referring to fig1 there is depicted an arterial cannula 10 constructed in accordance with the principles of the present invention implanted within an arterial lumen 20 . the cannula is shaped generally like a &# 34 ; t &# 34 ; and is comprised of two primary sections ; the tubular body 25 and the access leg 30 . the intravascular tube 25 is an elongated tube having a single lumen 26 , open on both ends . when implanted within the lumen 20 , the tubular body 25 will have an upstream end 27 , and a downstream end 28 , determined by the direction of blood flow in the vascular structure 20 . in fig1 the direction of blood flow is indicated by the arrow 21 . the cannula however , can be implanted in either orientation . the access leg 30 is an elongated tube having a single lumen 31 . a distal end 32 of the access leg 30 is connected to the tubular body 25 , generally near the mid - point thereof . the access leg 30 may extend from the tubular body 25 at any angle , including a 90 ° angle , but it is preferred that the access leg 30 of the cannula 10 extend from the tubular body 25 in a direction which is inclined toward the upstream end 27 of the tubular body 25 . the angle formed between the access leg 30 and the upstream end 27 of the tubular body 25 is an acute angle . the angle formed between the access leg 30 and the downstream end 28 of the intravascular tube 25 is an obtuse angle . a preferred angle between the access leg 30 and the upstream end 27 of the tubular body 25 is between 30 ° and 60 °, usually being approximately 45 °. a valve 40 is preferably located at the point of connection between the distal end 32 of the access leg 30 and the tubular body 25 . the preferred valve 40 is a slit valve . such valves are well known in the art . as best shown in fig3 the slit valve is comprised of a membrane 41 which has a slit 42 extending partially across the membrane 41 and completely through the membrane 41 . the membrane 41 acts to prevent fluid flow through the lumen 31 of the access leg 30 , except when adequate differential pressure exists on opposite sides of the membrane 41 to cause the slit 42 to open , as is shown in fig4 . the membrane 41 is located such that the side of the membrane 41 located towards the vascular structure is essentially flush with the inner wall of the intravascular tube 25 . when the catheter 10 is not in use , the membrane 41 of the valve 40 and the inner surface of the tubular body 25 form a continuous tube that has minimal impact on normal blood flow through the arterial lumen . in the preferred embodiment , the membrane 41 is comprised of a portion of the side wall of the tubular body 25 . to create the valve 40 , a slit 42 is cut in the side wall of the tubular body 25 to correspond to the point of connection of the access leg 30 . in this manner , when the valve is closed , the inner surface of the tubular body 25 is a continuous smooth surface which has minimal impact on normal blood flow . when the valve 40 opens , fluid flow between the lumen 31 and the access leg 30 and the lumen 26 of the intravascular tube 25 occurs . the outer circumference of the tubular body 25 is provided with expanded barbs 29 to hold cannula 10 in place within the vascular structure 20 . one each of these expanded barbs 29 may be placed proximate the upstream end 27 and proximate the downstream end 28 of the tubular body 25 . the expanded barbs 29 have an enlarged outer circumference which tends to slightly distend the wall of the arterial lumen 20 , providing a snug fit , but not preventing the continued viability of the arterial wall . additional areas of expanded outer diameter ( not shown ) may be spaced along the outer surface of the tubular body 25 . the fit between the arterial wall and the tubular body 25 must be of sufficient tightness to prevent passage of blood between the arterial wall and the outer surface of the tubular body 25 . optionally , it may be possible to place ties or clamps ( not shown ) about the outer wall of the artery adjacent to the expanded barbs 29 to hold the cannula 10 in place . all blood flowing through the arterial lumen should pass through the lumen 26 of the tubular member 25 . in use , the proximal end 33 of the access leg 30 of the cannula 10 may be connected to a subcutaneous port , or may extend transcutaneously ( i . e . through the skin ). the cannula 10 is suitable for use with any device requiring or facilitating intermittent vascular access . the cannula 10 of the present invention is particularly useful for arterial access in hemodialysis , since such treatment requires large quantity blood flow , and requires relatively frequent vascular access over a long period of time . for such use two cannulas 10 may be surgically implanted . one of the devices is implanted in an artery . the other device is implanted in a vein . usually , however , a conventional in - dwelling catheter will be used for the venous access since vein access is easer to establish . in this manner both the venous and arterial circulations are accessed separately , without fistulous communication . current use of shunts , which create a fistulous connection between artery and vein , not only involve a more extensive surgical procedure , but are fraught with problems including increased cardiac output requirements , damage to the vein due to arterial pressure waves , and frequent shunt occlusion or thrombosis . during hemodialysis , blood is removed from the arterial cannula 10 implanted in an artery and is subjected to the extracorporeal dialysis circuit . removal occurs by reducing the pressure in the access leg 30 of the cannula 10 , until the slit valve 40 opens , and blood flows from the tubular body 25 into the access leg 30 . the treated blood is returned to a cannula implanted in a vein . at the completion of the dialysis treatment of the access leg 30 of cannula 10 is filled with anti - coagulant fluid , to discourage thrombosis and occlusion of the access legs 30 . a similar process may be used for apheresis or exchange transfusion procedures . additionally , a single arterial cannula 10 may be used for frequent administration of medication into artery or vein , or for large volume fluid infusions . surgical implantation of the arterial cannula 10 is a straight forward procedure . the chosen artery is located and isolated , and a small incision is made in the lumenal wall . the tubular body 25 of the cannula 10 is inserted into the incision , with the access leg 30 extending out of the lumen through the incision . the incision is then sutured to provide a snug fit around the access leg 30 . the proximal end 33 of access leg 30 of the cannula 10 is then attached to a subcutaneous port ( described hereinafter ) or other device requiring intermittent vascular access . materials of construction well known in the art may be used for the manufacture of the cannula 10 . however , it is important that the tubular body 25 be particularly biocompatible with the arterial wall 20 , since it is intended that the wall in contact with the cannula 10 remain viable . since the cannula 10 , unlike most prior art catheters , is not designed to be pushed or threaded some distance into a blood vessel , the access tube of the cannula may be comprised of relatively flexible material . this may be accomplished by including a spring or other reinforcement element ( not shown ) within the walls of the cannula 10 to maintain hoop strength . the materials of construction of the tubular body should be of sufficient rigidity to maintain the preferred angle between the access leg 30 and the tubular body . the dimensions of the catheter 10 depend upon the size of the vascular structure 20 to be accessed . typically the outer diameter of the tubular body 25 will be between 3 and 10 mm , with a wall thickness of approximately 0 . 5 to 1 mm , yielding a lumen 26 diameter of between 1 and 8 mm . a typical length of the tubular body 25 from upstream end 27 to downstream end 28 is between 10 and 50 mm . the maximum diameter of the outer surface of the expanded barbs 29 is approximately 30 percent greater than the diameter of the tubular body 25 where no expanded barb 29 is present . the length and flexibility of the access leg can vary depending upon the use of the catheter 10 . for use with subcutaneous ports an access leg 30 length of approximately 25 mm to 700 mm , usually about 100 mm is generally sufficient . referring now to fig5 - 8 , an exemplary implantable port 100 will be described . the implantable port 100 may be used with either the arterial cannula 10 described above , or with more conventional in - dwelling cannula which may be used in systems for venous access , as described in more detail hereinafter . the port 100 includes a single hematologic chamber 125 , where the base and sides are formed by a circumferential wall 126 . the port 100 further includes wall 126 and a cover 120 which holds a replaceable diaphragm 127 in place . the cover 120 is removable to allow replacement of the diaphragm 127 if needed . a base 129 of the port 100 comprises a flange having apertures 130 which permit fastening of the port to underlying tissue , typically using sutures . a connector 128 open to one end of the chamber 125 is connectable to the free end of access leg 30 which forms part of the arterial cannula 10 described above . referring now to fig9 and 10 , an alternative embodiment of an arterial cannula 200 constructed in accordance with the principles of the present invention will be described . the cannula 200 includes both a tubular body 202 and an access leg 204 . the access leg 204 comprises a portion adjacent to the tubular body 202 including a plurality of circumferential ribs or corrugations 206 which provides substantial hoop strength to the leg without diminishing the desired flexibility . the remainder of the access leg 204 comprises larger sections 208 , with the distal end 210 being suitable for attachment to the vascular port 100 at connector 128 , as described previously . the tubular body 202 comprises a molded insert 230 including a main body portion 32 and a branch portion 234 . an isolation valve 36 is formed at the end of branch 234 , generally as described above with previous embodiments . tubular body 202 is connected to the adjacent end of the access leg 206 by over molding an exterior body 238 . usually , a titanium tube 240 is placed within the junction between the end of access leg 206 and the end of branch portion 234 . the tube may be titanium or other biocompatible metal . the insert 230 is typically formed from a relatively soft material , such as 40d to 50d silicone rubber . the outer portion 238 of the tubular body 202 is formed from a similar material , such as 50 d silicone rubber . the access tube may be also formed from silicone having a hardness of 40d to 50d . conventional molding techniques may be used to form all these parts . referring now to fig1 , the tubular body 202 of the arterial cannula 200 may be implanted within an artery a by first surgically exposing the artery and thereafter forming an incision in the side of the artery . the tubular body 202 is the introduced through the incision , and the incision sutured to hold the body within the arterial lumen . the access leg 204 is then moved to a location where the arterial port 100 is to be implanted . note that the entire assembly of the arterial cannula 200 and arterial port 100 may be implanted together within a single incision . alternatively , the arterial cannula 200 and the arterial port 100 may be separately implanted , with the access leg 204 being separately positioned therebetween . referring now to fig1 - 14 , a third embodiment of a vascular cannula 300 constructed in accordance with the principles of the present invention will be described . the cannula 300 includes both a tubular body 302 and an access leg 304 . the access leg 304 is generally as described above with respect to access leg 204 in the previous embodiment . the tubular body 302 , however , differs significantly from the tubular bodies described previously . in particular , tubular body 302 is intended and adapted for anastomotic attachment within a single blood vessel or between two blood vessels , typically an artery and a vein . in the embodiment of fig1 - 14 , the tubular body 302 comprises a continuous tube formed from a single material or composite structure , where the construction and material ( s ) are both of type generally employed for vascular grafts and implants . the construction of vascular grafts and implants is well known and well described in patent and medical literature . see , e . g ., u . s . pat . nos . 4 , 728 , 328 ; 4 , 731 , 073 ; 4 , 822 , 361 ; 4 , 842 , 575 ; 4 , 892 , 539 ; 4 , 955 , 899 ; and 4 , 957 , 508 , the full disclosures of which are incorporated herein by reference . preferred materials for forming the tubular body 302 include expanded polytetrafluoroethylene ( eptfe ), woven polyester , expanded polyurethane , and the like . the access leg 304 is joined to the tubular body by a valve assembly 306 including a flange 308 and a collar 310 . the flange is secured to an inside surface 312 of the tubular body 302 , typically by an adhesive , such as a silicone adhesive . the collar 310 extends out through an opening formed in the wall 312 , preferably at an angle in the range from 30 ° to 90 °, often from 30 ° to 60 °, typically being 45 ° as illustrated . the collar 310 is attached to a lower end of the access leg 304 . conveniently , such attachment may be effected using an inner sleeve 314 which is coaxially received in the collar in the end of the access leg 304 . these joints may also be formed or reinforced by an adhesive , usually a silicone adhesive . the valve assembly 306 further comprises a split - membrane valve 320 at its lower end . a split 322 extends in the axial direction of the tubular body 302 and opens and closes in response to a differential pressure across the valve . referring now to fig1 , instead of a flange 308 , as illustrated in fig1 and 14 , the valve assembly 306 of vascular cannula 300 can be formed with a full tubular insert 308 &# 39 ;, as shown in fig1 . all other aspects of the cannula 300 would remain unchanged . use of the tubular insert 308 &# 39 ; is advantageous since it forms a more secure attachment to the tubular body 302 . the flange construction 308 , in contrast , is advantageous in that it is less restrictive to the flow lumen through tubular body 302 . referring now to fig1 , a fourth embodiment of a vascular cannula 400 constructed in accordance with the principles of the present invention will be described . the cannula 400 includes a tubular body assembly 402 and an access leg 404 . the access leg 404 will generally be a silicone rubber or similar tube , generally of the type described above in connection with the previous embodiments . the tubular body assembly 402 comprises a rigid middle section 406 and two end sections 408 and 410 , where the end sections are generally formed from tubular material of a type employed for fabricating vascular grafts and implants , also as described above . the rigid middle section 406 may be a hard plastic , but will usually be a biocompatible metal , such as titanium , vanadium , stainless steel , or the like . the middle section will have a silicone slit valve 412 positioned adjacent its lumen in a boss 414 formed on the side of the section . the slit valve is held in place by a male connector 416 which will usually also be composed of a metal , more usually being titanium . an o - ring 418 helps maintain the seal , and the connector 416 may be attached to the boss 414 by threading or any other conventional attachment . the access leg 404 is attached over a barb 418 formed at the upper end of the connector 416 . the ends 408 and 410 are attached to barbs 420 and 422 formed at each end of the middle section 406 . the attachment may be effected using an elastic ring 430 or a clamp ( not shown ), or any equivalent means . the remote ends 408 and 410 may be connected to a blood vessel by conventional anastomotic techniques . referring now to fig1 and 18 , a fifth embodiment of a vascular cannula 500 constructed in accordance with the principles of the present invention will be described . instead of a tubular body , as described in previous embodiments , the cannula 500 includes a patch 502 which is used to secure the cannula to a blood vessel , typically a large vein . the patch 502 may be formed from any of the materials described above for tubular bodies , including eptfe , woven polyester , expanded polyurethane , preferably being formed from eptfe . an access leg 504 is constructed generally as described above for previous embodiments , except that it terminates in a small flange 506 , typically having a diameter in the range from 4 . 5 mm to 45 mm , usually from 15 mm to 25 mm . the flange 506 comprises slit valve 508 and is attached at its periphery to an aperture formed in the patch 502 . the patch 502 will be secured to the target blood vessel , typically being inserted through an incision , secured to the outside of the blood vessel , e . g . by suturing , by tissue adhesives , or the like , or sutured or otherwise secured into a region of the blood vessel which has been cut away . the slit valve 508 will thus be positioned adjacent to the blood vessel lumen , as with previous embodiments . although the foregoing invention has been described in some detail by way of illustration and example , for purposes of clarity of understanding , it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims .
a catheter with valve for implantation in a vascular structure of a living being . the catheter is in the general shape of a &# 34 ; t &# 34 ; with the top of the &# 34 ; t &# 34 ; implanted within the lumen of or anastomotically attached to a vascular structure . the lumen of the implanted portion of the catheter completely occupies or may be aligned with the lumen of the vascular structure , causing all blood flow through the vascular structure to be directed through the implanted portion of the catheter . a valve is placed in the wall of the implanted portion of the catheter which opens into the lumen of the leg of the &# 34 ; t &# 34 ; of the catheter upon application of sufficient differential pressure between the lumens of the two portions of the catheter . the leg of the &# 34 ; t &# 34 ; may be connected to the side wall of the implant portion of the catheter at an angle , such that the axis of the lumen of the leg of the &# 34 ; t &# 34 ; intersects the axis of the lumen of the implanted portion of the catheter at approximately a 45 ° angle .