Catheter for uniform delivery of medication

The present invention provides a catheter for the delivery of fluid medication across an anatomical region. In accordance with one embodiment, the catheter comprises an elongated tube with a plurality of exit holes along an infusion section of the catheter, and an elongated flexible porous member residing within the tube and forming an annular space between the tube and the member. In accordance with other embodiments, the catheter includes a tube having a plurality of exit holes in a side wall of the tube. The exit holes may combine to form a flow-restricting orifice of the catheter. Advantageously, fluid within the catheter flows through all of the exit holes, resulting in uniform distribution of fluid within an anatomical region. In one particular embodiment, the catheter comprises a tube having elongated exit slots therein. In accordance with other embodiments, the catheter includes an elongated tubular member made of a porous membrane. The porous membrane is configured so that a fluid introduced into an open end of the tubular member will flow through side walls of the tubular member at a substantially uniform rate along a length of the tubular member. In accordance with other embodiments, the catheter includes an elongated “weeping” tubular coil spring attached to an end of, or enclosed within, a tube. Fluid within the spring and greater than or equal to a threshold pressure advantageously flows radially outward between the spring coils. Advantageously, the fluid is dispensed substantially uniformly throughout a length of the spring.

RELATED APPLICATIONS

This application is a U.S. National Phase of International Application No. PCT/US00/19746, filed Jul. 19, 2000, which claims priority to U.S. patent application Ser. No. 09/363,228, filed Jul. 19, 1999, now U.S. Pat. No. 6,350,253, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to catheters and, in particular, to a catheter that delivers fluid medication uniformly across an infusion section of the catheter.

2. Description of the Related Art

Infusion catheters for delivery of fluid medication into anatomical systems, such as the human body, are well known in the art. Such catheters generally include a flexible hollow tube inserted into some region of the anatomy. The tube typically contains one or more axial lumens within which the fluid may flow. The proximal end of the catheter tube is connected to a fluid source from which fluid is introduced into the catheter tube. The fluid flows within one of the lumens under pressure supplied at the proximal end of the tube. For each lumen, there are commonly provided one or more exit holes along an infusion section near the distal end of the tube, for fluid to exit the tube. Such exit holes are created by piercing the side wall of the hollow tube.

In certain medical conditions, it is advantageous to deliver fluid medication to a plurality of sites within a wound area. For instance, some wounds which require pain medication may be in communication with many nerve endings, rather than a single nerve trunk. One example of such a wound is a surgical incision. As stated above, it is known to provide a plurality of exit holes through which the fluid medication exits the catheter tube. The exit holes may be provided at various axial and circumferential positions along the catheter tube in order to control the position of the medication delivery sites. An example of a catheter having this configuration is disclosed in U.S. Pat. No. 5,800,407 to Eldor. Also, in some cases it is desirable to deliver such medication under low pressure, so that the fluid is delivered at a relatively low rate. For example, some pain medications must be delivered slowly to avoid toxicity and other side effects. Furthermore, in many cases it is desirable to dispense fluid medication at a substantially uniform rate throughout the infusion section of the catheter, so that the medication is evenly distributed throughout the wound area.

Unfortunately, a limitation of prior art catheters with multiple exit holes, such as the catheter taught by Eldor, is that during low pressure delivery of fluid medication the fluid tends to exit only through the exit hole(s) nearest to the proximal end of the infusion section of the catheter tube. This is because fluids flowing through a tube more readily exit through the exit holes offering the least flow resistance. The longer the flow path followed by the fluid in the lumen, the higher the flow resistance and pressure drop experienced by the fluid. The most proximal holes offer the least flow resistance and pressure drop. Therefore, the fluid tends to exit the catheter tube primarily through these exit holes. As a result, the fluid medication is delivered only to a small region within the wound area. The tendency of the fluid to undesirably flow only through the most proximal exit holes depends upon the hole size, the total number of exit holes, and the flow rate. As the hole size or number of holes increases, the fluid becomes more likely to exit only through the most proximal holes. Conversely, as the flow rate increases, the fluid becomes less likely to do so.

The tendency of the fluid to undesirably exit only through the most proximal holes of the catheter can in some cases be overcome by increasing the flow rate or pressure of the fluid, which causes the fluid to flow through more of the exit holes of the catheter. Indeed, if the flow rate or pressure is sufficiently high, the fluid will flow through all of the exit holes. However, sometimes it is medically desirable to deliver medication at a relatively slow rate, i.e., at a low pressure. Also, even in those cases in which high pressure fluid delivery is acceptable or desirable, prior art catheters do not provide for uniform fluid delivery along the infusion section of the catheter. Rather, the flow rate through the exit holes nearer to the proximal end of the infusion section tends to be greater than that through the exit holes nearer to the distal end. This is because the fluid passing through the more proximal holes experiences a lower flow resistance and pressure drop. In contrast, the fluid flowing through the more distal holes experiences greater flow resistance and pressure drop, and consequently exits at a lower flow rate. The further distal the hole, the lower the exit flow rate of the fluid. As a result, there is an uneven distribution of medication throughout the wound area.

In another known type of infusion catheter, several lumens are provided within a catheter tube. For each lumen, one exit hole is provided by piercing a hole within the wall of the tube. The exit holes are provided at different axial positions along the infusion section of the catheter tube. In this manner, fluid medication may be delivered to several positions within the wound area. While this configuration offers improved fluid distribution, it has some disadvantages. One disadvantage is that the fluid flow rates through the exit holes are not equal, since the more distal exit holes offer a greater flow resistance for the same reasons discussed above. Another disadvantage is that the number of lumens, and consequently the number of fluid exit holes, is limited by the small diameter of the catheter tube. As a result, fluid may be delivered only to a very limited number of positions within the wound area. Yet another disadvantage is that the proximal ends of the lumens must be attached to a complicated manifold which increases the cost of manufacturing the catheter.

An example of a catheter providing a more uniform dispensation of fluid medication throughout an infusion section of the catheter is illustrated by U.S. Pat. No. 5,425,723 to Wang. Wang discloses an infusion catheter including an outer tube, an inner tube concentrically enclosed within the outer tube, and a central lumen within the inner tube. The inner tube has a smaller diameter than the outer tube, so that an annular passageway is formed therebetween. The outer tube has a plurality of evenly spaced exit holes defining the infusion section of the catheter. In use, fluid flowing within the central lumen passes through strategically positioned side holes within the side walls of the inner tube. In particular, the spacing between adjacent side holes decreases along a length of the inner tube to induce more fluid to pass through the more distal side holes. The fluid then flows longitudinally through the annular passageway before exiting through the exit holes in the outer tube wall. In the annular passageway, the fluid can flow in a distal or proximal direction, depending on the location of the nearest exit hole in the outer tube. This configuration is provided to induce a more uniform exit flow rate of fluid from the catheter.

Unfortunately, the Wang catheter is only effective for relatively high pressure fluid delivery. When used for relatively low pressure fluid delivery, the catheter disclosed by Wang does not provide uniform dispensation of fluid. Instead, the fluid tends to exit through the side holes of the inner and outer tubes that are nearest to the proximal end of the infusion section of the catheter, since these holes offer the least flow resistance. Even for high pressure fluid delivery, there are several limitations of this design. One limitation is that the concentric tubes design is relatively complex and difficult to manufacture. Both tubes must be flexible enough to permit maneuverability through an anatomical system, yet the annular passageway must remain open so that fluid may flow uniformly therein. Another limitation is that the annular passageway may be disturbed if there is a bend in the infusion section of the tube. A bend in the catheter may deform the annular passageway or even cause the inner and outer tubes to come into contact. This can cause an uneven fluid pressure within a longitudinal cross-section of the annular passageway, resulting in non-uniform fluid delivery.

Thus, there is a need for an improved infusion catheter for delivering fluid medication uniformly along its infusion section in a relatively simple, easy to manufacture design which is effective for both high flow rate and low flow rate fluid delivery. Furthermore, it is recognized that a particular class of catheters, such as the Wang catheter, may provide uniform fluid delivery only at high fluid pressure or flow rates. However, there is a need for an infusion catheter belonging to this class that has a relatively simple, easy to manufacture design and can maintain uniform fluid delivery while bent or otherwise physically deformed.

SUMMARY OF THE INVENTION

Accordingly, it is a principle object and advantage of the present invention to overcome some or all of these limitations and to provide an improved catheter for delivering fluid medication to a wound area of an anatomical region.

In accordance with one embodiment the present invention a catheter is provided for the uniform delivery of fluid across an anatomical region, comprising an elongated tubular member made of a porous membrane. The membrane is sized to be inserted through a subcutaneous layer surrounding the anatomical region, such as a person's skin. The membrane is configured so that a fluid introduced under pressure into an open end of the tubular member will flow through side walls of the tubular member at a substantially uniform rate along a length of the tubular member. The present invention also provides a method of uniformly delivering fluid throughout an anatomical region, comprising the steps of inserting the elongated tubular member into the anatomical region and introducing a fluid under pressure into an open end of the tubular member.

Another embodiment of the present invention provides a catheter and method for the uniform delivery of fluid throughout an anatomical region. The catheter comprises an elongated support and a porous membrane wrapped around the support. The support is configured so that one or more lumens are formed between the support and the membrane. Alternatively, the support may be a tubular member having a plurality of holes therein. The method comprises the steps of inserting the above-described catheter into the anatomical region and introducing a fluid under pressure into the proximal end of at least one of the lumens. Advantageously, the fluid passes through the membrane at a substantially uniform rate into the anatomical region. The present invention further provides a method of manufacturing this catheter comprising the steps of forming an elongated support and wrapping a porous membrane around the support so that one or more lumens are formed between the support and the membrane.

Another embodiment of the present invention provides a catheter and method for the uniform delivery of fluid throughout an anatomical region. The catheter comprises an elongated tube including a plurality of exit holes along a length thereof and a tubular porous membrane concentrically enclosed within the tube. The tube and membrane define a lumen. The method comprises the steps of inserting the above-mentioned catheter into the anatomical region and introducing a fluid under pressure into the proximal end of the lumen so that the fluid advantageously passes through the membrane and the exit holes at a substantially uniform rate into the anatomical region. The present invention further provides a method of manufacturing this catheter, comprising the steps of forming an elongated tube, providing a plurality of exit holes along a length of the tube, forming a tubular porous membrane, and concentrically enclosing the tubular porous membrane within the tube so that the tube and membrane define a lumen.

Yet another embodiment of the present invention provides a device and method for the uniform delivery of fluid throughout an anatomical region. The device is advantageously simple and easy to manufacture, comprising an elongated catheter having a plurality of exit holes along a length thereof. The exit holes may serve as the flow-restricting orifice. Alternatively, a flow-restricting orifice may be provided elsewhere within the catheter or proximal to the catheter. The exit holes may gradually increase in size along the length of the catheter, so that the largest exit hole is further distal than the smallest exit hole. Alternatively, the holes can be laser drilled and be of approximately the same size. Advantageously, a fluid flowing under pressure within the catheter will flow through substantially all of the exit holes at a substantially equal rate. The method comprises the steps of inserting the catheter into the anatomical region and introducing a fluid under pressure into the proximal end of the catheter. The fluid flows through the exit holes and enters the anatomical region, advantageously flowing through substantially all of the exit holes at a substantially equal rate. The present invention further provides a method of manufacturing this device, comprising the steps of forming an elongated catheter and providing a plurality of exit holes along a length of the catheter in a manner so that the exit holes gradually increase in size along the length of the catheter from the proximal end to the distal end thereof.

Yet another embodiment of the present invention provides a catheter and method for delivering fluid medication to an anatomical region. The catheter comprises a tube, a “weeping” tubular coil spring attached to a distal end of the tube, and a stop closing a distal end of the spring. The tube and spring each define a portion of a central lumen. The spring has adjacent coils in contact with one another so that fluid within the spring and below a threshold dispensation pressure is prevented from exiting the lumen by flowing radially between the coils. The spring has the property of stretching when the fluid pressure is greater than or equal to the threshold dispensation pressure permitting the fluid to be dispensed from the lumen by flowing radially between the coils, i.e. “weeping” through the spring. Alternatively, the fluid may weep through imperfections in the spring coil. Advantageously, the fluid is dispensed substantially uniformly throughout the length and circumference of a portion of the spring. In use, fluid is introduced into an open proximal end of the tube, allowed to flow into the spring, and brought to a pressure greater than or equal to the threshold dispensation pressure so that the fluid weeps through the spring.

Yet another embodiment of the present invention provides a catheter and method for delivering fluid medication to an anatomical region. The catheter comprises a distally closed tube and a “weeping” tubular coil spring, as described above, concentrically enclosed within the tube. A plurality of exit holes are provided in side walls along a length of the tube, defining an infusion section of the tube. The spring is enclosed within the infusion section so that a lumen is defined within the tube and spring. In use, fluid is introduced into a proximal end of the tube, allowed to flow into the spring, and brought to a pressure greater than or equal to the threshold dispensation pressure of the spring so that the fluid is dispensed from the lumen by weeping through the spring and then flowing through the exit holes of the tube.

Yet another embodiment of the present invention provides a catheter comprising an elongated tube and a solid flexible member positioned within the tube. The tube has a closed distal end and a plurality of exit holes in side walls of the tube. The exit holes are provided along a length of the tube defining an infusion section of the catheter. The tube is sized to be inserted into an anatomical region. The member is positioned within the tube and is sized so that an annular space is formed between the tube and the member. The member is formed of a porous material. Advantageously, the catheter is configured so that a fluid introduced into a proximal end of the tube will flow through the exit holes at a substantially uniform rate throughout the infusion section.

In yet another embodiment, the present invention provides a catheter comprising an elongated tube having a plurality of exit slots in side walls of the tube. The slots are provided along a length of the tube defining an infusion section of the catheter. The exit slots are oriented generally parallel to the longitudinal axis of the tube. Advantageously, the tube is configured so that a fluid flowing therein will flow through substantially all of the exit slots at a substantially equal rate. In one optional aspect, the slots increase in length from the proximal to the distal ends of the infusion section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-4illustrate an infusion catheter20according to one embodiment of the present invention. Catheter20preferably includes a flexible support22(FIGS. 2-4), a non-porous membrane24, and a porous membrane26. The membranes24and26are wrapped around the support22to form a plurality of axial lumens between the inner surfaces of the membranes24and26and the surface of the support22, as described in greater detail below. The non-porous membrane24defines a non-infusing section28of the catheter20, and preferably covers the support22from the proximal end thereof to a point30, shown inFIG. 1. Similarly, the porous membrane26defines an infusion section32of catheter20, and preferably covers the support22from the point30to the distal end of support22. Alternatively, the catheter20may be configured without a non-porous membrane24. In this configuration, the porous membrane26covers the entire length of the support22, so that the entire length of the support22corresponds to the infusion section of the catheter20. The infusion section can have any desired length. The proximal end of the catheter20may be connected to a fluid supply34containing a fluid36such as a liquid medication. The distal end of catheter20may include a cap48(FIG. 4) defining the endpoint of the axial lumens within the catheter20.

In use, the catheter20is inserted into an anatomical system, such as a human body, to deliver fluid medication directly to a wound area within the anatomical system. In particular, the catheter20is designed to deliver medication throughout a generally linear segment of the wound area, corresponding to the infusion section32of the catheter20. Thus, the catheter is preferably inserted so that the infusion section32is positioned within the wound area. By using well known methods, a physician or nurse may insert the catheter20with the aid of an axial guide wire46positioned within an axial guide wire lumen44of the catheter. Once the catheter is positioned as desired, the guide wire46is simply pulled back out through the proximal end of the catheter20. Alternatively, the catheter20may be provided without a guide wire or a guide wire lumen.

FIGS. 2 and 3illustrate a preferred configuration of the support22. The surface of the support22includes interruptions such as a plurality of ribs40as shown in the figures. The interruptions are configured so that when the membranes24and26are wrapped around the support22, the membranes form a portion of the walls of a plurality of axial lumens38within which the fluid36may flow. In a preferred configuration, a plurality of ribs40extend radially from a common axial center portion42of the support22. The ribs40also extend longitudinally along a length of the support22, and preferably along the entire length thereof. In the non-infusing section28, shown inFIG. 2, the non-porous membrane24is preferably tightly wrapped around the outer edges of the ribs40. As a result, the axial lumens38are formed between the inner surface of the non-porous membrane24and the outer surface of support22. Similarly, in the infusion section32, shown inFIG. 3, the porous membrane26is preferably tightly wrapped around the outer edges of the ribs40, so that the axial lumens38are formed between the inner surface of porous membrane26and the outer surface of support22.

In an alternative embodiment of the catheter20, the porous membrane26may be wrapped around the entire length of the support20, thus replacing the non-porous membrane24. In this embodiment, the entire length of the support22corresponds to the infusion section32. According to another alternative embodiment, the support22may extend only within the infusion section32, and a tube may be provided extending from the fluid supply34to the proximal end of the support22. In this embodiment, the tube replaces the non-porous membrane24and the portion of the support22extending within the non-infusing section28of the preferred embodiment. In other words, the tube defines the non-infusing section28.

In the preferred configuration, the number of ribs40equals the number of axial lumens38. Although five ribs40and axial lumens38are shown inFIGS. 2 and 3, any suitable number of ribs40and lumens38may be provided, giving due consideration to the goals of providing a plurality of lumens within the catheter20, maintaining flexibility, and, if desired, maintaining the fluid independence of the lumens. Herein, the terms “fluid independence,” “fluid separation,” and the like, when used to describe a plurality of axial lumens, simply mean that the lumens do not fluidly communicate with each other. The membranes24and26are preferably glued along the outer edges of the ribs40, utilizing any suitable glue, such as a medical grade glue or epoxy. This prevents the membranes24and26from slipping, which might occur as the catheter is inserted or removed from the anatomy. More preferably, the membranes are glued along the entire length of the outer edges of each of the ribs40. Alternatively, the membrane may be wrapped around the support and not secured to the support by a foreign substance. The membrane and support may also be secured to each other by other means known to those of skill in the art. This maintains the fluid independence of the lumens38. If desired, an axial guide wire lumen44may be provided within the axial central portion42of the support22. The guide wire lumen44is adapted to receive a guide wire46which may be used to aid in the insertion of the catheter20into the anatomy, as described above and as will be easily understood by those of skill in the art.

As shown inFIG. 4, the catheter20preferably includes an end portion or cap48secured to the distal end of support22. End portion48may be formed integrally with the support22or may be adhesively bonded thereto. Preferably, the proximal end of end portion48is circular and has a diameter such that the outer surface of the proximal end of end portion48is aligned with the outer edges of the ribs40of the support22, as shown. The porous membrane26is wrapped around the proximal end of the end portion48. The membrane26is preferably glued to the end portion48so that fluid36within the lumens38is prevented from exiting the catheter20without passing through the walls of the membrane26. End portion48blocks axial fluid flow through the distal end of catheter20. However, end portion48may optionally be formed from a porous material to permit some axial dispensation of fluid from the distal end of the catheter20, if desired. The distal end of end portion48is preferably dome-shaped, as shown, to permit the catheter20to more easily be inserted into an anatomical region.

The support22can be formed from a variety of materials, giving due consideration to the goals of flexibility, light-weight, strength, smoothness, and non-reactivity to anatomical systems, i.e., safety. Suitable materials for the support22include nylon, polyamide, teflon, and other materials known to those skilled in the art. The porous membrane26is preferably a sponge-like or foam-like material or a hollow fiber. The membrane26may be formed from a variety of suitable materials, giving due consideration to the goals of being flexible and non-reactive to anatomical systems. The membrane26preferably has a porosity resulting in substantially uniform dispensation of fluid along the surface area of the infusion section32of the catheter20, and has an average pore size sufficiently small to limit the flow of bacteria through the membrane walls. Some suitable materials for the membrane26are polyethylene, polysulfone, polyethersulfone, polypropylene, polyvinylidene difluoride, polycarbonate, nylon, or high density polyethylene. These materials are advantageously biocompatible. The porous membrane26may filter out unwanted bacteria from the fluid medication as it passes through the membrane26. It is known that the smallest bacteria cannot pass through a pore any smaller than 0.23 microns. Thus, the average pore size, or pore diameter, of the porous membrane26may be less than 0.23 microns to prevent bacteria from traversing the membrane26. The average pore size, or pore diameter, of the membrane26is preferably within the range of about 0.1 to 1.2 microns, more preferably within the range of about 0.3 to 1 micron, and even more preferably about 0.8 microns.

As mentioned above, the proximal end of catheter20may be connected to a fluid supply34. The catheter20may be configured so that each axial lumen38is fluidly independent. In other words, the lumens38would not fluidly communicate with one another. The catheter20may be connected to a single fluid supply34, so that the fluid36flows within each of the lumens38. Alternatively, the catheter20may be connected to a plurality of separate fluid supplies so that several different fluids may separately flow within the lumens38. According to this configuration, each lumen38may be connected to a separate fluid supply so that the total number of different fluids that may be delivered to the anatomy is equal to the number of lumens38. Alternatively, the fluid lumens need not be fluidly independent. For example, the membrane26may not be secured to the support22along the entire length of the support22, thus permitting fluid36to migrate between lumens38.

In operation, the catheter20delivers fluid directly to the area of the anatomy that is adjacent to the infusion section32. The fluid36from the fluid source34is introduced into the axial lumens38at the proximal end of the catheter20. The fluid36initially flows through the non-infusing section28. When the fluid36first reaches the infusion section32, it soaks into the porous membrane26. As more fluid36enters the infusion section32, it diffuses longitudinally within the walls of the membrane26until the entire membrane26and infusion section32are saturated with fluid. At this point the fluid36begins to pass through the membrane26, thereby exiting the catheter20and entering the anatomy. Moreover, the fluid36advantageously passes through the entire surface area of the porous membrane26at a substantially uniform rate, due to the characteristics of the membrane26. Thus, the fluid is delivered at a substantially equal rate throughout a generally linear segment of the wound area of the anatomy. Furthermore, this advantage is obtained for both low and high pressure fluid delivery.

FIGS. 5 and 6illustrate a catheter50according to an alternative embodiment of the present invention. According to this embodiment, the catheter50includes an elongated outer tube52and an inner elongated tubular porous membrane54. The tubular membrane54is preferably concentrically enclosed within the outer tube52. More preferably, the tube52tightly surrounds and supports the tubular membrane54so that a relatively tight fit is achieved between the inner dimensions of tube52and the outer dimensions of membrane54. A plurality of fluid exit holes56are provided within the tube52, preferably throughout the entire circumference thereof. The portion of tube52that includes the exit holes56defines the infusion section of catheter50. The tubular membrane54need only be provided along the length of the infusion section, but could be longer. Optionally, axial exit holes may be provided within the distal tip58of the tube52. Also, a guide wire and/or guide wire lumen may be provided to aid in the insertion of the catheter50into the anatomy, as will be understood by those skilled in the art.

The tube52may be formed from any of a variety of suitable materials, such as nylon, polyimide, teflon and other materials known to those skilled in the art, giving due consideration to the goals of non-reactivity to anatomical systems, flexibility, light-weight, strength, smoothness, and safety. In a preferred configuration, the tube52is preferably a 20 gauge catheter tube, having inside and outside diameters of 0.019 inches and 0.031 inches, respectively. The exit holes56of tube52are preferably about 0.015 inches in diameter and provided at equally spaced axial positions along the tube52. The holes56are preferably arranged so that every hole is angularly displaced about 120 relative to the longitudinal axis of the tube52, from the angular location of the previous hole. The axial separation between adjacent exit holes56is preferably within the range of about 0.125 to 0.25 inches, and more preferably about 3/16 inch. Also, the infusion section can have any desirable length. This configuration results in a thorough, uniform delivery of fluid throughout a generally linear segment of the wound area. Of course, the exit holes56may be provided in any of a variety of alternative arrangements.

The tubular porous membrane54is preferably a sponge-like or foam-like material or a hollow fiber. The tubular membrane54may have an average pore size, or pore diameter, less than 0.23 microns to filter bacteria. The pore diameter is preferably within the range of about 0.1 to 1.2 microns, more preferably within the range of about 0.3 to 1 micron, and even more preferably about 0.8 microns. The tubular membrane54may be formed from any of a variety of suitable materials, giving due consideration to the goals of non-reactivity to anatomical systems, maintaining flexibility, fitting within the size constraints of the tube52, and having a porosity resulting in the substantially uniform dispensation of fluid through all of the exit holes56in tube52. Some suitable materials for the membrane54are polyethylene, polysulfone, polyethersulfone, polypropylene, polyvinylidene difluoride, polycarbonate, nylon, or high density polyethylene. Preferable inside and outside diameters of the tubular membrane54are 0.010 inches and 0.018 inches, respectively. In the event that a guide wire46is provided, the guide wire may be a stainless steel wire about 0.005 inches in diameter. The tube52may be secured to the membrane54by epoxy or other means known to those skilled in the art. Alternatively, the membrane54may contact the tube52with an interference fit and not use other materials to secure the membrane54in the tube52.

In operation, the catheter50delivers fluid to the region of an anatomical system adjacent to the infusion section of catheter50. As the fluid flows into the infusion section, it initially soaks into the tubular porous membrane54. As more fluid enters the infusion section, the fluid diffuses longitudinally within the walls of the tubular member54. Once the membrane54and the tubular space therein are saturated, the fluid passes through the membrane54and exits the catheter50by flowing through the exit holes56of the tube52. Moreover, the fluid advantageously passes through the membrane substantially uniformly throughout the surface area of the membrane54, resulting in a substantially uniform flow through substantially all of the exit holes56. Thus, the fluid is delivered at a substantially equal rate throughout the wound area of the anatomy. Furthermore, this advantage is obtained for both low and high pressure fluid delivery.

FIG. 7illustrates a catheter70according to another embodiment of the present invention. Catheter70includes a tube72having a plurality of exit holes76in side walls of the tube, and a tubular porous membrane74concentrically enclosing the tube72. Catheter70operates in a similar manner to catheter50described above in connection withFIGS. 5 and 6. In use, fluid medication passes through the exit holes76and then begins to soak into the porous membrane74. The fluid diffuses longitudinally within the walls of the membrane until the membrane is saturated. Thereafter, the fluid leaves the membrane walls and enters the anatomy. Advantageously, the fluid is dispensed to the anatomy at a substantially uniform rate throughout the surface area of the membrane74. As in the previous embodiments, this advantage is obtained for both low and high pressure fluid delivery.

FIG. 8illustrates a catheter60according to another embodiment of the present invention. Catheter60is better suited for relatively high flow rate delivery of fluid to a region within an anatomical system. Catheter60includes a tube62having a plurality of exit holes64of increasing size. In particular, the more distal exit holes are larger in diameter than the more proximal exit holes. The position of the exit holes64on the tube62defines the length of the infusion section of the catheter60. The infusion section can have any desired length. The proximal end of catheter60is connected to a fluid supply, and a guide wire and/or guide wire lumen may also be provided for aiding in the insertion of catheter60into the anatomy.

As discussed above, for high or low pressure fluid delivery, exit holes nearer to the distal end of a catheter tube generally have increased flow resistance compared to exit holes nearer to the proximal end of the tube. Also, the fluid flowing through the more distal holes experiences a greater pressure drop. Consequently, there is generally a greater flow rate of fluid through the more proximal holes, resulting in non-uniform fluid delivery. In contrast, catheter60advantageously provides substantially uniform fluid delivery through substantially all of the exit holes64, under relatively high flow rate conditions. This is because the larger size of the more distal holes compensates for their increased flow resistance and pressure drop. In other words, since the more distal holes are larger than the more proximal holes, there is a greater flow rate through the more distal holes than there would be if they were the same size as the more proximal holes. Advantageously, the holes64are provided in a gradually increasing size which results in substantially uniform fluid delivery. In addition, the exit holes64may be sized so that they combine to form a flow-restricting orifice, as described below in connection with the embodiment ofFIG. 12.

As compared to prior art catheters, catheter60is advantageously simple and easy to manufacture. All that is required is to drill a plurality of exit holes64in the tube62. Furthermore, catheter60can sustain greater bending than prior art catheters while maintaining operability. In contrast to prior art catheters, such as the Wang catheter, if the tube62is bent somewhat, it will still deliver fluid relatively uniformly. This is because the tube62has a single lumen with a relatively large cross-section. When the tube62is somewhat bent, fluid flowing within the lumen is less likely to experience blockage and a consequent pressure change which might lead to non-uniform fluid dispensation.

The tube62of catheter60may be formed from any of a wide variety of materials, giving due consideration to the goals of non-reactivity to anatomical systems, flexibility, light-weight, strength, smoothness, and safety. Suitable materials include nylon, polyimide, teflon, and other materials known to those skilled in the art. The infusion section can have any desired length but is preferably about 0.5 to 20 inches long, and more preferably about 10 inches long. The diameter of the exit holes64preferably ranges from about 0.0002 inches at the proximal end of the infusion section to about 0.01 inches at the distal end thereof. The largest, i.e., most distal, exit hole64is preferably about 0.25 inches from the distal end of the tube62. In the preferred configuration, the axial separation between adjacent holes64is within the range of about 0.125 to 0.25 inches, and more preferably about 3/16 inch. Optionally, the holes64may be provided so that adjacent holes are angularly displaced by about 120 as in the embodiment ofFIG. 5. Of course, if too many exit holes64are provided, the tube62may be undesirably weakened.

FIGS. 9,10A, and10B illustrate a catheter80according to another embodiment of the present invention. The catheter80comprises a tube82, a “weeping” tubular coil spring84, and a stop86. The proximal end of the spring84is attached to the distal end of the tube82so that the tube and spring each define a portion of a central lumen. A preferably dome-shaped stop86is attached to and closes the distal end of the spring84. The portion of the spring84that is distal to the tube82comprises the infusion section of the catheter80. In an unstretched state, shown inFIG. 10A, the spring84has adjacent coils in contact with one another so that fluid within the spring and below a threshold dispensation pressure is prevented from exiting the lumen by flowing radially between the coils. The spring84has the property of stretching longitudinally, as shown inFIG. 10B, when the fluid pressure is greater than or equal to the threshold dispensation pressure of the spring, thereby permitting the fluid to be dispensed from the lumen by “weeping,” i.e., leaking radially outward between the coils. Alternatively, the spring may stretch radially without elongating to permit fluid to weep through the coils of the spring. Further, the spring may stretch both longitudinally and radially to permit weeping, as will be understood by those of skill in the art. Advantageously, the fluid between the coils of the spring is dispensed substantially uniformly throughout the length and circumference of the portion of the spring that is distal to the tube82, i.e., the infusion section. The catheter80can be used for both high or low flow rate fluid delivery.

In use, the catheter80is inserted into an anatomical region so that the spring84is in a region to which fluid medication is desired to be delivered. The spring is initially in an unstretched state, as shown inFIG. 10A. The fluid is introduced into a proximal end of the tube82of the catheter80and flows into and through the spring84until it reaches the stop86. As fluid is continually introduced into the proximal end of the tube82, the fluid builds inside of the spring84. When the spring84is filled with fluid, the fluid pressure rises more quickly. The fluid imparts a force directed radially outward onto the spring coils. As the pressure builds, the outward force becomes larger. Once the fluid pressure rises to the threshold dispensation pressure, the outward force causes the spring coils to separate slightly so that the spring stretches longitudinally, as shown inFIG. 10B. Alternatively, the coils may separate radially, as discussed above. The fluid then flows through the separated coils to be dispensed from the catheter80. Moreover, the dispensation is advantageously uniform throughout the infusion section of the catheter80. As fluid is continually introduced into the tube82, the spring84remains stretched to continually dispense fluid to the desired region within the anatomy. If the fluid introduction temporarily ceases, the fluid pressure within the spring84may fall below the threshold dispensation pressure. If so, the spring will compress so that the coils are once again adjacent and the fluid is no longer dispensed.

Several spring types will achieve the purposes of this invention. Suitable spring types are 316L or 402L, which can be readily purchased. In a preferred configuration, the spring84has about 200 coils per inch along its length. In this configuration, the spring can advantageously sustain a high degree of bending without leaking fluid from within, and only a severe bend will cause adjacent coils to separate. Thus, the spring84may be flexed considerably within an anatomical region without causing fluid to leak and therefore be dispensed to only one region within the anatomy. The spring84can have any desired length to define the length of the infusion section of the catheter80. The spring may be formed from a variety of materials, giving due consideration to the goals of strength, flexibility, and safety. A preferred material is stainless steel. In the preferred configuration, the inside and outside diameters of the spring are about 0.02 inches and 0.03 inches, respectively, and the spring wire has a diameter of about 0.005 inches. The proximal end of the spring84is preferably concentrically enclosed within the distal end of the tube82. The spring can be glued to the inside wall of the tube82using, for example, a U.V. adhesive, a potting material, or other bonding materials. Alternatively, the spring can be soldered within the tube82or be fitted with a proximal plug and tightly plugged into the tube82.

The tube82and stop86can be formed from any of a variety of materials, giving due consideration to the goals of flexibility, light-weight, strength, smoothness, and safety. Suitable materials include nylon, polyimide, teflon, and other materials known to those skilled in the art.

FIG. 11illustrates a catheter90according to another embodiment of the present invention. The catheter90comprises a distally closed tube92and a “weeping” tubular coil spring94concentrically enclosed within the tube92so that a lumen is defined within the tube and spring. A plurality of exit holes96are provided along a length of the tube92, in the side wall thereof. The length of the tube92including such exit holes96defines an infusion section of the catheter90. The exit holes96are preferably provided throughout the walls of the infusion section. The infusion section can have any desired length. In the preferred configuration, the axial spacing between adjacent holes96is within the range of about 0.125 to 0.25 inches, and more preferably about 3/16 inch. Adjacent holes96are preferably angularly spaced apart by about 120°. The spring94is preferably enclosed within the infusion section of the catheter and configured similarly to the spring84of the embodiment ofFIGS. 9,10A and10B. The spring94is preferably longer than the infusion portion and positioned so that all of the exit holes96are adjacent to the spring94. In this configuration, the fluid is prevented from exiting the lumen without flowing between the spring coils. A stop is preferably attached to the tube to close the distal end thereof. Alternatively, the tube92may be formed with a closed distal end. The catheter90can be used for high or low flow rate fluid delivery.

In use, the catheter90is inserted into an anatomical region so that the infusion section is in a region to which fluid medication is desired to be delivered. The fluid is introduced into a proximal end of the tube92of the catheter90and flows through the spring94until it reaches the closed distal end of the tube92. As fluid is continually introduced into the proximal end of the tube92, the fluid builds inside of the spring94. Eventually, the spring94becomes filled with fluid, the fluid pressure rises, and the fluid weeps through the spring coils as described above in connection with the embodiment ofFIGS. 9,10A, and10B. Moreover, the fluid flows through the spring coils substantially uniformly throughout the length and circumference of the spring94. The fluid then exits the tube92by flowing through the exit holes96of the infusion section. The exit holes are preferably equal in size so that the fluid flows at a substantially equal rate through the exit holes, advantageously resulting in a generally uniform distribution of fluid throughout a desired region of the anatomy. As fluid is continually introduced into the catheter90, the spring94remains stretched to continually dispense fluid from the catheter. If the fluid introduction ceases temporarily, the fluid pressure within the spring94may fall below the threshold dispensation pressure. If so, the spring may compress so that the coils are once again adjacent and the fluid is no longer dispensed.

In the preferred configuration, the spring94and tube92are in contact along the entire length of the spring, so that the fluid weeping through the spring is forced to flow through the holes96of the infusion section. Preferably, one end of the spring94is attached to the inside walls of the tube92, permitting the other end of the spring to be displaced as the spring stretches. The spring can be glued to the tube92with, for example, a U.V. adhesive, potting material, or other bonding materials. Alternatively, an end of the spring can be soldered onto the inner walls of the tube92. The tube92can be formed from any suitable material. The inside walls of the tube92are preferably smooth so that the spring can more freely stretch and compress.

FIG. 12illustrates a catheter100according to another embodiment of the present invention. The catheter100comprises a distally closed tube102having a plurality of exit holes104in side walls of the tube102. The portion of the tube102having exit holes104defines an infusion section of the catheter100. The exit holes104are sized to have a combined area of opening that is smaller than the area of any other flow-restricting cross-section or orifice of the catheter. Thus, the exit holes104are the flow-restrictor of the catheter100. In use, the catheter advantageously dispenses fluid through substantially all of the exit holes104. A fluid introduced into a proximal end of the tube102flows through the tube until it reaches the closed distal end thereof. At this point, the fluid builds within the infusion portion of the catheter. The fluid is substantially prevented from flowing through the holes104, due to their small size. Eventually, the infusion portion of the catheter becomes filled with fluid. As fluid is continually introduced into the proximal end of the tube102, the fluid pressure begins to build. At some point the pressure becomes sufficiently high to force the fluid through the exit holes104. Moreover, the fluid flows through substantially all of the exit holes104.

In this preferred configuration, the exit holes104are all equal in size so that the fluid is dispensed at a substantially equal rate through substantially all of the holes. The holes104are preferably laser drilled to achieve a very small hole diameter. A preferred diameter of the exit holes104is about 0.0002 inches, or about 5 microns. Numerous exit holes104may be provided within the tube102. The holes are advantageously provided throughout the circumference of the infusion portion of the catheter100, to more uniformly deliver the fluid throughout an anatomical region. A preferred axial spacing between adjacent holes104is within the range of about 0.125 to 0.25 inches, and more preferably about 3/16 inch. The catheter100can be used for high or low flow rate fluid delivery. The tube102can be formed from any of a variety of materials known to those skilled in the art and discussed previously.

FIG. 13illustrates a catheter200according to another embodiment of the present invention. Catheter200includes a distally closed tube202having a plurality of exit holes204therein along an infusion section of the catheter, as in the above-described embodiments. The holes204are desirably provided throughout the circumference of the tube202. Enclosed within the tube202is an elongated member206formed of a porous material. Preferably, the member206is generally cylindrical in shape, and solid. Preferably, the member206is positioned within the tube204so that an annular space208is formed between the outer surface of the member206and the inner surface of the tube202. Preferably, the member206extends from the distal end210of the tube202rearwardly to a point proximal of the infusion section of the catheter. Alternatively, the member206may extend along only a portion of the infusion section. The member206is preferably generally concentric with the tube202, but non-concentric designs will achieve the advantages of the invention. Preferably, the member206is manufactured of a flexible material to assist with the placement of the catheter200in the body of a patient.

In operation, fluid medication flowing in the tube202saturates the porous member206and flows into the annular region208. Once the member206is saturated, the fluid in the member206flows into the region208and out of the catheter200through the exit holes204. Advantageously, since the fluid pressure is uniform throughout the annular region208, the fluid flows substantially uniformly through all of the holes204. There are several advantages of the annular region208. One advantage is that it tends to optimize the uniformity of flow through the exit holes204. Also, the member206may be formed from a porous material that tends to expand when saturated with liquid. If so, the member206preferably expands into the annular region208without pressing against the tube202. This limits the possibility of high pressure regions at the interior surface of the tube202, which could cause uneven exit flow of the medication within the wound site. Alternatively, the member206may expand and come into contact with the tube202, and still accomplish the goals of the present invention.

The member206is formed of a porous material having an average pore size preferably within the range of 0.1-50 microns, and more preferably about 0.45 microns. The radial width W of the annular region208is preferably within the range of 0 to about 0.005 microns, and more preferably about 0.003 microns. The member206can be formed of any of a variety of materials, giving due consideration to the goals of porosity, flexibility, strength, and durability. A preferred material is Mentek.

The member206can be secured within the tube202by the use of an adhesive. In one embodiment, as shown inFIG. 13, the adhesive is applied at the distal end of the member206to form a bond with the interior surface of the distal end of the tube202. Preferably, adhesive is applied at or near the proximal end of the infusion section of the catheter200. Additionally, the adhesive can be applied to the circumference of the member206at any longitudinal position thereof, forming a ring-shaped bond with the interior surface of the tube202. For example, in the embodiment ofFIG. 13, a ring-shaped bond214is provided just proximal of the infusion section of the catheter200. Other configurations are possible. For example,FIG. 14shows an embodiment in which the adhesive is applied to the distal end of the member206to form a bond216, and also at generally the center of the infusion section to form a ring-shaped bond218.FIG. 15shows an embodiment in which the adhesive is applied only to the distal end of the member206to form a bond220.FIG. 16shows an embodiment in which the adhesive is applied only to the center of the infusion section to form a ring-shaped bond222. Those of ordinary skill in the art will understand from the teachings herein that the adhesive may be applied in any of a variety of configurations. Thus, for example, adhesive at the distal end of the catheter (i.e.,212,216, and220inFIGS. 13,14, and15, respectively) is not required.

In the current best mode of the invention, preferably two bonds are incorporated—one at the most proximal hole and one at the most distal hole of the catheter. Each bond is formed with an adhesive as described below.

The ring-shaped bond214can be formed by pouring the adhesive in liquid form through one of the exit holes204when the member206is in the tube202. The adhesive, having a generally high viscosity, tends to flow about the circumference of the member206, rather than into the body of the member. The adhesive thus forms a ring-shaped bond with the tube202, as will be understood by those of skill in the art. Also, the adhesive plugs the exit hole204through which it is poured. Any of a variety of different types of adhesives will be acceptable, a preferred adhesive being Loctite.

As mentioned above, the member206is preferably concentric with the tube202.FIG. 17shows a cross-section of a catheter200in which the member206is concentrically enclosed within the tube202. Alternatively, the member206may be positioned adjacent to the tube202, as shown inFIG. 18. The configuration ofFIG. 18may be easier to manufacture than that ofFIG. 17, since the member206does not have to be centered within the tube202.

Those of ordinary skill in the art will understand from the teachings herein that the member206can be of any desired length and can extend along any desired length of the infusion section of the catheter200. For example, the member206does not have to extend to the distal end of the tube202. Further, the proximal end of the member206may be either distal or proximal to the proximal end of the infusion section.

When any of the catheters of the above embodiments is used, the catheter may initially have air inside of the catheter tube. For example, the catheter200shown inFIG. 13may have air inside of the porous material of the member206. The introduction of liquid medication into the catheter forces the air to flow out of the exit holes. However, this may take several hours. If the catheter is inserted into a patient while air is inside, and liquid medication is introduced into the catheter, the patient's wound site may receive little or no medication until air is expelled from the catheter tube. Thus, it is preferred to run the liquid medication through the catheter prior to inserting the catheter into a patient, to ensure that the air is expelled from the catheter prior to use. Further, with reference toFIG. 19, an air filter224, as known in the art, can be inserted into the catheter tubing proximal the infusion section226of the catheter200. The filter224prevents undesirable air from entering the infusion section226of the catheter200.

FIGS. 20 and 21illustrate catheter tubes having elongated exit holes or slots. These catheter tubes may be used in place of the catheter tubes shown and described above.FIG. 20shows a tube230having exit holes or slots232that are elongated in the longitudinal direction of the tube230. The slots232are preferably provided throughout the circumference of the tube230, along the infusion section of the catheter. Compared to smaller exit holes, the elongated slots232tend to increase the flowrate of fluid exiting the catheter, by reducing the flow impedance experienced by the fluid. Preferably, the slots232may be oriented longitudinally on the catheter body so as not to compromise the structural integrity of the catheter200, as will be easily understood by those of skill in the art.

FIG. 21shows a tube234having exit holes or slots236whose lengths increase along the length of the tube in the distal direction. In the illustrated embodiment, the slots nearer to the proximal end of the infusion section of the tube234are shorter in length than the slots nearer to the distal end of the infusion section. As in the embodiment ofFIG. 8, the catheter tube234advantageously provides substantially uniform fluid delivery through substantially all of the exit slots236, under relatively high flow rate conditions. This is because the larger size of the more distal slots compensates for their increased flow resistance and pressure drop. In other words, since the more distal slots are larger than the more proximal slots, there is a greater flow rate through the more distal slots than there would be if they were the same size as the more proximal slots. Advantageously, the slots236are provided in a gradually increasing length, which results in substantially uniform fluid delivery. Further, the elongated slots result in generally higher exit flowrates, as in the embodiment ofFIG. 20.

With regard to all of the above embodiments of catheters, an independent guide wire lumen may be provided within or adjacent to the lumen(s) disclosed, as will be understood by those skilled in the art.

The catheters of the present invention can be used in various medical applications. With reference toFIG. 22, in one exemplary application a catheter20(reference numeral20is used to identify the catheter, but any of the above-described catheters can be used) is inserted into a blood clot240inside of a vein or artery242. Preferably, the infusion section of the catheter is within the blood clot240. Liquid medication is preferably introduced into the proximal end of the catheter tube. Advantageously, the medication exits the catheter20at a uniform rate throughout the infusion section to dissolve the clot240.

As will be easily understood by those of skill in the art, any of the catheter embodiments described herein may be used in a variety of applications including, but not limited to, peripheral nerve blocks, intrathecal infusions, epideral infusions, intravascular infusions, intraarterial infusions and intraarticular infusions, as well as in wound site pain management.

In addition, any of the catheters disclosed herein may be integral with a fluid line eminating from an infusion pump as opposed to being an independent catheter designed to be connected or secured to an infusion pump.