Abstract:
A catheter ( 100 ) having a first lumen ( 110 ) having a first distal tip ( 112 ) and a second lumen ( 130 ) having a second distal tip ( 132 ). The first and second distal tips ( 112,132 ) include openable portions that are normally closed when undeflected by lumen fluid pressure imbalance relative to the blood pressure of the patient. The first lumen ( 110 ) has an openable portion, flap ( 114 ) that opens proximally into the first lumen when the first lumen is under negative pressure to withdraw blood from the vessel through the first lumen to be dialysed (but that can open distally into the vessel under positive lumen pressure to permit blood flow into the vessel). The second lumen ( 130 ) extends distally beyond the first distal tip ( 112 ) to its second distal tip ( 132 ), and its openable portion is several lip sections ( 135 ) that are normally closed against each other when undeflected but that open outwardly when the second lumen is positively pressurized during hemodialysis, permitting blood to return to the patient&#39;s vessel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from U.S. Provisional Patent Application Ser. No. 60/679,098 filed May 9, 2005. 
    
    
     FIELD OF THE INVENTION 
     This relates to the field of medical devices and more particularly to catheters and catheter assemblies. 
     BACKGROUND OF THE INVENTION 
     Hemodialysis catheters are implanted into the vasculature of a patient, and have proximal ends that extend from the patient and are connectable to and disconnectable from tubing of a hemodialysis apparatus. Such catheters are provided with a first lumen and a second lumen coextending to respective distal tips that are carefully positioned at a selected site in a particular vessel of the patient, so that undialysed blood may be withdrawn from the patient&#39;s vessel while dialysed blood may be reintroduced into the patient&#39;s vessel simultaneously, at respective distal tip openings of the lumens. The catheter lumens may be coextending separate catheters or may be dual lumens of a single catheter separated by a septum wall. The distal tips of the two lumens are generally staggered along the vessel such that blood being withdrawn does not include any significant amount of dialysed blood that has been reintroduced into the vessel at the more distal of the two distal tips. 
     When a particular dialysis procedure has been completed, the proximal ends of the catheter are disconnected from the tubes of the hemodialysis apparatus, and the lumens are generally inactive until the subsequent dialysis procedure, although fluid medication or saline may be infused into at least one of the lumens, if and when desired, or a blood sample withdrawn. However, blood is highly susceptible to coagulation and clot formation. The addition of a specific agent or locking solution to the catheter or any extracorporeal blood-contacting surface can reduce the incidence of coagulation by interfering and/or inhibiting the hematological chemistry of blood and its interaction with synthetic materials, such as those from which catheters are made. 
     It is conventional, then, to introduce anticoagulant locking solutions such as heparin into an implanted catheter between hemodialysis treatments, to prevent clotting of blood within the catheter, and which then is withdrawn for the subsequent dialysis procedure. The blood pressure of the patient effectively maintains the locking solution within the catheter lumens by producing a pressure gradient against the locking solution, even though the distal lumen tips are open structures. However, certain amounts of locking solution are known to enter the patient&#39;s blood stream through the open distal tips. The amounts introduced into the patient are not at a level to cause toxicity or disrupt a patient&#39;s hematology. 
     It is desired to provide a catheter that will minimize or eliminate the small amounts of locking solution entering a patient&#39;s blood stream from an implanted catheter between dialysis treatments. 
     SUMMARY OF THE INVENTION 
     The catheter of the present invention includes a first lumen having a first distal tip, and a second lumen having a second distal tip, wherein the first and second distal tips having wall sections that are normally disposed in a closed position but are each openable under fluid pressure. While both lumens have openable distal tip wall sections, the first distal tip has a wall section openable both inwardly and outwardly when the first lumen is subjected to negative pressure and positive pressure, respectively, relative to the blood pressure of the patient in whom the catheter has been implanted; but, the second distal tip has a wall section openable only outwardly, that is, when the second lumen is subjected to positive pressure, and that closes when the second lumen is subjected to negative pressure. 
     In a preferred embodiment, the first lumen includes a flap section that is joined at a connected section to the wall of the first lumen and extends to a free end that extends to the opposite side of the first lumen to close the first distal tip when undeflected; the flap section is deflectable to open into the first lumen under negative pressure applied to the proximal end of the first lumen, and is deflectable to open outwardly from the first lumen under positive pressure applied to the proximal end of the first lumen. 
     The second lumen extends a selected distance distally of the first distal tip to a second distal tip that is a generally rounded tip when closed, and the second distal tip is defined by an openable section that is internally concave and may be formed by at least one slit cut into a closed rounded distal tip after extrusion of the lumen, defining at least two generally curved lip portions. The several lip portions are openable outwardly under positive pressure applied to the distal end of the second lumen, and a closable together under negative pressure applied to the second lumen. Near the second distal tip, in the side wall of the second lumen are one or more openable side port sections that are openable inwardly upon application of negative pressure to the proximal end of the second lumen. 
     The closable and openable sections of the first and second distal tip sections of the first and second lumens operate thusly: during hemodialysis, negative pressure is applied to the first lumen and blood is drawn from a patient&#39;s vessel into the first distal tip and through the first lumen; positive pressure applied to the second lumen when blood enters the proximal end of the second lumen and separates the several lip portions at the second distal tip to re-enter the vessel. Were the reverse of the pressures to be caused by an incorrect hemodialysis connection, blood traveling into the first lumen would open the flap to enter the vessel, while negative pressure on the second lumen would close the several lip sections but open the side ports for blood to enter from the vessel. Between dialysis procedures, locking solution injected under low pressure into the catheter would fill both lumens since the distal tips would be in their closed, undeflected conditions, and when removed, blood from the vessel would enter both distal tips due to negative pressure on both lumens. 
     The present invention also includes a method for maintaining a locking fluid in an implanted catheter; comprising the steps of: providing a catheter having a first lumen having a closed openable first distal end and a first proximal end, and a second lumen having a closed openable second distal end and a second proximal end; and injecting locking fluid into the first and second proximal ends, wherein the closed first and second distal ends retain the locking fluid in the first and second lumens. The present invention also includes a method of removing a lock solution from a catheter, comprising the steps of: providing a catheter having a first lumen having a closed openable first distal end and a first proximal end, and a second lumen having a closed second distal end and a second proximal end, and at least one closed openable side port disposed proximal of the second distal end; withdrawing the lock solution from the first proximal end, wherein the first distal end opens to allow blood into the first lumen; and, withdrawing the lock solution from the second proximal end, wherein the at least one flap opens to allow blood into the second lumen 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings: 
         FIG. 1  is a side view, in section, of a distal end of a catheter according to a first embodiment of the present invention; 
         FIG. 1A  is a distal end profile view, in section, of the catheter taken along lines  1 A- 1 A of  FIG. 1 ; 
         FIG. 2  is an enlarged portion of the catheter taken along oval  2  of  FIG. 1 ; 
         FIG. 3  is an enlarged distal end profile view, in section, of the catheter being operated in normal operation; 
         FIG. 4  is an enlarged distal end profile view, in section, of the catheter being operated in reverse operation; and 
         FIG. 5  is an enlarged distal end profile view, in section, of a catheter according to a second embodiment of the preferred invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The term “distal” in meant to describe the portion of a catheter according to the present invention that is inserted into a patient, and the term “proximal” is meant to describe the portion of a catheter according to the present invention that remains exterior of the patient. The terminology includes words specifically mentioned, derivatives thereof, and words of similar import. The following describes preferred embodiments of the invention. However, it should be understood based on this disclosure, that the invention is not limited by the preferred embodiments described herein. 
     Referring now to  FIG. 1 , a catheter  100  according to a first embodiment of the present invention is shown. The catheter  100  is a dual lumen catheter used for hemodialysis, wherein a first lumen  110  is used to draw blood from a vessel, such as the internal jugular vein, and a second lumen  130  is used to return blood to the vessel. Further, while the second lumen  130  is used to return blood to the vessel, the second lumen  130  may also be used to administer other fluids, such as medication, to the vessel. 
     The inventive aspect of the present invention is the distal end  102  of the catheter  100 . Consequently, the proximal end of the catheter  100 , which typically includes: a hub at the proximal ends of the first and second lumens  110 ,  130 ; a pair of extension tubes extending proximally from the hub, such that each extension tube is in fluid communication with one of the first and second lumens  110 ,  130  through the hub; and a luer connector on a proximal end of each of the extension tubes, is not shown, as the proximal end of the catheter  100  is known to those skilled in the art. 
     As seen in  FIG. 1A , the first lumen  110  preferably has a D-shaped cross section and the second lumen  130  preferably has a circular cross section. However, those skilled in the art will recognize that the cross sections may be other shapes, such as “Double D”, “Circle C”, or other lumen cross section configurations known to those skilled in the art. 
     A cross-sectional view of the distal end  102  of the catheter  100  is shown in  FIG. 1 . The first and second lumens  110 ,  130  are adjacent to and parallel to each other, and are separated from each other by a septum  104 . The second lumen  130  extends more distally than the first lumen  110 . The first and second lumens  110 ,  130  provide a smooth outer surface for insertion into a patient&#39;s blood vessel. 
     The distal end  112  of the first lumen  110  is enlarged in  FIG. 2 . The distal end  112  includes a flap  114  that extends obliquely from a connected distal portion  116  to a free proximal portion  118 . The flap  114  closes the distal end  112  of the first lumen  110  to restrict fluid flow into or out of the first lumen  110 . The connected distal portion  116  is sufficiently pliable to allow the flap  114  to pivot about the distal portion  116  to open the first lumen  110  during use, such as when blood is either being drawn into the first lumen  110  or when blood is being expelled from the first lumen  110 . 
     Referring back to  FIGS. 1 and 1A , the second lumen  130  includes an internally concave, generally dome-shaped tip or distal end  132  that is generally closed, but with a plurality of slits  134  extending along wall sections of the second distal portion proximally from the distal end, the slits being arranged, for example, as at least one pair of opposed slits generally bisecting the second distal portion and extending proximally from the distal tip  132 , whereby bisected or slit-divided portions of the second distal tip are movable apart allowing, the distal end  132  to open under pressure from the second lumen  130  such that the second distal end is a valve. Slits  134  are shown in  FIGS. 1 and 1A  arranged as two pairs of opposing slits. A generally curved lip portion  135  is formed between each slit  134 . As seen in  FIG. 1A , four lip portions  135  are formed, although those skilled in the art will recognize that more or less than four lip portions  135  may be formed. The shape of the distal end  132  and the cut of the slits  134  allow fluid flow from the second lumen  130 , through the distal end  132  and out of the second lumen  130 , but restrict fluid flow into the second lumen  130  from the distal end  132 . 
     A plurality of side ports  136  are formed in the walls of the second lumen  130  proximal of the distal end  132 , with a flap  137  covering each side port  136 . Each flap  137  is preferably generally bulbous-shaped, with a distal connected end  138  and a free proximal end  140 . In an unpressurized condition, each flap  137  closes off its respective side port  136  to restrict fluid flow through the side port  136  by being disposed within the thickness of the wall section. It may also be seen that the second distal end portion, the second distal tip  132  and the second movable portions  135  are formed to be integral with the wall section of the second lumen  130  that has a generally constant thickness. 
     To manufacture the catheter  100 , it is preferred that the lumens  110 ,  130  are co-extruded according to procedures well known to those skilled in the art. The distal end  102  is inserted into a tipping machine that forms the flap  114  over the distal end  112  of the first lumen  110  and forms the internally concave distal end  132  of the second lumen  130 . The flap  114  is then die cut to separate the free end  118  of the flap  114  from the distal end and to allow the flap  114  to rotate about the connected end  116 . The slits  134  are also cut to form the lip portions  135  in the distal end  132  of the second lumen  130 . The flaps  137  are also die cut to separate the free end  140  of each flap  137  from the wall of the second lumen  130 . 
     In operation, the catheter  100  is inserted into the patient&#39;s blood vessel according to techniques well known to those skilled in the art. When the proximal end of the catheter  100  is connected to an exterior device, such as a hemodialysis machine (not shown), blood flows from the vessel, through the catheter  100 , to the exterior device, back through the catheter  100 , and into the vessel again. 
     When the catheter  100  is correctly connected to the exterior device, standard operation of the catheter  100  is shown schematically in  FIG. 3 . Blood is drawn from the vessel V into the distal end  112  of the first lumen  110  along the direction of arrow “A”. Blood pressure acting on the flap  114  pivots the flap  114  about the connected end  116  so that the free end  118  travels generally proximally, opening the distal end  112  and allowing the blood to flow into the first lumen  110 . The blood then travels to the exterior device, where the blood is processed. 
     The processed blood is then transported to the second lumen  130 , where the blood enters the proximal end of the second lumen  130  and travels through the second lumen  130  to the distal end  132  of the second lumen  130 . The pressure of the flowing blood against the distal end  132  of the second lumen  130  separates the lip portions  135  from each other, opening the distal end  132 , and allowing the blood to exit the second lumen  130  along the direction of arrow “B”. 
     Occasionally, however, the catheter  100  may be incorrectly connected to the exterior device such that blood is drawn into the second lumen  130  and discharged through the first lumen  110 . Operation of the catheter  100  in this manner is shown schematically in  FIG. 4 . Blood is drawn into the vessel V into the second lumen  130  through the flaps  137  in the distal end  132  of the second lumen  130 , as shown by the arrows “C” in  FIG. 4 . The flaps  137  open into the second lumen  130  to allow blood to be drawn from the vessel V into the second lumen  130 . The blood then travels to the exterior device, where the blood is processed. 
     The processed blood is then transported to the first lumen  110 , where the blood enters the proximal end of the first lumen  110  and travels through the first lumen  110  to the distal end  112  of the first lumen  110  to the flap  114 . Blood pressure acting on the flap  114  pivots the flap  114  about the connected end  116  so that the free end  118  travels generally distally, opening the distal end  112  and allowing the blood to flow back into the vessel V, as indicated by arrow “D”. 
     In between treatments, when blood is not flowing through the catheter  100 , a catheter lock solution is injected into each of the first and second lumens  110 ,  130  from the proximal end of each of the first and second lumens  110 ,  130 . Regarding the first lumen  110 , the flap  114  biases toward the closed position to close the distal end  112  of the first lumen  110  and prevent the lock solution from dispersing from the first lumen  110  into the vessel V. Regarding the second lumen  130 , the lip portions  135  bias toward a closed position to close the distal end  132 , and the flaps  137  bias toward the wall of the second lumen  130  to close the flaps  137  to prevent the lock solution from dispersing from the second lumen  130  into the vessel V. 
     To prepare the catheter  100  for a subsequent treatment, a syringe (not shown) is connected to the proximal end of the first lumen  110  and the lock solution is vacuum drawn from the first lumen  110  into the syringes. The flap  114  biases toward the open position to allow blood into the distal end  112  of the first lumen  110  to make up for the now-depleted lock solution. The syringe (or a subsequent syringe) is connected to the proximal end of the second lumen  130  and the lock solution is vacuum drawn from the second lumen  130  into the syringe. The flaps  137  open to allow blood into the distal end  132  of the second lumen  130  to make up for the now-depleted lock solution. The syringe is removed and the proximal end of the catheter  100  is able to be connected to a hemodialysis machine. 
     In an alternate embodiment, shown in  FIG. 5 , a catheter  200  includes a first lumen  210  and a second lumen  230  that have distal ends  212 ,  232 , respectively, that are split apart from each other. A septum  204  that divides the first lumen  210  from the second lumen  230  splits off at a predetermined location to allow the distal end  212  of the first lumen  210  to separate from the distal end  232  of the second lumen  230 . 
     Optionally, as will be recognized by those skilled in the art, the septum  204  may be splittable such as by being constructed to have two layers initially joined to each other as shown in  FIG. 5 , to allow the distal end  212  of the first lumen  210  to be split away from the distal end  232  of the second lumen  230  at a variable location, as determined by the inserting physician during insertion of the catheter into the patient. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.