Abstract:
An access port for a catheter, comprises a housing including a needle opening extending to a fluid chamber defined within the housing and a self sealing septum mounted within the needle opening and engaging an interior perimeter of the needle opening and a compression element disposed between the septum and the housing directing a radially inward compressive force to the septum.

Description:
BACKGROUND 
       [0001]    Long term access to the vascular system is often required for the treatment of conditions requiring regular administration of therapeutic agents, nutrition, blood products and/or other fluids or the withdrawal of fluids therefrom. In these cases, a catheter is typically inserted to form a path to the vascular system by advancing a distal end of the catheter into a blood vessel while a proximal end remains accessible. 
         [0002]    For example, the proximal end of such a catheter may be connected to a port which may be subcutaneous to minimize interference with patient activities while reducing the probability of infection. In these cases, a needle is often used to pierce the skin and penetrate a self-sealing septum of the port. However, repetitive punctures degrade the ability of the septum to reseal itself, eventually requiring replacement of the port. Extending this “stick life” or “puncture life” of the septum reduces the number of these replacement procedures consequently reducing the discomfort and cost associated with the procedures. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention is directed to an access port for a catheter, comprising a housing including a needle opening extending to a fluid chamber defined within the housing and a self sealing septum mounted within the needle opening and engaging an interior perimeter of the needle opening in combination with a compression element disposed between the septum and the housing directing a radially inward compressive force to the septum. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0004]      FIG. 1  is an exploded view showing an access port according to an embodiment of the present invention; 
           [0005]      FIG. 2  is a cross sectional view of the access port shown in  FIG. 1 , and 
           [0006]      FIG. 3  is a cross sectional view of another embodiment of the access port according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0007]    The present invention may be further understood with reference to the following description and to the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to devices for accessing the vascular system via a catheter and, more specifically, relates to an access port for the injection and/or withdrawal of fluids via a subcutaneous central venous access catheter. 
         [0008]    The present invention provides a method and system increasing the puncture life of the septum by applying a radially compressive force to the septum. In one exemplary embodiment, septum compression rings are provided to generate the radial compression, while minimizing the resulting axial force that may be applied to the housing assembly and to joints and bonds of the port. For example, the force may result from the septum compression rings providing an interference fit between the septum and a housing of the port. The septum compression rings may be formed, for example, by beads of additional septum material disposed around an outer diameter of the septum. 
         [0009]    As shown in  FIGS. 1 and 2 , an access port  100  which may, for example, be a subcutaneous venous access port connected to an implanted catheter via a connector  114 . The port  100  comprises a housing  102  including a base  104  and an upper portion  106  which defines an internal fluid chamber  105  in fluid connection with an outlet/inlet  113  in the connector  114  for fluid connection to a catheter. The base  104  and upper portion  106  may be joined to one another by, for example, a friction fit, mechanical interlocks, by bonding or with an adhesive, among other options. The housing  102  may further comprise suture loops  124  or similar elements to secure the device to tissue. A needle opening  116  is provided on a side of the port  100  facing the underside of the skin so that a needle inserted through the skin can pass through the opening  116  into the chamber  105  to fluidly couple to the catheter and, consequently, to the vascular system. 
         [0010]    The port  100  comprises a septum  108  held in place between the base  102  and upper portion  106 . For example, a perimeter of the septum  108  may be held between opposing surfaces of the base  104  and upper portion  106 . A compression ring element  110  is formed by one or more rings  130  disposed on the outer diameter of the septum  108 . The compression ring element  110  is placed in radial interference with inner surfaces  126  of the upper portion  106  of the housing  102 . The radial interference causes a substantially radial force A that compresses the membrane  112  of the septum  108 . The force has a minimal axial component, so that only a small axial force is applied to the joints and bonds of the housing  102  during use. 
         [0011]    According to the invention, the size, shape and number of the individual rings or beads  130  forming the compression ring element  110  may be selected to tailor the forces applied to the housing  102  and the septum  108  to a desired level or to position the forces in a desired manner. For example, the friction between the compression ring element  110  and the upper portion  106  may be reduced by reducing the surface area of the beads  130  contacting the surface  126  during assembly of the device, such as when the septum  108  is pushed in place. 
         [0012]    In one exemplary embodiment, the compression ring element  110  comprises three rings or beads  130  having a substantially semi-circular cross section. As shown in  FIGS. 1 and 2 , the beads  130  form peaks  120  in interference contact with the inner surface  126  of the housing  102  to generate the compressive force. Troughs  122  are formed between the peaks  120  reducing the surface area of the compressive ring element  110  in contact with the inner surface  126  of the upper portion  106 . The reduced contact area lessens the friction that must be overcome when inserting the septum  108  in the housing  102 , and also lessens the axial force applied to the assembly. 
         [0013]    A desired radial compression of the septum  108  may be achieved by selecting an appropriate number, shape and location of the rings or beads  130 . For example, the amount of compression and the distribution of the compressive force on the membrane  112  may be modified by selecting different parameters of the compression ring element  110 . The geometry of the individual beads  130  may be changed to achieve a desired compressive force and friction with the housing. For example, in addition to the semi-circular cross section of the beads  130  shown in the drawings, different geometries may be used such as triangular, trapezoidal or block shaped beads. These parameters may be varied as necessary to normalize the septum compression distribution across the volume of the septum. 
         [0014]    In a different embodiment, the compression force on the membrane  112  may be achieved without the addition of specific rings or beads. Instead, in this embodiment an oversized diameter of the septum perimeter creates the interference with the housing of the port and the resulting radial compression of the septum. The oversized septum perimeter may have, for example, a diameter slightly larger than an inner diameter of the opening in the housing component within which it is to reside. 
         [0015]    In yet another embodiment, the compression ring features may be applied to the housing of the port rather than to the septum. As shown in  FIG. 3 , a port  200  according to a further embodiment of the invention includes a housing formed of an upper portion  202  defining an opening  207  within which a septum  210  resides. Beads  206  formed on an inner surface  204  of the upper portion  202  form radial compression elements causing interference with the perimeter of the septum  210  and the resulting radially compressive force applied thereto. 
         [0016]    According to the exemplary embodiments of the invention, the compression rings may be formed of the same material as that of which the septum is formed. For example, the septum and/or the compression rings may be formed of silicone or any of a variety of materials of different durometer values. 
         [0017]    The present invention has been described with reference to specific exemplary embodiments. Those skilled in the art will understand that changes may be made in details, particularly in matters of shape, size, material and arrangement of parts. Accordingly, various modifications and changes may be made to the embodiments. The specifications and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.