Abstract:
Devices and methods are disclosed for a catheterization process, particularly useful for self-performed catheterizations. A catheter is enclosed in a sheath made from a gas-permeable material. This sheath maximizes gas permeability to prevent air build-up at the distal end of the sheath, resulting in easy self-catheterization for even those with limited manual dexterity.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to catheter devices. More particularly, the present invention relates to urinary catheters having protective sheaths. 
     2. Background of the Invention 
     It has become relatively commonplace for the occasional, intermittent or periodic catheterization of an individual&#39;s urinary bladder to be employed, as opposed to placement and maintenance of an indwelling catheter that continuously drains urine from the bladder. Short-term or repeated catheterization is appropriate, or even required, for many persons who are in a hospital setting, a nursing home, doctor&#39;s office, rehabilitation facility, or in the home. For example, a patient is sometimes catheterized to treat such conditions as urinary retention, the inability to evacuate urine, or for the purpose of obtaining a sterile urine specimen from a patient in a doctor&#39;s office or for hospitalized patients. 
     The need for intermittent catheterization of an individual sometimes arises due to problems typically associated with long-term use of indwelling catheters, such as infections, urethral damage, and bladder damage. Long-term use of an indwelling catheter is also a risk factor for bladder cancer. This is often the case for persons having a neurogenic urinary condition, such as in a spinal cord injury, multiple sclerosis, stroke, trauma, or other brain injury. Conditions that interfere with the individual&#39;s ability to voluntarily void the bladder may also arise post-surgically or as a result of benign prostatic hypertrophy or diabetes. Many of the affected individuals are capable of, and would prefer to perform self-catheterization. For many, the level of risk and discomfort of repeated catheterizations carried out over the course of a day (at 3-6 hour intervals, for example) are offset by the accompanying convenience, privacy, or self-reliance that is achieved. Some of the major difficulties that arise in self-catheterization are the lack of satisfactory catheterization kits, the problem of maintaining the required level of sterility during the procedure, and the difficulty of sometimes performing the procedure under conditions of restricted space and privacy. 
     In assisted, or non self-catheterizations, it is common practice in hospitals to employ a catheterization tray, which typically includes a sterile drape, gloves, a conventional catheter, antiseptic solution, swabs, lubricant, forceps, underpad, and a urine collection container. Assisted catheterization is usually performed with the patient in a supine position. Maintaining a sterile field during the procedure can still be a problem, however, and the “cath tray” procedure is impractical for use with some individuals and situations today. 
     Many individuals with spinal cord injuries or other neurological diseases routinely perform intermittent catheterization several times a day using conventional catheters or kits and “clean technique.” Clean technique typically means that the urethral area is initially swabbed with antiseptic, and efforts are made to avoid contamination of the catheter during the procedure. The user&#39;s hands and catheter are not sterile and a sterile field is not maintained. Clean technique is used instead of sterile technique, generally, for two reasons. First, it is very difficult, if not impossible, for individuals who are performing self-catheterization to adhere strictly to sterile technique. Secondly, these individuals are required to catheterize themselves between 3 and 6 times a day, and the cost of a new sterile catheter and the accessories required to perform sterile catheterization becomes excessively expensive for some users. Sometimes an individual will reuse a “cleaned” catheter. As a result, the use of “clean technique” will many times result in contamination and subsequent infection of the urinary tract, causing significant morbidity and cost to the patient and society. 
     To maintain sterility many catheters are surrounded by sheaths. The user then holds the sheath while pulling the catheter through, avoiding direct contact with the catheter before and during insertion. While the user is pulling the catheter through the sheath, the sheath can tend to bunch up at the proximal end. Any excess air is then forced to the distal end. Towards the end of the insertion, the air can build up at the distal end inflating the sheath to a maximum, which makes it difficult to complete the insertion process. Completion can be particularly difficult for those with limited manual dexterity. 
     SUMMARY OF THE INVENTION 
     The present invention provides a catheter with a sheath that has the qualities that relieve these difficulties associated with self-catheterizations. A catheter using a sheath made from a gas-permeable, yet liquid-impermeable, material will allow excess air inside the catheter to leak through the sheath without compromising the integrity, and thus the sterility, of the sheath, relieving the build-up of air at the distal end of the sheath. This will allow even users with low manual dexterity to complete the self-catheterization process efficiently, and with ease. 
     Furthermore, the present invention can include components that further ease the catheterization process. Particular exemplary components include lubrication so the catheter slides smoothly down the urinary tract, and a guiding tip, which may also have a lubricant reservoir, to give the user something solid to line up the catheter to the urethra. Also, a hydrophilic coating is used on the catheter of certain embodiments to hold the lubricant onto the catheter while in the urinary tract. 
     An exemplary embodiment of the present invention is a sheath which is made from a silicon-based organic polymer. This sheath is made from low-density polydimethylsiloxane. This material has a gas-permeability much greater than that of conventional polyolefins allowing air to flow through four-hundred times faster. 
     Yet another embodiment of the present invention is a sheath made from a microporous polyolefin. This material is characterized with the unique property of containing tortuous sub micron-size passageways extending from one surface side to the other. This permits gases and vapors to permeate and prohibits the penetration of sample particles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows an external perspective view of a catheter surrounded by a sheath according to an exemplary embodiment of a conventional assembly. 
         FIG. 1B  shows an external perspective view of a catheter surrounded by a sheath with the sheath pulled back to expose the catheter and showing an air pocket created. 
         FIG. 2A  shows an external perspective view of a catheter surrounded by a sheath attached to a guide tip at the proximal end according to an exemplary embodiment of a conventional assembly. 
         FIG. 2B  shows a close-up view of a guiding tip according to an exemplary embodiment of the present invention. 
         FIG. 2C  shows an external perspective view of a catheter surrounded by a sheath attached to a guide tip at the proximal end with the sheath pulled back, forcing the catheter through the guide tip and showing an air pocket created. 
         FIG. 3A  shows an external perspective view of a catheter surrounded by a gas-permeable sheath according to an exemplary embodiment of the present invention. 
         FIG. 3B  shows an external perspective view of a catheter surrounded by a gas-permeable sheath with the sheath pulled back to expose the catheter and showing no air pocket. 
         FIG. 4A  shows an external perspective view of a catheter surrounded by a gas-permeable sheath attached to a guide tip at the proximal end according to an exemplary embodiment of the present invention. 
         FIG. 4B  shows an external perspective view of a catheter surrounded by a gas-permeable sheath attached to a guide tip at the proximal end with the sheath pulled back, forcing the catheter through the guide tip and showing no air pocket. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention includes devices and methods for urinary catheterization for patients who want to self-catheterize in a sterilie, safe, and efficient manner. In order to achieve the level of sterility required to avoid infection, a sheath  100  is used to cover the portion of the catheter that is insertable into the urethra  180 , as shown in  FIGS. 1A and 1B . The sheath covers the catheter  110  from time of manufacture and storage until it is fully inserted. The user pulls the catheter  110  through the sheath  100  without touching the catheter  110  itself. As the user pulls the catheter  110  through the sheath  100 , excess air builds up  160  at the distal end of the sheath  102 . This excess air  160  needs to be released from inside the sheath  100  to the outside atmosphere to allow further advancement of the catheter  110 . The sheath  100  in the present invention is made from a gas-permeable material, which allows air to flow through the sheath  100  preventing build-up  160  towards the distal end without compromising sterility. 
     “Gas-permeable,” as defined in the present disclosure, is the ability for air to penetrate through a medium. An exemplary embodiment of the present invention features a material in which gas can penetrate fast enough therethrough such that change in the air-pocketing of the media is noticeable by the human eye. The air inside the sheath is put under pressure when the sheath bunches up at the proximal end during use. While under pressure, the exemplary sheath transfers enough air to the outside atmosphere for the user to notice a reduction in the size of the sheath around the pressurized area. 
     One group of materials that has this gas-permeability is silicon-based organic polymers, also known as silicon oils. They are flexible, strong, and can retain their strength through a wide range of temperatures. They are very resistant to chemicals and ultraviolet rays, and are gas permeable. Silicon-based organic polymers are liquid-impermeable and do not allow bacteria or other harmful substances to pass, making them useful in medical applications such as the present invention. 
     An exemplary silicon-based organic polymer for use in the present invention is polydimethylsiloxane, also known as dimethicone or its trade name, SILICON ELASTOMER. Its density ranges from 1.1 to 1.5 g/cm 3 . Its density is proportional to its gas-permeability, so a less dense version of polydimethylsiloxane, 1.1 to 1.3 g/cm 3 , is useful in certain exemplary embodiments. 
     Another group of materials suitable for the present invention is microporous polyolefins. Unlike regular polyolefins, these microporous polyolefins have tortuous sub micron-size passageways extending from one surface side to the other. This allows the passage of gas and vapor while prohibiting the passage of particles and liquids. The microporous polyolefin material can be made by taking a microporous polyolefin matrix and sufficiently filling the pores with a moisture-vapor permeable, liquid-impermeable, hydrophilic material to prevent the passage of water and other liquids through the polyolefin material while readily permitting moisture vapor. One example of such a material is presented in U.S. Pat. No. 4,613,544, entitled “Waterproof, moisture-vapor permeable sheet material and method of making the same,” issued to Burleigh, which is incorporated by reference herein in its entirety. 
     An exemplary embodiment of a conventional assembly for a catheter with a sheath is shown in  FIG. 1A . The proximal end of the sheath  101  surrounds the proximal tip of the catheter  111  and is closed at the end. The distal end of the sheath  102  is attached near the distal end of the urethra insertable portion of the catheter  180  with plastic or elastomeric ties or bands  140  or heat sealed. Alternately, the distal end of the sheath  102  could be attached to the outlet  120  if the catheter employs one. This outlet  120  could then be used to attach a urine bag or the like. 
     In order to perform a catheterization using this device, the user must first open the proximal end of the sheath  100 , exposing the proximal end of the catheter  111 . The user then holds the proximal tip of the catheter  111  with the sheath  100  between the user&#39;s hand and the catheter  110  and pulls the sheath  100  with the other hand. As the user pulls the sheath  100 , which is attached to the catheter at its distal end  113 , the catheter  110  will be pushed through the sheath  100  and into the urethra, causing the sheath  100  to bunch up at the proximal end  101 . A gap is shown at the proximal end  101  to show the detail of this end but this gap is not of such size to allow venting into the sheath  100 . At the distal end of the sheath  102  the air will build up  160 , causing the sheath  100  to expand to a maximum, preventing the catheter  110  from furthering through the sheath. This is illustrated in  FIG. 1B . 
       FIG. 2A  shows an embodiment of a conventional assembly that also has a guiding tip,  FIG. 2B . This embodiment, as illustrated in  FIG. 2C , is also susceptible to inhibited catheter  270  movement caused by the air build-up  260  at the distal end of the sheath  202 . 
     In  FIG. 3A , there is an exemplary embodiment of the present invention shown, featuring a sheath  300  made from a gas-permeable, liquid-impermeable material  350 , such as the materials disclosed above, or similar in function. This material  350  will allow the air built-up inside the sheath to escape to the outside atmosphere  360  at a rate fast enough for the user to complete the catheterization process without undue pause, as illustrated in  FIG. 3B . 
     Referring to  FIGS. 3A and 3B , the catheter insertion process continues until the catheter  310  runs all the way through the urethra and into the bladder. Once inside, fluid from the bladder will stream into the catheter through the hole  312  at the proximal tip of the catheter  311 . Provided the catheter distal end  313  is lower in altitude than the catheter proximal end  311 , fluid will flow through the catheter, out the outlet  320 , and into a receptacle. When the bladder has been drained of all fluid the catheter  310  is then pulled out of the urethra by the user, and disposed. 
     In certain exemplary embodiments, the sheath  300  may be filled with enough lubricant  330  to coat the insertable length of the catheter  380 . This will be a water-based lubricant of the type used on rectal thermometers and enemas, such as KY-JELLY®, or the like. As the catheter  310  is pushed through the sheath  300 , the lubricant  330  is pushed through as well, lubricating the insertable portion of the catheter  380  on its way into the urethra. The lubricant  330  will ease the process of sliding the catheter  310  into the urethra by reducing the friction between the catheter  310  and the urethra. By reducing the friction the user can insert the catheter  310  faster and with less pain. 
     In another embodiment shown in  FIG. 4A , the catheter  470  has a guiding tip  430  at the proximal end of the catheter  411 . The guiding tip  430  helps the user hold the catheter  470  in place while inserting it into the urethra. The guiding tip  430  has a throughbore  420  in the center which the catheter  470  can slide through. In use,  FIG. 4B  illustrates the sheath&#39;s  400  ability to release built-up air to the outside atmosphere  460  even when the assembly includes a guiding tip  430  at the proximal end  411 . With no air built-up in the distal end of the sheath, the user can easily push the catheter through the sheath completely. 
     An exemplary embodiment of the guiding tip  430  is illustrated in  FIG. 2B  as tip  230 . Although described with respect to  FIG. 2B , the same guiding tip is applicable to the one shown in  FIGS. 4A and 4B . At the proximal end of the guiding tip  230  is a collar  210 , with a size of about 10-15 mm, which, during insertion, rests on the outside of the urethra. At the proximal end of the collar  210  is a short tube  220  just wider than the catheter  270 . This tube  220  ends in a rounded top with two cuts in the top  221 . When the catheter  270  is pushed through the top the tube  220  splits into four tabs  222 , allowing the catheter  270  to pass. Towards the distal end of the guiding tip  230  there is also a reservoir portion  230 . The distal half of the reservoir is a hollow cylinder  231  while the proximal half is a hollow frustoconical section  232 . The reservoir portion  231  contains the same lubricant that is held inside the sheath  200 . This makes the guiding tip  230  longer and bulkier, and gives the user more to hold onto while sliding the catheter  270  through. On the outside of the reservoir  231 , texture may be added for enhanced gripping. Other embodiments of the guiding tip can be found in U.S. Pat. No. 6,090,075, entitled “Disposable urinary catheterization assembly”, issued to House, which is incorporated by reference herein in its entirety. 
     In other embodiments the catheter may be coated with a hydrophilic substance, commonly known as hydrogel, particularly useful on indwelling catheters. This hydrophilic coating helps the catheter to hold the lubricant on its surface while inside the urinary tract. One such hydrophilic substance that can be used is agarose, known also under its trade name BIOGEL A. 
     The foregoing disclosure of the exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
     Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.