Patent Publication Number: US-9839763-B2

Title: Tip configurations for multi-lumen catheter

Description:
PRIORITY 
     This application is a division of U.S. patent application Ser. No. 13/687,919, filed Nov. 28, 2012, now U.S. Pat. No. 8,894,607, which is a division of U.S. patent application Ser. No. 10/884,291, filed Jul. 2, 2004, now U.S. Pat. No. 8,323,227, each of which is incorporated by reference in its entirety into this application. 
    
    
     BACKGROUND OF THE INVENTION 
     In various medical applications catheters with three or more lumens are needed to deliver and/or withdraw fluid from the patients&#39; circulatory system. For example, the physician may need to divert blood from the circulatory system through a first lumen in the catheter and at the same time reintroduce the removed blood back into the circulatory system through a second lumen. A third lumen in the catheter may be used to introduce medications and/or nutrition supplements. In another example, each of the lumens within a multi-lumen catheter may be used to introduce a different drug into a patient&#39;s circulatory system. The use of separate lumens for each drug may prevent premature mixing of the medications. 
     One common application of a triple lumen catheter is the use of the catheter for apheresis and for delivery of medications during chemotherapy treatment of a cancer patient. Apheresis is a process that involves the removal of whole blood in a dialysis-like fashion. In this process, blood is circulated continuously from the patient to an instrument that acts as a centrifuge or filter, allowing for the separation of specific blood parts. The processed blood is re-circulated back into the patient&#39;s body. For example, apheresis may be utilized to separate out stem cells from the blood prior to chemotherapy treatments. This is generally accomplished by hormonally stimulating the production of bone marrow to produce a high number of stem cells. The stem cells are separated from the rest of the blood parts using the triple lumen apheresis catheter. Chemotherapy drugs are then administered using a third lumen in the catheter. After a given length of Chemotherapy treatment time, the stem cells are infused back into the patient&#39;s circulatory system. 
     To allow these blood draws and infusions, a good access to the blood stream in a large vein may be desirable. For example, the triple lumen catheter may be inserted into the patient&#39;s subclavian vein that runs behind the clavicle to establish a central line. The proximal end of the catheter may be tunneled under the skin for 2-4 inches to emerge from the chest close to the nipple. The triple lumen catheter may be used for the collection of stem cells and for support of the patient during therapy. In addition to the chemotherapy agent, antibiotics, anti-nausea medications, blood products, and fluids may also be infused through the implanted catheter. 
     Examples of various multi-lumen catheters are disclosed in U.S. Pat. No. 4,894,057, titled “FLOW ENHANCED MULTI-LUMEN VENOUS CATHETER DEVICE” issued to Howes, dated Jan. 16, 1990; U.S. Pat. No. 5,221,255, titled “REINFORCED MULTIPLE LUMEN CATHETER” issued to Mahurkar et al., dated Jun. 22, 1993; U.S. Pat. No. 5,378,230, titled “TRIPLE-LUMEN CRITICAL CARE CATHETER” issued to Mahurkar, dated Jan. 3, 1995; U.S. Pat. No. 5,395,316, titled “TRIPLE LUMEN CATHETER” issued to Martin, dated Mar. 7, 1995; U.S. Pat. No. 5,399,168, titled “IMPLANTABLE PLURAL FLUID CAVITY PORT” issued to Wadsworth, Jr. et al., dated Mar. 21, 1995; U.S. Pat. No. 5,451,206, titled “TRIPLE LUMEN CATHETER” issued to Young, dated Sep. 19, 1995; U.S. Pat. No. 5,486,159, titled “MULTIPLE-LUMEN CATHETER” issued to Mahurkar, dated Jan. 23, 1996; each of which is incorporated herein by reference in its entirety. 
     Due to design constraints, such as dimension/size limitations for insertion into a blood vessel, maintenance of structural integrity during aspiration of blood, etc., a typical multi-lumen catheter tends to possess one or more of the following undesirable properties: high recirculation of blood, low flow rate for blood circulation and medication delivery, high phlebitis, and high tendency for aspirating lumen to suck against the vessel wall. These properties limit the catheter&#39;s efficiency in blood circulation and medication delivery, which could minimize the effectiveness of the medical intervention. 
     Thus, an improved multi-lumen catheter with high blood circulation efficiency and high throughput for medication delivery is desirable. The improved design may incorporate one or more of the following performance characteristics: low recirculation of blood, high flow rates of blood and medications, high flow volume of blood and medications, low phlebitis, delivery of infusates in separate lumens, no dead end openings, limited sucking against vessel wall during aspiration, durable catheter structural design, capable of being produced in high volume, low production cost, capable of being placed over a guide-wire and/or a tunneler, and attractive appearance. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, described herein are various multi-lumen catheters each having three or more lumens where at least two of the lumens have distal openings that are staggered along the length of the catheter. The distal openings of the catheters are arranged in various configurations. These modified catheter configurations may improve fluid throughput efficiency and decrease recirculation in the catheter. 
     In one variation, the catheter comprises a plurality of three or more lumens where the lumen openings at the distal portion of the catheter are staggered along the length of the catheter. Preferably, the lumens are angularly spaced apart and every one of the lumen openings directs the outflow in the axial direction toward the distal end of the catheter. The lumens of the catheter may have a pie-shape cross-section with each lumen becoming narrower toward the axis of the catheter and widening toward the outer circumferential surface of the catheter. In one example, the catheter comprises three staggered lumen openings in intervals of 2.5 cm. Each of two proximal lumens open at approximately a 150 degree angle with respect to one another, while a third lumen opens distally thereof. 
     In another variation, the catheter comprises two or more lumens exiting at the distal end of the catheter, and at least one lumen exiting proximally along the length of the catheter. In one example, the catheter comprises three lumens, with two of the three lumens exiting distally and the third lumen exiting proximally. Preferably, the third lumen is centrally located relative to the two other lumens. The separation between the single proximal and the dual distal lumens may decrease the possibility of recirculation while maximizing flow rate. The catheter may further comprise a beveled tip for increasing the catheter&#39;s ease of insertion while keeping infusates injected through the lumens separate until entering the high blood volume regions of the body. 
     In yet another variation, the catheter comprises one distal lumen opening, and a plurality of proximal lumen openings. In one variation, the proximal lumens are grouped together along the length of the catheter. The proximal lumen openings may be located at approximately the same axial location along the length of the catheter. In one example, the catheter comprises a single lumen exiting at the distal end of the catheter and two other lumens terminating at the same plane along the length of the catheter proximal to the first lumen opening. In one variation, the two lumens with proximal openings are not offset angularly. In an alternative design, the two lumens may be angularly spaced when viewed from the distal end of the catheter. 
     These and other embodiments, features and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following more detailed description of the invention in conjunction with the accompanying drawings that are first briefly described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows one variation of a triple lumen catheter with staggered lumen configuration. In this variation, all three lumens are staggered along the length of the catheter with the distance between the distal lumen opening and the mid-lumen opening being marked as L 1 , and the distance between the mid-lumen opening and the proximal lumen opening being marked as L 2 . 
         FIG. 1B  shows the cross-sectional view of the catheter from  FIG. 1A  sectioned at the proximal portion of the catheter. In this variation, the interior of the catheter at the proximal end is divided into three pie-shape lumens. 
         FIG. 1C  illustrates another variation of a triple lumen catheter where the walls of the two proximal lumens extend distally to form flanges around the lumen openings thereof. 
         FIG. 1D  illustrates another design variation with a circular distal lumen and two proximal lumens staggered at intervals along the length of the catheter. 
         FIG. 1E  shows the plain view of the catheter from  FIG. 1D , viewed from the distal end of the catheter down the tubing axis. The interior of the catheter at the distal portion comprises a circular lumen and two semi wedge/pie shape lumens. 
         FIG. 1F  illustrates another variation of the staggered lumen design with a primary circular lumen opening and two staggered proximal lumen openings. The two proximal lumens are configured with extended flanges at their distal openings. 
         FIG. 1G  illustrates the cross-sectional view of the catheter from  FIG. 1F  at the proximal portion of the catheter. 
         FIG. 1H  illustrates yet another variation of the triple lumen staggered design with side openings on the circumferential surface for providing additional fluid exits for the distal lumen. 
         FIG. 1I  illustrates another variation of the staggered lumen design. In this variation, the two proximal lumens are configured with openings on the circumferential surface of the catheter. 
         FIG. 1J  shows the cross-sectional view of the catheter from  FIG. 1I  at the proximal portion of the catheter. 
         FIG. 2A  illustrates another variation of a triple lumen catheter with the stagger design. In this variation, the catheter comprises two distal lumens which are positioned side-by-side and one proximal lumen. The distal lumens are designed with gradually expanding inner lumens. 
         FIG. 2B  shows the frontal view of the catheter from  FIG. 2A , as seen directly down the axis of the catheter with the two distal openings showing. 
         FIG. 2C  shows the cross-sectional view of the catheter from  FIG. 2A  at the proximal portion of the catheter. As shown, the interior of the catheter at the proximal portion comprises three pie-shape lumens. 
         FIG. 2D  shows another variation of the dual distal lumen design. The distal end of the catheter is configured with a sharper profile as compared to the catheter shown in  FIG. 2A . 
         FIG. 2E  illustrates another variation of the dual distal lumen design where the lumens of the catheter extend linearly along the length of the catheter with constant lumen cross-sectional areas along the length of the catheter. 
         FIG. 2F  shows the cross-sectional view of the catheter from  FIG. 2E  at the proximal portion of the catheter. 
         FIG. 2G  illustrates another variation of the dual distal lumen design where the three lumens have varying shapes and cross-sectional areas. 
         FIG. 2H  illustrates a plain view of the catheter from  FIG. 2G , seen from the distal end of the catheter down the axial length of the catheter. As shown, in this variation, each of the three lumens has a semi-pie-shape cross-section. 
         FIG. 3A  illustrates another variation of the stagger lumen design where the catheter comprises two proximal lumens positioned side-by-side and a distal lumen centrally positioned relative to the two proximal lumens. 
         FIG. 3B-1  shows the plain view of the catheter from  FIG. 3A  seen from the distal end of the catheter down the longitudinal axis of the catheter. 
         FIG. 3B-2  shows the cross-sectional view of the catheter from  FIG. 3A  at the proximal portion of the catheter. 
         FIG. 3C  illustrates another variation of the dual proximal lumen design with a non-circular distal lumen. 
         FIG. 3D  illustrates yet another variation of the dual proximal lumen design with side openings integrated on the circumferential surface of the catheter. 
         FIG. 3E  illustrates another variation of a dual proximal lumen design where side openings are provided for accessing the distal lumen. 
         FIG. 3F  illustrates one variation of a proximal end configuration for a triple lumen catheter. 
         FIG. 4A  illustrates a plain view of one variation of a catheter with a single distal lumen and two proximal lumen configuration where a trifurcation is connected to the proximal end of the catheter. 
         FIG. 4B  illustrates the distal portion of the catheter shown in  FIG. 4A . 
         FIG. 4C  illustrates the cross-sectional view of the trifurcation from the catheter system shown in  FIG. 4A . The figure illustrates the independent fluid communications provided by the three separate lumens. 
         FIG. 4D  is the side view of the distal portion of the catheter shown in  FIG. 4A . 
         FIG. 4E  is the cross-sectional view of the distal portion of the catheter shown in  FIG. 4D . The cross-section is taken from the center of the catheter dividing the two proximal lumens. 
         FIG. 4F  is the cross-section view at the proximal portion of the catheter shown in  FIG. 4A . 
         FIG. 5A  shows one variation of an access port having three independent cavities each of which has an independent fluid communication path to one of the lumens at the access port connection interface. 
         FIG. 5B  illustrates an example of a triple lumen catheter with staggered lumen openings connected to an access port with three fluid cavities. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description should be read with reference to the drawings, in which like elements in different drawings are identically numbered. The drawings, which are not necessarily to scale, depict selected preferred embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
     Before describing the present invention, it is to be understood that unless otherwise indicated this invention need not be limited to applications in humans. As one of ordinary skill in the art would appreciate, variations of the invention may be applied to other mammals as well. Moreover, it should be understood that embodiments of the present invention may be applied in combination with various fluid delivery devices and/or reservoirs for intravascular fluid/medication administration. 
     A triple lumen catheter is used herein as an example application to illustrate the various aspects of the invention disclosed herein. Variations of the inventions may comprise three or more lumens. It must also be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, the term “an opening” is intended to mean a single opening or a combination of openings, “a fluid” is intended to mean one or more fluids, or a mixture thereof. 
     In one aspect of the invention, the catheter comprises three or more lumens with staggered openings at the distal portion of the catheter which exit into the blood stream in intervals of predefined distance(s). Preferably, each of the lumens in the catheter has a separate opening at the distal end so that each of the lumens is in independent fluid communication with the interior of a blood vessel.  FIG. 1  illustrates one variation of the catheter  2 , with three lumens  4 ,  6 ,  8 . The openings  12 ,  14 ,  16  for the three corresponding lumens  4 ,  6 ,  8  are staggered along the length of the catheter  2 . The distance between the distal opening  12  and the middle opening  14  is indicated as “L 1 ”, and the distance between the middle opening  14  and the proximal opening  16  is indicated as “L 2 .” L 1  may be larger, smaller, or equal to L 2 . Preferably, the staggered distance between the openings (e.g., L 1 , L 2 ) is between about 0.5 cm to about 10 cm, more preferably between about 1 cm to about 5 cm, even more preferably between about 2 cm to about 3 cm, and most preferably about 2.5 cm. For example, openings may be configured such that L 1 =L 2 =2.5 cm. In another variation, L 1 =1 cm, and L 2 =2.5 cm. 
     In light of the disclosure herein, one of ordinary skill in the art would appreciate that the catheter may have four, five, six, seven or more lumens, each with a corresponding opening such that the openings are staggered along the length of the catheter in various configurations that are described herein. In some variations the staggered distances between the various openings are the same, in other variations the staggered distances between lumen openings may vary. Furthermore, although in the figures shown herein, each lumen has one opening at the distal portion of the catheter, one of ordinary skill would appreciate that each lumen in the catheter may be configured with additional openings. 
     In the example shown in  FIG. 1A , the lumens  4 ,  6 ,  8  have pie-shaped cross-sectional areas. This non-circular lumen cross-sectional design may provide improved flow rate along the length of the catheter for the three lumens. Each of the lumens  4 ,  6 ,  8  is bound by two interior walls and a portion of the outer catheter wall, and the two interior walls merge toward the central region of the catheter  2 . The three interior walls may meet at the central axis of the catheter, or alternatively, they may meet off the central axis. The first  22  and the second  26  interior walls form an angle “A 1 ”, the second  26  and the third  24  interior walls form an angle “A 2 ”, and the third  24  and first  22  interior walls forms the angle “A 3 ”. In one variation, the two proximal lumens  6 ,  8  open at 120 degree angles with respect to each other, and the third lumen  4  forms the distal opening (i.e., A 1 =A 2 =A 3 =120 degree), as shown in  FIG. 1A . Alternatively, the distal portion of the catheter may be configured such that A 1 =150 degree, A 2 =150 degree and A 3 =60 degree. In light of the disclosure herein, one of ordinary skill in the art would appreciate that the inner walls between the lumens may be configured such that the interface angles A 1 , A 2 , A 3  may have various combinations. The inner walls&#39; arrangement at the proximal portion  30  of the catheter may be configured to match the corresponding walls at the distal portion of the catheter. For example, at the proximal portion, the three interior walls  22 ,  24 ,  26  separating the three lumens may merge at the central region of the catheter  2  to form three wedge-shaped lumens  4 ,  6 ,  8 , each having an angle of 120 degree (A 1 =A 2 =A 3 =120 degree) as shown in  FIG. 1B . Alternatively, at the proximal portion of the catheter, the three interior walls  22 ,  24 ,  26  separating the three lumens may have a distinct configuration in relation to the interior walls at the distal portion of the catheter. For example, the lumens at the proximal portion of the catheter may comprise of three cylindrically shaped lumens, and transition into three pie-shaped lumens at the distal portion of the catheter. 
     In one variation the three lumens  4 ,  6 ,  8  have the same cross-sectional area. In another variation, the lumen  4  with the distal opening and the lumen  8  with the proximal opening have the same cross-sectional area while the lumen  6  with the middle opening has a smaller cross-sectional area in comparison to the other two lumens  4 ,  8 . In this variation, the catheter may be implemented for dialysis, where the lumen  8  with the proximal opening may be used to aspirate blood, while the lumen  4  with the distal opening may be used to infuse the processed blood and the third lumen  6  with a smaller opening may be used to infuse medications or nutrients into the patient. In another variation, the lumen  4  with the distal opening may have a larger cross-sectional area in relation to the other two lumens  6 ,  8 , and the two proximal lumens  4 ,  8  may have the same cross-sectional areas. In yet another variation, the three lumens  4 ,  6 ,  8  may have different cross-sectional areas. 
     The different combination of cross-sectional lumen sizes described above may be implemented in the various catheter designs described herein, and the catheters may have different cross-sectional lumen shapes. For example the lumens may have a circular or square shape instead of the pie-shapes described above. Furthermore, in light of the description herein, one of ordinary skill in the art would appreciate that any two of the three lumens on the catheter may be used for aspirating and infusing blood for dialysis or apheresis purposes, and the third lumen may be used independently for infusing fluids (e.g., saline, medications, nutrients, etc.) or extracting blood from the patient (e.g., taking blood samples). Preferably, the lumen used for aspirating blood has an opening that is proximal from the lumen used for infusing the processed/filtered blood. Also preferably, the lumens used for aspiration and infusion of blood (e.g., for filtering and/or processing) have larger lumens relative to the third lumen in order to maximize the blood processing/filtering rate. However, one of ordinary skill in the art would appreciate that this is not a necessary requirement. For some applications, it may be desirable to use a larger third lumen for delivery of medications or chemotherapy agents. 
       FIG. 1C  illustrates another variation similar to the design shown in  FIG. 1A ; however, the walls of the proximal lumens  6 ,  8  have extended flanges  36 ,  38 ,  40  around their openings, which may direct blood flow and may provide a smoother surface profile for the catheter to minimize resistance and/or abrasion during insertion of the catheter into an orifice, such as a blood vessel. In addition, theses extended flanges  36 ,  38 ,  40  may reduce stress concentration at transitions between profiles. 
     Referring to  FIG. 1D , yet another variation of the staggered lumen design is shown. In this variation, the catheter  2  comprises a primary lumen  4  that has a circular cross-section, while the two proximal lumens  6 ,  8  have non-circular cross-sections. The semi-pie-shaped lumens  6 ,  8 , allow one to provide two additional lumens around a primary circular lumen without significantly increasing the diameter of the overall catheter. The frontal view of this catheter  2  seen from the distal end down the longitudinal axis of the catheter is shown in  FIG. 1E . The proximal portion of the catheter may be configured with three pie-shaped lumens similar to the one shown in  FIG. 1B . 
     Preferably, the two proximal lumens  6 ,  8  open at approximately 110 to 170 degree angles with respect to each other. More preferably, the two proximal lumens  6 ,  8  open at approximately 145 to 155 degree angles with respect to each other. And most preferably, the two proximal lumens  6 ,  8  open at approximately 150 degree angles with respect to each other. The catheter design with two proximal lumens  6 ,  8  having this pie-shape/semi-pie-shape design may be implemented in a catheter having a circular or semicircular distal lumen  4 . In addition, the two proximal lumens  6 ,  8  having this pie-shape/semi-pie-shape design may be implemented in a catheter having the staggered lumen design described above, or in another design where the two proximal lumens are adjacent to one another along the length of the catheter. Such a design will be described in more detail below. The staggered design may maximize the process efficiency by decreasing recirculation of previously apheresed blood at a preferred flow rate (about 120 ml/min), while allowing the infusion of medications or TPN (Total Parenteral Nutrition) through the third lumen at a preferred flow rate (e.g., equivalent flow of a 5 Fr single lumen PICC). In addition, this design with one distal lumen formed centrally may be optimal for intravenous placement of the catheter via either a guidewire or tunneler, and may be produced in high volumes using radio frequency forming techniques. 
       FIG. 1F  illustrates another design variation with a circular distal lumen opening and two proximal lumens openings  6 ,  8  which are staggered along the length of the catheter. The two proximal lumens  6 ,  8  are configured with extending flanges  36 ,  38 ,  40  at their lumen openings. As shown in  FIG. 1G , in this variation the proximal portion  30  of the catheter  2  comprises three pie-shape lumens. 
     Preferably, the opening for each of the lumens is positioned at the distal region of the corresponding lumen, and each of the lumen openings has an outflow direction towards the distal region of the catheter along the axis of the catheter. The distal direction is shown as the Z-axis in  FIG. 1A . Although lumens with openings exiting toward the distal direction of the catheter are preferred, additional side openings may also be added along the length of the catheter to increase the fluid outflow and/or intake rate. For example, side openings  52 ,  54  may be added to the distal portion  50  of the catheter  2  to facilitate fluid outflow from the distal lumen  4 , as shown in  FIG. 1H . 
     In another variation, the two proximal lumens of the catheter are configured with side openings  62 ,  64  that open on the circumferential surface of the catheter as the primary inflow/outflow openings, as shown in  FIG. 1I . The catheter comprises three lumens. The distal lumen  72  has a circular cross-section at the distal end  68  of the catheter. The two proximal lumens are angularly positioned relative to each other, also shown in  FIG. 1I . The proximal openings  62 ,  64  for the two proximal lumens  74 ,  76  are staggered along the length of the catheter and are angularly displaced from each other. The circumferential profile along the length of the catheter at the distal portion where the openings of the lumens are located is configured with a slightly tapered profile, such that the overall cross-sectional surface of the catheter decreases along the length of the catheter towards the distal end  68  of the catheter  2 . In this variation, the proximal portion of the catheter comprises three pie-shaped lumens. Preferably, the three pie-shaped lumens are of equal sizes, see  FIG. 1J . 
     In another aspect of the invention, the catheter comprises three lumens  82 ,  84 ,  86  where two  82 ,  84  of the three lumens  82 ,  84 ,  86  exit distally with a single centrally positioned lumen exiting proximally along the axial length of the catheter, as shown in  FIGS. 2A, 2D, 2E , and  2 G. The catheter may have a beveled tip to increase the catheter&#39;s ease of insertion. The two independent lumens  82 ,  84  at the distal end  88  allow the user to keep infusates separate until exiting the catheter into the blood stream of the patient. The proximal lumen  86  may be used for aspirating blood out of the patient&#39;s circulatory system for apheresis or dialysis applications. 
     The separation between the single proximal lumen  86  and dual distal lumens  82 ,  84  (identified as “d” in  FIG. 2A ) may minimize the recirculation while maximizing the flow rate. In one variation, the catheter is configured for 120 ml/min circulation rate (apheresis/dialysis flow rate) through one distal and one proximal lumen, and an equivalent flow rate of a 5 Fr PICC for the other distal lumen. Furthermore, utilizing radio frequency forming techniques, one may fabricate the catheters described above and achieve lumens with large cross-sectional areas. 
     Induction heating is observed when conductive materials are subjected to a radio frequency (RF) field. RF energy induces eddy currents in a tipping die made of a conductive material, and heating occurs primarily by I 2 R heating, that is the power dissipation in a resistive circuit. When the tipping die is also a magnetic material, additional heating effects occur from hysteresis heating, due to the friction created by the magnetic material&#39;s resistance to the rapidly changing magnetic field within the induction coil. The tipping die is placed in an induction coil forming a solenoid and the die is heated by the energy transferred from the magnetic field. The specific configuration of the solenoid may depend on the particular design requirement. By varying the current running through the solenoid, the forming temperature changes so that the thermoplastic tubing may be molded into the desired shape. One of ordinary skill in the art would appreciate that RF tipping technique such as the one described above may be implemented in the fabrication of the various catheters described herein. Furthermore, the radio frequency forming techniques may allow efficient production of catheters that are reliable and have low incidence of breakage during use. In addition, the radio frequency tipping process may allow inexpensive reproduction of catheters in large quantities in a high volume production process. 
     In one variation, the two distal lumens  82 ,  84  are configured such that the internal lumen cross-sections increase along the length of the catheter as they approach the distal end  88  of the catheter  2 . In one example shown in  FIG. 2A , once the two distal lumens  82 ,  84  pass the proximal lumen opening  90 , the diameter of the two distal lumens  82 ,  84  gradually increases along the length of the catheter  2  toward the distal end  88  of the catheter. This expansion in lumen diameter may allow the flow in the lumen of the catheter to have a decreased exit velocity in comparison to the fluid flow velocity along the proximal portion of the catheter where the cross-sectional area of the lumen is smaller. In the example shown in  FIG. 2A , the catheter is designed to have an overall diameter that is about the same along the length of the catheter  2 . The catheter&#39;s overall cross-sectional area (perpendicular to the longitudinal axis of the catheter) at the distal dual openings  92  is slightly smaller than the overall cross-sectional area at the proximal portion  94  of the catheter.  FIG. 2B  illustrates the frontal view (down the longitudinal axis) of the catheter as seen from the distal end  92  of the catheter  2 , and  FIG. 2C  illustrates the cross-sectional view of the catheter at the proximal portion  94  of the catheter  2 . In an alternative design, the distal portion  98  of the catheter may be configured with a larger cross-sectional area than the proximal portion  94  of the catheter. This may further decrease the exit velocity of the fluid coming out of the two distal lumens  82 ,  84 .  FIG. 2D  illustrates another example of a dual distal lumen design. In this example, the distal end of the catheter  88  is configured with a sharper profile in comparison with the catheter shown in  FIG. 2A . 
     Alternatively, the distal portion  98  of the catheter may be configured with a smaller cross-sectional area than the proximal portion  94  of the catheter. For example, the three lumens  82 ,  84 ,  86  of the catheter  2  may have constant cross-sectional areas along the length thereof, as shown in  FIG. 2E . The two walls  102 ,  104  separating the two distal lumens  82 ,  84  from the proximal lumen  86  continue linearly along the length of the catheter after passing the opening  90  of the proximal lumen  86 .  FIG. 2F  illustrates the cross-sectional view of the catheter from its proximal portion. 
     Referring to  FIG. 2G , another variation is shown where the two distal lumens  82 ,  84  have different cross-sectional areas. In this example, the right distal lumen  82  is larger than the left distal lumen  84  at the distal portion of the catheter, as shown in  FIG. 2H . One may implement this catheter for apheresis applications such that the proximal lumen  86  is used to aspirate blood, the blood is processed and infused back into the circulatory system through the right distal lumen  82 , and the left distal lumen  84  is used to infuse medications and/or nutrients. Although medications may be infused through either the right  82  or left  84  distal lumen, it may be preferable to infuse the processed blood through the larger lumen  82  to increase the blood filtering/processing rate. 
     In yet another aspect of the invention, the catheter  2  is designed with two proximal lumens  112 ,  114  and one distal lumen  116 . Examples of this design are shown in  FIGS. 3A, 3C, 3D and 3F . This design may minimize recirculation due to the distance “x” (as shown in  FIG. 3A ) between the two proximal  112 ,  114  and one distal  116  lumen while simultaneously maximizing the flow rates and flow volumes. For example, the catheter may be configured for 120 ml/min circulatory flow rate at 250 mmHg through the distal and one proximal lumen, and an equivalent flow rate that is equal or better than 5 Fr PICC for the other proximal lumen. Preferably, the recirculation of the catheter is less than 5% at 120 ml/min. In addition, the single distal lumen  116  may allow easy placement of the catheter  2  using a guidewire or tunneler through the distal lumen  116 . Infusate such as medications, chemotherapy agents or nutrients may be delivered independently through one of the proximal lumens while the other proximal lumen may be used for aspiration of blood or for delivery of other fluids. In addition, similar to the other catheters described above, this design may be easily produced in high volume relatively inexpensively utilizing radio frequency techniques. 
     In one variation, the catheter comprises a central lumen  116  with a circular cross-sectional area at the distal end, and two proximal lumens  112 ,  114  with their openings  118 ,  120  positioned side-by-side and proximal to the distal end  124  of the catheter. The distance between the two proximal lumen openings  118 ,  120  and the distal lumen opening  122  is indicated as “x”. Preferably, x is between about 1 cm to about 10 cm, more preferably about 2 cm to about 5 cm, even more preferably about 2 cm to about 3 cm, and most preferably about 2.5 cm. As shown in  FIG. 3A , in this example, the two proximal lumens  112 ,  114  open at 120 degree angles with respect to each other. Alternatively, the two proximal lumens may be designed to open at other angles (e.g., 150 degrees). The cross-sectional areas of the lumen openings may be pie-shaped. In this example, all three of the lumens  112 ,  114 ,  116  direct fluid flow to exit along the axial direction of the catheter toward a distal region beyond the catheter.  FIG. 3B-1  illustrates the frontal plain view of the catheter  2  seen from the distal end of the catheter down the longitudinal axis of the catheter, showing the distal opening  116  centrally positioned in relation to the two proximal lumen openings  118 ,  120 . In this particular variation, the three lumens are designed to have three equal pie-shape lumens along the length of the catheter from the proximal end of the catheter to the proximal openings  118 ,  120 . The cross-sectional view of the catheter at the proximal portion of the catheter is represented by  FIG. 3B-2 . The two proximal lumens  112 ,  114  terminate at  118  and  120  at the distal portion of the catheter, and the distal lumen  116  continues to extend in the distal direction. As shown in  FIG. 3A , in this design the distal portion of the catheter expands radially along the length of the catheter from the proximal opening  118 ,  120  to the distal tip  124  of the catheter. The inner lumen cross-section along this distal region (i.e., between the proximal openings  118 ,  120  and the distal opening  124 ) transition from a pie-shape lumen to a circular lumen. In this design, the cross-sectional area of the distal circular opening  124  is larger then the cross-sectional area of the pie-shape opening of the distal lumen at the proximal region of the catheter. Alternatively, the catheter may be designed such that the distal circular opening has the same cross-sectional area as the cross-sectional pie-shape area of the lumen at the proximal portion of the catheter. Furthermore, the two proximal lumens&#39; openings  118 ,  120  may be configured with the same cross-sectional area to support fluid flow at the same rate. 
     In an alternative design, one of the two proximal lumens is configured with a larger cross-sectional area than the other one of the proximal lumens. One may utilize the large proximal lumen in combination with the distal lumen to provide apheresis or dialysis, and utilize the smaller proximal lumen for infusion of medications and/or nutritional supplements. 
       FIG. 3C  illustrates another example of a dual proximal lumen catheter. In this example, the central lumen  116  has a non-circular cross-section. In another variation, the distal portion  122  of the catheter may be expanded such that the internal cross-sectional area of the central lumen  116  increases along the length of the catheter toward the distal end  124  of the catheter  2 . For example, the catheter&#39;s tip portion  122  distal of the two proximal lumens  112 ,  114  may expand gradually towards the distal end  124  such that it has a funnel-shaped lumen. The increase in cross-sectional diameter of the central lumen  116  at the distal end  124  may decrease exit velocity of the fluid being infused through the central lumen  116 . 
     The various catheter designs described herein may be further modified to reduce the risk of sucking to the blood vessel walls. This is a common design consideration in all dialysis/continuous flow catheters in order to maximize aspiration rates. In order to decrease the incidence of blockage due to sucking, side holes may be provided on the circumferential surface of the catheter. For example, side holes/openings may be provided on the distal portion of one or both of the proximal lumens that are used for aspirating blood. One variation of a catheter having side openings  51 ,  53  for a proximal lumen is illustrated in  FIG. 3D . The side openings may allow aspiration of blood even if blockage occurs due to suction at the primary opening  55  of the lumen, and may increase flow rates and flow volumes. In another variation, side holes/openings may also be provided for the distal lumen to facilitate outflow of infused blood/fluids. Examples of catheters with side openings  52 ,  54  for the distal lumen are shown in  FIGS. 1H and 3E . The side openings on the distal lumen may allow enhanced exit flow and provide for alternative flow paths if the end of the catheter is blocked by fibrins/clots. As one of ordinary skill in the art would appreciate, the side holes may be provided at various locations along the length of the catheter, and both the proximal and/or the distal lumens may have side holes added to facilitate aspiration and/or infusion of fluids. 
     In another aspect of the invention, the proximal section or the proximal end of the catheters may be molded to fit a connector of specific shape/configuration. For examples, three-lumen catheters with various distal tip designs, such as the ones shown in  FIGS. 1-3 , may be configured such that their proximal ends are provided with three lumens of equal proximal openings  132 ,  134 ,  136  (as shown in  FIG. 3F ) where each of the three proximal openings is configured to provide independent fluid communication to one of the lumens in the distal section and its corresponding distal opening. Alternatively, the lumen distribution pattern at the proximal end of the catheter may reflect the specific catheter tip design at distal end of the catheter and an adaptor may be used to connect each of the lumens to a corresponding fluid source and/or suction source. For example, the catheter may have two large pie-shape/semi-pie-shape lumens and one smaller lumen, and an adaptor with matching connectors may be used to connect the two large lumens to an apheresis or dialysis device while the third lumen is connected to a medication or chemotherapy agent infusion device (e.g., drug pump, syringe, etc.). 
     In one variation, the catheter  2  may be connected to a trifurcation  142  having three separate fluid lines (e.g., tubings)  144 ,  146 ,  148  for providing independent fluid infusion/aspiration for each of the corresponding lumens  152 ,  154 ,  156  in the catheter. For example, a triple lumen catheter with a distal lumen  152  and two proximal lumens  154 ,  156  may be adapted with a trifurcation  142  for fluid infusion and aspiration, as shown in  FIG. 4A . The distal lumen  152  has an opening  182  at the distal tip  158  of the catheter. The proximal lumens each have an opening  184 ,  186  located proximal to the distal opening  182  along the length of the catheter, as shown in  FIG. 4B . In this particular configuration, the two proximal lumens&#39; openings  184 ,  186  are aligned next to each other along the length of the catheter. The left fluid line  144  is configured to provide independent fluid communication to the proximal lumen on the left  154 , and the right fluid line  148  is configured to provide independent fluid communication to the proximal lumen on the right  156 , and the central fluid line  146  is configured to provide independent fluid communication to the distal lumen  152 , as shown in  FIGS. 4A and 4C . Optionally, tubing clamps  162 ,  164 ,  166  may be provided to seal off individual fluid lines  144 ,  146 ,  148  as desired by the operator. 
     Furthermore, in this example the distal portion  172  of the catheter  2  is configured with a tapered profile around the two proximal lumens&#39; distal openings  184 ,  186 . As shown in  FIG. 4D , the walls of the proximal lumens  154 ,  156  have fringes  192 ,  194 ,  196  extending along the length of the catheter to provide a smoother transition surface profile at the proximal lumen opening  184 ,  186  (L 42 =0.2 inches). From the proximal lumen openings  184 ,  186  toward the distal lumen opening  182 , the catheter&#39;s height in the Y direction expands. As shown in  FIG. 4E , the distal lumen&#39;s inner diameter expands along the length of the catheter at this portion  102  (i.e., between the proximal lumen opening and the distal lumen opening). At the most distal region  104  of the catheter, the outer diameter of the catheter tapers inward toward the axis of the distal lumen  152  (L 43 =0.1 inches). At the distal tip  158  of the catheter the outer diameter D 41  of the catheter is 0.09 inches, and the inner diameter D 42  of the distal lumen is 0.07 inches.  FIG. 4F  illustrates the cross-sectional view of the catheter  2  at the proximal portion  174  of the catheter. The outer diameter D 43  of the proximal portion  174  of the catheter is 0.158 inches. The thickness T 41  of the inner lumen dividing walls is 0.015 inches. The outer wall thickness T 42  is 0.015 inches. The proximal portion of the catheter comprises three pie-shaped lumens  154 ,  156 ,  158  each has a 120 degree inner wall angle A 41 . 
     In another variation, a triple cavity port  110 , such as the one shown in  FIG. 5A , may be connected to the proximal end of the catheter  2  to provide the fluid infusion/aspiration interface. In this example, the access port comprises three independent fluid cavities  112 ,  114 ,  116 , each of which is covered with a septum  122 ,  124 ,  126 . The right cavity  112  is in independent fluid communication with the right lumen  132  of the connection interface  130 . The left cavity  116  is in independent fluid communication with the left lumen  134  of the connection interface  130 . The center cavity  114  is in independent fluid communication with the center lumen  136  of the connection interface. The connection interface may be configured to receive a proximal end of the catheter having three pie-shaped lumens, similar to the one shown in  FIG. 3F . For example, a triple lumen catheter  142  having two proximal lumens and a distal lumen may be connected to a triple cavity port  110 , as shown in  FIG. 5B . An operator may insert a needle through one of the septums  122 ,  124 ,  126  to access any one of the cavities  112 ,  114 ,  116  and selectively inject or aspirate fluids through any one of the proximal and distal lumens in the catheter  142 . Other multi-lumen ports, including but not limited to the ones described in U.S. Pat. No. 5,399,168, may also be implemented with the catheters described herein. In light of the disclosure herein, one of ordinary skill in the art would appreciate that other fluid input interfaces may also be adapted for use with the various catheter designs disclosed herein to provide a system for infusing and/or aspirating fluids from a patient&#39;s circulatory system. 
     The various multi-lumen catheters described above may comprise various elastomeric materials. For example, silicone, poly/silicone blend, Tecothane, Carbothane, Tecoflex, Chronoflex, and other biocompatible elastomeric materials may be utilized to fabricate the catheters described above. Other polymeric materials that are well known to one of ordinary skill in the art that are suitable for use in manufacturing of catheters may also be applied in the present invention. These materials may be made radiopaque through the use of known radiopacifiers such as barium sulfate. For example, the catheter body may comprise of Carbothane 80A-85A with 20% BaSO 4 . 
     In light of the disclosure herein one of ordinary skill in the art would appreciate that the various multi-lumen catheter designs described may be implemented in various medical procedures where independent/separate infusion and/or aspiration of two or more fluids is desired. For example, the staggered three-lumen design may be particularly useful in apheresis, dialysis, or other medical procedures requiring placement of a central line. Moreover, the catheters described herein may be placed into a patient&#39;s body with various surgical procedures well known to one of ordinary skill in the art. One example of implementing a triple lumen catheter having staggered lumens is described below. 
     Before implantation of the triple lumen catheter, the physician may determine proper size of catheter to use depending on the physical size and/or weight of the patient. Non-invasive imaging techniques may also be applied to assist the physician in making such determination. In one approach, a catheter having a central distal lumen and dual proximal lumens is inserted into the right internal jugular vein. The catheter is then advanced into the patient&#39;s body along the internal jugular vein. Further advancement will place the distal section of the catheter into the superior vena cava (SVC). Ultrasound, fluoroscope, radiograph, and/or other imaging devices may be utilized to assist the physician in the placement of the catheter. A radiopaque ribbon may be provided at the distal portion of the catheter and/or along the length of the catheter to improve contrast of the catheter within the images captured by the imaging device. The position of the catheter may be adjusted within the SVC and/or right atrium depending on the physician&#39;s preference. For example, it may be desirable to position the dual proximal lumen openings next to the SVC/jugular vein junction. Alternatively the openings for the dual proximal lumen may be placed next to the SVC/Right-Atrium junction. In another variation, it may be desirable to place the distal end of the catheter into the right atrium of the heart. Once the catheter is placed in the desired position, the physician may then secure the catheter in place. Optionally, the proximal end of the catheter may be tunneled underneath the skin so that it exits the skin just beneath the right clavicle and distant from the insertion site. Once the catheter has been placed, a hemodialysis machine or an apheresis machine may be connected to the catheter to start the treatment process. For example, the proximal end of the catheter may have a trifurcation connector to facilitate the connection process. Blood may then be removed through suction delivered through the catheter to one of the proximal openings of the catheter, and processed blood may be infused back into the patient&#39;s circulatory system through a distal opening on the catheter. Chemotherapy agents, antibiotics, anti-nausea medications, blood products, fluids and other medications or nutrients may be infused through a third lumen with a proximal opening on the catheter. 
     This invention has been described and specific examples of the invention have been portrayed. While the invention has been described in terms of particular variations and illustrative figures, those of ordinary skill in the art will recognize that the invention is not limited to the variations or figures described. In addition, where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. Therefore, to the extent there are variations of the invention, which are within the spirit of the disclosure or equivalent to the inventions found in the claims, it is the intent that this patent will cover those variations as well. Finally, all publications and patent applications cited in this specification are herein incorporated by reference in their entirety as if each individual publication or patent application were specifically and individually put forth herein.