Abstract:
The invention relates to a method of manufacturing a catheter, wherein the catheter comprises an elongate portion having a proximal end and at least one lumen at said proximal end, at least one extension tube having a passage, and a coupling element, the distal portion of the extension tube being capable of communicating with a lumen of the elongate portion via a passage in the coupling element wherein the method comprises a step wherein a removable insert element locates and holds the extension tube in contact with the elongate portion during the manufacture of a coupling element. The invention also relates to a removable insert for use in the manufacturing of catheters.

Description:
The present invention relates to catheters which can be inserted into the human or animal body for various medical purposes. More particularly the present invention relates to catheters formed by moulding. 
   BACKGROUND OF THE INVENTION 
   A catheter includes an elongate slender flexible portion for insertion into a body cavity such as a vein or artery. The elongate portion has at least one lumen, but typically has a plurality of lumens, and extends from a proximal end at a coupling element to a distal end, which in use is inside the human or animal body. The lumens within the elongate portion can be used to introduce or remove fluid from the human or animal body or alternatively carry means allowing measurement of blood pressure, blood flow or such like. As each lumen typically contains different means performing different functions, the means within each lumen may be attached to particular components or equipment. The means within each lumen within the elongate portion are connected to particular components or equipment via extension tubes, which attach to the proximal end of the lumens of the elongate portion via the coupling element. 
   The extension tubes are commonly attached to the proximal end of the lumens of the elongate portion via plastic adapters. These plastic adapters may be glued in position using adhesive such that the adhesive bonds the extension tube to the elongate portion. However this method of gluing adapters to the extension tube is very labour intensive and requires long drying times for the adhesive to set and harden. Further, the adhesive may flow into one or more of the lumens of the elongate portion and completely or partially block the lumens. 
   An alternative method used, that eliminates the need for gluing, is the insertion of wire mandrels through an extension tube and into a lumen of the elongate portion. A mould tool is then placed around the elongate portion and extension tube and a coupling element formed by moulding plastic into the mould tool. The coupling element formed around the extension tube and the proximal end of the elongate portion, secures the extension tube to the elongate portion. Removal of the wire mandrels from the lumens of the elongate portion and from the extension tube creates passages in the coupling element allowing passage of fluid or other means from the extension tube into the lumens of the elongate portion. 
   This alternative method of attaching the extension tubes to the elongate member also has a number of disadvantages in that large diameter extension tubes or elongate portions tend to melt in the mould, while small diameter extension tubes or elongate portions allow the plastic being moulded to “flash” out of the mould alongside the extension tubes or elongate portions. In addition the hot plastic used for moulding can cause kinking or collapse of the lumens within the elongate portion. 
   The moulding method described above to attach the extension tubes to the elongate portion has been improved by including an insert element in the catheter as described in U.S. Pat. No. 4,670,009. The insert element of the catheter surrounds the extension tubes, holding the extension tubes in place in the finished catheter and preventing the injected plastic from “flashing” out around the extension tubes during the moulding process. During manufacture the use of an integral insert element in the catheter means the mould need not be sized to accommodate any particular number or diameter of extension tubes, provided the mould can close off around the insert element such that no plastic flashes through the moulding insert interface. 
   The use of an insert element which is incorporated into the final catheter product to secure the extension tubes to the elongate element requires that the integral insert element is pre-fabricated for each catheter being produced. The fabrication of an integral insert element adds to the cost of the production of the catheter. Further the use of an integral insert element in the catheter adds to the number of components and material within the catheter and this again contributes to the production cost of the catheter. 
   It would be advantageous if a catheter could be produced which did not require an integral insert element to be fabricated for and included in each catheter produced. The use of a releasable insert element(s) or an insert element integral to the mould tool would be advantageous as the use of such an insert would reduce the expense of fabrication of the catheter and further reduce the cost of the material required to make the catheter. 
   SUMMARY OF THE INVENTION 
   According to the present invention there is provided a method of manufacturing a catheter wherein the catheter comprises an elongate portion having a proximal end and at least one lumen at said proximal end, at least one extension tube having a passage, and a coupling element, the distal portion of the extension tube being capable of communicating with a lumen of the elongate portion via a passage in the coupling element wherein the method comprises the use of a removable insert element to locate and hold the extension tube during the manufacture of coupling element. 
   The invention further provides a catheter made according to this method. 
   Accordingly the invention provides a removable insert to locate and hold at least one extension tube during the manufacture of a catheter. 
   Preferably the removable insert element is comprised of metal, composite, or high melting temperature plastic. 
   Preferably the removable insert element is capable of being positioned in the mould tool to locate the extension tubes within the coupling element. 
   Preferably the removable insert element is formed of a single section. 
   Alternatively the removable insert element is formed by a plurality of sections. 
   Preferably the coupling element includes plastic material which is moulded over the elongate element. 
   Preferably the catheter comprises a plurality of extension tubes and the elongate portion comprises a plurality of lumens, the passages of extension tubes corresponding with the respective lumens of the elongate portion. 
   Alternatively the catheter comprises a plurality of extension tubes and the elongate portion comprises a plurality of lumens, wherein a passage of an extension tube corresponds with at least two lumens of the elongate portion. 
   Preferably the passages in the coupling element are formed using wire mandrels extending from the extension tubes into the lumen of the elongate portion. 
   Preferably the elongate portion is flexible and sized to be received within the vein or artery. 
   Prefereably the removable insert element provides a recess volume in the coupling element to accept an extension tube. 
   Alternatively the removable insert element may create a feature to connect at least one extension tube to at least one lumen of the elongate portion. 
   Preferably a mandrel guide is used to position the wire mandrels extending from an extension tube into a lumen of the elongate portion. 
   Preferably a mandrel guide is used to position the wire mandrels in combination with a releasable insert element. 
   Preferably the mandrel guide has locating features on a first end wherein the locating features are capable of locating the mandrel guide in a particular orientation relative to the removable insert element. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which 
       FIG. 1  is an isometric view of the catheter, 
       FIG. 2  is a sectional view of the catheter along line  2 - 2 , 
       FIG. 3  is an enlarged sectional view along line  3 - 3 , 
       FIGS. 4   a  and  b  are isometric drawings depicting the main steps involved in forming the catheter, 
       FIG. 5  shows a removable insert able to create a recess volume in the connecting element to accept an extension tube, 
       FIG. 6  shows a removable insert able to connect an extension tube to more that one lumen of the catheter body, 
       FIG. 7  shows a mandrel guide, and 
       FIG. 8  shows an alternative mandrel guide. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a catheter  10  which comprises an elongate portion  12 , extension tubes  14 , and a connecting element  16 . The connecting element  16  receiving at least part of the extension tube  14  and the elongate portion  12  such that it is capable of retaining these within the connecting element  16 . 
   In the embodiment shown in  FIG. 1  the elongate portion  12  comprises four lumens  18  although different elongate portions could contain greater or fewer numbers of lumens. In the embodiment shown in  FIG. 1  each of the lumens  18  of the elongate portion  12  correspond to a distinct passage  20  of an extension tube  14 . Each particular extension tube  14  may be connected to different pieces of equipment (not shown) to allow each of the lumens  18  to contain different elements such as conductive wires, thermistors, pressure sensing apparatus, means for infusing solutions or the like. 
   The elongate portion  12  may be constructed of a biocompatible plastic material such as PVC, the proximal end  22  of the elongate portion  12  being received by the coupling means  16 . The extension tubes  14  may be of equal or different diameter to each other and may be constructed of a suitable plastics material such as PVC. 
   The coupling element  16  is also constructed of a suitable plastics material such as polyester or low melting temperature plastic, metal or composite, which allows it to be bonded to the plastic of the elongate portion  12  and the extension tubes  14  during the moulding process. As shown in  FIG. 2  wire mandrels  24  are passed through the passages  20  of the extension tubes  14  into the lumens  18  of the elongate portion  12  such that during the moulding process they are able to form passages  42  in the coupling element linking the elongate portion  12  to the extension tubes  14 . 
   Moulding of the coupling element may be performed by any means known in the art including introducing powdered plastic into the mould tool and heating the mould or injecting plastic into the mould tool. In the embodiment described injection moulding is the preferred method of forming the coupling element. 
   During the moulding process a removable insert  28  is used to hold the extension tubes  14  in place within the coupling means  16  and prevent the plastic from flashing out of the mould at the position at which the extension tubes exit the mould tool  32 . 
   The removable insert element  28  may be constructed of metal, composite or a suitable high melt plastic. The removable insert element comprises at least one passage  34 . In the embodiment shown four passages are present that extend through the removable insert element  28  from a first face of the removable insert element  28 , which faces the elongate element to a second opposite face. The passage  34  through the removable insert element  28  is sized such that it grips extension tube  14  pushed through the passage  34  of the removable insert element  28 . Further the removable insert element  28  may comprise a flange portion  29  to aid location of the removable insert element  28  in the mould tool  32 . 
   As shown in  FIGS. 4 and 5  the preferred method of manufacturing the catheter is a predetermined portion  15  of at least one extension tube  14  is passed through the passage  34  of the removable insert element  28  such that the portion  15  of the extension tube  14  extends beyond the second face of the removable insert element  28  such that when the removable insert element  28  is located within the mould tool  32 , the portion  15  of the extension tube  14  which extends beyond the removable insert element  28  enters into the space  30  within the mould tool  32  into which the plastic is to be injected or entered into the mould. 
   As the extension tubes  14  are frictionally held within the passages  34  of the removable insert element  28  when the removable insert element is located within the mould tool  32 , the extension tubes  14  are suitably located in the coupling element  16  when it is formed by the moulding process. 
   The elongate portion  12  is located and held by the coupling element  16  using a sleeve  36 . The sleeve  36  is a thin walled flexible tube, capable (using its inner face  38 ) of tightly gripping the outer face of the proximal end of the elongate portion  12 . 
   The sleeve  36  being attached to the connecting element  16  via its outer face  40  during the moulding process. 
   During the manufacture of the catheter the sleeve  36  containing the elongate portion is suitably positioned in the mould tool  32  such that the coupling element can be around it. 
   The sleeve  36  is pliable such that it is able to take up variances in the diameter of the elongate portion  12  created during the production of the elongate portion  12 . 
   Wire mandrels  24  are inserted through the extension tubes  14  and into the respective lumens  18  of the elongate portion where they are held in place by friction. Removal of the wire mandrels  24 , following moulding enables passages through the coupling element  16  to be created. 
   As shown in  FIG. 4   b  the mould tool  32  comprises sections  50  and  52  which can be moved relative to each other away from each other to an open position or toward each other to a closed position. In the open position the removable insert element  28  can be located within the mould tool  32 . The sleeve  36  can also be positioned in the mould tool  32 , the sleeve  36  gripping the proximal end of the elongate tube  12  such that it will be suitably located within the coupling element  16  when the coupling element is formed by the moulding process. 
   Once the removable insert element  28  and sleeve  36  have been located in the mould tool, mould tool sections  50  and  52  can be moved to a closed position such that the mould tool  32  forms a tight fit around the removable insert element  28 . Further the closed mould tool has a tight fit around the sleeve  36 . 
   When the mould tool sections  50  and  52  are in the closed position, hot plastic may be injected or entered into the space  30  via inlet  54  to form the connecting element  16 . The tight fit of the removable insert element  28  ensures that no plastic flashes out around the removable insert element  28 , while the tight fit of the mould tool  32  around the sleeve  36  ensures that plastic cannot flash out between the mould tool  32  and the sleeve  36 . 
   The grip of the sleeve  36  on the elongate portion  12  further ensures that plastic cannot flash out between the sleeve  36  and the elongate portion  12 . 
   The plastic of the coupling element  16  forms around the portion  15  of the extension tubes  14 , which extends beyond the removable insert means  28  into the cavity  30 , and the sleeve  36 , which grips the elongate portion  12 . Once cured the plastic which forms the coupling element therefore holds the extension tubes  14  and the sleeve  36  in the coupling element  16 , but does not grip or attach the removable insert element  28 . 
   The injected plastic and plastic entered into the mould tool flows around the wire mandrels  24  causing the mandrels when removed to leave passages  42  through the coupling element. After the plastic of the coupling element cures the mould sections  50   52  can be relatively moved away from each other to an open position. The extension tubes  14  are pulled through the passages of the removable insert element  28  and the catheter including extension tubes  14 , wire mandrels  24 , connecting element  16 , sleeve  36  and elongate member  12  can be removed from the mould. The removable insert means may then be reused to hold extension tubes to form a second or subsequent catheter, saving on material and production costs of insert elements. 
   The wire mandrels  24  can then be removed from the extension tubes  14  and lumens  18  of the elongate portion  12  to form passages  42  in the coupling element  16 . 
   In an alternative embodiment of the present invention the wire mandrels  24  may be held in position within the mould tool  32  by a mandrel guide member  60 . This mandrel guide member  60  can be of any suitable shape such that it can be positioned between the wire mandrels  24 . The mandrel guide member  60  having a series of grooves  62  around its perimeter in which the wire mandrels  24  can be located to suitably position them in the coupling element  16 . 
   The mandrel guide member  60  prevents the wire mandrels  24  touching each other and thereby prevents interpassage leaks in the coupling element  16 . 
   As shown in  FIGS. 7 and 8  the mandrel guide may be cylinder shaped or cone shaped depending on how the mandrels are to be arranged. 
   Various embodiments of the present invention can be envisaged without departing from the scope of the present invention. For example the removable insert element  28  may be shaped as shown in  FIG. 5  with a protrusion  70  extending from the surface of the removable insert element  28  which contacts the coupling element during moulding. This protrusion  70  may be used to create a recess volume  74  in the coupling element  16 , this recess volume  74  providing a feature which allows the attachment of an extension tube  12  at a period after formation of the coupling element  16 . 
   Alternatively the removable insert element  28  may be shaped such that it is able to connect one extension tube to more than one lumen in the elongate member. As shown in  FIG. 5 , a larger passage  72  may be created in the removable insert element  28  able to accommodate an extension tube into which a plurality of mandrels linking to a plurality of lumens  18  in the elongate portion  12  can be placed.