Abstract:
A medical device needle receiving port configured to stop a needle&#39;s penetration without physically engaging the needle&#39;s tip thereby reducing the likelihood of tip damage. The port preferably incorporates a particulate chamber for collecting particulates larger then a fluid outlet dimension.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional application 60/549,288 filed 02 Mar. 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to medical devices and more particularly to a port suitable for use in an implantable drug delivery device for exchanging fluid with a hypodermic needle.  
       BACKGROUND OF THE INVENTION  
       [0003]     Various medical devices, e.g., implantable drug delivery devices, have one or more needle receiving ports (e.g. to access a reservoir or a catheter) which may include a needle access hole dimensioned to deny access to needles larger than a predetermined diameter. For example, U.S. Pat. No. 6,293,922 describes a port comprised of a conical depression leading to a central access hole which has “a diameter substantially the same as the predetermined diameter for preventing access to the septum” by oversized hypodermic needles. Needles having diameters smaller than the predetermined diameter are able to pass through the access hole and septum to exchange fluid with the reservoir or catheter. Generally, a physical stop, e.g., a pad made of firm, biocompatible polymer material, is inserted below the septum to engage the needle&#39;s tip to limit penetration and provide a tactile feedback to the user advising that the tip of the needle has bottomed. Unfortunately, however, the fragile needle tip can sometimes engage a surface which may cause it to curl up like a fish hook. The hook portion can then damage the septum when the needle is withdrawn from the port.  
         [0004]     Implantable medical device ports may also incorporate some type of filtering means, e.g., a sintered or mesh material, to prevent the introduction of particulate matter into the reservoir or catheter.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is directed to a medical device needle receiving port configured to stop a needle&#39;s penetration without physically engaging the needle&#39;s tip thereby reducing the likelihood of tip damage.  
         [0006]     Typical hypodermic needles have a cannula or barrel portion whose outer diameter D 1  indicates the needle&#39;s size, e.g., a 25 gauge needle has an outer diameter between 0.0205 and 0.0195 inches. The distal end of the cannula typically includes a beveled surface which forms a needle point end having an axial length L 1  and an outer diameter which diminishes from D 1  adjacent to the cannula to D 2  at the needle tip. A port, in accordance with the present invention, includes a needle stop member having a hole defining a diameter D 3  where D 1 &gt;D 3 &gt;D 2  such that the needle point end can extend into the hole but is prevented from passing therethrough as a consequence of the point end surface engaging the stop member adjacent to the hole. The hole is configured to define an obstruction-free axial length, or depth, L 2  where L 2 &gt;L 1 . Thus, the fragile needle tip is prevented from engaging any stop surface and damage to the tip is avoided.  
         [0007]     A port in accordance with the invention preferably also includes a particulate collection chamber located beyond the needle stop hole. The collection chamber has one or more fluid outlets dimensioned to prevent particulate matter, introduced by the needle&#39;s insertion, from passing through to the reservoir or catheter. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0008]      FIG. 1  is a plan view of an exemplary implantable drug delivery device having two needle receiving ports;  
         [0009]      FIG. 2  is an enlarged sectional view taken substantially along the plane  2 - 2  of  FIG. 1  showing a preferred port construction in accordance with the present invention;  
         [0010]      FIG. 3  is a plan view of  FIG. 2  showing the port entrance opening;  
         [0011]      FIG. 4A  is an enlarged view of  FIG. 2  showing how the penetration of a hypodermic needle is stopped without engaging the needle tip;  
         [0012]      FIG. 4B  is identical to  FIG. 4A  but shows the needle rotated by 90°.  
         [0013]      FIG. 5  is an exploded perspective view of the needle receiving port of  FIG. 3 ; and  
         [0014]      FIG. 6  is a sectional view taken substantially along the plane  6 - 6  of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0015]     Attention is initially directed to  FIG. 1  which is a plan view of an exemplary implantable drug delivery device  10  intended to be configured in accordance with the present invention. The device  10  comprises a housing  12  enclosing an interior volume (not shown) and defining first and second needle receiving ports  14  and  16 . Port  14  is adapted for accessing an internal fluid drug reservoir (not shown) to fill or evacuate the reservoir. Port  16  is adapted for accessing, via port  18 , a catheter  19  to either extract a sample and/or introduce a fluid into the catheter. The housing  12  includes one or more interior fluid passageways (not shown) for coupling the reservoir via a controllable fluid transfer device (not shown), e.g., a pump or valve, to the port  16  for delivering fluid medication via. catheter  19  to a patient&#39;s body site.  
         [0016]     As depicted in  FIG. 1 , port  14  typically includes a conical side wall  20  converging toward a central needle receiving entrance hole  21 . The hole  21  is preferably dimensioned to have a diameter small enough to prevent the entry of needles larger than a given size. As depicted, port  16  includes a side wall  23  converging toward a needle receiving entrance opening  24  which is shown for exemplary purposes as comprising a slot having a width narrow enough to prevent the entry of needles larger than a given size. A port in accordance with the present invention ( FIGS. 2-6 ) can be configured with an entrance opening in the form of either a hole, e.g.  21 , or a slot, e.g.  24 .  
         [0017]     Attention is now directed to  FIGS. 2-6  which illustrate a preferred embodiment of an exemplary port, e.g., port  16 , in accordance with the present invention. The needle receiving port  16  is comprised of an inverted cup shaped port body  30  defining an interior cavity  31  having an internal diameter  32 . A septum  34 , typically a pliable self healing membrane, is mounted in the cavity  31  above a needle stop member  36 . A bottom cover  40  is sealed along interface  42  to the inside wall of cavity  31  to retain the septum  34  and stop member  36  in place. The sealed interface  42  is fluid tight to prevent leakage.  
         [0018]     The needle stop member  36 , in a preferred embodiment, includes a funnel shaped recess  44  having a side wall  45  which converges from an entrance mouth  47  to a needle stop hole  48 . In accordance with the present invention, the hole  48  has a diameter D 3  ( FIG. 4A ) selected such that D 3  is less than the outer diameter D 1  of the cannula of an acceptable hypodermic needle N 1  ( FIG. 4A ).  
         [0019]     More particularly,  FIGS. 4A and 4B  depict an exemplary needle N 1  having a cannula  49  and a point end  50  formed by an oblique surface  51 . The point end terminates at a needle tip  52 . As depicted in  FIG. 4A , the outer diameter of the cannula  49  is represented by D 1 . The point end  50  has an outer diameter which diminishes from D 1  adjacent to the cannula to D 2  (close to zero) at the needle tip  52 . The axial length of the point end  50  is represented by L 1 . In accordance with the present invention, the stop hole  48  diameter D 3  is selected to be less than D 1  and greater than D 2 . Furthermore the depth of stop hole  48  is selected such that L 2 , the sum of the hole&#39;s axial length plus an obstruction-free depth therebeneath, is longer than the axial length L 1  of the needle point end  50 .  
         [0020]     In use, the needle point end  50  will be inserted into the port to pierce the septum  34 . The point end will then be guided by side wall  45  of recess  44  into stop hole  48 . Because D 1 &gt;D 3 &gt;D 2 , the point end  50  will project into hole  48  with the oblique, or bevel, surface  51  engaging the stop member  36  adjacent to the hole  48 . Because L 2 &gt;L 1 , the needle tip  52  is held out of engagement with any surface thereby avoiding tip damage.  
         [0021]     In the preferred embodiment of the invention, the needle stop member  36  is relieved at  54  to form a particulate chamber  38  between the bottom cover  40  and the stop member  36 . The hole  48  opens into the particulate chamber  38 . The circumferential wall  58  ( FIG. 6 ) of the particulate chamber  38  has one or more radial openings  60  dimensioned no larger in any direction than a dimension M. The opening(s)  60  extend radially outward from the inner surface  62  to the outer surface  64  of the circumferential wall  58  to a circumferential fluid passageway  66 . An inlet tube  68  ( FIG. 2 ) and an outlet tube  70  are coupled to the passageway  66 . The inlet tube  68  typically carries fluid from the aforementioned reservoir and fluid transfer means (not shown) and the outlet tube typically carries fluid to the catheter port  18 . By limiting the dimensions of openings  60 , the chamber  38  will retain any particulate matter greater than the dimension M, which otherwise could be disadvantageously introduced by the needle into the fluid flow to the catheter.  
         [0022]     From the foregoing, it should be recognized that an improved needle receiving port has been disclosed herein characterized by a stop member having a hole dimensioned to receive a needle point end for stopping axial penetration of the needle without engaging the needle tip. Moreover, the preferred embodiment efficiently incorporates a chamber for trapping oversized particles.  
         [0023]     Although only a single specific embodiment has been described in detail herein, it should be understood that this embodiment is exemplary of various alternative configurations which may occur to those skilled in the art which are consistent with the teachings of the present invention and within the scope of the appended claims.