Reinforced Venous Access Catheter
A catheter for medical procedures comprises a shaft portion having a distal end insertable into a body lumen, the shaft portion having a wall defining a working lumen extending therewithin and a first strengthening element coupled to the wall to increase a burst pressure of the shaft portion, wherein the first strengthening element cooperates with a base material of the wall to define a flexible region of the shaft portion allowing the shaft portion to be atraumatically inserted into the body lumen.
The treatment of chronic disease often requires repeated and prolonged access to a patient's vascular system to, e.g., to administer medications, blood products, nutrients and other fluids and/or to withdraw blood. When such procedures must be frequently repeated, it may be impractical and/or dangerous to insert and remove the catheter and the needle for each session. In this case, a semi-permanent catheter, (e.g., a peripherally inserted central catheter (PICC)), may be used. As would be understood by those skilled in the art, a PICC is a catheter that is inserted in a vein at a peripheral location, such as the arm or leg and threaded through the vein to the chest, in proximity to the heart.
To simplify the insertion process and reduce patient discomfort, PICCs and other semi-permanent catheters are generally made small and thin. Accordingly, their structural strength is limited by the thickness and type of material forming the catheter's walls. The amount of pressure and flow rate that the catheter can support without damage is also limited. If the maximum pressure the catheter can withstand (the burst pressure) or the maximum flow rate is exceeded, the catheter may be damaged or may completely fail possibly spilling fluids from the catheter into the body. During high pressure injections, escaping fluid may also damage the surrounding tissues.
Modern medical procedures rely considerably on visualization techniques to diagnose and treat diverse conditions. Some of these techniques include the injection of a contrast media to the vascular system to improve visualization of blood vessels and other biological structures during fluoroscopy, radiology, or other imaging. The contrast media is generally a liquid that is opaque to the visualization method used, so that body lumens containing the media appear distinct from other tissues. Typically, contrast media is introduced using a separate catheter designed to withstand the high injection pressures and flow rates necessary to disperse the media throughout the organs of interest. For example in the case of fluoroscopy, the contrast media may be a substance opaque to X-ray radiation. More modern visualization methods such as, for example, enhanced computed tomography (CT) may require the introduction of different contrast media, as would be understood by those skilled in the art.
Conventional PICC catheters are unable to withstand the high pressures and flow rates associated with the introduction of visualization media which are often substantially above what is used for the infusion of medications. Thus, it is often necessary to insert one or more additional catheters dedicated to the contrast media increasing patient discomfort and the time and costs associated with the procedure. If the patient exhibits poor peripheral venous access, the insertion of an additional contrast media catheter may be difficult.SUMMARY OF THE INVENTION
In one aspect, the present invention is directed to a catheter for medical procedures comprising a shaft portion having a distal end insertable into a body lumen, the shaft portion including a wall defining a working lumen extending therewithin and a first strengthening element coupled to the wall to increase a burst pressure of the shaft portion, wherein the first strengthening element cooperates with a base material of the wall to define a flexible region of the shaft portion allowing the shaft portion to be atraumatically inserted into the body lumen.
The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The invention is related to medical devices used to introduce a contrast media fluid into a patient, preferably at high pressure and with a large flow rate. Specifically, the devices according to the invention may be used to inject the contrast media using a PICC.
As described above, where repeated access to the vascular system is required, a semi-permanent central venous catheter may be inserted in a vein kept in place for up to two years. A PICC typically comprises a flexible elongated portion tunneled from a remote peripheral location (an arm or leg) to a location near the heart. The proximal end of the PICC may be accessed via a port placed, for example, subcutaneously in the arm or chest of the patient or which may remain outside of the body.
As would be understood by those skilled in the art, the pressure exerted by the fluid is a function of the flow rate, the viscosity and the cross sectional flow area of the catheter, among other variables. Accordingly, limitations on the fluid pressure and/or flow rate are often specified for various types of catheters to ensure that the catheter will not be damaged during use by excessive strains. However as mentioned above, modern imaging methods often rely on the introduction of contrast fluids at high flow rates.
The catheter according to the present invention, may be used for both central venous access and the injection of contrast media decreasing patient discomfort and the time and expense of procedures. The catheter according to this invention, e.g., a PICC venous catheter, is at least partially reinforced to enhance its burst pressure and maximum flow rate to levels suitable for the introduction of contrast media without compromising kink resistance or increasing the cross sectional profile of the catheter, as compared to conventional PICC devices.
For example, a catheter according to the present invention will withstand a flow rate of about 4 to about 6 cc/sec and a pressure of more than about 300PSi typical of power injection devices. A reinforcement is included in the exemplary catheter according to the invention to increase the burst pressure. In one embodiment, both the shaft of the catheter and an extension tube thereof are reinforced, to give a substantially uniform resistance to the increased pressure. Alternatively, only the shaft may be reinforced.
It is often necessary, in the course of a catheterization procedure, to adjust the length of the portion of the catheter inserted into the patient. Generally, the surgeon cuts a distal portion of the catheter to a desired length. Thus, in the case of a catheter 100 reinforced according to the present invention, the reinforcing material is preferably selected so that it can be easily cut with a blade. The exemplary materials described above fall within this category, so that the reinforced catheter 100 may be cut to a desired length using conventional methods. Alternatively, a material that is more difficult to cut may be used and/or a portion of the catheter 100 may be left unreinforced so that it may be cut. For example, the weakest portions of the catheter, such as the portion immediately distal to the suture wing, may be reinforced, leaving a 20-40 cm section of the tip of the catheter unreinforced. Because the portion immediately distal to the suture wing is one of the weakest and most likely to fail, reinforcement around the weak areas will prevent most failures from occurring. The unreinforced section of the catheter will continue to permit surgeons to easily cut the catheter in conventional manners, such as with a blade.
According to the present embodiment, the catheter 100 may be composed of various layers with each layer being formed of a material of different hardness, thereby allowing the catheter 100 to be atraumaticly inserted while exhibiting an improved resistance to the pressures associated with high flow rate power injection. As would be understood by those skilled in the art, the manufacture of the catheter 100 may be accomplished using a co-extrusion or a lamination process. For example, the softer, more flexible outer layer 104 of the shaft wall 102 may be co-extruded with the stiffer, higher durometer inner layer 106. This configuration provides both the flexible outer portion and the pressure resistant inner portion of the catheter 100.
The co-extrusion process may be carried out with polymers that are either compatible or non-compatible with one another. If non compatible polymers are used, it may be necessary to provide an intermediate tie layer along an interface 112 between the outer layer 104 and the inner layer 106. In this exemplary embodiment, a soft thermoplastic polyurethane (TPU) may be used for the outer layer 104 while a stiff polyester block-amide (PEBA), a stiff polyether block-amide, polyolefin or polytetrafluoroethylene (PTFE) may be used for the inner layer 106. The outer TPU exhibits softening while within the body, giving the desired flexibility, etc., and allowing atraumatic insertion. However the PEBA of the inner layer 106 retains its inherent strength and resistance to pressure.
A further exemplary embodiment of a catheter shaft according to the invention is shown in
A variation of the braid reinforcement is shown in cross section in
In a different embodiment, the reinforcement braid may be disposed on the outside of the catheter body. For example,
To further improve the pressure resistance and ultimate hoop strength of the base catheter material, micro particles may be added to the compound forming the catheter wall. The micro particles (sometimes referred to as nano-particles, depending on their size) may include clay and fumed silica.
As an alternative to introducing strengthening particles into the catheter material, cross linking agents may be incorporated into the base material of the catheter shaft. For example, agents such as silanes, dicumyl peroxide, maleic anhydride and functionalized polymers may be added. These agents are effective in partially cross-linking thermoplastic polymers. Activation of the cross linking agents may be accomplished in a conventional manner, for example through secondary exposure to high energy sources such as electron beams to increase the strength of the base material. As indicated above, both the radial and tangential distribution of cross linking agents through the material of the catheter shaft may be selected to obtain desired mechanical properties, as would be understood by those skilled in the art.
It will be apparent to those of skill in the art that the various methods described herein to increase the strength of a catheter shaft wall may be applied selectively to certain portions of the catheter in question. For example,
In one exemplary application, the longitudinal variation in the strength of catheter wall 208 may be used to allow the user to trim the distal end of the catheter shaft 200, to provide a better fit in the patient. Leaving the unreinforced portion 202 without the reinforcement elements 206 included elsewhere (i.e., in reinforced portion 204) to increase pressure resistance allows the user to cut the wall 208 more easily, The reinforcement elements 206 may thus be selected to have greater strength, since it is not necessary that the user be able to cut therethrough to trim the catheter shaft 200 to the desired length. In one example, between about 15 cm and 20 cm of the distal end of catheter shaft 200 may form the unreinforced portion 202.
In another exemplary application, the wall of shaft 200 may be composed of varying materials, or may be otherwise reinforced by different amounts along its length to allow for increased strength and durability at specified stress points. These points of increased stress may occur during power injection of a fluid only at certain locations, such as near the injection point or near bends in the catheter. In this manner, the additional material used to strengthen the catheter may be targeted where it is most effective, without having to reinforce the entire catheter. This construction may be simpler and less costly than forming a catheter with reinforcements along its entire length.
According to another exemplary embodiment of the invention, the catheter shaft or the extension tube may be constructed with an inherent weak point designed to fail before the rest of the device does. When the catheter experiences excessive pressure, the extension tube will fail and release the pressure, leaving the catheter shaft intact. The extension tube may be formed with a tapered region of lesser strength, or by profiling the wall thickness of the tube to create the designated failure point. As shown in
In another embodiment, the inherent weak point may be formed by making either or both of the inside and outside diameters of the tube irregular in cross section. The non uniform wall thickness thus created, for example in the extension tube, defines specific sites for failure of the tube. As shown in the example of
The present invention has been described with reference to specific embodiments, and more specifically to a MC catheter used for power injection of contrast media used in CT imaging. However, other embodiments may be devised that are applicable to other medical devices and procedures, without departing from the scope of the invention. Accordingly, various modifications and changes may be made to the embodiments, particularly with regard to dimensions and materials, without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive illustrative rather than restrictive sense.
55. A catheter, comprising:
- an elongated shaft extending from a proximal end to a distal end and having a first channel extending longitudinally therethrough, the elongated shaft comprising a reinforced portion extending along a first predetermined length thereof and a non-reinforced portion separated from the reinforced portion along a longitudinal axis of the catheter, the non-reinforced portion extending along a second predetermined length of the shaft, reinforced portion comprising a first inner layer defining an outer wall of the first channel and having a first material with a first durometer and a second outer layer forming an outer wall of the elongated shaft and having a second material with a second durometer, the first durometer being greater than the second durometer and the non-reinforced portion comprising the second material.
56. The catheter of claim 55, wherein the elongated shaft further comprises a partition wall separating the first channel from a second channel extending longitudinally through the catheter.
57. The catheter of claim 56, wherein the partition wall is formed of the second material.
58. The catheter of claim 56, wherein the partition wall is formed of the first material.
59. The catheter of claim 55, further comprising a strengthening material embedded within the second outer later.
60. The catheter of claim 59, wherein the strengthening material is one of a braid, a mesh, a layered multi-material composite structure and a plurality of reinforcing particles.
61. The catheter of claim 59, wherein the strengthening material is formed of one of metal, stainless steel, a shape-memory material, a polymer, a polyolefin, kevlar, vectran and silk.
62. The catheter of claim 55, further comprising a strengthening material disposed around an outer surface of the second outer layer.
63. The catheter of claim 62, wherein the strengthening material is bonded to the outer surface of the second outer layer.
64. The catheter of claim 62, wherein the strengthening material is longitudinally slidable relative to the outer surface.
65. The catheter of claim 55, further comprising a designated failure point of the elongated shaft configured to withstand a pressure reduced with respect to the reinforced portion.
66. The catheter of claim 65, wherein the designated failure point is a reduced thickness portion of the elongated shaft.
67. The catheter of claim 65, wherein the designated failure point is an extension tube having one or both of an irregular inner cross-section and an irregular outer cross-section.
68. The catheter of claim 67, wherein the inner cross-sectional shape is substantially rectangular and the outer cross-sectional shape is substantially circular.
69. A catheter for introducing a contrast media into a patient, comprising:
- an elongated shaft extending from a proximal end to a distal end and having a first channel extending longitudinally therethrough, the shaft further comprising: a substantially flexible outer layer defining an outer wall of the elongated shaft and configured for atraumatic insertion into a body; a substantially rigid inner layer defining an outer wall of the channel, the inner layer having a durometer greater than a durometer of the outer layer, the rigid inner layer configured to raise a burst pressure of the elongated shaft to permit an increased flow rate through the channel
70. The catheter of claim 69, further comprising a strengthening material embedded within the inner layer.
71. The catheter of claim 70, wherein the strengthening material is longitudinally aligned with a longitudinal axis of the elongated shaft.
72. The catheter of claim 71, wherein the strengthening material is one of a braid, a mesh and a layered multi-material composite structure.
International Classification: A61M 25/00 (20060101); A61B 6/00 (20060101);