fig1 illustrates an implantable drug port system 10 that includes a main body 11 which has a self - sealing septum 9 . the main body 11 has a connector 13 to which a catheter 14 is attached . an example of a similar port is product no . ap 06016 as marketed by arrow international , inc . the distal end of the catheter 14 has a generally hemispherical shape to minimize damage to the vessel walls where the catheter is inserted into a blood vessel of a human subject . near the distal end of the catheter is a cylindrical tube 17 that is the check valve of the present invention . fig2 is a longitudinal cross section of a distal portion of the catheter 14 having an elastomer cylindrical tube check valve 17 that is placed over an opening 18 . fig2 also shows a generally hemispherical , smooth distal tip of the catheter . the end portion 15 of the catheter can be formulated from a softer ( lower durometer ) plastic as compared to the catheter 14 . this attribute results in minimizing trauma to the vessel wall during insertion and long - term use . the tip 15 is joined to the main cylindrical portion of the catheter 14 at the junction 15 a . fig3 is an enlarged longitudinal cross section of the portion of the catheter 14 where the cylindrical tube check valve 17 is placed over a cylindrical groove 16 of essentially the same length as the tube 17 , which groove 16 is formed into the catheter 14 . an opening 18 having a length “ l ” is placed in the groove 16 directly under the check valve 17 . the length “ l ” of the groove 16 is typically between 5 % and 95 % as long as the length of the cylindrical tube check valve 17 . the length of the tube 17 should be approximately between 1 and 10 mm . an adhesive strip 19 on the side of the groove 16 opposite the opening 18 is used to fixedly attach the tube 17 into the groove 16 of the catheter 14 . the attachment of the tube 17 to the catheter 14 could also be accomplished by ultrasonic welding of the tube 17 to the catheter 14 . it is clearly seen from fig3 that , even if the tube 17 is not joined to the catheter 14 by means of an adhesive or by ultrasonic welding , the edges of the cylindrical groove 16 would by themselves cause the tube 17 to remain in the position shown in fig3 . to further guarantee that the tube 17 will not come out of the groove in the catheter 14 , the tube 17 would be shrunk into the cylindrical groove 16 . as is well known in the art of catheters , shrinking the tube 17 into the groove 16 can be accomplished by solvent swelling of the tube 17 , placing it over the groove and then allowing the solvent to evaporate which causes the tube 17 to shrink into the groove 16 . this effect can also be accomplished by heat shrinking of the tube 17 . in either case , the final inside diameter of the shrunk tube 17 , if unrestrained by the cylindrical groove 16 , would be smaller than the outer diameter of the groove 16 . this causes the tube 17 to be in tension which provides further assurance of a tight seal over the opening 18 . the hoop tension of the tube 17 also further guarantees that it will not come off the catheter 14 when fluid is injected into the catheter 14 . fig4 is a transverse cross section of the catheter 14 at section 4 — 4 of fig3 showing the catheter 14 , tube 17 , opening 18 and adhesive strip 19 . the opening 18 should have a width “ w ” that is approximately between 10 % and 95 % of the inside diameter of the catheter 14 . fig5 is a preferred embodiment of a distal portion of a check valve and catheter system 20 which includes a catheter 21 having a central lumen 27 and a generally cylindrical groove 29 . a multiplicity of holes 24 are placed through the wall of the catheter 21 within the generally cylindrical groove 29 . ideally there would be between one and ten of such holes , each of which could have a diameter that lies approximately between 10 % and 95 % of the inside diameter of the catheter 21 . the holes 24 can have a variety of distributions within the groove 29 , but an optimum distribution would have approximately three holes 24 aligned in an axial direction . the inside diameter of the catheter 21 would typically be between 0 . 2 and 5 mm , and the length of the groove 29 would typically be between 0 . 5 and 10 mm . shrunk into the groove 29 is a generally cylindrical elastomer tube check valve 22 that can be fixedly attached to the groove 29 by means of an adhesive strip 23 ( or ultrasonic bond ) along a line that is diametrically opposite from the holes 24 . because the tube 22 , if unrestrained by the groove 29 , would have an inside diameter that is smaller than the outside diameter of the groove 29 , there is formed an indentation 26 of the tube 22 into the holes 24 . such indentations still provide a continuously smooth , crack - free outer surface for the check valve catheter system 20 so that there will be no tendency for blood clots to form on the system &# 39 ; s outer surface . an important aspect of the design of the system 20 is the angled junction 25 where the proximal and distal ends of the tube 22 join to the proximal and distal ends of the groove 29 . the angled junction 25 , when used with a tube 22 that is shrunk into the groove 29 , assures that there will be no crack formed at the junction 25 into which a blood clot could form . if formed , such a blood clot could prevent the proper functioning of the check valve . the optimum angle “ a ” for the angled junction 25 would be approximately between 10 and 60 degrees with respect to the longitudinal axis of the catheter 21 . fig6 a and 6b are transverse cross sections of the system 20 at section 6 — 6 of fig5 . fig6 a shows the normal , unactuated position of the tube 22 and fig6 b shows the position of the tube 22 ′ when pressurized fluid is being delivered through the lumen 27 of the catheter 21 . fig6 a shows the catheter 21 having a lumen 27 and the tube 22 fixedly attached to the catheter 21 by an adhesive strip 23 . in the position of the tube 22 shown in fig5 and 6a , no blood from the vascular system of the human subject can enter into the lumen 27 . when a drug under pressure is placed through the lumen 27 , the open system 20 ′ is formed as shown in fig6 b . the pressurized drug would force an opening 28 to form between the catheter 21 and the expanded tube 22 ′. thus the drug can be delivered into the vascular system of the human subject . after the injection of drug is completed , the expanded tube 22 ′ will return to its normal diameter as shown for the tube 22 of fig5 and 6a . fig1 - 3 and 5 clearly show an elongated cylindrical catheter 14 or 21 and check valves 17 and 22 which together have a continuously smooth outer surface that would preclude the formation of blood clots on the systems outer surface , which blood clots could interfere with the functioning of the check valves . this superior design should provide highly reliable performance within a human artery or vein for many years without requiring frequent flushing with saline or heparin . although the catheter with check valve described herein is well suited for use with an implanted drug port , it should be understood that the catheter plus check valve can be used with any percutaneous drug delivery systems as well as any form of implanted drug delivery system . although catheters formed from a single plastic material are shown in fig2 - 5 , it should be understood that the catheters could be formed with one plastic material on the inside of the catheter and a second plastic material coaxially extruded over the first material . plastic materials such as ( but not limited to ) polyurethane , polyethylene , silicon rubber , teflon and nylon can be used to form the catheter or for either layer of a two layer catheter . furthermore , any plastic material that is a low durometer , highly elastic , biocompatible elastomer can be used for the check valve . examples of such a plastic are ( but are not limited to ) polyurethane , polyethylene and silicone rubber . it is expected that this simple check valve , which is merely a single elastomer tube placed over one or more openings , would be simple to build and operate and therefore it would be comparatively inexpensive and highly reliable . furthermore , it is expected that the designs described herein would have distinct advantages over slit - valve catheters which have a crack that can have a blood clot formed therein and also those catheters typically require some periodic flushing at least with saline solution . still further , the present invention can clearly be used in conjunction with multi - lumen catheters such as central venous catheters . in this regard , one or more lumens could have a check valve and one or more other lumens could have a continuous fluid connection into the blood vessel or have a slit valve . furthermore , although fig1 and 2 show the check valve to be located near the catheter &# 39 ; s distal end , it should be understood that the check valve is able to be located anywhere along the length of the catheter . when not injecting a drug or any other type of liquid through the catheter , it is desirable to retain a solution in the catheter that has the same osmolality as blood . this attribute would diminish any tendency for changing the nature of the liquid within the catheter because of osmosis of some component of the blood through the catheter wall . for this purpose , a normal saline solution could be used . the solution could also contain some anti - bacterial agent to prevent bacteria from forming within the catheter . various other modifications , adaptations and alternative designs are of course possible in light of the teachings as presented herein . therefore it should be understood that , while still remaining within the scope and meaning of the appended claims , this invention could be practiced in a manner other than that which is specifically described herein .
disclosed is a check valve for placement near the distal end of a catheter . a continuously smooth outer surface for the catheter with check valve system assures that there is no propensity for a blood clot to form in cracks on the system &# 39 ; s outer surface . the check valve is a formed from a low durometer , highly elastic , elastomer cylindrical tube that is shrunk into a cylindrical groove that would typically be located near the catheter &# 39 ; s distal end . when pressurized fluid is injected through the catheter , the cylinder that is placed over one or more holes in the cylindrical groove in the catheter is forced to expand radially outward which allows the fluid to be injected into the blood vessel . when the pressure is removed , the elastomer tube retracts to its normal position which position tightly covers the holes thereby preventing any blood from entering the catheter .