extent to a second inner diameter and/or a second inner radial extent. 
     As discussed above, the plurality of apertures  32 , or other weakening features formed in the wall of outer sheath  30  may be positioned adjacent to, radially outward of, in communication with, and/or directly over the one or more folds  34  formed in liner  20 . As mentioned above, in some examples, the plurality of apertures  32 , or other weakening features formed in the wall of outer sheath  30  may be arranged in one or more longitudinal lines along the length of the expandable introducer  10 , liner  20  and/or outer sheath  30 . Accordingly, in some examples, the plurality of apertures  32  or other weakening features formed in the wall of outer sheath  30  may be arranged in one or more longitudinal lines adjacent to, radially outward of, in communication with, and/or directly over the one or more folds  34  and/or the two or more secondary folds formed in liner  20 . In some examples, the one or more longitudinal lines may directly correspond to the one or more folds  34  and/or the two or more secondary folds. In some examples, there may be more longitudinal lines than folds and/or secondary folds (i.e., 2 folds with 3 or more lines of openings, cutouts, etc., 3 folds with 4 or more lines of openings, cutouts, etc.). In some examples, the reduced thickness region and/or a substantially thinner thickness of outer sheath  30  may be disposed adjacent to, radially outward of, in communication with, and/or directly over the one or more folds  34  and/or the two or more secondary folds of liner  20 . 
       FIG.  6    is a perspective view of an example spine member  40  including reinforcement members  38  extending from a distal end  26  of spine  40  to a proximal end  24  of spine  40 .  FIG.  6    shows spine member  40  member having an openings  46  defined between adjacent reinforcement members  38 . While  FIG.  6    shows spine member  40  having three reinforcement members  38 , it is contemplated that spine member  40  may have less than or greater than three reinforcement members  38 . For example, spine member  40  may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more reinforcement members  38 . Further,  FIG.  6    shows that in some examples, the width of reinforcement members  38  may be substantially uniform. In other words, the width of reinforcement members  38  may remain substantially uniform along spine member  40  from proximal end  24  to distal end  26 . Additionally,  FIG.  6    shows reinforcement members  38  spaced substantially equidistant around longitudinal axis  34 . However, it is further contemplated that reinforcement members  38  may be spaced at variable distances around longitudinal axis  34 . 
       FIG.  7    illustrates another example spine member  48 . The spine member  48  of  FIG.  7    may be similar to the spine member  40  shown in  FIG.  7   . However, the spine member  48  of  FIG.  7    may include one or more reinforcement members  38  having a variable width along the length of spine member  48 . For example,  FIG.  7    shows an example reinforcement member  38  having a width “A” at one location and a different width “B” at a different location. As shown in  FIG.  7   , in some examples width “B” may be substantially less than width “A.” In other examples, width “B” may be substantially greater than width “A.” Further, it is contemplated that the width of one or more of reinforcement members  38  may taper in any direction along spine member  48 . As illustrated in  FIG.  7   , the width of reinforcement members  38  may taper from width “A” to a width “B,” whereby width “B” remains substantially constant in at least a portion of the distal region  26  of introducer  10 . Additionally, it can be appreciated that any example spine member described herein may include a given wall thickness at various locations along its length. It can further be appreciated that the wall thickness of any spine member described herein may vary along its length  FIGS.  6  and  7    show spine members  40  and  48  including collar portions  82 . 
     Collars  82  may be utilized during the manufacturing process and may or may not be positioned at the distal  26  and/or proximal  24  end of spine members  40  and  48 . In some instances, collars  82  may be removed during the manufacturing process. 
     In some instances, manufacturing introducer  10  may result in introducer  10  having one or more radially extending bumps (e.g., raised portions, ridges, etc.). The raised portions may extend radially away from the outer surface of introducer  10 . For example, the one or more raised portions may extend radially away from the outer surface of outer sheath  30 . For example, in some examples a raised portion may substantially align with (e.g., be positioned above) a folded portion  34  of liner  20 . 
     In some instances it may be desirable to remove at least a portion of raised portion prior to performing one or more manufacturing steps (e.g., adding a tip member).  FIG.  8    illustrates an example section of liner  20  which may be removed prior to performing one or more manufacturing steps. For example,  FIG.  8    shows a line  70  along which a cut, skive, grinding, shaving, etc. may be performed to remove material prior to performing one or more manufacturing steps. It can appreciated that any suitable method may be utilized to remove a portion of liner  20 . 
     In some examples, the material removed from liner  20  may include a portion of one or more folded sections  34 . For example,  FIG.  8    shows line  70  which may represent a cut which removed a portion of folded section  34 . Additionally,  FIG.  8    shows reinforcement members  38 . Reinforcement members  38  may have material removed from a distal end thereof. For example, one or more reinforcement members  38  may include a tapered, beveled or chamfered distal end. 
     Additionally, in some examples the distal end of the liner  20 , sheath  30  and/or spine  40  may have material uniformly removed prior to performing additional manufacturing steps (e.g., adding a tip member).  FIG.  9    shows a general illustration of the end of liner  20 , which may or may not include outer sheath  30  and/or reinforcement members  38 . For example, reference number  76  may define a liner  20 , outer sheath  30 , spine  40  or any combination thereof. Additionally, reference numeral  74  may define a spine member or folded section  34  of liner  20 . 
     As shown in  FIG.  9   , the distal end  26  of example member  76  may include a radius, chamfer and/or bevel around the circumference example member  76 . This bevel, chamfer and/or radius may represent material which has been removed from the distal end of example member  76  prior to performing additional manufacturing steps. Additionally, it is contemplated that in some examples, the liner/spine  20 / 40  discussed in  FIG.  4    may have a bevel, chamfer and/or radius applied to its distal end during the manufacturing process. 
     In some examples it may be desirable to add a tip member to the distal end of any of the examples disclosed herein.  FIG.  10    shows an example tip member  56  disposed along the distal region  26 . Tip member  56  may be designed with a low durometer material. In some instances, a lower durometer material may provide tip member  56  with the ability to radially expand (e.g., flex) outward and radially contract as a variety of medical devices are advanced through tip member  56 . Further, tip member  56  may include a taper. As shown in  FIG.  10   , tip member  56  may taper from a first diameter in which it contacts outer sheath  30  to a second diameter at the distal end of introducer  10 . While not intended to be limiting, in some examples the shape of tip member  56  may resemble a bull-nose. 
     Additionally, tip member  56  may include a radiopaque material. The radiopaque material may allow tip member  56  to be visualized by a clinician during a medical procedure. Additionally,  FIG.  10    shows the portion  54  of fold  34  which had been removed (as discussed with respect to  FIG.  8   ) prior to the application of tip member  56 . In some instances, portion  54  may correspond to a portion of fold  34  which had been cut off prior to application of tip member  56 . In some examples, tip member  56  may include one or more preferential tear regions  80 . Tear regions  80  may be defined as a slit, score, skive, groove, etc. which may preferentially tear upon radially expansion of tip member  56 . 
     In some examples, the example expandable introducer  10  may be disposed about or inserted over a guidewire (not shown), although the guidewire is not required. In some examples, the expandable introducer  10  and/or liner  20  may include a proximal non-expandable section and a distal expandable section. In examples having a proximal non-expandable section, the proximal non-expandable section may have an inner diameter or extent sufficient to accept a medical device passing therethrough, while the distal expandable section may have an inner diameter or radial extent in a relaxed condition that is less than a maximum outer diameter or extent of the medical device. The expandable introducer  10  and/or liner  20  may be formed using any of the techniques or structures discussed herein. 
     A method of use of introducer  10  may include inserting introducer  10  into and/or navigated within a vessel or body lumen to a target site or area of interest. In some embodiments, the vessel or body lumen may include a partial or total occlusion or obstruction formed therein. Importantly, the introducer  10  may be used in a vessel or body lumen that does not include a partial or total occlusion therein. 
     After navigating the introducer  10  to the target site or area of interest, an elongate dilator may be inserted into the lumen  22  of the liner  20  and advanced distally toward the distal end  26  of introducer  10 , liner  20 , and/or outer sheath  30 . As the dilator reaches, encounters, and/or engages the lumen  22  of the liner  20 , the dilator may exert a radially outward force from within the lumen  22  upon the wall of the liner  20  and/or the outer sheath  30 . The radially outward force may cause the outer sheath  30  to separate, split, or tear along and/or through the plurality of openings, cutouts, perforations, notches, holes, apertures, or other weakening features formed in the wall of the outer sheath  30  as the dilator is advanced distally through the lumen  22  of the liner  20 . As the outer sheath  30  separates, splits, or tears apart, the one or more folds  34  of the liner  20  are permitted to unfold and increase the inner diameter of the lumen  22 . In a vessel or body lumen having a partial or total occlusion, when the dilator may be advanced through the occlusion and/or the outer sheath  30  is opened/expanded within the occlusion, the vessel or body lumen may be deformed or distended by the rigidity of the dilator moving the occlusive material radially outward. Once positioned appropriately adjacent the target site, introducer  10  may be utilized as an access pathway for additional medical devices. 
     In some examples, introducer  10  may be made from materials such as metals, metal alloys, polymers, ceramics, metal-polymer composites, or other suitable materials, and the like. Some examples of suitable materials may include metallic materials such as stainless steels (e.g. 304v stainless steel or 316L stainless steel), nickel-titanium alloys (e.g., nitinol, such as super elastic or linear elastic nitinol), nickel-chromium alloys, nickel-chromium-iron alloys, cobalt alloys, nickel, titanium, platinum, or alternatively, a polymeric material, such as a high performance polymer, or other suitable materials, and the like. The word nitinol was coined by a group of researchers at the United States Naval Ordinance Laboratory (NOL) who were the first to observe the shape memory behavior of this material. The word nitinol is an acronym including the chemical symbol for nickel (Ni), the chemical symbol for titanium (Ti), and an acronym identifying the Naval Ordinance Laboratory (NOL). 
     In some examples, the introducer  10  may be made from materials such as, for example, a polymeric material, a ceramic, a metal, a metal alloy, a metal-polymer composite, or the like. Examples of suitable polymers may include polyurethane, a polyether-ester such as ARNITEL® available from DSM Engineering Plastics, a polyester such as HYTREL® available from DuPont, a linear low density polyethylene such as REXELL®, a polyamide such as DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem, an elastomeric polyamide, a block polyamide/ether, a polyether block amide such as PEBA available under the trade name PEBAX®, silicones, polyethylene, Marlex high-density polyethylene, polyetheretherketone (PEEK), polyimide (PI), and polyetherimide (PEI), a liquid crystal polymer (LCP) alone or blended with other materials. In some examples, a suitable polymeric material may have a yield strain of at least 20%, at least 30%, at least 40%, at least 50%, or more. In some examples, the sheath, the membrane, and/or the plurality of corrugations may be made from a material having a low coefficient of friction. In some examples, the sheath, the membrane, and/or the plurality of corrugations may be formed from a fluoropolymer, such as polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP). 
     Portions of introducer  10  may be made of, may be doped with, may include a layer of, or otherwise may include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique such as X-ray during a medical procedure. This relatively bright image aids the user of device in determining its location. For example, one or more of the elements described above (i.e., the sheath, the membrane, the medical device, etc.) may include or be formed from a radiopaque material. Suitable materials can include, but are not limited to, bismuth subcarbonate, iodine, gold, platinum, palladium, tantalum, tungsten or tungsten alloy, and the like. 
     It should be understood that although the above discussion was focused on percutaneous medical procedures within the vasculature of a patient, other examples or methods in accordance with the disclosure can be adapted and configured for use in other parts of the anatomy of a patient. For example, devices and methods in accordance with the disclosure can be adapted for use in the digestive or gastrointestinal tract, such as in the mouth, throat, small and large intestine, colon, rectum, and the like. For another example, devices and methods can be adapted and configured for use within the respiratory tract, such as in the mouth, nose, throat, bronchial passages, nasal passages, lungs, and the like. Similarly, the devices and methods described herein with respect to percutaneous deployment may be used in other types of surgical procedures as appropriate. For example, in some examples, the devices may be deployed in a non-percutaneous procedure. Devices and methods in accordance with the disclosure can also be adapted and configured for other uses within the anatomy. 
     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. The disclosure&#39;s scope is, of course, defined in the language in which the appended claims are expressed.