Abstract:
A flexible conduit for insertion into a body lumen comprises a plurality of elements coupled end to end to define a conduit lumen. A first one of the elements includes a male portion and a female portion. A second element includes a female portion having an inner surface configured to engage a male portion of an outer surface of the first element to form a first ball joint. A third element includes a male portion, an outer surface of the male portion of the third element configured to engage an inner surface of the female portion of the first element to form a second ball joint. The male and female portions of the first element are adapted to fictionally engage the female portion of the second element and the male portion of the third element to establish a rigid connection therebetween.

Description:
PRIORITY CLAIM 
     This application is a continuation of U.S. patent application Ser. No. 13/241,546, filed Sep. 23, 2011, now U.S. Pat. No. 8,439,084 B2, which is a continuation of U.S. patent application Ser. No. 12/481,258, filed Jun. 9, 2009, now U.S. Pat. No. 8,047,236 B2, which claims the benefit of priority to U.S. Provisional Application No. 61/096,529, filed Sep. 12, 2008. The contents of all of the above-identified applications is incorporated herein by reference. 
    
    
     BACKGROUND 
     Many procedures for the exploration and treatment of the gastro-intestinal (GI) tract involve the insertion of an endoscope into the GI tract. During examinations, a user may navigate the GI anatomy using a steerable endoscopic tip, or alternatively by performing a series of torquing, pushing and pulling maneuvers at the proximal end of the device to advance and direct the distal end. The forces applied to the endoscope are transferred to the surrounding tissue and may be problematic and painful. Movement of the endoscope may cause spasms and may, in certain cases, even perforate the intestine. It is therefore necessary to perform the procedure slowly and at times, it may not be possible to reach remote areas without unduly traumatizing surrounding tissue. 
     Various guides have been developed in order to absorb this stress and facilitate insertion of the endoscope while minimizing the impact on the lumenal walls. However, the current guides are often expensive, bulky and/or require added steps which unduly complicate the procedures. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a flexible conduit for insertion into a body lumen, the conduit comprising a plurality of elements coupled end to end with lumens of the elements aligned to define a conduit lumen. The plurality of elements include a first element including a male portion and a female portion and a second element including a female portion having an inner surface extending along a curve corresponding to a curve of the male portion of an outer surface of the first element so that, when the male portion of the first element is received within the female portion of the second element, the first and second elements form a first ball joint. A third element includes a male portion, an outer surface of the male portion of the third element being curved along a shape corresponding to a curve of an inner surface of the female portion of the first element so that, when the male portion of the third element is received within the female portion of the first element, the first and third elements form a second ball and socket joint, the male and female portions of the first element being adapted to frictionally engage respectively, the female portion of the second element and the male portion of the third element to establish a rigidity of the conduit sufficient to retain its shape and absorb forces applied thereto as a flexible instrument is inserted through the conduit lumen. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing an element of a flexible conduit according to a first embodiment of the invention; 
         FIG. 2  is a partial cross-sectional side view of the element of  FIG. 1 ; 
         FIG. 3  is a perspective view showing multiple connected elements of a flexible conduit according to a first embodiment of the invention; 
         FIG. 4  is a partial cross-sectional side view of the flexible conduit of  FIG. 3 ; 
         FIG. 5  is a perspective view showing an element of a flexible conduit according to a second embodiment of the invention; 
         FIG. 6  is a partial cross-sectional side view showing the element of  FIG. 5 ; 
         FIG. 7  is a perspective view showing multiple connected elements of a flexible conduit according to a second embodiment of the invention; 
         FIG. 8  is a partial cross-sectional side view of the flexible conduit of  FIG. 7 ; 
         FIG. 9  is another partial cross-sectional side view showing forces applied to the flexible conduit of  FIG. 7 ; 
         FIG. 10  is a perspective view showing forces applied to an element of a flexible conduit of  FIG. 7 ; 
         FIG. 11  is a partial cross-sectional view showing the element of  FIG. 9 ; 
         FIG. 12  is a side view of the element and forces shown in  FIG. 9 ; 
         FIG. 13  is a side view showing another embodiment of a flexible conduit according to the invention, in a flexible state; 
         FIG. 14  is a side view showing the flexible conduit of  FIG. 13  in a locked state; 
         FIG. 15  is a side view showing yet another embodiment of an element of a flexible conduit according to the invention; and 
         FIG. 16  shows a flexible conduit formed of the elements shown in  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be further understood with reference to the following description and to the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to guides for the insertion of flexible endoscopes or other flexible elongate instruments along tortuous body lumen paths. The exemplary embodiments are described herein in conjunction with flexible endoscopes. However, those skilled in the art will understand that the guides may be used to facilitate the insertion of any flexible instrument through a body lumen and that the discussion of endoscopes is exemplary only and is not intended to limit the invention. For example, embodiments of the flexible instrument guide according to the invention may be used to improve colonoscopy, enteroscopy, exploration of the biliary tree, exploration of the GI tract and of extra-luminal space among others. These methods and devices are useful for screening and diagnostic purposes, as well as for the treatment of many conditions. 
     A guide according to the present invention is sufficiently longitudinally flexible to be inserted along a path defined by an endoscope while remaining sufficiently longitudinally plastically deformable to ease insertion through the endoscope without kinking, as those skilled in the art will understand. As the endoscope is inserted through the guide, the stress exerted outward from the endoscope to the body lumen is absorbed by the guide and is not transferred to surrounding tissue. The longitudinal rigidity of guides according to certain embodiments of the invention may be varied during the procedure so that the guide may be inserted and removed while in a more flexible state and rigidized when it has assumed a desired shape. The guides according to the invention are also preferably torsionally rigid to facilitate the placement of distal ends thereof at desired locations and/or in desired rotational orientations within the body. A working lumen extending through the guides is sized to allow passage therethrough of a flexible instrument to be used in accordance with an exemplary treatment procedure. Those skilled in the art will understand that, as used in this application, the term axial refers to a longitudinal axis of the conduit (i.e., a path along which one of the discrete elements of the conduit is situated) unless specifically defined otherwise. 
     As shown in  FIGS. 1-4 , a guide according to a first embodiment of the invention comprises a plurality of elements  100  connected together to form a conduit  150 . Each of the elements  100  is substantially tubular and comprises a slotted portion with a curved outer surface formed of a unibody cylindrical disk, as will be described in greater detail hereinafter. Those skilled in the art will understand that, although the elements  100  are described as being substantially tubular, this refers to a shape of the elements  100  when linked together to form a conduit and does not require that the elements be strictly cylindrical. Generally, the elements  100  will have a substantially smooth, atraumatic outer surface with a cross-section which may be circular, elliptical or any other shape which facilitates the passing therethrough of selected instruments or which facilitates travel through target body lumens. 
     Each of the cylindrical elements  100  comprises a female portion  102  and a male portion  104  joined to one another. An inner surface  110  of the female portion  102  is sized and shaped to slidingly receive an outer surface  108  of the male portion  104  to form a ball and socket joint. That is, a curve of the inner surface  110  of the female portion  102  and a curve of the outer surface  108  of the male portion  104  are shaped and sized to closely fit one another while allowing for rotation about lines substantially perpendicular to the longitudinal axis of the element  100 . For example, the surfaces  108  and  110  may form parts of spheres with a diameter of the inner surface  108  exceeding that of the outer surface  110  by a tolerance amount selected to maintain adjacent ones of the elements  100  bonded to one another while allowing the desired rotation and while providing a desired level of frictional engagement of the mated elements  100 . As would be understood by those skilled in the art, the level of frictional engagement between adjacent elements  100  may be adjusted through material choice, setting of the tolerance between the surfaces  108  and  110  and by applying, for example, a surface treatment to all or parts of the surfaces  108  and  110 . The desired level of frictional engagement is set to achieve a desired resistance to bending of the conduit  150  as an endoscope is inserted therethrough while maintaining a level of flexibility sufficient to enable the conduit  150  to be slid through a body lumen along an endoscope without unduly traumatizing tissue. Furthermore, those skilled in the art will understand that the frictional engagement of adjacent elements  100  may be adjusted to vary a degree of flexibility of the conduit  150  along its length in any desired pattern. For example, a distal end portion of the conduit  150  may be formed with enhanced flexibility to enable this distal end portion to follow the full range of motion of a steerable distal tip of an endoscope while a proximal portion of the conduit  150  shows an increased resistance to bending. 
     In the exemplary embodiment, one or both of the male portion  104  and the female portion  102  is preferably formed of a material which is plastically deformable to aid in assembling the conduit  150 . That is, such a material allows either or both of the male portion  104  and the female portion  102  to deflect as the male portion  104  is inserted through the female portion  102  and then return to its original shape as a point of maximum diameter of the surface  108  aligns with a point of maximum diameter of the surface  110 . Examples of suitable materials include plastics, such as, polypropylene, ABS, polystyrene, Nylon, etc. 
     In one exemplary embodiment, the ball and socket joint between adjacent elements  100  may allow approximately 30 degrees of rotation of the elements  100  relative to one another about a line substantially perpendicular to the axis. However, as described above, greater flexibility may be desired in parts of the conduit  150  to, for example, allow for steering by the steerable distal tip of an endoscope (not shown). As shown in  FIGS. 3 and 4 , when many elements  100  are stacked together, a flexible conduit or catheter  150  having a solid but flexible structure is formed with a longitudinal lumen  112  extending therethrough. Those skilled in the art will understand that the rigidity of the conduit  150  may be varied significantly by changing any or all of materials, surface treatments, tolerances, etc. to achieve a rigidity desired for any given application. The radius of curvature may also be varied by altering the tolerances and size of the components as would be understood by those skilled in the art. In one exemplary embodiment, the conduit  150  is designed to permit radii of curvature of 2.75 inches and greater. However, those skilled in the art will understand that conduits for various applications may dictate different minimum radii of curvature. Depending on how a scope is anchored within a lumen and the stiffness of the conduit, a conduit such as the conduit  150  advanced thereover may act to straighten the endoscope or conform to the shape of the endoscope. 
     It may be useful to select a desired angular orientation of a distal end of the conduit  150  by transmitting a torque along the length of the conduit  150  from the proximal end of the conduit  150 . According to the present invention, an optional linkage is provided between adjacent elements  100  that allows the conduit  150  to transmit a torque applied to its proximal end along its length to the distal end while retaining its longitudinal flexibility. That is, the conduit  150  is torsionally stiff while remaining longitudinally flexible. As shown in  FIGS. 1 and 3 , one or more protrusions  130  project radially outward from the outer surface  108  of the male portion  104 , each mating with a corresponding receptacle  132  on the female portion  102 . For example, a pair of protrusions  130  may be located one opposite points of the male portion  104 , separated from one another by 180°. In one exemplary embodiment, the protrusion  130  is substantially cylindrical although other shapes may be utilized. 
     The receptacles  132  are formed on the female portion  102  at locations corresponding to the protrusion(s)  130  so that, when coupled to one another, each protrusion  130  of an element  100  is received within a receptacle  132  of an adjacent cylindrical element  100 . For example, where the male portion  104  includes two projections  130  180° apart from one another, these projections  130  are preferably offset by 90° from the receptacles  132  of the same cylindrical element  100 . When this first cylindrical element  100  is mated to an adjacent second cylindrical element  100 , the projections  130  of the first element  100  are received in the receptacles  132  of the second element  100  with the second element  100  rotated 90° relative to the first element  100 . As a chain of elements  100  is linked together, the individual elements  100  are each offset by 90° relative to the proximal and distal adjacent elements  100 . Those skilled in the art will understand that the torsional stiffness of the conduit  150  is enhanced by selecting the dimensions of the projections  130  and the receptacles  132  so that little, if any, play is allowed in the circumferential direction while a desired degree of longitudinal flexibility is obtained by allowing axial movement of the projections  130  relative to the receptacles  132  within which they are received. For example, where the projections  130  are substantially cylindrical, the receptacles  132  may be formed as slots, a length of which is selected to be greater than a diameter of the projections  130  by a predetermined amount (e.g., wherein the projections  130  have a diameter of approximately 0.127 cm. the receptacles  132  may have a length of approximately 0.254 cm.), while the width thereof (i.e., dimension in the circumferential direction) is selected to fit the diameter of the projections  130  with just enough clearance to allow the projections  130  to slide axially in the receptacles  132 . This arrangement allows torque to be efficiently transmitted along the length of the conduit  150 . 
     Those of skill in the art will understand that the details of the features and of the slots formed on the cylindrical elements  100  may be varied. For example, the position of the slots and protrusions may be interchanged, so that protrusions extending inward from the inner surface  110  are received in slots formed in the outer surface  108 . Other shapes may be used to transmit a rotational force, such as ridges protruding from both elements, keyways, etc. According to the invention, any combination of features that prevents relative rotation of adjacent cylindrical elements  100  while permitting longitudinal flexibility may be used. 
     As shown in  FIGS. 5-16 , alternative embodiments of the present invention allow for dynamic adjustment of the stiffness of the conduit so that the conduit may be placed in a flexible state as it is slid along an endoscope and then stiffened to absorb forces applied as the endoscope is inserted further into the body lumen. According to the invention, application of a force directed radially outward within the lumen  112  forces the male portion  104  to exert a force on the female portion  102  within which it resides, thus increasing the friction between the outer surface  108  and the inner surface  110  of the adjacent elements  100 . The increased frictional resistance between the adjacent elements  100  increases the longitudinal stiffness of the conduit  150 . In cases where flexibility is desired, the radial force is reduced or withdrawn entirely to reduce the frictional resistance between adjacent elements  100 . 
     As shown in  FIGS. 5-11 , an element  200  of a conduit  300  is formed substantially similarly to the elements  100  of the conduit  150  except that the male portion  204  is slotted to form a plurality of tabs  220  separated from one another by slits extending substantially parallel to the longitudinal axis of the conduit  300  enhancing the ability of the male portion  204  to flex radially outward from the axis. 
     Each of the cylindrical elements  200  comprises a female portion  202  and a male portion  204  joined to one another to form a unitary element  200 . As with the elements  100 , an inner surface  210  of the female portion  202  is sized and shaped to slidingly receive an outer surface  208  of the male portion  204  to form a ball and socket joint. A curve of the inner surface  210  of the female portion  202  and a curve of the outer surface  208  of the male portion  204  are shaped and sized to closely fit one another while allowing for rotation about lines substantially perpendicular to the axis. However, if desired, the elements  200  may be more loosely joined to one another than the elements  100  to form a conduit  300  which, in an unstressed state, is more flexible than the conduit  150 . For example, the surfaces  208  and  210  may form parts of spheres (or any other suitable curves) with a diameter of the inner surface  208  exceeding that of the outer surface  210  by a tolerance amount selected to maintain adjacent ones of the elements  200  bonded to one another while allowing the desired rotation. 
     As described above, the male portion  204  is divided into a plurality of tabs  220  separated from one another by slits  222 . The slits  222  provide a clearance so that the tabs  220  can deflect radially outward from the axis of the lumen  212  extending through each cylindrical element  200 . The material forming the male portion  204  is preferably elastic so that, after being deflected by an external force, the tabs  220  return to their original shape and location. For example, as the male portion  204  of one element  200  is inserted into the female portion  202  of another element  200 , the tabs  220  deflect inward and then return to their original shape as a point of maximum diameter of the surface  208  aligns with a point of maximum diameter of the surface  210 . The curvature of the inner and outer surfaces  208 ,  210  serves to couple adjacent elements  200  together. 
     Those skilled in the art will understand that the number of slits  222  and of tabs  220  may be varied to achieve a desired degree of flexibility of the resulting conduit  300 . The shape of the tabs  220  may also be varied with the tabs  220  of any element  200  being identical to one another or including two or more different shapes. For example, an exemplary embodiment comprises two slits defining two identical tabs. In another example, eight substantially identical tabs  220  are placed symmetrically around the longitudinal axis of the conduit. In yet another example, the tabs  220  are different from one another and may also be placed at variable intervals around the circumference of the element  200 . 
     In one exemplary embodiment, the ball and socket joint between adjacent elements  200  allows about 30 degrees rotation of the elements relative to one another about a line substantially perpendicular to the axis. As shown in  FIGS. 7 and 8 , when many elements  200  are stacked together, a flexible conduit or catheter  300  having a solid but flexible structure is formed with a longitudinal lumen  212  extending substantially the length of the conduit  300 . In addition, as described above, the flexibility of the conduit  300  may be varied along its length by any of the manners mentioned above in regard to the conduit  150  to achieve the same goals. 
     In addition, the conduit  300  may be made torsionally stiff through the inclusion of a linkage similar to that described above in regard to the conduit  150 . As shown in  FIGS. 5 and 7 , one or more protrusions  230  project radially outward from the outer surface  208  of the male portion  204 . In one exemplary embodiment, the protrusion  230  is substantially cylindrical although other shapes may be utilized. For example, a pair of protrusions  230  may be located one opposite points of the male portion  204 , separated from one another by 180°. 
     A receptacle  232  is formed on the female portion  202  at a location corresponding to each protrusion  230  so that, when coupled to one another, each protrusion  230  of a cylindrical element.  200  is received within a receptacle  232  of an adjacent cylindrical element  200 . For example, where the male portion  204  includes two projections  230  180° apart from one another, these projections  230  are preferably offset by 90° from the receptacles  232  of the same cylindrical element  200 . When this first cylindrical element  200  is mated to an adjacent second cylindrical element  200 , the projections  230  of the first element  200  are received in the receptacles  232  of the second element  200  with the second element  200  rotated 90° relative to the first element  200 . As a chain of elements  200  is linked together, the individual elements  200  are each offset by 90° relative to the proximal and distal adjacent elements  200 . Those skilled in the art will understand that the torsional stiffness of the conduit  300  is enhanced by selecting the dimensions of the projections  230  and the receptacles  232  so that little, if any, play is allowed in the circumferential direction while a desired degree of longitudinal flexibility is obtained by allowing axial movement of the projections  230  relative to the receptacles  232  within which they are received. For example, as described above where the projections  230  are substantially cylindrical, the receptacles  232  may be formed as slots, a length of which is selected to be greater than a diameter of the projections  230  by a predetermined amount, while the width thereof (i.e., dimension in the circumferential direction) is selected to fit the diameter of the projections  230  with just enough clearance to allow the projections  230  to slide axially in the receptacles  232 . This arrangement allows torque to be efficiently transmitted along the length of the conduit  300 . 
     Those of skill in the art will understand that the details of the features and of the slots formed on the cylindrical elements  200  may be varied. For example, the position of the slots and protrusions may be interchanged, so that protrusions extending inward from the inner surface  210  are received in slots formed in the outer surface  208 . Other shapes may be used to transmit a rotational force, such as ridges protruding from both elements, keyways, etc. According to the invention, any combination of features that prevents relative rotation of adjacent cylindrical elements  200  while permitting longitudinal flexibility may be used. 
     The embodiments according to the present invention provide for the conduit to have a stiffness which can be dynamically adjusted by a user. Application of a force directed radially outward against the flexible tabs  220  causes the male portion  204  to press more firmly against the female portion  202  of an adjacent element  200  increasing the friction between the outer surface  208  and the inner surface  210 . This impedes relative movement between the adjacent elements  200 , increasing the longitudinal stiffness of the conduit  300 .  FIGS. 9-12  show a schematic representation of exemplary forces F 1  acting on the tabs  220  in the radial direction to stiffen the conduit  300 . 
     Various methods of applying the adjustable radial force F 1  to the flexible tabs  220  may be used according to the invention, as will be described below. In one exemplary embodiment, the radial force F 1  is provided by an inflatable element (not shown) located radially inward of the tabs  220 . The inflatable element (e.g., a balloon) is coupled to a supply of inflation fluid operable by the user to expand and deflate the inflatable element (not shown) so that a pressure in the inflatable element adjusts a magnitude of the force F 1  applied to the radially inner surfaces of the cylindrical element  200  and, specifically, the flexible tabs  220 . As the exemplary female portion  202  is substantially rigid, it is not significantly affected while the flexible tabs  220  of the male portion  204  are deflected radially outward to press against the inner surface  210  of the adjacent element  200  to vary the force F 1  exerted on the flexible tabs  220  and the friction between the adjacent elements  200  to a desired level. 
     In one exemplary embodiment shown in  FIGS. 13 and 14 , a conduit  400  is formed by joining together a plurality of elements  402  defining a lumen  412  that may be used, for example, to provide a passage for a scope or for other medical instruments. An optional coil spring  414  is placed in the lumen  412  to stabilize it, especially when in the flexible state shown in  FIG. 13  and an outer cover  416  is placed over outer surfaces of the cylindrical elements  402 , to protect the internal components of the conduit  400 . For example, the outer cover  416  may comprise a braid and/or a PVC cover. 
     Each of the exemplary cylindrical elements  402  is formed of a male portion  404  and a contiguous female portion  406  similar to the male and female portions  204 ,  202 , respectively, described above. As described above, the male portion  404  of one element  402  fits in the female portion  406  of an adjoining element  402 . Both male and female portions,  404 ,  406  have opposing curved surfaces that slide one over the other, to form a ball and socket joint as described above in regard to the elements  200 . The male portions  404  comprise tabs (not shown) that can be flexed radially outward to press against the female portions  406  and adjust a longitudinal stiffness of the conduit  400 . 
     According to the invention, a hydraulic balloon sleeve  410  is disposed radially inward of inner surfaces of the cylindrical element  402 , along the length of the variable conduit  400 .  FIG. 13  shows the conduit  400  in a flexible state in which the hydraulic balloon sleeve  410  is deflated and applies no outward force to the male elements  404 . When an inflation fluid (e.g., water) is introduced under pressure to the hydraulic balloon sleeve  410  as shown in  FIG. 18 , outer surfaces of the balloon sleeve  410  move radially outward, flexing the male elements  404  radially outward against the female elements  406  to increase friction between adjacent elements  402  and enhance the rigidity of the conduit  400 . 
     As would be understood by those skilled in the art, alternative embodiments of the invention may be devised, where the relative position of the male elements, female elements and inflatable elements are changed. For example, the inflatable element may be radially outside the cylindrical elements, such that inflating it produces a radially inward force which presses against the cylindrical elements. In this embodiment, the female elements may flex radially inward to engage substantially rigid male elements to increase a stiffness of the conduit. In other embodiments, a force may be applied to frictional elements that do not face in a radial direction, such that the deflection of the friction elements and/or the force acting on them is not in the radial direction. 
     As shown in  FIGS. 15 and 16 , a conduit  450  according to another embodiment of the invention comprises multiple substantially cylindrical elements  452  stacked together in a manner similar to that of the above-described embodiments. As described above, each cylindrical element  452  has a male portion  454  that fit in and interlocks with a female portion  456  of an adjacent element  452  to allow longitudinal flexing of the adjacent elements  452  relative to one another about an axis perpendicular to a longitudinal axis of the conduit  450  while preventing relative rotation between adjacent elements  452  about the longitudinal axis. The male and female portions  454 ,  456  slide relative to one another on opposite curved surfaces forming a ball and socket joint as described above. 
     A hydraulic or pneumatic inflatable element  460  disposed within the lumen  462  of the conduit  450  may be, for example, a balloon catheter or similar device. As shown in  FIG. 15 , when inflated, an inflatable element  460  applies a substantially radial force F 2  outward against the male portion  454  to frictionally engage the female portion  456  of the adjacent element  452  to rigidize the portion of the conduit  450 .  FIG. 16  shows a similar arrangement with a more extensive conduit  450  including a more elongated element  460  inflated with, for example, water, air or another fluid to apply radially outward force to the male portions  454  of a plurality of elements  452  to rigidize this portion of the conduit  450  in the same manner described above in regard to  FIG. 15 . Those skilled in the art will understand that the length of the rigidizable portions of the conduit  450  may be varied and that a single element  460  may rigidize substantial portion of the length of the conduit  450 , only a selected smaller portion or that multiple elements  460  may be employed to dynamically alter the rigidity of various sections of the conduit  450  independently of one another. In the mean time, the conduit  450  may optionally include one or more portions which are always relatively flexible (i.e., which are not acted on by inflation of an element  460 ) in any desired pattern. 
     Those skilled in the art will understand that any other suitable arrangement for imparting a radial force to deflect an element of such a ball and socket joint to selectively enhance the frictional engagement of adjacent elements may be employed without departing from the scope of the inventions. For example, in place of an inflatable element, a spring like structure or mesh may be mechanically expanded and constricted. In addition, as described above, this force may be directed radially inward to deflect a radially outer element against a radially inner element or vice versa. 
     By varying a pressure at which the inflation fluid is supplied the stiffness of the conduit may be varied to a desired level up to and including levels required to resist forces to which the conduit is likely to be exposed in the environment within which it is to be deployed. That is, conduits according to the invention may be made stiff enough to retain their shape against anatomical forces to which they will likely be exposed as well as to resist bending forces applied thereto by flexible instruments such as endoscopes inserted therethrough. As would be understood by those skilled in the art, any conventional pump, compressor, storage device for pressurized fluid or other device may be used to provide the fluid used to inflate the expandable inflatable elements according to the invention. 
     The present invention has been described with reference to specific exemplary embodiments. Those skilled in the art will understand that changes may be made in details, particularly in matters of shape, size, material and arrangement of parts. Accordingly, various modifications and changes may be made to the embodiments. The specifications and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.