Abstract:
This invention provides an apparatus and method for an insertion medical device that dilates internal strictures. The insertion medical device includes a flexible dilator having an enclosed, hollow chamber substantially filled with crystalline tungsten powder. More particularly, a bougie is disclosed. The crystalline tungsten powder provides the bougie with improved flowability and performance when placing the bougie in the stricture. In another aspect, the invention provides improved flowability and adequate weight to other medical devices such as feeding tubes and endoscopy instruments.

Description:
FIELD OF THE INVENTION 
     This invention relates to an insertion medical device and, more particularly, to hollow rubber dilators filled with flowable material for treating constricted, internal passageways. 
     BACKGROUND OF INVENTION 
     Stenosis, or esophageal stricture, is a narrowing or constricting of the diameter of a patient&#39;s esophagus and prevents the normal peristaltic activities of the esophagus. It may impede the patient&#39;s ability to swallow and/or block access to the digestive tract. Treatment often requires dilation of the esophagus at its junction with the stomach. 
     As noted in U.S. Pat. No. 5,366,471, there are several esophageal dilators known in the art. One such dilator is a bougie having a hollow, central channel extending the length of the bougie, for insertion of a guide wire previously placed in the patient. This type of dilator is most often used with tight strictures that are 1.2 centimeters, or less, in diameter. Another type of dilator is a wire-guided balloon dilator. The guide wire locates the balloon in the stricture and, thereafter, the balloon is slowly inflated. The balloon dilator is best used in asymmetrical strictures that are 1.2 centimeters, or more, in diameter. 
     Another type of esophageal dilator is the Mercury-filled rubber bougie. The bougie comprises a rubber sheath filled with Mercury, and having a tapered tip. The bougie is inserted, tip-first, through a patient&#39;s mouth and into the esophagus, applying light pressure to enlarge the diameter of the stricture. The rubber bougie is best used in treating strictures which are symmetrical and more than 1.2 centimeters in diameter. Since most esophageal strictures meet these requirements, the rubber bougie is the most commonly used esophageal dilator. 
     The Mercury core provides the weight necessary for proper performance of the dilator, and, because Mercury is liquid at ambient and body temperatures, it allows flexing of the dilator. 
     Ribs can form in the surface of a rubber dilator at the location of a tight bend, and can cause damage to the interior lining of the patient&#39;s esophagus. The Mercury core also prevents ribs from forming in the outer surface of the sheath at the location of a tight bend. 
     One disadvantage to the use of Mercury as the core of a rubber bougie is that Mercury is toxic to humans. The quantity of Mercury held in a bougie could result in a fatality if it were to escape into the patient. The flowability of liquid Mercury enhances the danger, since even a small crack in the sheath of the bougie could result in leakage of the entire quantity of Mercury leaking out of the bougie and into the patient&#39;s mouth, esophagus or stomach. If Mercury enters the bloodstream, it can cause mercury poisoning. In addition, the physical action of a large quantity of Mercury on the digestive tract can cause severe effects. Thus, there are significant health risks associated with the use of Mercury. 
     U.S. Pat. No. 5,366,471 (“the &#39;471 patent”) discloses an esophageal dilator where instead of using Mercury, a solution of Tungsten powder suspended in silicone is used. This invention seeks to achieve the benefits of Mercury but without the health risks. The &#39;471 patent teaches that the Tungsten powder, if not suspended in silicone, may cake up, or pack together, forming clumps. The &#39;471 patent teaches that Tungsten powder, if not suspended in silicone, may not have adequate flowability properties and ribs may form in the bougie and this could damage the patient&#39;s esophagus. However, one disadvantage of the suspension of Tungsten in silicone claimed in the &#39;471 patent is that the silicone fluid has the potential of leakage in the event the bougie is cracked. 
     What is desired, therefore, is a medical device that is filled with a material that possesses adequate flowability properties such that, when inserted into a constricted, internal passageway, the device does not form ribs and can be easily maneuvered to effect dilation. What is also desired is that the material substantially fill the bougie in order to allow the bougie to be inserted deep into the passageway and still maintain adequate weight for maneuverability and to be free from forming ribs throughout the bougie. What is further desired is a material that would not easily flow from a damaged or cracked bougie into the patient&#39;s body. 
     SUMMARY OF INVENTION 
     Accordingly, it is the object of this invention to provide an apparatus and method for making an insertion medical device. 
     It is another object to provide an apparatus for dilating internal strictures using a flexible tube of adequate weight and flowability comprising crystalline tungsten powder. 
     It is another object to provide a bougie comprising crystalline tungsten powder for dilating internal strictures wherein, while maneuvering through narrow and curved passageways, said bougie maintains a smooth, uninterrupted surface free from creases. 
     It is another object to make an apparatus that provides adequate weight and flowability to facilitate the use of other insertion devices such as feeding tubes and endoscopy instruments. 
     Yet another object is to provide a method for making a bougie substantially filled with crystalline tungsten powder. 
     These and other objects of the invention are achieved by an apparatus and method for making an insertion medical device comprising a flexible, silicone rubber tube with a tapered tip; said flexible, silicone rubber tube having an enclosed, hollow space; and crystalline tungsten powder substantially filling said enclosed, hollow space. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is side view of the insertion medical device. 
     FIG. 2 is flowchart of the steps for making a bougie. 
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments of the invention will be described in detail with reference to FIGS. 1-2 attached hereto. 
     The embodiment shown in FIG. 1 depicts an insertion medical device  10  for dilating internal strictures comprising a tube  12  having requisite flexibility and an enclosed, hollow space  14  substantially filled with crystalline tungsten powder  16 . 
     In the preferred embodiment, the tube  12  is made of a flexible and waterproof material, such as silicone rubber. Flexibility is desired because the tube  12  must conform to the curves and tight bends normally found in internal passageways. Further, a flexible tube would be most comfortable for the patient. In the past, some esophageal bougies had metal guide wires within the tube for facilitating placement of the tube  12  inside the passageway, and that this caused pain to the patient; thus, in the preferred embodiment, such wires are omitted. A waterproof material is used because it is desired to keep the internal medical device&#39;s  10  contents dry and separate from the patient&#39;s internal fluids. This prevents accidental toxicity and keeps the device working properly. Silicone rubber is used because it provides the necessary flexibility and waterproof properties. 
     Also in the preferred embodiment, the tube  12  is tapered at the distal end  20  to facilitate insertion into the internal stricture and has an enclosed, hollow space  14  that extends upwardly towards the proximal end  22 . The enclosed, hollow space  14  will substantially extend the entire length of the tube  12  in order to allow crystalline tungsten powder  16  (“CTP”) to be added to provide adequate weight to the flexible tube  12 . Further, the enclosed, hollow space  14  will have a resealable opening through which the CTP  16  can be added and contained within the flexible tube  12 . 
     CTP  16  is preferably used to substantially fill the enclosed, hollow space  14  because it has the necessary flow and weight characteristics to permit placement of the insertion medical device  10  while still maintaining sufficient flexibility in the tube  12 . 
     CTP  16  is a crystallized form of tungsten and is not to be confused with regular tungsten powder. CTP particles are approximately 2 to 4 times larger than regular tungsten powder and have a body-centered cubic. Further, CTP  16  has a Hall Flow rate of approximately 6 to 10 seconds/50 grams in contradistinction to standard tungsten powder that does not exhibit any flow characteristic and cannot be measured using the Hall Flow test. In addition, CTP  16  has a rougher surface than standard tungsten powder and this prevents the tungsten from clumping or packing together. Because of the foregoing, CTP  16  possesses flowability properties not found in standard tungsten powder. Because of its flowability, CTP  16  is effective when used by itself. However, if desired, CTP  16  can be suspended in a fluid, such as silicone, in order to vary flowability. 
     CTP  16  has a Scott Density of approximately 140 to 160 grams/cc and this density has been found to be adequate for providing the necessary weight to the tube  12  in order to enable the user to maneuver the insertion medical device  10 . The density further provides the firmness necessary to enable the physician to push upon the insertion medical device  10  to force open a constricted passageway without a guide wire. 
     CTP  16  is made by an alkaline process where tungsten powder is chemically enlarged. CTP  16  particles are in the shape of crystals and are approximately 40 to 75 microns. This large size is a factor in the CTP&#39;s favorable flow rate. Further, when the insertion medical device  10  is bent, the surface of the insertion medical device  10  remains free from creases and this reduces pain to the patient due to the non-clumping properties of the large size crystal. CTP  16  is also non-toxic to humans and makes CTP  16  more desirable for a rupture in the flexible tube  12  will not cause a health concern to the patient. In addition, because CTP  16  is preferably in a solid state, the CTP  16  will not rapidly exit via the rupture and enter the patient&#39;s body, thereby making CTP  16  a desirable product to be used in the insertion medical device  10 . 
     In order to provide an insertion medical device  10  that is capable of dilating strictures deep within a passageway and to accommodate large individuals, the insertion medical device  10  should be at least 30 inches in overall length and have a uniform diameter typically in the range of 0.21 inches to 0.79 inches. The tip  18  is typically about 6 inches in length, with a rounded end having a diameter of approximately 0.19 inches and is tapered so that its outer surface smoothly meets the outer surface of the tube  10  at its distal end  20 . Further, the CTP  16  should substantially fill the enclosed, hollow space  14  in order to provide adequate flowability that is necessary throughout the insertion medical device  10 . 
     In the preferred embodiment, the insertion medical device  10  is a bougie. Alternatively, CTP  16  can be used with any flexible tube having a hollow chamber in order to provide adequate weight and flowability. The wide array of medical devices that can be produced using CTP  16  includes, but is limited to, feeding tubes and endoscopy instruments. It is envisioned that any instrument that is to be inserted requires adequate weight in order to be inserted within the human body. Further, such instrument requires adequate flowability from a non-toxic substance, yet firmness in order to facilitate maneuverability. All these advantages are provided with CTP  16  and this makes CTP  16  versatile and adaptable to a variety of instruments beyond the preferred embodiment. 
     The embodiment shown in FIG. 2 depicts a process  40  for making a bougie  42  substantially filled with CTP  16  for dilating internal strictures. The process comprising: enlarging tungsten powder using an alkaline process to produce CTP  16  at  43 , filtering the CTP  16  through a 200 mesh screen  44  at  45 , again filtering the CTP  16  through a 325 mesh screen  46  at  47 , selecting the CTP  16  not filtered through the 325 mesh screen  46  at  49 , making a first section  48  of silicone rubber having an aperture  50  and an internal, hollow space  14  substantially the entire length of the first section  48  at  51 , substantially filling said first section  48  with the selected CTP  16  that filtered through the 200 mesh screen  44  but not through the 325 mesh screen  46  at  53 , and making a second section  54  of silicone rubber used to mate with and seal said aperture  50  at  55 . 
     In the preferred embodiment, the first section  48  has a tapered tip at the distal end  20  and is made of silicone rubber. The first section  48  also includes an aperture  50  just large enough to allow CTP  16  to pass. The aperture should not exceed 3.0 mm and is preferably between 2.0 and 2.5 mm. This embodiment may be made by any of a number of methods including, but not limited to, injection molding, blow molding, and machining. 
     In the preferred embodiment, the second section  54  is also made of silicone rubber and may be made using the same method as for the first section  48 . The second section  54  will ideally have a diameter equal to the first section  48  and will further comprise a portion that mates with the aperture  50  of the first section  48 . Preferably, this mating portion is a male member  58  that has a diameter the same size as or larger than the diameter of the aperture  50 . This will allow a tight fit to properly seal in the CTP  16  and ensure that no CTP  16  will leak out. 
     After filling the first section  48  with CTP  16 , the second section  54  can then seal the aperture  50  permanently. It is preferred to permanently seal the aperture  50  because CTP  16  is not known to break down or decompose prior to the tube  12  being discarded for wear or sanitation purposes. Therefore, once a substantial amount of CTP  16  has been filled, there is no need to reopen the aperture  50 . Hence, the first and second sections  48  and  54  may be sealed using a non-toxic sealant or other adhesive. Other methods of permanently sealing include, but are not limited to, ultrasonic welding, heating, and chemical bonding. 
     It is desirable to make the first and second sections  48  and  54  the same material because identical materials form the strongest bond upon sealing. Alternatively, similar materials may be used but this does not produce the strong bond identical materials form.