Abstract:
A catheter comprising a dual lumen catheter tube with a molded plastic bolus formed at the distal end of the tube. The tube and bolus assembly which results has arterial and venous ports which overlap each other longitudinally but are oriented on opposite sides of the tube and bolus assembly.

Description:
RELATED APPLICATIONS 
       [0001]    This PCT application is based on regular application Ser. No. 13/035,634 filed Feb. 25, 2011, and claims priority therefrom. The entire priority application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates in general to catheters. It relates more particularly to hemodialysis catheters. In addition, the invention relates to any corporeal catheter where aspiration and infusion are occurring simultaneously through the same multiple lumen tube. 
       BACKGROUND OF THE INVENTION 
       [0003]    Quinn U.S. Pat. No. 6,461,321 B1 and Quinn U.S. Pat. Appln. No. 2005/0182354 A1 provide background for the present application. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention introduces new concepts to hemodialysis catheters. The arterial port and the venous port are located at points where the most distal portion of the arterial port that is formed where its periphery meets the imaginary cylindrical portion of the catheter is opposite the most proximal portion of the venous port beneath it. In other words, one port partially over-laps the other. Unlike all other hemodialysis catheters, there is not any complete space between the ports. This positioning ensures that the fast and directed flow from the venous port moves quickly away from the slower and more concentrated inflow to the arterial port before they can mix, and vice versa in the reverse mode. 
         [0005]    Both ramps serving the arterial port and the venous port are identical. In the hemodialysis catheter described in the application U.S. 2005/01182354 A1, the main portion of the arterial ramp climbed from the main longitudinal catheter axis at 21°. This angle has been determined to be ideal for directing fluid upward and forward away from the catheter body. In the new invention, the forward venous ramp now also climbs at an identical 21° rather than the previous catheter and climbed in a slightly concave arc and actually offered increased resistance to forward flow, thereby slightly increasing unwanted diffusion of flow around the bolus instead of forward an up. 
         [0006]    In the most recent previous hemodialysis catheter, the flow to or from the arterial port was immediately directed by a sidewall or rail extending from the septum separating the two D lumens that assisted in directing the flow forward. In this new invention this same sidewall or rail is added to the distal venous lumen design to further compliment the flow directional aspects of the added 21° ramp. Both lumens now utilize the flow directional rails. 
         [0007]    In the most recent previous catheter, the ramp of both ports incorporated a flat surface on the 21° portions of the ramps. In the new invention this flat surface, that tends to minimize flow around the sides of the ramps, has been increased and extends into the convex curve that competes the ramp areas. 
         [0008]    To further assist in forward flow, the venous lumen has been changed from a tapering “D” to ovoid shape, to a continuous D shape in the new design. This change speeds flow and makes it more directional, thereby minimizing diffusion and resultant mixing as flow exits from the venous port. 
         [0009]    To further accommodate the changes made to the venous port, the X and Y axis of the taper on the existing longitudinal over-molded bolus has been changed from 9° to 13°. This modification provides the ability to more easily introduce the catheter over a guide wire in a patient&#39;s vein. 
         [0010]    The invention also relates to any corporeal catheter where aspiration and infusion are occurring simultaneously such as duel lumen gastric sumps, i.e., Salem Sumps, where gastric juices are being aspirated from the stomach in one lumen and air is being drawn into the stomach via a lumen line. If the pressure in the stomach is to remain balanced, it is vital that there is no mixing between the aspiration gastric juice lumen and the air replacement infusion lumen. The partially overlapping port design of the invention applies to any situation where infusions and aspiration are occurring with a multi-lumen catheter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention is illustrated more or less diagrammatically in the drawings in which: 
           [0012]      FIG. 1  is a side elevational view of a portion of a hemodialysis catheter embodying features of the invention. 
           [0013]      FIG. 2  is a cross section view taken along line  12 - 12  of  FIG. 11 . 
           [0014]      FIG. 3  is a top plan view of the catheter of  FIG. 1 . 
           [0015]      FIG. 4  is a bottom plan view of the catheter of  FIG. 1 . 
           [0016]      FIG. 5  is a longitudinal sectional view taken through the catheter of  FIG. 3 . 
           [0017]      FIG. 6  is a longitudinal sectional view of a catheter being inserted over a guide wire and over an introducer sheath. 
           [0018]      FIG. 7  is a bottom plan view of the catheter and guide wire showing their relative orientation, as the catheter is led around a turn in a patient&#39;s vein. 
           [0019]      FIG. 8  is a longitudinal sectional view of a catheter being inserted over a guide wire with the guide wire passing along the side of the catheter tip. 
           [0020]      FIG. 9  is a cross sectional view taken along line  9 - 9  of  FIG. 7 . 
           [0021]      FIG. 10  is a cross sectional view of the basic catheter  12  portion of the catheter  10  without the front over-molded bolus portion  14 . 
           [0022]      FIG. 11  is a view of the catheter as shown in  FIG. 1  denoting cross-sectional views. 
           [0023]      FIGS. 12-19  are cross sectional views taken through  FIG. 11 . 
           [0024]      FIG. 20  is a cross sectional view of the venous lumen showing cross sectional area as seen in  FIG. 12 . 
           [0025]      FIG. 21  is a side elevational view as seen in  FIG. 1  showing the cross sectional area of the arterial port periphery. 
           [0026]      FIG. 22  is a top and bottom plan of the catheter showing the relationship and cross sectional areas of the arterial and venous ports from a top and bottom view. 
           [0027]      FIG. 23  is formula for calculating the total effective areas of the arterial and venous ports. 
           [0028]      FIG. 24  is a bottom plan view that shows the normal flow pattern into the arterial port and out of the venous port. 
           [0029]      FIG. 25  is a top plan view that shows the reversed flow pattern from the arterial port and flow into the venous port. 
           [0030]      FIG. 26  is a side view as seen in  FIG. 5  that shows the relationship of the 45° skived ports and the beginning of the ramps. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Now referring to the drawings particularly to  FIGS. 1-5  and especially  FIG. 5 , a dual lumen catheter embodying features of the invention is illustrated generally at  10 . The catheter  10  comprises a skived cylindrical extruded dual lumen tube  12  and an over-molded bolus  14  that form the complete catheter  10 . The tube  12  has a distal end  16 . The over-molded bolus  14  has a distal end  19 . 
         [0032]    Still referring to  FIGS. 1-5 , the catheter  10  is a 14.5 French tube formed of Carbothane® polyurethane material or another suitable thermoplastic polymer. The tube  12  has an outside diameter, OD, of 0.190″. The cylindrical tube  11  is divided into two identical D shaped lumens  18 A and  18 B by septum  20 . The lumen  18 A is normally referred to as an arterial lumen and the lumen  18 B is referred to as a venous lumen. Each lumen  18 A and  18 D has a D shaped cross sectional area of about 0.0067 in 2 . 
         [0033]    Still referring to  FIGS. 1-5 , tube  12  is skived at a 45° angle to form exit port  22 A for the arterial lumen  18 A. The skive levels at 0.030″ from the top of septum  20  to form a wall or rail  24 A that rises 0.030″ from the level of the top surface of septum  20 . Likewise, the bottom side of tube  12  is skived at a 45° angle to form port  22 B for the venous lumen. The venous wall or rail  24 B is also skived to form a wall or rail 0.030 in height. The purpose of both the arterial rail  24 A and the venous out flow rail  24 B is to assist in directing the arterial inflow and venous outflow to and from the respective ports in a direct line to the port openings  22 A and  22 B. This flow direction is especially important in directing flow forward during the normal outflow function of the venous port  22 B through the radial arterial port  28 B to the ascending ramp  26 B. The rails direct the flow forward and concentrate flow up and forward rather than around the edges of the over-molded bolus  14 . In the reverse mode when flow is out of the arterial port  22 A through the radial venous port  28 A the flow is also directed forward and up over ascending ramp  26 A. 
         [0034]    Still referring to  FIGS. 1-5 , but more specifically to  FIGS. 3 ,  4  and  5 , ramps  26 A and  26 B incline at a 21° angle from the septum floor  20 . The beginning of the incline of both ramps  26 A and  26 B is at the imaginary point  30 A and  30 B where the 45° angles of exit ports  22 A and  22 B meet the floor of septum  20 . Testing has shown that the 21° angle is ideal to carry the flow in an upward direction while minimizing the spread of the fluid around the edges of the bolus tip  14 , thus minimizing mixing of flow between the two lumens  18 A and  18 B. Both ramps have a flat straight surface to the height  32 A and  32 B where the surface begins to taper convexly. At this point the friction between the fluid and the bolus  14  begins to decrease as it encounters a convex rather than a flat surface  32 A and  32 B are at a perpendicular height of  0 .049″ from the surface of septum  20 . 
         [0035]    Now referring to  FIG. 1 , from the top of the flat ramp  26 A the bolus curves in a continuing convex arc  34  with a radius of 0.529″. Arc  34  continues to where it meets the OD of the cylinder comprising the catheter  10  at  36 . Arc  34  continues past the top point  36  and meets long arc  38  that forms the long top surface of bolus  14 . Arc  38  has a radius of 0.927″. The beginning  30 B of ramp  26 B is directly perpendicular under the top  36  of arc  34 . Therefore, the beginning of venous outflow ramp  26 B begins at the end of arterial radial port  28 A. 
         [0036]    Now again referring to  FIGS. 5 , the tip  19  of over-molded bolus  14  is has a radius of 0.066″ or an OD of 0.132″. The elongated portion of bolus  14  under the top radius  38  angles downwardly at 13° to septum  20 . This angle allows the tip to present an effective bullet tip shape during insertion and in situ to prevent damage to vessel walls that can result in the build up of fibrin sheaths that could occlude the catheter  10  lumens. The distal tip  19  of the bolus  14  tapers from an OD of 0.132″ to the full OD 0.190″ of the cylindrical tube at arc  40 . 
         [0037]    Now referring to  FIGS. 5-9 . The effective longitudinal axis Y of the forward portion of over-molded bolus  14  from radial point  36  to the bolus tip  19  is inclined to longitudinal axis Y at an angle of 13°. The side surfaces  40  of bolus  14  are curved inwardly to tip  19 . The bolus  14  is inclined forwardly to the X axis at a angle of 77°. 
         [0038]    The aforementioned size, shape and orientation the nose of bolus  14  provides several advantages in the use of the catheter  10 . First, its smaller size facilitates easy entry into, and travel through, a patient&#39;s vein by the bolus  14 . Second, the offset nose  19  section of bolus  14  places a portion of its periphery tangent to a hypothetical cylinder in which the outer surface of the bolus  14  passage lies, even though it is considerably thinner than the remainder of the bolus  14  over-molded over the tube  12 . Third, when guide wire  44  insertion is employed, the nose section  19  flexes radially away from the wire where is emerges from port  22 A without forcing either the nose section or the wire substantially outside of the aforementioned cylinder into the vein wall. Fourth, when traveling around curves in a vein during insertion, the bolus nose resists bending sideways and catching on the vein wall. It is also seen that the periphery of nose section  19  engages a vein wall when the top of the port  22 B does. This prevents the trailing top edge of port  22 B from having the vein wall wrap around it and become abraded. Likewise, The top of the arc  36  on the over-molded bolster  14  also meets the outside periphery of the imaginary catheter  10  cylinder and prevents the trailing edge of  22 A from abrading the vein wall. 
         [0039]    During insertion, as seen in  FIGS. 6-9 , the guide wire  44  causes the nose section to flex outwardly until its axis Y is substantially parallel to the axis X of the bolus.  FIG. 6  illustrates that maximum width of the bolus  14  is 0.148″ and the guide wire has an OD of 0.0038″ for a total of 0.186″. 
         [0040]    Now referring to  FIGS. 5 ,  10  and  12 , unlike the venous lumens described in Quinn U.S. Pat. No. 6,461,321 B1 and Quinn Application U.S. 2005/0182354 A1, the venous lumen  18 B does not transition to a slightly larger oval port at port  22 B. Lumen  22 B maintains its same dimensions through its entire length in catheter  10 . The purpose of this new configuration is to maintain flow speed and force, not to lower them. Because the invention introduces the same 21° ramp on the venous port as the arterial port it is advantageous to maintain faster flow forwardly and upwardly across flat ramp  26 B. The invention also introduces a flatter and larger ramp section that transitions flow up, forward and away from the tip and therefore away from arterial inflow port  22 A. In the catheters of the aforementioned Quinn patent and patent application, the leading arterial ramp also has a slightly concave curved ramp that also slows and diffuses flow. The present invention is designed to send flow forward while minimizing the slowing of flow and the diffusion of flow. Flow is meant to continue forward over the tip of the catheter tip  19 . 
         [0041]    In  FIGS. 3 &amp; 4 , the flat ramps  26 A and  26 B raise at 21° to level  32 A and  32 B. At this point the center portion of the ramp remains flat to minimize the diffusion of flow around the edges of the tip. However, this flat area beyond  32 A and  32 B begins a concave curve to again minimize resistance to flow. This concave curve continues over the top of the catheter periphery at  36  to maintain a gradual curved surface where the periphery of the catheter  10  engages the vein wall. 
         [0042]    In  FIG. 10  is the side view of skived catheter  12 .  FIG. 11  is the side elevational view of catheter  10  shown in  FIG. 1 . which serves a vehicle for cross-sectional views of the catheter.  FIGS. 12  is a cross-sectional view of the catheter at a point before it is skived.  FIG. 13  shows a cross-section at the point where the top skive shows the creation of rail or wall  24 A.  FIG. 14  shows the beginning of ramp  26 A at the point where the ramp has risen at 21° to the top of rail  24 A.  FIG. 15  shows the rail rising to the top of the 21° portion of ramp  26 A.  FIG. 16  shows the ramp at its apex at  36  and the beginning of venous ramp  26 B and rail  24 B.  FIG.18 &amp; 19  shows the bolus  14 . The cross sectional portion of the bolus is elliptical which assists in the prevention of the tip from twisting laterally. 
         [0043]    Now referring to  FIGS. 20-23 , the cross-sectional area 0.0067 in2 of lumen  18 B is shown at  47 .  48 A shows the cross-sectional area of the side view of arterial port  28 A within its peripheral cylindrical shape.  48 B shows the identical shape and 0.0121 in2 area for  48 B. The top view area and shape calculation for arterial port  48 A and venous port  48 B are shown as 0.0622 in2 at  50 A and  50 B. The ports overlap each other at  52 . The beginning of ramp  26 B starts at  30 B.  30 B is also the point of the apex of ramp  26 A. Therefore the 45° skive  22 B of radial port  28 B begins before point  36  and port  28 B begins before  28 A ends. The ports are slightly superimposed over each other. 
         [0044]    The simple formula in  FIG. 23  describes that the total approximate open area for flow in both the arterial and venous ports formed by the periphery of these ports where they meet the imaginary cylinder of the catheter  10 . This port area is over 10 times the cross-sectional area of either D lumen. The function of these large ports is at least fourfold. First, the size and depth of the ports prevent the vein walls from occluding the protected D lumens in the aspiration mode. Second, the tapered shape of the expanded ports eliminates any dead space for the collection of debris. Third, the shape of the ports protects the vein walls from abrasion by the trailing edges of the ports that can cause fibrin sheath build up at these edges. Fourth, in the outflow mode the blood is diffused over the bolus tip, which causes it to mix with the patient&#39;s venous blood without causing “whipping” due to concentrated flow associated with open ports. Essentially, the invention&#39;s ports have the free outflow advantages of open cut off tip ports while also protecting the port from vein damage and allowing inflow in the aspiration mode. 
         [0045]      FIG. 26  shows the relationship between the 45° skived arterial port  22 A and venous port  22 B to the initiation of ramps  26 A and  26 B from the floor of septum  20  at points  30 A and  30 B. So as to not restrict flow, the ramps do not begin to rise until the septum floor exits the 45° angle of the port. The point where the flat ramp  26 A meets the convex continuing arc rises 0.049″ from the floor of septum  20 . The total height from the septum floor to the cylindrical OD of the catheter  10  is 0.086″. In the case of both ramp  26 A and  26 B this perpendicular height from the septum floor is more than 55% of the total height 0.086″. The total length of the invention from the proximal edge of port  22 A to the end of tip  19  is 0.752″. The catheter tip of U.S. patent application U.S. 2005/0182354 A1 is 1.162″ in length. Moving the ports closer together results in a tip that is 35% shorter than the previous design. 
         [0046]      FIG. 24  shows flow in the normal use of the invention hemodialysis catheter. Blood flows out of the venous port  28 B into the venous stream and returns to the lungs. The flow is forward and away from the catheter  10 . Blood is aspirated into arterial port  28 A and returned to the dialysis machine for cleansing before being returned to port  28 B. The blood aspirated into radial port area  28 A is pulled into the port from an area very proximal to the port. This fact coupled with the fact that the fluid emerging from the venous port  28 B is at its highest velocity reduces the opportunity of the blood mixing between the two ports. Situations do occur where the arterial aspiration port  28 A may become occluded. In this situation it is common practice to reverse the flow. This situation is shown in  FIG. 25 . In this invention the desirable characteristics shown in  FIG. 24  still apply because the outflow ramps in both ports are identical. There are more tendencies for mixing in the reverse flow mode shown in  FIG. 25  because the outflow must pass over the inflow port. In the catheter of the aforementioned Quinn patent and application, mixing in the reverse mode can be reduced from the common 40% plus rate with Mahurkar catheters to less than 7%. In this invention the mixing is reduced to near zero % in the reverse mode. 
         [0047]    While preferred embodiments of the invention have been described, it should be understood that the invention is not so limited, and modifications may be made without departing from the invention.