Abstract:
A tubular member useful as an inner liner for the working channel of a flexible endoscope has a distal portion which is specially treated to make it highly flexible and resistant to kinking or collapsing when it bends with the flexible section of the endoscope. The tubular member is also useful as a catheter device or as a component of a catheter device or catheter system. A multiplicity of external ridges on the distal portion of the tubular member reinforce the tubing wall and prevent kinking or buckling of the wall or collapsing of the inner lumen. The external ridges may be formed by convolutions of the tubing wall or by external threads which are formed on the exterior of the tubing wall within the flexible distal portion. An outer helical reinforcing coil may be added between the external ridges to further reinforce the flexible distal portion of the tubular member from kinking or collapsing. The flexible distal portion of the tubular member may be coated with a layer of a flexible polymer to fill in the spaces between the external ridges and to cover the helical reinforcing coil. Manufacturing methods for the tubular member are also disclosed.

Description:
RELATIONSHIP TO OTHER APPLICATIONS 
     This application is a continuation of U.S. Pat. No. 08/746,249, filed Nov. 7, 1996, now U.S. Pat. No. 5,938,587, which claims the benefit of U.S. Provisional Patent Application No. 60/016,216, filed Apr. 25, 1996. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to endoscopes for diagnostic and therapeutic medical applications, as well as borescopes for industrial applications. More particularly, it relates to a disposable flexible inner liner for the working channel of a flexible endoscope or borescope. The present invention also relates to catheters for insertion into a body lumen or cavity with or without the guidance of an endoscope. 
     BACKGROUND OF THE INVENTION 
     Endoscopes are frequently used in a medical setting for diagnostic and therapeutic procedures. Borescopes, their industrial counterpart, are frequently used in industrial settings for internal inspection of machines and manufactured parts. Endoscopes and borescopes are sometimes manufactured with one or more working channels through the scope for passing instrumentation through for performing diagnostic or therapeutic procedures within the field of view of the scope. The working channel in an endoscope is also sometimes referred to as the biopsy channel of the scope. It is common to use an inner liner within the working channel of endoscopes and borescopes. Sometimes, the inner liner is a single-use, disposable item. The inner liner provides a low friction surface to facilitate passage of instruments and helps to avoid damage to the interior of the scope by the instruments as they pass through the working channel. The inner liner also helps to avoid contamination of the interior of the scope by the instruments as they pass through the working channel. This is especially important in medical applications where the small diameter working channels may be difficult to clean and sterilize between uses. A sterile, disposable inner liner can be used to keep the working channel of the endoscope clean. For rigid endoscopes and borescopes, which typically use rod optics for image transfer through the scope, the working channel can be lined with a simple thin-walled tube without concern for the flexibility of the liner. However, for flexible endoscopes and borescopes, which use flexible fiberoptics for image transfer through the scope, the inner liner for the working channel must be sufficiently flexible to bend with the scope without kinking or collapsing, which would compromise the inner lumen of the working channel. Flexible endoscopes and borescopes may be made flexible along their entire length or they may be made with a flexible distal section and a relatively rigid proximal section. It is important that the flexible portion of the working channel liner be at least as long as the flexible section of the scope for which it is intended. The present invention provides an improved flexible inner liner for the working channel of flexible endoscopes and borescopes. For the sake of brevity, endoscopes and borescopes will both be referred to as endoscopes in the following detailed description of the invention. However, it should be kept in mind that, except where specifically stated to the contrary, the description and the accompanying comments apply equally well to medical endoscopes and to industrial borescopes. 
     Another technical area relevant to the present invention involves catheters. The term “catheter” embraces a wide variety of elongated, generally tubular, devices for insertion into a body lumen or cavity for diagnostic or therapeutic purposes. These include inter alia cardiovascular catheters, urology catheters, visceral catheters and catheter introducers. Catheters can be introduced into the body through the working channel of an endoscope or they can be introduced independently under endoscopic, fluoroscopic or ultrasonic guidance. The construction of the disposable flexible inner liner of the present invention will also be beneficial for the construction of many varieties of catheters. 
     SUMMARY OF THE INVENTION 
     In accordance with the foregoing discussion, the present invention takes the form of an elongated tubular inner liner for the working channel of a flexible endoscope. At least a portion of the length of the elongated tubular inner liner is highly flexible so that it will freely bend with the flexible section of the endoscope. The flexible portion of the inner liner is specially treated to make it resistant to kinking or collapse when it bends with the flexible section of the endoscope. Various means are disclosed for treating the flexible portion to make it flexible and kink resistant. A first embodiment of the flexible endoscope liner has a convoluted flexible distal portion. In a second embodiment, the convoluted flexible distal portion has an additional outer layer of a flexible polymer. A third embodiment of the flexible endoscope liner has a helically convoluted flexible distal portion with an outer helical reinforcing coil. In a fourth embodiment, the helically convoluted flexible distal portion has a helical reinforcing coil and an outer layer of a flexible polymer. A fifth embodiment of the flexible endoscope liner has a helically threaded flexible distal portion. In a sixth embodiment, the helically threaded flexible distal portion has an outer layer of a flexible polymer. In a seventh embodiment, the helically threaded flexible distal portion has an outer helical reinforcing coil. In an eighth embodiment, the helically threaded flexible distal portion has a helical reinforcing coil and an outer layer of a flexible polymer. Manufacturing methods for each of the embodiments are also disclosed. 
     The various constructions and manufacturing methods described for the disposable flexible inner liner of the present invention will also be advantageous for constructing a flexible tubular member for use in a variety of catheters. The flexible tubular member may be used alone, without significant modification, as a diagnostic or therapeutic catheter, a guiding catheter or a catheter introducer. Alternatively, the flexible tubular member may also be used as one component of a more complex catheter device or a catheter system. A flexible tubular member built according to the disposable flexible inner liner construction will be especially useful as a catheter component where the advantages of flexibility, kink resistance and an uncompromised inner lumen are important to the catheter performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A shows a first embodiment of the flexible endoscope liner having a convoluted flexible distal portion. FIG. 1B is an enlarged detail view of the convoluted flexible distal portion of the flexible endoscope liner of FIG.  1 A. FIG. 1C is a cross section of the convoluted flexible distal portion of the flexible endoscope liner of FIG.  1 A. 
     FIG. 2A shows a second embodiment of the flexible endoscope liner with a convoluted flexible distal portion having an outer layer of a flexible polymer. FIG. 2B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG.  2 A. 
     FIGS. 3A,  3 B,  3 C and  3 D are a series of drawings showing the fabrication steps for the flexible endoscope liners of FIGS. 1A and 2A. 
     FIG. 4A shows the flexible endoscope liner of FIGS. 1A or  2 A bent into a curved configuration as it would be in use. FIG. 4B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG. 4A in the curved configuration. 
     FIG. 5A shows a third embodiment of the flexible endoscope liner with a helically convoluted flexible distal portion having an outer helical reinforcing coil. FIG. 5B is an enlarged detail view of the flexible distal portion of the flexible endoscope liner of FIG.  5 A. FIG. 5C is a cross section of the flexible distal portion of the flexible endoscope liner of FIG.  5 A. 
     FIG. 6A shows a fourth embodiment of the flexible endoscope liner with a helically convoluted flexible distal portion having a helical reinforcing coil and an outer layer of a flexible polymer. FIG. 6B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG.  6 A. 
     FIGS. 7A,  7 B,  7 C,  7 D and  7 E are a series of drawings showing the fabrication steps for the flexible endoscope liners of FIGS. 5A and 6A. 
     FIG. 8A shows the flexible endoscope liner of FIGS. 5A or  6 A bent to a curved configuration as it would be in use. FIG. 8B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG. 8A in the curved configuration. 
     FIG. 9A shows a fifth embodiment of the flexible endoscope liner having a helically threaded flexible distal portion. FIG. 9B is an enlarged detail view of the flexible distal portion of the flexible endoscope liner of FIG.  9 A. FIG. 9C is a cross section of the helically threaded flexible distal portion of the flexible endoscope liner of FIG.  9 A. 
     FIG. 10A shows a sixth embodiment of the flexible endoscope liner with a helically threaded flexible distal portion having an outer layer of a flexible polymer. FIG. 10B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG.  10 A. 
     FIG. 11A shows a seventh embodiment of the flexible endoscope liner with a helically threaded flexible distal portion having an outer helical reinforcing coil. FIG. 11B is an enlarged detail view of the flexible distal portion of the flexible endoscope liner of FIG.  11 A. FIG. 11C is a cross section of the flexible distal portion of the flexible endoscope liner of FIG.  11 A. 
     FIG. 12A shows an eighth embodiment of the flexible endoscope liner with a helically threaded flexible distal portion having a helical reinforcing coil and an outer layer of a flexible polymer. FIG. 12B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG.  12 A. 
     FIGS. 13A,  13 B,  13 C,  13 D and  13 E are a series of drawings showing the fabrication steps for the flexible endoscope liners of FIGS. 9A,  10 A,  11 A and  12 A. 
     FIG. 14A shows the flexible endoscope liner of FIGS. 9A,  10 A,  11 A or  12 A bent to a curved configuration as it would be in use. FIG. 14B is a cross section of the flexible distal portion of the flexible endoscope liner of FIG. 14A in the curved configuration. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1A shows a first embodiment of the flexible endoscope liner  100  of the present invention. In this exemplary embodiment, the flexible endoscope liner  100  is an elongated tubular member which includes a convoluted flexible distal portion  102  and a relatively inflexible proximal portion  104 . The flexible endoscope liner  100  has a tubular construction with an inner lumen  110  which extends from the proximal end  116  to the distal end  118  of the flexible endoscope liner  100  through the relatively inflexible proximal portion  104  and the convoluted flexible distal portion  102 . The convoluted flexible distal portion  102  of the flexible endoscope liner  100  is specially treated to increase its flexibility and to make it resistant to kinking or collapse when it bends with the flexible section of the endoscope. The overall length of the flexible endoscope liner  100  is made to match the length of the working channel of the endoscope for which it is intended. The convoluted flexible distal portion  102  should be at least as long as the flexible section of the endoscope, with the relatively inflexible proximal portion  104  making up the remainder of the length. Typically, the overall length of the flexible endoscope liner  100  is between 30 and 250 cm, and the length of the convoluted flexible distal portion  102  is typically between 4 and 25 cm, but can extend the full length of the device. It should be noted that these length dimensions are highly variable, depending on the actual design of the endoscope. For use with flexible endoscopes which are flexible along their entire length, the convoluted flexible distal portion  102  may extend the full length of the flexible endoscope liner  100  and the relatively inflexible proximal portion  104  may be totally absent. 
     FIG. 1B is an enlarged detail view of the flexible endoscope liner  100  of FIG. 1A showing the transition between the relatively inflexible proximal portion  104  and the convoluted flexible distal portion  102 . FIG. 1C shows a longitudinal cross section of the transition between the relatively inflexible proximal portion  104  and the convoluted flexible distal portion  102  of the flexible endoscope liner  100 . The inner lumen  110  is continuous through the relatively inflexible proximal portion  104  and the convoluted flexible distal portion  102  of the flexible endoscope liner  100 . In the relatively inflexible proximal portion  104  of the flexible endoscope liner  100 , the inner lumen  110  is surrounded by a tubular proximal wall  106 . In the convoluted flexible distal portion  102  of the flexible endoscope liner  100 , the inner lumen  110  is surrounded by a tubular distal wall  108  which is folded into a convoluted configuration to increase its flexibility and to make it resistant to kinking or collapse so that the internal diameter of the inner lumen  110  is not compromised when it bends with the flexible section of the endoscope. 
     In one preferred embodiment of the invention, the internal diameter of the inner lumen  110  and the external diameter of the flexible endoscope liner  100  remain relatively constant throughout the length of the relatively inflexible proximal portion  104  and the convoluted flexible distal portion  102  of the flexible endoscope liner  100 . To accomplish this, the relatively inflexible proximal portion  104  is made with a relatively thick proximal wall  106  and a relatively thinner distal wall  108  so that the distal wall  108  can follow the convolutions and maintain the same external diameter at the peaks of the convolutions  112  and the same internal diameter at the troughs of the convolutions  114  as the thicker proximal wall  106 . Typically, the relatively thinner distal wall  108  will have approximately 30-70 percent of the wall thickness of the thicker proximal wall  106 . Typical embodiments of the flexible endoscope liner  100  will have a proximal portion  104  and a flexible distal portion  102  with an internal diameter of approximately 1.8-4.0 mm and an external diameter of approximately 2.0-4.5 mm. However, the internal diameter and external diameter can vary widely depending on the actual design of the endoscope for which the flexible endoscope liner  100  is intended. In this illustrative embodiment, the proximal wall  106  and the distal wall  108  are made from a continuous polymeric material. In other possible embodiments, the proximal wall  106  and the distal wall  108  may be made from dissimilar materials. Many different polymeric materials are suitable for construction of the proximal wall  106  and the distal wall  108  of the flexible endoscope liner  100 , including highly lubricious polymers, such as fluoropolymers (e.g. PTFE, EPTFE, PFA) and polyolefins, like polyethylene (e.g. LDPE, HDPE), polypropylene and polyolefin copolymers; high strength polymers, such as polyamides (e.g. nylon  11 , nylon  12 , polyamide copolymers); thermoplastic elastomers (e.g. polyurethane); and thermoset polymers. Alternatively, the proximal wall  106  and/or the distal wall  108  of the flexible endoscope liner  100  may be made from a composite material, for example a thermoplastic or thermoset polymer matrix with wire or fiber reinforcement which may be braided, spiral wound, counterwound or randomly oriented within the matrix material. Additionally, the proximal wall  106  and/or the distal wall  108  may be made from multiple layers of tubing. For example, the flexible endoscope liner  100  may be made with an inner tubular layer of a highly lubricious polymer and an outer tubular layer of a polymer chosen for another desirable property, such as high strength or flexibility. Advantageously, lubricious coatings may also be added to the interior and/or exterior surfaces of the flexible endoscope liner  100 . 
     FIG. 2A shows a second embodiment of the flexible endoscope liner  200  which is a modification of the flexible endoscope liner  100  shown in FIG.  1 A. Similar to the previously described embodiment, the flexible endoscope liner  200  is an elongated tubular member with an inner lumen  210  which extends from the proximal end  216  to the distal end  218 . The flexible endoscope liner  200  includes a relatively inflexible proximal portion  104  having a relatively thick proximal wall  206  and a convoluted flexible distal portion  202  having a thinner distal wall  208  which is folded into a convoluted configuration. FIG. 2B shows a longitudinal cross section of the transition between the relatively inflexible proximal portion  204  and the convoluted flexible distal portion  202  of the flexible endoscope liner  200 . The convoluted flexible distal portion  202  of the flexible endoscope liner  200  has an additional outer layer  220  of a flexible polymer. The flexible outer layer  220  fills in between the peaks of the convolutions  212  on the convoluted flexible distal portion  202  to create a smooth exterior surface. Preferred materials for the flexible outer layer  220  include flexible thermoplastic elastomers, such as ethylene vinyl acetate (EVA) or polyamide copolymers (e.g. PEBAX from ELF ATOCHEM) and thermoplastic polyurethanes and flexible thermoset polymers, such as silicone, latex or thermoset polyurethanes. The hardness of the flexible outer layer  220  material can vary from approximately 50 Shore A durometer to approximately 35 Shore D durometer. 
     FIGS. 3A,  3 B,  3 C and  3 D are a series of drawings illustrating one preferred method for fabricating the flexible endoscope liners of FIGS. 1A and 2A. In the first step of the fabrication method shown in FIG. 3A, an extruded polymer tube  300  is cut to an appropriate length and a straightened wire mandrel  304  is inserted into the inner lumen  302  of the tube  300 . The wire mandrel  304  is preferably made of stainless steel or another nontoxic, high strength material. The external diameter of the wire mandrel  304  should closely match the internal diameter of the inner lumen  302  with only about 1-3 thousandths of an inch clearance. A nontoxic lubricant or a lubricious coating, such as PTFE, may be used on the wire mandrel  304  to allow easy insertion and removal. In the second step, shown in FIG. 3B, one end of the tube  300  is drawn to reduce its external diameter, thereby creating a drawn distal portion  306  and an undrawn proximal portion  308 . The drawing step may be performed by various means appropriate for the material chosen for the extruded polymer tube  300 . The drawn distal portion  306  may be created by stretching one end of the extruded polymer tube  300  by hand or by machine, either at room temperature or at an elevated temperature. Alternatively, the drawn distal portion  306  may be created by pulling one end of the extruded polymer tube  300  through a tapered die by hand or by machine, either at room temperature or at an elevated temperature. In the third step, shown in FIG. 3C, the drawn distal portion  306  is axially compressed, as shown by arrows  310 , to create the convoluted flexible distal portion  312 . The axial compression causes the wall of the drawn distal portion  306  to fold into annular convolutions. The wire mandrel  304  maintains the inner lumen  302  in the convoluted flexible distal portion  312  as the drawn distal portion  306  is compressed. If precise control over the external diameter of the convoluted flexible distal portion  312  is desired, a tubular mold (not shown) may be placed over the exterior of the drawn distal portion  306  as it is axially compressed to form the convoluted flexible distal portion  312 . The axial compression step may be performed at room temperature or at an elevated temperature. For some polymeric materials, an additional stress relieving or annealing step at an elevated temperature may be required between the drawing step and the axial compression step. FIG. 3D shows an optional fourth step of applying a flexible outer coating  314  to the convoluted flexible distal portion  312 . The flexible outer coating  314  may be applied by dissolving a flexible polymer in an appropriate solvent and dipping, spraying or casting one or more layers of the polymer onto the convoluted flexible distal portion  312 . Alternatively, the resin and hardener of a flexible thermoset polymer can be mixed and applied to the convoluted flexible distal portion  312  as a liquid by dipping, spraying or casting. The flexible outer coating  314  may also be applied by insert molding a thermoplastic elastomer over the convoluted flexible distal portion  312 . The wire mandrel  304  is then withdrawn from the tube  300  and the proximal and distal ends are cut to the desired length to complete the flexible endoscope liner. 
     FIG. 4A shows the flexible endoscope liner  400  of the present invention bent into a curved configuration as it would be in actual clinical use. The flexible endoscope liner  400  shown in FIG. 4A is representative of the flexible endoscope liner in either FIG. 1A ( 100 ) or FIG. 2A ( 200 ) in use. In use, the flexible endoscope liner  400  is inserted into the working channel of a flexible endoscope (not shown) before the endoscope is inserted into the patient&#39;s body through an incision or through a natural body orifice. Once in place, the flexible distal section of the endoscope may be flexed into a curved configuration to view various internal body structures. When the endoscope flexes, the flexible endoscope liner  400  must flex with it. In some applications, the flexible distal section of the endoscope and the flexible endoscope liner  400  may be repeatedly flexed into bends of up to a 180 degrees, with a radius of curvature of 0.5-1.5 inches, as represented in FIG.  4 A. FIG. 4B shows a longitudinal cross section of the transition between the relatively inflexible proximal portion  404  and the convoluted flexible distal portion  402  of the flexible endoscope liner  400  of FIG. 4A when it is in the curved configuration. As can be seen in the cross section of FIG. 4B, when the convoluted flexible distal portion  402  of the flexible endoscope liner  400  bends, the convolutions on the inside of the curve  412  compress together and the convolutions on the outside of the curve  414  expand apart. This allows the convoluted flexible distal portion  402  to flex freely with the flexible distal section of the endoscope without kinking or collapsing which would compromise the internal diameter of the inner lumen  410 . If the flexible endoscope liner  400  is made with a flexible outer coating  420  over the convoluted flexible distal portion  402 , the flexible outer coating  420  (shown in phantom lines) elastically deforms with the convoluted flexible distal portion  402 , compressing with the convolutions on the inside of the curve  412  and expanding with the convolutions on the outside of the curve  414 . 
     FIG. 5A shows a third embodiment of the flexible endoscope liner  500  with a helically convoluted flexible distal portion  502  having an outer helical reinforcing coil  522 . As in the previously described embodiments, the flexible endoscope liner  500  is an elongated tubular member with an inner lumen  510  which extends from the proximal end  516 , through a relatively inflexible proximal portion  504  and a flexible distal portion  502 , to the distal end  518 . FIG. 5B is an enlarged detail view of the flexible endoscope liner  500  of FIG. 5A showing the transition between the relatively inflexible proximal portion  504  and the flexible distal portion  502 . FIG. 5C shows a longitudinal cross section of the transition between the relatively inflexible proximal portion  504  and the flexible distal portion  502  of the flexible endoscope liner  500 . In contrast to the annular convolutions of the previously described embodiments, the present embodiment has a helically convoluted flexible distal portion  502  which is reinforced with an outer helical reinforcing coil  522 . The outer helical reinforcing coil  522  strengthens the thin distal wall  508  and increases the kink resistance of the helically convoluted flexible distal portion  502  without compromising its flexibility. 
     Preferred materials for the proximal wall  506  and the distal wall  508  of the flexible endoscope liner  500  include fluoropolymers, polyethylenes, polypropylenes, polyolefin copolymers, polyamides, polyamide copolymers, thermoplastic elastomers, polyurethanes, thermoset polymers and composite materials. The outer helical reinforcing coil  522  is preferably made of a resilient, biocompatible, high strength filamentous material, such as metal wire, glass fibers, carbon fibers, high strength polymer fibers or filaments, or a composite material. The cross section of the outer helical reinforcing coil  522  filament may be circular, as shown, rectangular or any other convenient cross section. The filament diameter of the outer helical reinforcing coil  522  is typically from about 0.004 inches to 0.015 inches. The outer diameter of the helical reinforcing coil  522  is typically from about 1.8 mm to 5 mm. In one particularly preferred embodiment, the outer helical reinforcing coil  522  is made of series  300  stainless steel wire (e.g.  302  or  304  stainless steel). The stainless steel wire of the outer helical reinforcing coil  522  is preferably used in a work hardened, unannealed condition (condition B) or slightly stress relieved to a spring temper, because the high strength and excellent resilience of the wire in this condition improves the flexibility characteristics and kink resistance of the helically convoluted flexible distal portion  502 . Annealed stainless steel wire or softer alloys are also usable for the outer helical reinforcing coil  522 , but it has been found that these softer, more malleable wires do not protect the helically convoluted flexible distal portion  502  as well from kinking or collapse. 
     FIG. 6A shows a fourth embodiment of the flexible endoscope liner  600  which is a modification of the flexible endoscope liner  500  shown in FIG.  5 A. Similar to the embodiment of FIG. 5A, the flexible endoscope liner  600  is an elongated tubular member with an inner lumen  610  which extends from the proximal end  616 , through a relatively inflexible proximal portion  604  and a helically convoluted flexible distal portion  602 , to the distal end  618 . FIG. 6B is a longitudinal cross section of the flexible endoscope liner  600  showing the transition between the relatively inflexible proximal portion  604  with its relatively thick proximal wall  606  and the helically convoluted flexible distal portion  602  with its thinner distal wall  608  which is reinforced with a outer helical reinforcing coil  622 . The helically convoluted flexible distal portion  602  of the flexible endoscope liner  600  has an additional outer layer  620  of a flexible polymer. The flexible outer layer  620  fills in between the peaks of the convolutions  612  and the coils of the outer helical reinforcing coil  622  to create a smooth exterior surface on the helically convoluted flexible distal portion  602 . Preferred materials for the flexible outer layer  620  include flexible thermoplastic elastomers, such as ethylene vinyl acetate (EVA), polyamide copolymers (e.g. PEBAX from ELF ATOCHEM) and thermoplastic polyurethanes, and flexible thermoset polymers, such as silicone, latex or thermoset polyurethanes. The hardness of the flexible outer layer  620  material can vary from approximately 50 Shore A durometer to approximately 35 Shore D durometer. 
     FIGS. 7A,  7 B,  7 C,  7 D and  7 E are a series of drawings illustrating one preferred method for fabricating the flexible endoscope liners of FIGS. 5A and 6A. In the first step of the fabrication method shown in FIG. 7A, an extruded polymer tube  700  is cut to an appropriate length and a straightened wire mandrel  704  is inserted into the inner lumen  702  of the tube  700 . The wire mandrel  704  is preferably made of stainless steel or another nontoxic, high strength material. The external diameter of the wire mandrel  704  should closely match the internal diameter of the inner lumen  702  with only about 1-3 thousandths of an inch clearance. A nontoxic lubricant or a lubricious coating, such as PTFE, may be used on the wire mandrel  704  to allow easy insertion and removal. In the second step, shown in FIG. 7B, one end of the tube  700  is drawn to reduce its external diameter, thereby creating a drawn distal portion  706  and an undrawn proximal portion  708 . The drawing step may be performed by various means appropriate for the material chosen for the extruded polymer tube  700 . The drawn distal portion  706  may be created by stretching one end of the extruded polymer tube  700  by hand or by machine, either at room temperature or at an elevated temperature. Alternatively, the drawn distal portion  706  may be created by pulling one end of the extruded polymer tube  700  through a tapered die by hand or by machine, either at room temperature or at an elevated temperature. In the third step, shown in FIG. 7C, a previously made helical reinforcing coil  714  with separated coils is placed over the drawn distal portion  706 . In the fourth step, shown in FIG. 7D, the helical reinforcing coil  714  and the drawn distal portion  706  are axially compressed, as shown by arrows  710 . The wall of the drawn distal portion  706  folds into a helically convoluted configuration between the coils of the helical reinforcing coil  714  to create the helically convoluted flexible distal portion  712 . The wire mandrel  704  maintains the inner lumen  702  in the helically convoluted flexible distal portion  712  as the drawn distal portion  706  is compressed. If precise control over the external diameter of the convoluted flexible distal portion  712  is desired, a tubular mold (not shown) may be placed over the exterior of the drawn distal portion  706  as it is axially compressed to form the helically convoluted flexible distal portion  712 . The axial compression step may be performed at room temperature or at an elevated temperature. For some polymeric materials, an additional stress relieving or annealing step at an elevated temperature may be required between the drawing step and the axial compression step. FIG. 7E shows an optional fifth step of applying a flexible outer coating  716  to the convoluted flexible distal portion  712 . The flexible outer coating  716  may be applied by dissolving a flexible polymer in an appropriate solvent and dipping, spraying or casting one or more layers of the polymer onto the helically convoluted flexible distal portion  712 . Alternatively, the resin and hardener of a flexible thermoset polymer can be mixed and applied to the helically convoluted flexible distal portion  712  as a liquid by dipping, spraying or casting. The flexible outer coating  716  may also be applied by insert molding a thermoplastic elastomer over the helically convoluted flexible distal portion  712 . The wire mandrel  704  is then withdrawn from the tube  700  and the proximal and distal ends are cut to the desired length to complete the flexible endoscope liner. 
     FIG. 8A shows the flexible endoscope liner  800  of the present invention bent into a curved configuration as it would be in actual clinical use. The flexible endoscope liner  800  shown in FIG. 8A is representative of the flexible endoscope liner in either FIG. 5A ( 500 ) or FIG. 6A ( 600 ) in use. In use, the flexible endoscope liner  800  is inserted into the working channel of a flexible endoscope (not shown) before the endoscope is inserted into the patient&#39;s body through an incision or through a natural body orifice. Once in place, the flexible distal section of the endoscope may be flexed into a curved configuration to view various internal body structures. When the endoscope flexes, the flexible endoscope liner  800  must flex with it. In some applications, the flexible distal section of the endoscope and the flexible endoscope liner  800  may be repeatedly flexed into bends of up to a 180 degrees, with a radius of curvature of 0.5-1.5 inches, as represented in FIG.  8 A. FIG. 8B is a longitudinal cross section of the flexible endoscope liner  800  of FIG. 8A in the curved configuration, showing the transition between the relatively inflexible proximal portion  804  and the helically convoluted flexible distal portion  802  reinforced with an outer helical reinforcing coil  822 . As can be seen in the cross section of FIG. 8B, when the helically convoluted flexible distal portion  802  of the flexible endoscope liner  800  bends, the convolutions and the reinforcing coils on the inside of the curve  812  compress together and the convolutions and the reinforcing coils on the outside of the curve  814  expand apart. This allows the helically convoluted flexible distal portion  802  to flex freely with the flexible distal section of the endoscope without kinking or collapsing which would compromise the internal diameter of the inner lumen  810 . If the flexible endoscope liner  800  is made with a flexible outer coating  820  over the convoluted flexible distal portion  802 , the flexible outer coating  820  (shown in phantom lines) elastically deforms with the convoluted flexible distal portion  802 , compressing with the convolutions and the reinforcing coils on the inside of the curve  812  and expanding with the convolutions and the reinforcing coils on the outside of the curve  814 . 
     FIG. 9A shows a fifth embodiment of the flexible endoscope liner  900  having a helically threaded flexible distal portion  902 . As in the previously described embodiments, the flexible endoscope liner  900  is an elongated tubular member with an inner lumen  910  which extends from the proximal end  916 , through a relatively inflexible proximal portion  904  and a flexible distal portion  902 , to the distal end  918 . FIG. 9B is an enlarged detail view of the flexible endoscope liner  900  of FIG. 9A showing the transition between the relatively inflexible proximal portion  904  and the flexible distal portion  902 . FIG. 9C shows a longitudinal cross section of the transition between the relatively inflexible proximal portion  904  and the flexible distal portion  902  of the flexible endoscope liner  900 . In contrast to the annular or helical convolutions of the previously described embodiments, the present embodiment has a helically threaded flexible distal portion  902 . The helically threaded flexible distal portion  902  has an external reinforcing thread  912  that traces a helical path around the distal wall  908  of the flexible endoscope liner  900 . A land  914  having a reduced wall thickness traces a helical path around the distal wall  908 , separating adjacent turns of the reinforcing thread  912 . The width of the lands  914  is typically 100-150 percent of the width of the external reinforcing thread  912 . Typically, the thickness of the distal wall  908  at the lands  914  is approximately 60-80 percent of the total wall thickness measured at the peaks of the external reinforcing thread  912 . The external reinforcing thread  912  may be made as a single helix, as shown in FIG. 9A, or as a double, triple or multiple helix. The external reinforcing thread  912  may be made with a semicircular profile, as shown in FIG. 9C, or it may be made with a rectangular, triangular, trapezoidal, or semi-elliptical profile or other desired profile. In a particularly preferred embodiment, the proximal wall  906  of the relatively inflexible proximal portion  904  and the distal wall  908  and external reinforcing thread  912  of the helically threaded flexible distal portion  902  are all formed integrally of a single polymeric material. An advantage of this embodiment is that it gives the inner lumen  910  of the flexible endoscope liner  900  a smooth, continuous inner surface  924  for smooth passage of instruments through the working lumen of the endoscope. Suitable materials for this embodiment of the flexible endoscope liner  900  include fluoropolymers, polyethylenes, polypropylenes, polyolefin copolymers, polyamides, polyamide copolymers, thermoplastic elastomers, polyurethanes, thermoset polymers and composite materials. 
     Typically, the overall length of the flexible endoscope liner  900  is between 30 and 250 cm, and the length of the helically threaded flexible distal portion  102  is between 4 and 25 cm, with the relatively inflexible proximal portion  904  making up the remainder of the length. For some applications, the flexible endoscope liner  900  would be made with the helically threaded flexible distal portion  102  extending the full length of  415  the device. Preferably, the external diameter of the helically threaded flexible distal portion  902 , measured at the peaks of the external reinforcing thread  912 , is approximately the same as the external diameter of the relatively inflexible proximal portion  904 , although, in some applications it may be acceptable to have the external diameter of the helically threaded flexible distal portion  902  larger or smaller than the external diameter of the relatively inflexible proximal portion  904 . Typically, the relatively inflexible proximal portion  904  and the helically threaded flexible distal portion  902  have an external diameter of approximately 2.0-4.5 mm and an internal diameter of approximately 1.82-4.0 mm. It should be noted, however, that the length dimensions and the internal and external diameters of the flexible endoscope liner  900  can vary widely depending on the actual design of the endoscope for which it is intended. 
     FIG. 10A shows a sixth embodiment of the flexible endoscope liner  1000  which is a modification of the flexible endoscope liner  900  shown in FIG.  9 A. Similar to the embodiment of FIG. 9A, the flexible endoscope liner  1000  is an elongated tubular member with an inner lumen  1010  which extends from the proximal end  1016 , through a relatively inflexible proximal portion  1004  and a helically threaded flexible distal portion  1002 , to the distal end  1018 . FIG. 10B is a longitudinal cross section of the flexible endoscope liner  1000  showing the transition between the relatively inflexible proximal portion  1004  and the helically threaded flexible distal portion  1102 . The relatively inflexible proximal portion  1004  has a relatively thick proximal wall  1006  and the helically threaded flexible distal portion  1102  has a thinner distal wall  1008  reinforced by an external reinforcing thread  1012 . The helically threaded flexible distal portion  1002  of the flexible endoscope liner  1000  has an additional outer layer  1020  of a flexible polymer. The flexible outer layer  1020  fills in the lands  1014  between the peaks of the external reinforcing thread  1012  to create a smooth exterior surface on the helically threaded flexible distal portion  1002 . Preferred materials for the flexible outer layer  1020  include flexible thermoplastic elastomers, such as ethylene vinyl acetate (EVA), polyamide copolymers (e.g. PEBAX from ELF ATOCHEM) and thermoplastic polyurethanes, and flexible thermoset polymers, such as silicone, latex or thermoset polyurethanes. The hardness of the flexible outer layer  1020  material can vary from approximately 50 Shore A durometer to approximately 35 Shore D durometer. 
     FIG. 11A shows a seventh embodiment of the flexible endoscope liner  1100  which is another modification of the flexible endoscope liner  900  shown in FIG.  9 A. Similar to the embodiment of FIG. 9A, the flexible endoscope liner  1100  is an elongated tubular member with an inner lumen  1110  which extends from the proximal end  1116 , through a relatively inflexible proximal portion  1104  and a helically threaded flexible distal portion  1102 , to the distal end  1118 . FIG. 11B is a longitudinal cross section of the flexible endoscope liner  1100  showing the transition between the relatively inflexible proximal portion  1104  and the helically threaded flexible distal portion  1102 . The relatively inflexible proximal portion  1104  has a relatively thick proximal wall  1106  and the helically threaded flexible distal portion  1102  has a thinner distal wall  1108  reinforced by an external reinforcing thread  1112 . The helically threaded flexible distal portion  1102  of the flexible endoscope liner  1100  has an additional outer helical reinforcing coil  1122  which occupies the lands  1114  between the peaks of the external reinforcing thread  1112 . The outer helical reinforcing coil  1122  strengthens the thin distal wall  1108  and increases the kink resistance of the helically threaded flexible distal portion  1102  without compromising its flexibility. 
     The outer helical reinforcing coil  1122  is preferably made of a resilient, biocompatible, high strength filamentous material, such as metal wire, glass fibers, carbon fibers, high strength polymer fibers or filaments, or a composite material. The cross section of the outer helical reinforcing coil  1122  may be rectangular, as shown, circular or any other convenient cross section. In a rectangular configuration, the filament width of the outer helical reinforcing coil  1122  is typically 0.008-0.020 inches and the thickness is typically 0.003-0.015 inches. In one particularly preferred embodiment, the outer helical reinforcing coil  1122  is made of rectangular cross section series  300  stainless steel wire (e.g.  302  or  304  stainless steel) with dimensions of approximately 0.015 by 0.004 inches. Preferably, the outer helical reinforcing coil  1122  is trimmed to length with a square cut proximal end  1126  and an angle cut distal end  1128 . The stainless steel wire of the outer helical reinforcing coil  1122  is preferably used in a work hardened, unannealed condition (condition B) or slightly stress relieved to a spring temper, because the high strength and excellent resilience of the wire in this condition improves the flexibility characteristics and kink resistance of the helically convoluted flexible distal portion  1102 . Annealed stainless steel wire or softer alloys are also usable for the outer helical reinforcing coil  1122 , but it has been found that these softer, more malleable wires do not protect the helically convoluted flexible distal portion  1102  as well from kinking or collapse. 
     FIG. 12A shows an eighth embodiment of the flexible endoscope liner  1200  that combines the features of the flexible endoscope liners shown in FIG. 10A ( 1000 ) and FIG. 11A ( 1100 ). The flexible endoscope liner  1200  is an elongated tubular member with an inner lumen  1220  which extends from the proximal end  1226 , through a relatively inflexible proximal portion  1204  and a helically threaded flexible distal portion  1202 , to the distal end  1228 . FIG. 12B is a longitudinal cross section of the flexible endoscope liner  1200  showing the transition between the relatively inflexible proximal portion  1204  and the helically threaded flexible distal portion  1202 . The relatively inflexible proximal portion  1204  has a relatively thick proximal wall  1206  and the helically threaded flexible distal portion  1202  has a thinner distal wall  1208  reinforced by an external reinforcing thread  1222 . The helically threaded flexible distal portion  1202  of the flexible endoscope liner  1200  has an outer helical reinforcing coil  1222  which occupies the lands  1224  between the peaks of the external reinforcing thread  1222 . The outer helical reinforcing coil  1222  strengthens the thin distal wall  1208  and increases the kink resistance of the helically threaded flexible distal portion  1202  without compromising its flexibility. The helically threaded flexible distal portion  1202  of the flexible endoscope liner  1200  also has an additional outer layer  1220  of a flexible polymer. The flexible outer layer  1220  fills in the lands  1214  between the peaks of the external reinforcing thread  1212  and the coils of the outer helical reinforcing coil  1222  to create a smooth exterior surface on the helically threaded flexible distal portion  1202 . Preferred materials for the flexible outer layer  1220  include flexible thermoplastic elastomers, such as ethylene vinyl acetate (EVA), polyamide copolymers (e.g. PEBAX from ELF ATOCHEM) and thermoplastic polyurethanes, and flexible thermoset polymers, such as silicone, latex or thermoset polyurethanes. The hardness of the flexible outer layer  1220  material can vary from approximately 50 Shore A durometer to approximately 35 Shore D durometer. 
     FIGS. 13A,  13 B,  13 C,  13 D and  13 E are a series of drawings illustrating one preferred method for fabricating the flexible endoscope liners of FIGS. 9A,  10 A,  11 A and  12 A. In the first step of the fabrication method shown in FIG. 13A, an extruded polymer tube  1300  is cut to an appropriate length and a straightened wire mandrel  1304  is inserted into the inner lumen  1302  of the tube  1300 . The wire mandrel  1304  is preferably made of stainless steel or another nontoxic, high strength material. The external diameter of the wire mandrel  1304  should closely match the internal diameter of the inner lumen  1302  with only about 1-3 thousandths of an inch clearance. A nontoxic lubricant or a lubricious coating, such as PTFE, may be used on the wire mandrel  1304  to allow easy insertion and removal. In the second step, shown in FIG. 13B, an external helical thread is formed on one end of the tube  1300 , to create a threaded distal portion  1306  and an unthreaded proximal portion  1308 . The threading step may be performed by hand or by machine using various means appropriate for the material chosen for the extruded polymer tube  1300 . One method for forming the threaded distal portion  1306  on the end of the tube  1300 , involves placing the tube  1300  over a wire mandrel and rotating the tube  1300  in contact with a cutting tool which advances along the length of the tube  1300  to cut a helical thread into the wall of the tube  1300 . Alternatively, a deforming tool can be used in place of the cutting tool to form a helical thread in the wall of the tube  1300  by deforming the material without cutting. Depending on the characteristics of the material of the polymer tube  1300 , the thread forming step can be performed at room temperature or at an elevated temperature by heating either the thread forming tool or the polymer of the tube  1300 . The threaded distal portion  1306  may also be created by drawing one end of the extruded polymer tube  1300  through a threading die, while rotating either the tube  1300  or the threading die, to cut a helical thread into the wall of the tube  1300 . Alternatively, the threaded distal portion  1306  may be made by drawing one end of the extruded polymer tube  1300  through a threading die which deforms the walls of the tube  1300  into a helically threaded configuration without cutting. Once again, depending on the characteristics of the material chosen for the polymer tube  1300 , the thread forming step can be performed at room temperature or at an elevated temperature by heating either the threading die or the polymer of the tube  1300 . At this point, the flexible endoscope liner is in the form of the flexible endoscope liner  900  of FIG.  9 A. Alternatively to steps one and two, the entire flexible endoscope liner, including the threaded distal portion  1306  and an unthreaded proximal portion  1308 , can be injection molded in one step. 
     In an optional third step, shown in FIGS. 13C and 13D, a previously made helical reinforcing coil  1314  is threaded onto the threaded distal portion  1306 . After the helical reinforcing coil  1314  is assembled onto the threaded distal portion  1306 , the flexible endoscope liner in FIG. 13D is in the form of the flexible endoscope liner  1100  of FIG.  11 A. 
     FIG. 13E shows an optional fourth step of applying a flexible outer coating  1316  to the threaded flexible distal portion  1312  and the helical reinforcing coil  1314 . The flexible outer coating  1316  may be applied by dissolving a flexible polymer in an appropriate solvent and dipping, spraying or casting one or more layers of the polymer onto the helically convoluted flexible distal portion  1312 . Alternatively, the resin and hardener of a flexible thermoset polymer can be mixed and applied to the helically convoluted flexible distal portion  1312  as a liquid by dipping, spraying or casting. The flexible outer coating  1316  may also be applied by insert molding a thermoplastic elastomer over the helically convoluted flexible distal portion  1312 . The wire mandrel  1304  is then withdrawn from the tube  1300  and the proximal and distal ends are cut to the desired length to complete the flexible endoscope liner. After the flexible outer coating  1316  is applied, the flexible endoscope liner in FIG. 13E in is the form of the flexible endoscope liner  1200  of FIG.  12 A. 
     Alternatively, the second step of FIGS. 13C and 13D may be bypassed, and the flexible outer coating  1316  applied directly to the threaded flexible distal portion  1312  in FIG. 13B to create a flexible endoscope liner in the form of the flexible endoscope liner  1000  of FIG.  10 A. 
     FIG. 14A shows the flexible endoscope liner  1400  of the present invention bent into a curved configuration as it would be in actual clinical use. The flexible endoscope liner  1400  shown in FIG. 14A is representative of the flexible endoscope liner in either FIG. 9A ( 900 ), FIG. 10A ( 1000 ), FIG. 11A ( 1100 ) or FIG. 12A ( 1200 ) in use. In use, the flexible endoscope liner  1400  is inserted into the working channel of a flexible endoscope (not shown) before the endoscope is inserted into the patient&#39;s body through an incision or through a natural body orifice. Once in place, the flexible distal section of the endoscope may be flexed into a curved configuration to view various internal body structures. When the endoscope flexes, the flexible endoscope liner  1400  must flex with it. In some applications, the flexible distal section of the endoscope and the flexible endoscope liner  1400  may be repeatedly flexed into bends of up to a 180 degrees, with a radius of curvature of 0.5-8.0 inches, as represented in FIG.  14 A. FIG. 14B is a longitudinal cross section of the flexible endoscope liner  1400  of FIG. 14A in the curved configuration, showing the transition between the relatively inflexible proximal portion  1404  and the helically threaded flexible distal portion  1402 , optionally reinforced with an outer helical reinforcing coil  1422 . As can be seen in the cross section of FIG. 14B, when the helically threaded flexible distal portion  1402  of the flexible endoscope liner  1400  bends, the threads and the reinforcing coils on the inside of the curve  1412  compress together slightly and the threads and the reinforcing coils on the outside of the curve  1414  expand apart slightly. This allows the helically threaded flexible distal portion  1402  to flex freely with the flexible distal section of the endoscope without kinking or collapsing which would compromise the internal diameter of the inner lumen  1410 . If the flexible endoscope liner  1400  is made with a flexible outer coating  1420  over the threaded flexible distal portion  1402 , the flexible outer coating  1420  (shown in phantom lines) elastically deforms with the threaded flexible distal portion  1402 , compressing with the threads and the reinforcing coils on the inside of the curve  1412  and expanding with the threads and the reinforcing coils on the outside of the curve  1414 . 
     All of the various constructions and manufacturing methods for the disposable flexible inner liner of the present invention described above will also be advantageous for constructing a flexible tubular member for use in a variety of catheters for diagnostic or therapeutic purposes. The flexible tubular member may be used alone as a diagnostic or therapeutic catheter, a guiding catheter or a catheter introducer, with only minor modifications, such as adding a Luer lock hub or other catheter fitting to the proximal end of the device. Alternatively, the flexible tubular member may also be used as one component of a more complex catheter device or a catheter system. The benefits of the disposable flexible inner liner construction as a flexible tubular member can be used to add the properties of flexibility, kink resistance and an uncompromised inner lumen to the performance of any catheter. The flexible tubular member construction may find its way into the construction of cardiovascular catheters, urology catheters, visceral catheters catheter introducers and a wide variety of other catheters, as well as minimally invasive surgical devices. For catheter applications such as these, the outer diameter of the flexible tubular member would typically be from 1 mm to 3 mm, but could range from 0.5 mm to 10 mm for some applications. The length of the flexible tubular member for use in catheter applications would typically range from 10 cm to 300 cm. Catheters and surgical devices made using a flexible tubular member built according to the disposable flexible inner liner construction of the present invention can be introduced into the body through the working channel of an endoscope or they can be introduced independently under endoscopic, fluoroscopic or ultrasonic guidance.