Abstract:
A device including a hollow pipe with a variable diameter is used for medical procedures. Means are provided for reducing the diameter either internally or externally so that the pipe can be inserted into a patient&#39;s body through an incision or an opening until the distal end of the pipe reaches a desired position. Thereafter, the diameter of the pipe is increased to allow various surgical devices to be introduced through the pipe.

Description:
RELATED APPLICATIONS 
     This is the U.S. National Stage of International Application No. PCT/US2011/036987, filed May 18, 2011, which was published in English under PCT Article 21(2), which in turn claims the benefit of U.S. Provisional Patent Application No. 61/345,861 filed May 18, 2010 and U.S. Provisional Patent Application No. 61/353,394 filed Jun. 10, 2010, which are incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system for accessing a body cavity by creation of an access channel and by providing radial expansion of small diameter access channels. 
     BACKGROUND OF THE INVENTION 
     Interventional procedures which provide access to body cavities have varied applications for various medical indications. For example, ureteroscopy is often performed using a ureteral access sheath. The small diameter of ureters presents a challenge when attempting to insert an access sheath that is small enough to insert without damaging the ureter and large enough to pass surgical instruments or other objects through to and from the bladder. Other examples of applications which require access to body cavities include intubations, percutaneous procedures, vascular procedures, procedures for the gastrointestinal tract, reproductive tract, lymphatic system or others. 
     An access pathway may be created through a natural channel in the body, or may be artificially created, depending on the procedure or indication. 
     Frequently, an access system cannot be easily introduced through a urinary system or other vessels, due to tortuosity in the vessel, strictures within the vessel, or other causes. More particularly, systems which have diameters sufficient to treat the vessel or organ may be too large to pass through problematic areas within the body or body lumen. Systems which can be introduced in a contracted state, and later expanded when within the body, have been developed. 
     A commonly known technique for enlarging an initial access puncture involves successively introducing larger diameter rods through the access hole and into the internal organ. Systems designed to minimize trauma associated with such techniques include the use of an outer sheath which is radially expandable through various methods. An example of such a system is disclosed in U.S. Pat. No. 5,183,464 to Dubrul et al, entitled “Radially Expandable Dilator.” The dilation tube, or access sheath, is radially expandable from a small diameter to a larger diameter by axial insertion of an expansion member through the axial lumen of the dilation tube. 
     This system is useful for expanding a puncture site and does not require a contraction to retract the dilator from the body. A catheter for insertion into vasculature is disclosed in U.S. Pat. No. 5,944,691 to Querns et al. This catheter is designed with stripes of rigid material and stripes of expandable material, wherein an expanding member inserted through the catheter causes the catheter to irreversibly expand in the radial direction. 
     An example of an expandable medical access sheath is disclosed in US Patent Publication 2008/0200943. An elongate tubular member is made of expandable material which can be folded when in its contracted state. The sheath is then expanded by introduction of a dilator through the lumen of the sheath. The material has a first configuration which is collapsed, and a second configuration which is enlarged and which includes elements or structures within the sheath which resist re-collapse. However, pressure within the vessel may cause the sheath to collapse due to the generally flexible nature of the material. 
     It would therefore be beneficial to have a system and method for accessing a vessel in the body which has a variable diameter, which can be contracted for removal from the vessel, and which will maintain rigidity when open in the vessel. 
     SUMMARY OF THE INVENTION 
     These needs are addressed by the present invention which comprises in one aspect a tube formed by rolling a sheet of spring-like flexible material onto itself to form an access sheath which is configured and adapted to be inserted in a lumen such as a vessel in a body. The resulting tube has a diameter which can be expanded when a hollow pipe of greater external diameter than the internal diameter of the tube is inserted in the tube, thereby causing the coiled sheath to uncoil slightly and expand the internal diameter. The tube is also adapted to coil by the sheath rolling back into itself when the pipe is extracted; the tube can then be easily removed from the lumen. 
     In some embodiments, the sheath has a tooth-like locking device which can lock the tube at different diameters. After the pipe has forced the tube to be expanded (by uncoiling the sheath), and the pipe is extracted, the expanded diameter does not return to its original diameter until the tooth-like locking device is pulled out. Pulling out the tooth-like locking device causes the sheath to collapse back into its original rolled state, thereby allowing it to be easily extracted. 
     In other embodiments, the access sheath includes a bar attached to strategically spaced hinges connecting it to legs, which are in turn attached to sliding bars running parallel to the inside of the access sheath and are equipped with stoppers which stop them from moving forward. In these embodiments, the inner bar can be pushed, which causes the legs to change angle within the access sheath, thereby causing the sliding bars to move away from each other and the spring to open. Once the spring is locked in place, the entire opening mechanism is able to be extracted so that tools can be easily inserted and removed into the access sheath tube. The tooth-like locking device can be pulled out independently of the access sheath, in which case the sheath to collapse into its original rolled space (having the smallest diameter), thereby permitting the sheath to be easily extracted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and further advantages of the present invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
         FIGS. 1A and 1B  are schematic illustrations of a system in a first configuration and a second, expanded configuration, respectively, in accordance with embodiments of the present invention; 
         FIGS. 2A-2C  are cross sectional illustrations of the system of  FIG. 1A  in a collapsed configuration and  FIG. 1B  in an expanded configuration, respectively, in accordance with embodiments of the present invention; 
         FIGS. 3A-3C  are illustrations of the expandable body of the system of  FIGS. 1A  and  1 B, shown in perspective view, and in cross-sectional views, in a contracted configuration and an expanded configuration respectively, in accordance with one embodiment of the present invention; 
         FIGS. 4A-4C  are schematic illustrations of the system of  FIGS. 1A and 1B , in accordance with another embodiment of the present invention; 
         FIG. 5  is a perspective illustration of the system of  FIGS. 1A and 1B  in accordance with yet additional embodiments of the present invention; 
         FIGS. 6   a -C are schematic illustrations of the system of  FIGS. 1A and 1B  in accordance with yet additional embodiments of the present invention; 
         FIGS. 7A and 7B  are cross-sectional illustrations of the system of  FIGS. 1A and 1B  in accordance with additional embodiments of the present invention; 
         FIGS. 8A and 8B  are a cross-sectional view and a close-up cross-sectional view, respectively of the system of  FIGS. 1A and 1B  in accordance with additional embodiments of the present invention; 
         FIG. 9A  is a perspective view of an expandable body of the system of  FIGS. 7A-7B  and  8 A- 8 B, in accordance with an embodiment of the present invention; 
         FIG. 9B  is a schematic representation of the expandable body of  FIG. 9A  having varying diameters along its length; 
         FIG. 10A  is a schematic illustration of another embodiment of the system in a first rolled configuration, in perspective view; 
         FIG. 10B  is a schematic view of the access tube in a closed, rolled state and an expansion pipe about to be inserted; 
         FIG. 10C  is a side, perspective view of an embodiment of the tube with a first locking device; 
         FIG. 10D  is a side, perspective view of an embodiment of the tube with a second locking device having teeth; 
         FIG. 11  is a cross-sectional view of an embodiment of the invention which includes the sliding bar used to expand the diameter of the access sheath when the plunger is pressed, and a pull ring locking mechanism, each being operated by a hand of an operator; 
         FIG. 12  shows a side elevational view of another embodiment wherein the body of the system includes a coil with a mechanism for selectively winding and unwinding the coil to decrease and increase its diameter; 
         FIGS. 13A-13E  are schematic illustrations of the steps of a method of using the system of the present application. It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. Moreover, some of the blocks depicted in the drawings may be combined into a single function. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to a system and method for the purpose of performing a percutaneous procedure via an access channel. Before explaining the embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. In discussion of the various figures described herein below, like numbers refer to like parts. The drawings are generally not to scale. As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. 
     It will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and structures may not have been described in detail so as not to obscure the present invention. The principles and operation of a system and method according to the present invention may be better understood with reference to the drawings and accompanying descriptions. 
     Reference is now made to  FIGS. 1A and 1B , which are schematic illustrations of a system  10  in a first configuration and a second, expanded configuration, respectively. It should be understood that the system  10  is generic to all the other embodiments shown in the remaining figures, unless otherwise noted. In embodiments of the present invention, system  10  forms an access sheath for providing access to a body lumen or organ, such that upon deployment of system  10 , procedures may be performed on the body lumen or organ via insertion and/or removal of objects through the access sheath. System  10  includes an elongate member  11  having a proximal end  12 , a distal end  14  and an expandable body  16  having a length L extending at least partway from proximal end  12  to distal end  14 . Expandable body  16  includes at least a portion of elongate member  11 , and in some embodiments, may extend the entire length of elongate member  11 . In some embodiments, expandable body  16  may have different sections along its length with variable expansion capacities, as will be described further herein below. 
     Expandable body  16  has at least two configurations, wherein in a first configuration, expandable body  16  has a smaller outer diameter d, as shown in  FIG. 1A , and in a second configuration, expandable body  16  has a larger outer diameter D, as shown in  FIG. 1B . It should be noted that throughout the present application, drawings are not to scale and are for illustration purposes only. For the purposes of the present invention, “first” and “second” are not indications of an order of operation, but are merely used to designate two different configurations. In some embodiments, the first configuration may be implemented before the second configuration, while in other embodiments, the first configuration may be implemented after the second configuration. Moreover, switching between configurations may be possible as well. In addition, any number of intermediate configurations is possible as well, wherein each intermediate configuration has a different diameter. The change in diameter from a contracted to an expanded state varies in accordance with the particular application. For example, in a urological application, the contracted body  16  may have an outer diameter of approximately 2-3 French, while the expanded body may have an outer diameter as large as 15 to 20 French. For an intubation, the contracted body may have an outer diameter of 2 mm and an expanded body may have an outer diameter of 20 mm, in some embodiments, and up to 40 mm in other embodiments. 
     Elongate member  11  has a lumen  18  extending therethrough which is configured for receiving devices for accessing the vessel, such as, for example, guidewires, sensor devices, pharmaceutical delivery devices, or any other access or treatment devices. Lumen  18  is further configured for removing items from within the vessel, such as, for example, debris, blood, foreign objects, or any other item which may be removable from a vessel. Lumen  18  extends from proximal end  12  until distal end  14 . A hub  19  is positioned at proximal end  12 . Hub  19  is coupled to elongate member  11 , providing access to lumen  18  from outside of the treatment site or body. Hub  19  may include external control components  32  for controlling expansion and contraction of expandable body  16 , as will be described in further detail herein below. A distal opening  23  at distal end  14  of elongate member  11  provides access from lumen  18  to an internal site for treatment or access. 
     In accordance with embodiments of the present invention, the capacity for multiple configurations, each with a different diameter, is obtained by the use of at least one seam  24  and overlappable portions, as will be described in further detail. 
     Reference is now made to  FIG. 2A  and  FIG. 2B , which are cross sectional illustrations of system  10  as shown in  FIG. 1A  in a collapsed configuration and  FIG. 1B  in an expanded configuration, respectively, in accordance with embodiments of the present invention. As shown in  FIG. 2A , expandable body  16  has a seam  24  running longitudinally along its length. Seam  24  divides expandable body  16  into two sides, with a first side having a first longitudinal edge  25  and a second side having a second longitudinal edge  27 . Reference is now made to  FIG. 2C , which is an illustration of expandable body  16  in a flat configuration. As shown in  FIG. 2C , a first overlappable portion  26 —depicted until the dotted line—extends transversely from first longitudinal edge  25 , and a second overlappable portion  28 —also depicted by a dotted line—extends transversely from second longitudinal edge  27 . In practice, expandable body  16  is used in a closed or semi-closed substantially tubular configuration, wherein first and second longitudinal edges  25  and  27  are in contact or in close proximity to one another. First overlappable portion  26  and second overlappable portion  28  are configured to at least partially overlap one another in a contracted configuration, as shown in  FIG. 2A , and to separate from one another in an expanded configuration, as shown in  FIG. 2B . Dimensions of the diameter of lumen  18  thus depend on a width of each of first and second overlappable portions which are in overlapping contact with one another. This width is referred to herein as overlapping width  30 , and may be fixed or variable. The larger the overlapping width  30 , the smaller the diameter of lumen  18 , and thus, the smaller the overall diameter of system  10 . Thus, by controlling the overlapping width  30  of first and second overlappable portions  26  and  28 , dimensions of system  10  may be controlled or adjusted as needed. It should be readily apparent from the descriptions herein that system  10  may thus be expanded or contracted as needed. For example, when inserted into a vessel, system  10  may be in a contracted state. Once in place, system  10  may be expanded. In one embodiment, the edges are sized and shaped so that they interlock when in the expanded position. For example, a separate element (not shown) may be provided having a longitudinal groove receiving the edges of the  25 ,  27 . Finally, once the procedure is finished, system  10  may once again be contracted and removed from the vessel. For example, if an interlocking member is used, this interlocking member is first pulled out completely, thereby releasing the edges. The invention is not limited to the description included herein, and may further include other configurations of variably contracting and expanding states. Moreover, certain portions of system  10  may be configured to expand while other portions are configured to contract or remain the same. In some embodiments, multiple seams  24  may be provided, as will be described further herein below. Control of overlapping width  30  may be done with an overlap control mechanism  32 , as described with reference to several different embodiments in  FIGS. 3-9 . The overlap control mechanism includes an internal control portion  31 , positioned on or within expandable body  16 , and an external control portion  33 , located outside of expandable body  16 , and configured to stay outside of the human body during operation. External control portion  33  may be positioned, for example, on or in hub  19  or at some other external location. 
     Reference is now made to  FIG. 3A-3C , which are illustrations of expandable body  16  of system  10 , shown in perspective view, and in cross-sectional views, in a contracted configuration and an expanded configuration respectively, in accordance with one embodiment of the present invention. Elongate body  16  includes seam  24 , which forms first and second longitudinal edges  25  and  27 . In some embodiments, two or more seams  24  may be present, which splits expandable body into two or more independent pieces. For the embodiment depicted in  FIGS. 3A-3C , overlap control mechanism is a magnetic mechanism  132 . Internal control portion  31  of magnetic mechanism  132  includes a first magnetic connector  134  positioned on or within first overlappable portion  26 , and a second magnetic connector  136  positioned on or within second overlappable portion  28 . First and second magnetic connectors  134  and  136  may be, for example, magnetic threads. First and second magnetic connectors  134  and  136  may extend fully or partially along length L of expandable body  16 . In one embodiment, activation of first and second magnetic connectors  134  and  136  by application of an electrical charge causes a magnetic attraction between them, which causes first and second overlappable portions  26  and  28  to overlap one another, as shown in  FIGS. 3A and 3B . This overlapping position is maintained for as long as activation is maintained. When activation is not maintained, expandable body  16  assumes its expanded configuration, wherein diameter D is larger, and overlappable portions  26  and  28  are separated, as shown in  FIG. 3C . In another embodiment, activation of first and second magnetic connectors  134  and  136  by application of an electrical charge causes a magnetic repulsion—causing first and second overlappable portions  26  and  28  to be separated, as shown in  FIG. 3C . This separate position is maintained for as long as activation is maintained. When activation is not maintained, expandable body  16  assumes its contracted configuration, wherein diameter d is smaller, and overlappable portions  26  and  28  are overlapping, as shown in  FIGS. 3A and 3B . In some embodiments, multiple magnetic strands may be used, thus allowing for variable diameters. Thus, the diameter of system  10  may be increased or decreased incrementally depending on the number of strands that are negatively charged. 
     Expandable body  16  may be comprised of any suitable material, such as a rigid or semi-rigid material, including, for example, silicone, silicone-based materials, ceramic, carbon fiber reinforced materials, titanium or other bio-compatible metals, etc. In some embodiments, seam  24  may remain open. In other embodiments, such as upon introduction of fluids, for example, it may be necessary to close seam  24 . This may be accomplished, for example, by provide a thin coating on or around expandable body  16 , wherein the coating remains intact even though expandable body  16  has a seam or a gap. In some embodiments, a piece of fabric or other flexible type of material may be attached to each of longitudinal edges  25  and  27 , wherein the material may fold or unfold, but will maintain an envelope around expandable body  16  for sealing purposes. Materials used for producing vascular grafts or other types of biocompatible mesh or cloth-like materials may be used. 
     External control portion  33  of magnetic mechanism  132  includes a source of electrical current, for example, switchable by a suitable electric switch and at least some of the magnets may be electric coils energized by the electric current. 
     Reference is now made to  FIGS. 4A-4C , which are schematic illustrations of system  10 , in accordance with one embodiment of the present invention. Expandable body  16  includes seam  24 , which forms first and second longitudinal edges  25  and  27 . In some embodiments, two or more seams  24  may be present, which splits expandable body into two or more independent pieces. For the embodiment depicted in  FIGS. 4A-4C , overlap control mechanism  32  is a loop closure mechanism  232 . Expandable body  16  is comprised of any material which can incorporate a wire mesh structure, such as, for example, a polymer, a metal, a composite or any other suitable material. Loop closure mechanism  232  includes a thread  234  woven or braided throughout expandable body  16 . Thread  234  may be a metallic thread, such as a stainless steel or titanium ultra-thin thread. Alternatively, thread  234  may be another suitable material. Multiple threads  234  may be used. For example, when two independent pieces are present, a thread  234  may be included within each independent piece. A torquing mechanism  236  is positioned on expandable body  16 , and may include one or multiple control knobs. Rotation of torquing mechanism  236  causes thread  234  to tighten or loosen, which causes expandable body  16  to contract or expand. 
     In some embodiments, seam  24  may remain open. In other embodiments, such as upon introduction of fluids, for example, it may be necessary to close seam  24 . This may be accomplished, for example, by provide a thin coating on or around expandable body  16 , wherein the coating remains intact even though expandable body  16  has a seam or a gap. In some embodiments, a piece of fabric or other flexible type of material may be attached to each of longitudinal edges  25  and  27 , wherein the material may fold or unfold, but will maintain an envelope around expandable body  16  for sealing purposes. Materials used for producing vascular grafts or other types of biocompatible mesh or cloth-like materials may be used. In one embodiment the body is made of two segments that have the cross-section of a curved arc, the segments being nested together so they overlap, at least partially. Rotating about a longitudinal axis using the torquing mechanisms causes one segment to rotate with the other until their respective edges abut or overlap to form a lumen. 
     Reference is now made to  FIG. 5 , which is a perspective illustration of system  10  in accordance with yet additional embodiments of the present invention. In this embodiment, overlap control mechanism is a screw mechanism  332 . Screw mechanism  332  may be, for example, a threaded screw  334 . Screw  334  is designed to be flexible along its length, but rigid in diameter, such that it does not inhibit insertion of system  10  into the body, but maintains its integrity during insertion and during the entire procedure. Screw mechanism  332  may be embedded within expandable body  16 , for example, by placing screw  334  through a channel within expandable body  16 . A thread  336  may also be placed through expandable body  16  or embedded therein, in a configuration which allows for body  16  to contract or expand upon turning of screw  334 . For example, thread  336  may have a slinky configuration, wherein an angle of the slinky determines the number of rotations of screw  334  needed to expand or contract expandable body  16 . Alternatively, the body  16  is made with diagonal slots (not shown) that engage the threads of the screw  336  in manner similar to a hose clamp. 
     Reference is now made to  FIG. 6 , which is an illustration of system  10  in accordance with yet additional embodiments of the present invention. Overlap control mechanism  32  is an inflatable mechanism  432 , including an inflatable portion  434  placed between longitudinal edges  25  and  27 . Inflatable portion  434  extends along a length L of expandable body  16  to proximal hub  16 . An inflation hub may be provided for providing fluid or air to inflatable portion  434 . In a contracted configuration, inflatable portion  434  is uninflated, and may lie between overlappable portions  26  and  28 . In an expanded configuration, inflatable portion  434  is inflated via inflation fluid through hub  19 , causing inflatable portion to expand, thus separating overlappable portions  26  and  28  from one another. 
     Reference is now made to  FIGS. 7A-7B , which are cross-sectional illustrations of system  10  in accordance with additional embodiments of the present invention. Expandable body  16  comprises an inner expandable tube  116  and an outer expandable tube  118  which is coaxial to inner expandable tube  116 . Inner and outer expandable tubes  116  and  118  are comprised of a rigid material such as a metal or composite. In some embodiments, outer expandable tube  116  is comprised of a more flexible material than inner expandable tube  118 . This may be accomplished by using different materials for each of inner and outer expandable tubes  116  and  118 , by treating one or the other or both of inner and outer expandable tubes  116  and  118  to change the material properties thereof, or by mechanical means. Mechanical means may include addition of certain elements, such as composite fibers, for example. Other mechanical means may include structural configurations of each of inner and outer expandable tubes  116  and  118 . In some embodiments, connectors  117  are positioned between inner expandable tube  118  and outer expandable tube  116 , connecting inner and outer expandable tubes  118  and  116  to each other. In one embodiment, connectors  117  are separators, wherein there is no possibility of substances passing from one compartment to the next. In other embodiments, connectors  117  are permeable or semi-permeable to fluid or other substances. Permeability may be accomplished either by choice of material, or by providing a woven or porous structure. In one embodiment, as depicted in  FIG. 7A , only a single seam  24  may be incorporated into each of inner and outer expandable tubes  116  and  118 , and expandable body  16  has a contracted and an expanded configuration similar to those described above with reference to  FIGS. 3-6 , but with both inner and outer expandable tubes having this configuration so that they can remain substantially coaxial. 
     In another embodiment, as shown in  FIG. 7B , multiple seams  24  are incorporated into both inner and outer expandable tubes  116  and  118 , thus forming multiple inner overlappable portions  126  and outer overlappable portions  128 . Thus, longitudinal edges of inner overlappable portions  126  are in overlapping contact with one another in a contracted configuration, as shown in  FIG. 7A , and are separated from one another (either partially or fully) in an expanded configuration so as to form a more cylindrical shape, as shown in  FIG. 7B . Overlap control mechanism  32  is a circumferential inflatable mechanism  532 . Circumferential inflatable mechanism includes a sealed flexible chamber  534  comprised of an inner wall  536  and an outer wall  538 . Essentially, sealed flexible chamber  534  is similar to a balloon, and may be formed of any suitable material, such as silicone, for example. Sealed flexible chamber  534  is sandwiched between inner and outer expandable tubes  116  and  118  and runs longitudinally along expandable body  16 . An inflation lumen is provided at proximal hub  19  of system  10  to provide air, gas, or other fluid into sealed flexible chamber  534  for expansion thereof. Upon expansion of sealed flexible chamber  534 , outer expandable tube  118  expands outward, thereby increasing a diameter of outer expandable tube  118 . Since inner expandable tube  116  is more rigid than outer expandable tube  118 , when outer expandable tube  118  expands outward, inner expandable tube  116  is pulled along with it and also expands outward. Moreover, when connectors  117  are used, expansion of outer expandable tube  118  further pulls inner expandable tube in an outward direction. It is possible that during expansion of inner expandable tube  118  there will be some movement towards the inside of the lumen—that is, inner expandable tube  118  may be pushed in a direction wherein a diameter of inner expandable tube decreases slightly and wherein sealed flexible chamber  534  expands, pushing inner and outer expandable tubes in opposite directions. However, the tubes are designed such that outer expandable tube  116  is at least 2-3 times more flexible, and possibly even 4 or 5 times more flexible or even more than inner expandable tube  118 , thereby minimizing such opposing effects. The embodiment shown in  FIGS. 7A and 7B  may be particularly suitable for larger applications such as intubations. Reference is now made to  FIGS. 8A and 8B , which are cross-sectional illustrations of system  10 , in accordance with yet additional embodiments of the present invention. Expandable body  16  comprises an inner expandable tube  116  and an outer expandable tube  118  which is coaxial to inner expandable tube  116 .Inner and outer expandable tubes  116  and  118  are comprised of a rigid material such as a metal or composite. In some embodiments, outer expandable tube  116  is comprised of a more flexible material than inner expandable tube  118 . This may be accomplished by using different materials for each of inner and outer expandable tubes  116  and  118 , by treating one or the other or both of inner and outer expandable tubes  116  and  118  to change the material properties thereof, or by mechanical means. Mechanical means may include addition of certain elements, such as composite fibers, for example. Other mechanical means may include structural configurations of each of inner and outer expandable tubes  116  and  118 . Connectors  117  are positioned between inner expandable tube  118  and outer expandable tube  116 , connecting inner and outer expandable tubes  118  and  116  to each other. In one embodiment, connectors  117  are separators, wherein there is no possibility of substances passing from one compartment to the next. In other embodiments, connectors  117  are permeable or semi-permeable to fluid or other substances. 
     Permeability may be accomplished either by choice of material, or by providing a woven or porous structure. Similar to the embodiments described above with respect to  FIGS. 7A and 7B , one or multiple seams (not shown) are incorporated into both inner and outer expandable tubes  116  and  118 , thus forming one or more multiple inner overlappable portions  126  and outer overlappable portions  128 . Thus, longitudinal edges of inner overlappable portions  126  are in overlapping contact with one another in a contracted configuration, and are separated from one another (either partially or fully) in an expanded configuration while remaining substantially coaxial. 
     Overlap control mechanism  32  is a compartmentalized inflatable mechanism  632 . Circumferential inflatable mechanism includes multiple inflation chambers  634  separated from one another by connectors  117 . Connectors  117  are situated circumferentially around expandable body  16 , thus creating chambers  635  within a space between inner and outer expandable tubes  116  and  118 . Connectors  117  may extend longitudinally along the length of expandable body  16 , such that chambers  635  extend along a length of expandable body  16 , as shown in  FIG. 9A . In one embodiment, connectors  117  are separators, wherein there is no possibility of substances passing from one compartment to the next. In other embodiments, connectors  117  are permeable or semi-permeable to fluid or other substances. Permeability may be accomplished either by choice of material, or by providing a woven or porous structure. Chambers  635  may include two or more inflation chambers  634 . In some embodiments, all of chambers  635  are inflation chambers  634 . In other embodiments, only some of chambers  635  are inflation chambers  634 , while others do not include an inflation component. 
     In most cases, it will be necessary to position inflation chambers  634  symmetrically around expandable member  16  so as to provide uniform expansion of expandable member  16 . However, in certain applications it may be desirable to position inflation chambers  634  asymmetrically so as to provide different shapes for expandable member  16 . 
     Reference is now made to  FIG. 8B , which is an enlarged illustration of section A of  FIG. 8A , showing an inflation chamber  634  in greater detail. Inflation chamber  634  includes an inflation element  636 . Inflation element  636  includes an inlet  646 , an outer segment  638 , and an inner segment  640 . Outer segment  638  is adjacent to or in contact with outer expandable tube  118 , and inner segment  640  is close to inner expandable tube  116 . Inlet  646  is a passage for fluid such as air, gas, or liquid, and leads directly into inflation element  636 . Outer and inner portions  638  and  640  are connected to one another, thus forming a sealed element, wherein gas or liquid introduced through inlet  646  fill up a space created by outer and inner portions  638  and  640 . Outer segment  638  is comprised of expandable material such as latex, or an elastic or elastomeric material, or a balloon-type of material such that upon filling with air or fluid, outer segment  638  is configured to expand or extend in an outward direction. Outer segment  638  extends along most or all of a length of a section of outer inflatable tube  116  which is included in the particular inflatable chamber  634  being described. Inner segment  640  is comprised of a more rigid material, such as titanium, stainless steel or any other rigid material. Inner segment  640  extends from edges of outer segment  638  (referred to herein as extended portion  642  of inner segment  640 ) towards inner expandable tube  116  (referred to herein as inward facing portion  644  of inner segment  640 ). Inward facing portion  644  leads directly into inlet  646 . Thus, inner segment  640  is shaped such that inflation element  636  is relatively wide at its extended portion  642 , which is adjacent to outer segment  638 , and is relatively narrow at its inward facing portion  644 , which is adjacent to inlet  646 . Thus, inflation element  636  may take on a funnel or mushroom shape, for example. An inflation lumen is provided at a proximal end of system  10  to provide air, gas, or other fluid into inflation element  636 . In one embodiment, a single inflation lumen is provided and is split into each of inflation elements  636 , thus providing uniform inflation around a circumference of expandable body  16 expandable body  16 . In another embodiment, separate inflation lumens are provided to each of inflation elements  636 , providing control over an amount of inflation of each of inflation elements  636 . 
     Upon expansion of inflation elements  636 , outer segments  638  expand outward, pushing against outer expandable tube  118 , thereby increasing a diameter of outer expandable tube  118 . Since inner segments  640  of inflation elements  636  are more rigid than outer segments  638 , and since a surface area of outer segments  638  is larger than a surface area of inner segments  640 , an outward force is created, pushing outer expandable tube  118  outward. Since inner expandable tube  116  is connected to outer expandable tube  118  by connectors  117 , when outer expandable tube  118  expands outward, inner expandable tube is pulled along with it and also expands outward. The embodiment shown in  FIGS. 8A and 8B  may also be particularly suitable for larger applications such as intubations. 
     Returning again to  FIG. 9A , an additional feature is shown which may apply to either of the embodiments described above with respect to  FIGS. 7A and 7B  and  8 A and  8 B. As shown in  FIG. 9A , expandable body  16  may be further compartmentalized in a longitudinal direction, such that separate sections (shown herein as  702  and  704 ) are formed along a length of expandable body  16 . Each of the separate sections may be separately controllable in terms of expansion diameter. Thus, as shown in  FIG. 9B , a first section  702  may be expandable to a first diameter D 1  and a second section  704  may be expandable to a second diameter D 2 . This feature is not limited in the number of separate sections that may be used, and may be particularly useful for an application wherein different vessels of varying sizes are entered during a procedure. For example, in an ureteroscopy procedure, system  10  is configured to first enter a ureter, to pass through the bladder, into the urethra, and finally into the kidney. Each of these sections has a different anatomy and it would be advantageous to use a system such as the one described herein to adjust the expansion capacity as needed for each particular vessel or organ being entered. A set of radiopaque markers may be incorporated into expandable body  16  at the edges of each section so that the user can determine which section is in which location in the body at any given time. In some embodiments, expansion sensors may be included on each of the separate sections so that a reading of diameter and/or other expansion characteristics may be provided to the user. An example of such a sensor is a spiral-like metal sensor wrapped around the particular section of expandable body, and wherein separation of the spiral ends from one another signals an amount of expansion of that section. Other sensors are commonly known in the art, and any type of sensor which can convey this information may be used. 
     In both of the embodiments described above with respect to  FIGS. 7A and 7B  and  FIGS. 8A and 8B , contraction of expandable body  16  is done by removing air or fluid via hub  19 , which may in some cases be done with vacuum. 
     It is a particular feature of the present invention, that in all of the embodiments disclosed herein, the expanded configuration of system  10  maintains its rigidity or integrity, and thus, does not buckle under pressure from blood flow, vessel collapse, obstructions, or other causes. 
     Reference is now made to  FIGS. 10A-10D  which is a schematic illustration of another embodiment of the system In a first rolled configuration of this embodiment, shown in, perspective view, a tube is formed by rolling a sheet  900  of spring-like flexible material onto itself to form an access sheath which is configured and adapted to be inserted in a lumen such as a vessel in a body and the resulting tube has a diameter which can be expanded when a hollow pipe of greater external diameter than the internal diameter of the tube is inserted in the tube, thereby causing the coiled sheath to uncoils slightly and expand the internal diameter. The tube is also adapted to coil by the sheath rolling back into itself when the pipe is extracted, and the tube can then be easily removed from the lumen. A tool  902  with a conical tip  904  can be used to selectively expand the tube  904  after insertion. 
       FIG. 10C  shows another embodiment in which the edges A and B of the sheet  900  are connected by an intermediate piece  906  to insure that they maintain their spacing, and therefore the sheet  900  maintains an expanded diameter. The intermediate piece can be inserted after the sheet has been opened by tool  902 , and then removed, to allow the sheet to collapse to the configuration shown in  FIG. 10A . In a version shown in more detail in  FIG. 10D , sheath  900  has a tooth-like locking device  908  attached to each of the edges A and B which can lock the tube at different diameters. When the pipe is extracted (after it has forced the tube to be expanded by uncoiling the sheath), the expanded diameter does not return to its original diameter until the tooth-like locking devices is pulled out. This action causes the sheath to collapse back into its original rolled state, thereby allowing it to be easily extracted. 
     Another embodiment is shown in  FIG. 11 . In this embodiment, an access sheath  950  is formed of any suitable material as described and, has a first configuration in which the sheath  950  has a relatively small diameter. In this configuration, the sheath is inserted into a body cavity, such as the urethra, or through a proper incision to a body cavity or organ. 
     At one end, the sheath  950  is attached to a spreading mechanism that spreads the sheath  950  until its diameter increases to a new diameter. Once this new diameter is achieved, preferably the spreading mechanism is withdrawn and the appropriate locking mechanism is used to maintain the sheath in its expanded configuration until it is collapsed. 
     The spreading mechanism includes a handle  952  that is positioned near or is attached to the proximal end of sheath  950 . The mechanism further includes a central member  954  selectively inserted through the sheath. The central member terminates with a thumb pad  956  and is longitudinally movable in sheath  950 . At regular intervals along the central member  950  there are provided a plurality of expandable elements  960 . Each element  960  includes a plurality of bars (from two to six bars per element)  964  extending longitudinally. Each bar is in intimate contact with the interior wall of the sheath  950 . Each bar is connected to a hinged arm  966 . Each arm is further connected by hinges  968  to the central member  954 . 
     This embodiment operates as follows. Once the sheath  950  and central member  954  are in place and the bars  966  are in contact with the wall of sheath  950 , the operator pushes the central member  954  forward using thumb pad  956  while holding handle  952  in place. This action causes the arms  966  to open radially outwardly thereby pushing against the internal wall of sheath  950  and causing the sheath to expand. A stopper  976  is used to limit how far the sheath is inserted. Once the sheath  950  is locked in its expanded position, the expansion member can be withdrawn. In an alternate embodiment, a wire  980  can be disposed inside the member  954  and provided with fingers  984  that move in position and force the hinges  968  to rotate, causing the arms to rotate outward. As previously mentioned, once the procedure is complete, the interlocking mechanism (such as teeth) are disengaged or opened, allowing the sheath to collapse to its smaller diameter configuration. 
     Another embodiment is shown in  FIG. 12 . In this example, a spring type metal device  1000  is created using a flat wire shaped into a spring. Preferably a memory metal such as nitinol is used for the flat wire. Alternatively, a nitinol tube can be used, and a laser pattern can be cut into the tube, thus creating a memory spring-like structure. (Other similar material, such as a plastic having appropriate memory and strength characteristics may be used) The resting diameter of the tube can be the expanded or collapsed state. 
     Device  1000  includes a spring-like body  1002 . It should be understood that the body  1002  is described as having a spring-like body  1002  only because it has the appearance of a spring. However, typically, a spring is primarily designed to compress and/or expand along the longitudinal axis to provide damping or biasing forces. In this case, the movement is along the horizontal axes of the “spring” like structure, specifically the diameter. The device  1000  is not made to be stretched or compressed along its longitudinal axis. The device has a resting state diameter that is either the contracted or the expanded diameter. In this case, a center wire/cable  1003  running up the length of the device, attached to the inside far end of the body  1002 , locks on to it, then with a winding procedure, winds the spring down from the expanded diameter to the collapsed diameter. This allows for insertion and removal. 
     In an emergency case, the body can be “unscrewed” from the urethra and ureter, by manually turning the device, or using a hand crank. 
     The spring body  1002  has a silicone or rubber sleeve around it (not shown), which itself may be coated with a hydrophilic coating, which will facilitate the unscrewing from the urological tract. It will also protect the internal mucosa during this procedure. However, it is preferable to collapse the device prior to removal. 
     Typically, the body  1002  is made from a flat wire having a square or rectangular cross section with a thickness and height ranging from 0.025 mm to about 1.00 mm. 
     In one embodiment, the body  1002  is made from a nitinol tube having a thickness of 0.2 mm. If a spiral cut is made in the tube having a width of 0.2 mm thick, the cross section would reveal a square cross section. In one example, it is preferable to have the cut be greater than 0.2 mm, so that the distance between the wire turns is actually wider than deeper. 
     In  FIG. 12 , body  1000  includes one portion  1004  that is expanded, and a second portion  1004  that has been twisted by the internal wire  1003  so that it has a much smaller diameter. 
     Reference is now made to  FIGS. 13A-13E , which are illustrations of a method of using system  10  within a vessel, in accordance with embodiments of the present invention. 
     The application shown herein is a urology application. However, it should be readily apparent that system  10  may be designed for use in many different medical applications. Reference is now made to  FIG. 13A , which shows system  10  as its being inserted into a urethra  802 . Also shown are additional components of the urogenital system, including a bladder  804 , ureters  806  and kidneys  808 . Reference is now made to  FIG. 13B , which is an illustration of system  10  after it has been advanced through the urogenital system and into a kidney  808 . Expandable body  16  is in a contracted configuration, in accordance with, but not limited to, any of the embodiments disclosed herein. A closer view of contracted expandable body  16  is shown in  FIG. 13C . System  10  is then expanded, as shown in  FIG. 13D , to a larger diameter (or to several larger diameters at different sections along a length of system  10 —not shown). It is a particular feature of the present invention that expansion of expandable body  16  may be done in a single step, without the need for multiple slow increases of diameter. Moreover, expansion of expandable body  16  is controlled by control mechanism  32 , which a user may control via external control portion  31  from outside of the body using the various methods described herein. Next, items such as surgical instruments, fluids, drugs, etc. may be introduced through lumen of expandable body  16  into the vessel being treated (i.e. the kidney in the currently described method). This is shown schematically in  FIG. 13E  by use of arrows  810  for insertion of items and arrows  812  for removal of items from the vessel. Alternatively, or in addition to the above, items such as debris or kidney stones or other unwanted items may be removed through expandable body  16 . After the procedure is done, expandable body  16  is contracted via control mechanism  32 , and system  10  again resembles the configuration shown in  FIGS. 13B and 13C . It should be noted that if the diameter of expandable body  16  is not as small after contraction as it had been before expansion, it still may be sufficient to safely remove expandable body  16  from the body. Finally, expandable body  16 , in its contracted state, is removed from the body. 
     System  10  may be used in similar methods for intubation, vascular access or any other procedure which requires access to vessel in the body. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination. 
     Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.