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BACKGROUND OF THE INVENTION
The present invention is directed to an implan-table device providing access to the blood circulatory system. While applications for the device can be for a variety of purposes, it is anticipated that principal uses will be in the field of hemodialysis of chronic uremic patients, as access for blood sampling and for treatment of diseases such as diabetes and for forms of chemotherapy and hyperalimentation.
Various approaches to implanted blood access devices are known; however, none of these have been enti-rely satisfactory. Shunt techniques have problems of in-fection, clotting and erosion. The arteriovenous fistula has some advantages over shunts, but there is a need for recurring needle puncture and there still are infection problems as well as other disadvantages.
It is also known to provide implanted blood ac-cess devices wherein access to the circulatory system is accomplished by means of a percutaneous spigot valve.
BRIEF DESCRIPTION_ OF TE~E INVENTION
In accordance with the present invention, an implantable ~enerally tubular T-shaped structure is provi-ded in which the stem of the T is constructed and arranged to cooperate with a novel needle structure that penetrates the seal means at the junction of the stem of the T with the balance of the T structure. By reason of the struc-ture of the invention, the interior stem portion of the T
can be rinsed clean and sterilized between each use without elaborate procedures, thus minimizing the likelihood of infection as a result of access to the circulatory system.
The invention thus provides an implantable blood access device which may be semi-permanently installed into the circulatory system and used repeatedly. This invention 1 ~ 62~2 also has a low profile body external portion which mini-mizes the possible catching o~ clothing and the like on the external portion.
Cooperating structures include needle assemblies which provide access to the circulatory system through the septum and a flexible cap for sealing the stem of the im~
plantable de~ice from the outside atmosphere.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exploded pictorial view of a de-vice in accordance with the invention including the implan-table portion, a two needle cooperating member and a modi-fied forceps for use in assembly and disassembly of the implanted septum assembly;
Figure 2 is a plan top view of the implantable T-shaped assembly;
Figure 3 is a side elevational view partly in section as taken along the lines 3-3 of Figure 2;
Figure 4 is a plan view of the septum;
Figure 5 is a section view along lines 5~5 of Figure 4i Figure 6 is a plan view of the bottom or interior facing side o~ the septum;
Figure 7~s a sec Lonal view of a device in ac-cordance with the invention with the cooperating needle assembly in operative engagement with the implantable portion;
Figure 8~is a side elevational view partly in section of the T-shaped implantable structure and cover assembly;
Figures 9 and 10 illustrate a needle and sheath assembly showing respectively the sheath covering the opening in the needle end and withdrawn to expose the opening;
Figure ll is a top plan view of an assembly in-cluding a pressure plate with an aligning peg;
Figure 12 is a side cut away view of the assembly of Figure ll where the coating with pyrolytic carbon is not included;
Figure 13 is a side elevational view, partially cut away of a modified sealing cap.
DETAILED DESCRIPTION OF THE INVENTION
_ . . _ Referring to the drawings, there will be seen in Figure l a device in accordance with the invention which includes a T-shaped unitary tubular body generally desig-nated 10 having a stem portion ll and a straight tube por-tion 12. Body 10 is formed of a unitary body of a biolo-gically compatible material such as titanium. It is highly advantageous that body 10 be of a unitary construction to eliminate extraneous caviti~s at points of assembly of non-unitary bodies. At least the e~ternal surfaces of body 10 may be coated with a continuous layer o~ pyroly-tic carbon to enhance biocompatibility. This is particu-larly of importance for surfaces that will be blood con-tacting surfaces such as the bore when blood is a flow therethrough. Pyrolytic carbon coatings are known to be biologically compatible materials and have been used in implanted structures. See, for example, U. S. Patent No.
3,783,868. Alternatively, the body 10 may be uncoated titanium or other rigid material. As illustrated in Figure 7, a snugly fitting sleeve member 34 of graphite lines the interior of tube 12 and underlies coating 13.
For coating the interior of a tube, it has been found desirable to have the graphite sleeve to serve as a sub-strate for the pyrolytic carbon.
Expanded polytetrafluorethylene tubes 14 are shown joined to ends of 12 by slipping over these ends.
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Jacron (polyethyleneterephthalates) or other body compatible polymeric materials may be used rather than polytetrafluor-ethyiene (Teflon*). The expanded polytetrafluorethylene slipped over the ends of 12 may be provided as an interme- ¦
diary for joining blood vessels to the assembly 10. A
Teflon* shrink band 57 aids in holding the sleeve on. A
suitabl~ expanded polytetrafluorethylene is sold under the trade name Gore-Tex by W. L. Gore! Company of Newark, Dela-ware. It should be understood tha~ tubes 14 are elective in that it is not necessary that they be present.
Alternatively, an uncoated device 10 as shown in Figure 12 may be directly placed in a blood vessel. In such a case, the blood vessel would be slit longitudinally for a sufficient distance for the device 10 to be inserted and the vessel drawn around the device and sutured into place. A collar member 29, as described below, would be used around a portion of the stem to aid in tissue in-growth to the stem portion.
As can best be seen in Figures 3 and 7 body 10 is formed with an internal extension 15 which substantially provides a separation of the internal chamber of T-shaped member 11 from the cavity of portion 12 except for the openings 16 and 17. Member 15 provides a support surface for a septum member 18. Member 18 is formed of an elas-tomer such as natural rubber a~d, as can be seen in Figures 2, 4, 5 and 6, has a broadly elliptical configura-tion. The purpose of this shape i5 best understood with reference to Figuxe 2.
In Figure 2, there is seen a top view of stem 11. As can be seen, stem 11 has a generally round opening.
There is provided an internal shape in the opening along the axis of tube 12 which conforms generally to the ends 19 of the septum 18 for indexing purposes.
* Trade Mark 3 62d~2 As can be seen in Figures 2, 4, 5 and 6, septum 18 is pre-cut in a three-directional star or tricuspid form 20. Preferably, although not mandatorily, the hole 21 may be completely through septum 18. These cuts faci-litate passage of a needle through the septum. At the outer surface of the septum 18, there is a counter sunk region 36 for receiving a needle. The cuts 20 are posi-tioned so that when member 18 is indexed into the opening of T-stem 11, cuts 20 are centred on openings 16 and 17.
As a preferred alternative, the needle opening in septum 18 may be actually formed into the septum at the time the septum is fabricated. When the septum is pressed into place, the compression will seal the openings 21 (see Figures 11 and 12 also1.
Overlying septum 18 is a pressure plate 22 of titanium ~r the like which defines openings 23 which are spaced to conform in position to slits 20 and openings 16 and 17. Pressure plate 22 is, in turn, locked into enga-gement with septum 18 by a spring retaining ring 240 A cap member 26 snaps over a flanged edge 27 as `seen in Figure 8 and is held in sealed relationship there-with by a retaining ring 28. The lower flared edge 70 of cap 26 will be spaced, in use, slightly above the skin 2S
o~ the user. Pressure contact with the skin by edge 70 is undesirable as necrosis may occur. Overall t there is provided a profile for the exposed external portion of member 10 that is less likely to catch an object such as clothing. Cap 26 also provides a means whereby an anti-septic such as Betadine* (iodine polyvinylpyrolidone complex) may be included in cavity 30 to maintain the unit sterile between usage.
The assembly described above is implantable in the patient by surgical techniques that are known and orm * Trade Mark ( 1 1 62~52 no part of the invention. It is desirable to have the amount of the stem protruding above the skin line at a minimum amount compatible with permittiny a cap member seal. Implantation may be in various manners and modes including, but not limited to, the following: by anasto-mosis to 14, i.e. by splicing the ends of a blood vessel to opposite ends of assembly 10. Assembly 10 may be positioned into a blood vessel that has been longitudinal-ly slit for a distance sufficient to permit insertion of the device. In this latter case, the blood vessel is su-tured about the device to form a seal, and the sleeves 14 are not ~sed.
To aid in accomplishing tissue growth onto the portion of the stem 11 below the skin line 25, a collar member 29 ~f porous plastic material such as polyethylene-terephthalate, soId by E.I. Dupont under the trade mark Dacron may ~e used. The portion of stem 11 above the dermis region is uncoated to reduce the risk of infection occurring by bacteria making their way down along the collar 29. If the external surface of stem 11 is titanium, the titanium may have a matte surface in the region of collar 29 and thus, eliminate need of collar 29.
When access is to be made to the blood system, the cap 26 is removed~ The interior cavity region 30 thus exposed can be rinsed with appropriate sterilizing agents that are removed prior to insertion of a needle through openings 23, 20 and 16. It is prefPrred that ca-vity 30 be filled with and holds a sterilizing solutipn, such as described previously, between usage. This steri-lizing solution can be placed in cavity 30 before closingwith cap 26, or a hypodermic may be used to inject the solution through the cap. Desirably, the needle used to penetrate the septum will have a closed rounded end with *Trade Mark -- ~ D~2~l52 an opening 34 at the side thereof. A blood sample can be drawn or material such as drugs inserted through the need-les as desired.
The device described can be implanted into a patient and remain essentially permanently. However, if a need arises to replace the septum 18 after prolonged use, this can readily be done without need of surgical proce-dures. A modified forceps 31 is machined or ground to provide tips 32 of a size to be positioned into holes or recesses 33 in retaining ring 24. The ring may be with-drawn along with pressure plate 22 and septum 18 for cleaning and/or replacement. Of coursel steps should be taken to block the body blood pressure so as to prevent appreciable blood flow outwardly through openings 16 and 17 during the assembly or disassembly.
To insure a tight seal of septum 1~, with the interior wall of stem 11, it may be desirable to shape the side walls 35 of the septum in a concave manner as shown.
A second purpose in such shaping is to provide for the displaced material of septum 18 resulting from introduc-tion of needles through the septum.
While the implanted assembly 10 can be used with conventional hypodermic assemblies, it is desirable to uti-lize a cooperating assembly such as a member 40. Even when a simple needle is on a standard syringe, it is desirable that the needle have a rounded end as will be described below. Member 40 is constructed of a cylindrical block of metal 41 through which two hollow needle members 42 and 43 extend in sealed relationship to member 41. These neeale members are positioned so as to index with openings 23 in pressure plate 22. As can best be seen in Figure 7, the needles have rounded closed ends 44 and have a side opening 45 and 46, respectively. As shown, the needle i5
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solid (cavityless) below the lower edge of openings 45 and 46. This construction is highly advantageous. The roun-ded closed end readily passes through septum 18 with a reduced tendency to cut and break pieces of a septum as a result of passage therethrough over use of a conventional hypodermic needle. The solid lower end avoids the pre-sence of entrapped air. One can also position the openings in the needles so that, if blood flow is in the direction shown by arrow ~7, the needle opening 45 is directional to withdrawal of blood while opening 46 is directional to return of blood. The top of the needle can be jointed to any suitable construction to be connectable to external blood flow tubing or other types of apparatus.
Referrin~ now to Figures 9 and 10, there is illu-strated a form of needle assembly generally designated 50 for use with the implanted portion 10. In this form, there is provided a block of plastic or metal 51 which is of a size to fit down into the cavity of stem 11 in a manner similar to that shown in Figure 7. However, in this in-stance, member 51 includes an off-centre opening there-through 52 for use as will be described below. Needle members 53 and 54 pass through member 51 and in conjunc-tion with some type of tubing, syringe or the like (not shown). The needle members are of a substantially inden-tical configuration to that described with respect to Figure 7. A sheath assembly 55 is provided having two rigid sleeve members 56 and 57, respectively, that are of a hollow configuration, such as a 51ip over need-~es 53 and 54, respectively. Members 56 and 57 are welded or other-wise secured to plate 55. In an uncompressed condition,the assembly 55 i5 held in position as seen in Fi~ure 9-by a spring member 58. In this position, the openings 59 and 60, as best seen in Figure 10, are covered by sleeves 1:1 624$~ `
56 and 57. As can be seen in Figures 9 and 10, the sleeve members have a rounded shoulder 61 at the lower edge there-of which facilitates the penetration of the openings through septum 18. The length of sleeves 56 and 57 are sufficient to insure that the openings 59 and 60 do not act as a cut-ting edge to slice material of the septum off as the need-les are penetrated through the septum. Once the sleeves have penetrated through the septum by assertion of the assembly into the top of stem 11, resistance of the pres-sure plate 22 and retaining ring 24 force spring 58 into a flat shape as illustrated in Figure 10, and the sleeves 56 and 57 no longer cover openings 59 and 60.
With reference to Figures 11 and 12, it will beseen that the implanted portion of the device is substantially identical to what has heen described previously with res-pect to Figures 1 through ~, except for the absence of pyrolytic coating and other diffexences to be described.
The differences lie in the usage of a pressure plate 62 which has projecting upwardly therefrom an off-centre lo-cator pin 63 which is positioned so as to co~perate withopening 52 of the needle assembly as illustrated in Figures 9 and 10. This locator pin provides two functions. First, when one it utilizing the needle assembly~ it insures pxo-per alignment of the needle members with the openings through the pressure plate and septum. Second, when the implanted device is not being used to gain access to the blood vessels, the pin 63 is utilized as a further atta-ching means to secure a cap 64 (see Figure 13~ to the exposed portion of stem 11. As can be best seen in Figure 13, the cap member is adapted to slip over the edges of the stem portion member 10 to provide a sealing engagement therewith. In this instance, rather than h~ing a retain-ing ring 28 completely surround the cap and stem por~i~n, . _g_ B2~
a built-in retaining ring 65 aids in gripping the locater stem 63 insuring that the cap is held in tight relation-ship with stem 11. ~s in the instance of the description with regard to Figure 8, the cavity between the pressure plate 22 and the top of the stem 11 is again normally kept full of a sterilizing solution so as to insure that the device is ready for the next actual access use to the bloodstream.
It will be noted in Figures 11 and 12 that the septum member 18 is shown as having a precast opening 21 therethrough described above. As the septum has been squeezed into place in the stem, the hole has been closed by the natural resiliency of septum 18, although it readi-ly opens to accept needles.