Patent Document

BACKGROUND OF THE INVENTION 
   This invention relates in general to blood treatment catheters and more particularly to a design for use in hemo-dialysis in which the occlusion of the distal ports due to fibrin buildup is substantially eliminated. 
   Hemo-dialysis is the process of mass transfer, in which certain chemical substances, accumulated in the blood because of kidney failure, are transferred from the blood across a semi permeable dialysis membrane to a balanced salt solution. The efficiency of a hemo-dialysis procedure depends on the amount of blood brought into contact with the dialysis membrane. A flow of 250 milliliters of blood per minute under a pressure gradient of 100 millimeters of mercury is considered a minimum requirement for adequate dialysis. Over the past several years, flow rate between 350 milliliters per minute and 400 milliliters per minute have become common. 
   At the place where the catheter is inserted into the patient, the body reacts by creating a sheath of material that includes fibrin and other materials that grow down the outer wall of the catheter from the point of insertion in the vein. This material is referred to herein as occlusive material. This occlusive material when it grows down to the site of ports, and most particularly the aspirating port, tends to block the ports rendering the catheter essentially useless. 
   Accordingly, it is the primary object of this invention to create a catheter design that substantially eliminates or reduces the build up of occlusion at the infusion and aspirating ports. 
   BRIEF DESCRIPTION 
   In brief, the catheter disclosed has both aspirating and infusion lumens. At a distal zone, the tube carrying the aspirating lumen extends distally of the end of the tube defining the infusion lumen. At its distal end, the infusion lumen is substantially annular around the aspirating tube and has infusion ports that provide emission of fluid over substantially 360° as a jet like emission having a significant radial component. A nose of a built up zone on the outside of the aspirating tube, immediately adjacent to and distal of the exit port from the infusion lumen, provides a wall for the exit port to assure that the jet of fluid exits in a substantially radial direction. 
   This jet of infusion fluid abrades the occlusion that tends to grow down these catheters from the point of insertion into the patient. Thus the 360° infusion jet prevents such occlusive material not only from clogging the infusion port but also prevents further distal growth along the aspirating tube. This means that occlusion of the end of the aspirating tube by occluding material is avoided. 
   Definitions 
   The term occlusion or occlusive material refers to the well known coating that builds up on the exterior of these catheters. It starts at approximately the point where the catheter is inserted through the vein and builds down along the outside surface of the catheter. This occlusion build up is believed to be composed of a number of materials such as fibrin, and/or muscle cells and/or blood clot. 
   This invention is addressed to a technique of preventing the occlusion build up from extending down over the end of the aspirating port or ports and causing the aspirating ports to block. 
   Infusion and Aspirating Port and Ports 
   The preferred embodiments, shown in  FIGS. 3 through 6  contain a plurality of infusion exit ports. As discussed in connection with  FIG. 7 , a design can be provided in which there is a single circumferential exit port. An essential feature is that there is a substantial 360° jet having a substantial radial component which serves to abrade and clear away occlusion that grows down the outer wall of the catheter. The aspirating port, though shown as a single end port can be a plurality of circumferential ports and the term “port” is used to include the multiple port arrangement. 
   Accordingly, it should be understood herein that the terms “port” or “ports” or “port arrangement” in the specification and claims are used to include a single port and/or a set of ports, such as the ports  26   a  of FIG.  3  and the ports  26   b  of FIG.  5 . 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a schematic illustration of the positioning of the hemo-dialysis catheter of this invention through the jugular vein. In  FIG. 1 , the catheter is inserted into the patient at point A and into the vein at point B. 
       FIG. 2  is an elevation view of a catheter of this invention showing the infusion tube  18  and aspirating tube  20  combined at juncture  22  to form the main portion  24  of the catheter. Infusion ports  26  are at the distal end of the infusion lumen. Aspirating port  34  is at the distal end of the aspirating tube  20 . 
       FIG. 3  is a larger scale elevation view of the zone around the distal infusion port of an embodiment of the  FIG. 2  catheter having a plurality of angled infusion ports  26   a.    
       FIG. 4  is a partial longitudinal sectional view through the  FIG. 3  catheter portion. 
       FIG. 5  is a larger scale elevation view of the zone around the distal infusion port of a second embodiment of the  FIG. 2  catheter showing a plurality of arcuate circumferential ports  26   b.    
       FIG. 6  is a partial longitudinal sectional view along the  FIG. 5  catheter portion. 
       FIG. 7  is a longitudinal sectional view of a further embodiment of the  FIG. 2  catheter in which the infusion port  26  is substantially a 360° circumferential port. 
       FIG. 8  is a cross-sectional view along the plane  8 — 8  of  FIG. 7  showing a three chamber section of the circumferential infusion lumen  11  immediately adjacent to the infusion port  26 . 
       FIG. 9  is a schematic illustration of the infusion of filtered blood at the infusion ports of the infusion lumen.  FIG. 9  illustrates the umbrella-like shape of the infusion  40  that results from the combined effect of the radial jet of filtered blood from the infusion ports  26   b  and the downward flow of the patient&#39;s blood. 
       FIG. 10  is a schematic illustration of blood flow into and from the catheter of this invention at the right atrium. 
       FIG. 11  is an elevation view of a generic showing of the catheter of this invention. It is used to illustrate three embodiments of this invention which differ in the configuration of the infusion and aspirating lumens over the proximal 80 to 90 percent of the catheter that is between the juncture  22  and the infusion port  26 . 
       FIGS. 12A ,  12 B,  12 C and  12 D are cross-sectional views along the planes A—A, B—B, C—C and D—D respectively, of  FIG. 11  showing a presently preferred embodiment of this invention. These cross-sectional FIGS. show the transition from the semi-circular lumens  11 ,  12  that exist along about eighty percent of the length of the catheter to the coaxial lumen arrangement immediately proximal of the infusion port  26 . 
       FIG. 13  is a cross-sectional view along the plane A—A of  FIG. 11  illustrating a further embodiment of this invention showing two shaped lumens  11 , 12  that exist over at least eighty percent of the length of the catheter.  FIGS. 12C and 12D  illustrate the transition of the  FIG. 13  embodiment to the coaxial lumen arrangement immediately proximal of the infusion port  26 . 
       FIG. 14  is a cross-sectional view along the plane A—A of  FIG. 11  illustrating another embodiment of this invention in which the two lumens  11 ,  12  are coaxial along the entire length from the juncture  22  to the infusion port  26 . In the  FIG. 14  embodiment, the support web shown at  FIG. 8  would be employed. 
       FIG. 15  is a longitudinal sectional view through the connector  22  for the  FIGS. 12A-12D  embodiment having the substantially semicircular lumens  11  and  12 .  FIGS. 15A ,  15 B and  15 C are cross-sectional views along the planes A—A; B—B and C—C, respectively, of FIG.  15 . 
       FIG. 16  is a longitudinal sectional view of the connector for the  FIG. 14  embodiment in which the lumens  11 ,  12  are concentric from juncture  22  to infusion port  26 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The catheter  10  of this invention has an infusion lumen  11  and an aspirating lumen  12 . The distal end  16  of the aspirating lumen extends distally beyond the distal end  14  of the infusion lumen  11 . 
   More particularly with respect to  FIGS. 1 and 2 , a standard infusion tube  18  and aspirating tube  20  are combined at a juncture  22  to provide a single tube  24  distal of the juncture  22 . The tube  24  contains infusion and aspirating lumens. The tube  24  is inserted into a patient at point A and passed into the jugular vein  25  at point B to be positioned at a desired location; often in the right atrium  38  as shown in FIG.  10 . 
     FIGS. 3 and 4  illustrate a presently preferred embodiment of this invention in which the infusion port set  26  is constituted by ten ports  26   a  each having a major axis at an angle of approximately 45° to a circumferential line through the ports  26   a . In this embodiment, each of the ports is approximately 50 mils (0.050 inches) by 20 mils (0.020 inches). These ports  26   a  are at the distal end of the infusion lumen  11 . 
   As can best be seen in  FIG. 4 , the infusion lumen  11  is a circumferential lumen around the aspirating lumen  12  in the zone that is immediately proximal of the infusion exit ports  26   a . An inner wall  28  defines the aspirating lumen  12 . The infusion lumen  11  is defined by the inner wall  28  and the outer wall  30 . Each port  26   a  is a port in the outer wall  30 . The outer wall  30  merges into the inner wall  28  at the zone  36 . This provides a terminal wall for the infusion lumen  11  and assures that the infusing filtered blood is ejected through the set of ports  26   a  in a substantially radial direction. 
     FIGS. 5 and 6  illustrate a modified version of the  FIGS. 3 and 4  embodiment. The difference in this embodiment is that the distal infusion exit port  26  is composed of a plurality of circumferential ports  26   b . Each of these circumferential ports  26   b  is approximately 20 mils (0.020 inches) wide. 
   In one embodiment, six such openings are involved. Each opening covers an arc of about 70°. The two subsets of three circumferentially aligned openings are axially spaced from one another by 45 mils (0.045 inches) centerline to centerline. The  FIGS. 5 and 6  embodiment is the same as that of  FIGS. 3 and 4  including the employment of the buildup section or nose at the zone  36  that serves to provide an end wall for the infusion lumen  11  and that provides an exit passageway that assures the infusing blood will exit in a substantially radial direction. 
     FIGS. 7 and 8  illustrate a third embodiment of this invention in which the exit port  26  is a 360° circumferential port. 
   In order to assure that the 360° port is maintained open and to prevent the wall  30  from collapsing onto the wall  28  over a portion of the exit port arrangement, a web design, shown in  FIG. 8 , is employed at the exit port  26 . This web design involves three thin webs  32  which extend from the zone  36  proximally for about three millimeters in the embodiment shown. 
   The web  32  supports are not required in the design shown in  FIGS. 3 through 6 . In those designs, the outer wall  30  extends past the ports  26   a  or  26   b  to merge into the wall  28  of the aspirating lumen and thus does not require extra support. However, it should be understood that the design of this invention includes an embodiment in which the  FIG. 8  web extends the length of the catheter from junction  22  to infusion exit port  26 . Such a design is not presently preferred because it provides a stiffer catheter than do the designs disclosed herein. 
   In all three of the embodiments shown in  FIGS. 3 through 8 , the jet of fluid provided at the infusion port  26  serves to prevent buildup of occlusion distal of those ports. It is believed that a key factor is that the occlusion is physically abraded by the jet of fluid. 
   As shown in highly schematic form in  FIG. 9 , the jet of filtered blood  40  exits from the ports  26   b  in a radial direction and then as it joins the flow of patient&#39;s blood, becomes more axially oriented. As shown in  FIG. 9 , the occlusion  42  builds up on the outer wall  30  and extends down to the ports  26   b  where the abrading action of the jet of filtered blood prevents further growth of the occlusion  42 . 
   As shown schematically in  FIG. 10 , the hemo-dialysis catheter is frequently placed in the right atrium  38 . Of the blood flow  46  coming up from the inferior vena cava into the right atrium, a portion  44  is taken in at the aspirating port  34  to be processed and filtered. The filtered blood  40  is returned as a jet from the infusion lumen. This filtered blood  40  joins the blood flow  46  coming down from the superior vena cava into the right atrium to then be circulated throughout the body. 
     FIG. 10  shows the catheter extending down into the right atrium. The procedure may also be such that the hemo-dialysis catheter is extending up into the right atrium. In such a situation, the infusion would be into blood from the inferior vena cava and the aspiration would be from blood from the superior vena cava. As shown in  FIG. 10 , the aspirating port can be in the right atrium providing it is positioned to aspirate blood flow from one of the two vena cavas and so that the infusion is sufficiently distal to provide filtered blood that merges with blood flow from the other vena cava. 
   A further feature of this invention can best be understood by reference to  FIG. 10. A  catheter design which places the aspirating port substantially distal of the infusion port  26  provides a device which reduces irritation to the walls of the right atrium  38  when disposed as shown in FIG.  10 . 
   To avoid problems relating to the immediate recirculation through the filtering system of filtered blood, known types of catheters place the infusion port distal of the aspirating port, maintaining those two ports separated by a relatively small 1.5 to 2.5 centimeters apart. In those designs, the aspirating port is placed in the blood flow  46  in the superior or inferior vena cava. Thus vena cava blood is the source of blood to the aspirating port. The more distal infusion port that provides filtered blood is positioned at the right atrium to supply filter blood to the right ventricle. 
   The design of this invention has the aspirating tube extend substantially beyond the end of the infusion tube (four centimeters or more) so that the aspirating port  34  can be placed in substantial communication with the blood flow  46  from the inferior vena cava while the filtered blood  40  is supplied to the patient&#39;s heart without being partially re-circulated through the aspirating port. 
   The portion of the aspirating tube that extends distally of the infusion tube has a smaller diameter than the rest of the catheter. This smaller diameter together with its length makes it more flexible and less likely to irritate the walls of the right atrium  38 . 
   Thus the design of this invention reduces immediate re-filtering of filter blood while providing the surgeon with greater choice in the positioning of the catheter while minimizing irritation. 
     FIG. 11  is a sub-generic illustration of this invention. It is the basis for the disclosure of various specific arrangements of the infusion lumen  11  and aspirating lumen  12  in the tube  24  between the juncture  22  and the infusion port  26 . The length of the catheter between juncture  22  and port  26  generally constitutes between 80 and 90 percent of the total catheter length. 
     FIG. 12A  shows a preferred arrangement of the lumens  11  and  12 . In this embodiment, the  FIG. 12A  arrangement exists through about 85% or more of the distance from the juncture  22  to the infusion port  26 . This  FIG. 12A  arrangement involves two substantially semi-circular in cross-section lumens  11  and  12  separated by a partition  48 . In order to assure the substantially 360° infusion jet at the infusion port  26 , the coaxial arrangement shown in  FIG. 12D  is desired. To transition from the  FIG. 12A  arrangement to the  FIG. 12D  arrangement, the cross-sectional arrangement shown in  FIGS. 12B and 12C  are employed. 
   As shown in  FIG. 12A , it is generally desirable that the cross-sectional area of the two lumens  11  and  12  be equal to one another. This equality is maintained as much as possible through the transition so that the cross-sectional area of the lumens  11  and  12  at the infusion exit port  26 , as shown in  FIG. 12D , are approximately equal. This equality of cross-sectional areas is desirable and is maintained in all embodiments of the invention disclosed herein. 
   The wall thickness of the partitions  48  can be in the range of 10 to 15 mils (0.010 through 0.015) inches). 
   Approximately eighty percent of the catheter is constituted by the two semi-circular lumen arrangement shown in FIG.  12 A. This is a preferred arrangement because there is less blocking of a lumen when the catheter has to bend. 
     FIG. 13  shows an alternate embodiment of this invention in which the cross-section at A—A of  FIG. 11  illustrates shaped lumens  11  and  12  that are substantially equal in a cross-sectional area. The  FIG. 13  lumen design transitions to the coaxial design shown in  FIG. 12D  at the infusion exit port  26  by way of the intermediate arrangement that is shown in FIG.  12 C. 
     FIG. 14  illustrates a further embodiment in which the coaxial design is maintained throughout the tube  24  from juncture  22  to infusion exit port  26 . Thus, the  FIG. 14  embodiment requires the use of the  FIG. 8  web  32  support arrangement over a short distance at the infusion exit port  26 . 
   In the  FIG. 14  arrangement, the  FIG. 8  web  32  arrangement is limited to a length of three to five millimeters. The use of these radial webs  36  over greater lengths tends to excessively reduce flow through lumen compression when the catheter goes around bends. 
     FIG. 15  is a longitudinal section illustrating the manner in which the  FIG. 12  semi-circular lumens  11  and  12  arrangement is achieved where the infusion tube  18  and aspirating tube  20  are joined. Specifically, as shown in  FIG. 15C , the two lumens  11  and  12  become part of the juncture  22 . As shown in  FIG. 15B , these two lumens are shaped into the approximately semi-circular modes desired. As shown in  FIG. 15A , a wall  24  is provided to define these two lumens  11  and  12 . This wall  24  is the outer tube  24 . 
   The juncture  22  for the shaped lumens of  FIG. 13  would be in all respects like that of  FIG. 15  except for the curvature of the lumens at the cross-sections A—A and B—B. 
     FIG. 16  is a longitudinal sectional view of the juncture  22 , similar to that of  FIG. 15 , showing the arrangement to provide the  FIG. 14  co-axial lumen design.

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