FLUID DELIVERY CATHETER

Abstract

Fluid delivery systems comprising catheters used to deliver a fluid into a medical device to which the catheter is attached. Methods and devices for eliminating the effects angular strain on the catheters that lead to kinking and pinching of the catheter.

Claims

1. A fluid delivery system for delivering a fluid to an enclosed reservoir in a device, the fluid delivery system comprising: a flexible catheter having a lumen extending therethrough for delivering the fluid to the enclosed reservoir, the flexible catheter comprising a fill end and a delivery end, wherein the delivery end is configured to be coupled to a wall of the enclosed reservoir, the flexible catheter further comprising an initial outer diameter and an initial inner diameter, where the flexible catheter further includes a region of diametral reduction having a passage; where the region of diametral reduction comprises an outer diameter and an inner diameter, where at least one of the outer diameter and the inner diameter is respectively less than the initial outer diameter and the initial inner diameter, where the region of diametral reduction is located adjacent to the delivery end of the flexible catheter and extends along a length of the flexible catheter towards the fill end.

2. The fluid delivery system of claim 1, where a first end of the region of diametral reduction is located within the enclosed reservoir and a second end of the region of diametral reduction is located exterior to the enclosed reservoir.

3. The fluid delivery system of claim 1, where a first end of the region of diametral reduction is located at a wall surrounding the enclosed reservoir and a second end of the region of diametral reduction is located exterior to the enclosed reservoir.

4. The fluid delivery system of claim 1, wherein the region of diametral reduction has a critical radius and where the region of diametral reduction extends beyond the wall of the enclosed reservoir along a length at least greater than (pi times the critical radius) divided by 10 and at least no less than two times pi times the critical radius.

5. A medical device for positioning in a patient: a balloon member having an internal reservoir, wherein delivery of a fluid into the internal reservoir expands the balloon member; a flexible catheter having a lumen extending therethrough, the flexible catheter comprising a fill end and a delivery end, wherein the delivery end is coupled to the balloon member such that the lumen is in fluid communication with the internal reservoir, the flexible catheter further comprising an initial outer diameter and an initial inner diameter comprising the lumen having, where the flexible catheter further includes a region of diametral reduction having a passage and located adjacent to the balloon member; and the region of diametral reduction including an outer diameter and an inner diameter comprising the passage, where at least one of the outer diameter and the inner diameter is respectively less than the initial outer diameter and the initial inner diameter.

6. A method of producing a fluid delivery system for a medical device using a catheter configured to deliver a fluid to an enclosed reservoir in the medical device in a patient, the method comprising: selecting a suitable catheter that meets a requirement for the fluid delivery system; identifying a section of the catheter to produce the diametrally-reduced region; inserting a mandrel into a lumen of the catheter, the mandrel having a diameter equal to a desired diameter of the diametrally-reduced region and a length extending past a length of the diametrally-reduced region; applying a heat and a radially inward-directed pressure to the section; ceasing application of the heat and the radially inward-directed pressure; and removing the mandrel from the catheter.

7. The method of claim 6, where applying the heat and the radially inward-directed pressure occurs simultaneously.

8. The method of claim 6, further comprising protecting the catheter from the heat and pressure at one or more lengths of the catheter adjacent to the section.

9. The method of claim 6, further comprising removing the mandrel after a cooling-off period.

10. The method of claim 6, wherein applying the heat and the radially inward-directed pressure includes use of a heat-shrink tubing.

11. The method of claim 6 wherein the catheter is protected from the heat and the radially inward-directed pressure outside of the region of diametral reduction by segments of a metal tubing.

12. A fluid delivery system for delivering a fluid to an enclosed reservoir in a device, the fluid delivery system comprising: a flexible catheter having a lumen extending therethrough, the flexible catheter comprising a fill end and a delivery end, wherein the delivery end is configured to be inserted through a wall of the enclosed reservoir, the flexible catheter further comprising an initial outer diameter and an initial inner diameter comprising the lumen, where the flexible catheter further includes a region of diametral reduction; where the region of diametral reduction comprises an outer diameter being less than the initial outer diameter and an inner diameter being less than the initial inner diameter, where the region of diametral reduction is located adjacent to the delivery end of the flexible catheter and extends along a length of the flexible catheter towards the fill end, the region starting at or inside the wall of the enclosed reservoir and extending towards the fill end.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The foregoing and other objects, features and advantages of the methods, devices, and systems described are shown the following description in conjunction with the accompanying drawings, in which reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention.

[0039] FIG. 1 illustrates a gastric balloon device.

[0040] FIGS. 2A and 2B illustrate a fluid delivery catheter connected to an unfilled balloon.

[0041] FIG. 3 illustrates a fluid delivery catheter connected to a filled balloon.

[0042] FIG. 4 is a cross-section view of a strain relieved catheter being displaced.

[0043] FIG. 5 illustrates a cross-section view one embodiment of a tapered strain relief when the catheter is displaced.

[0044] FIG. 6A illustrates a cross-section view of an embodiment of a tapered strain relief.

[0045] FIG. 6B illustrates a cross-section view of a stepped embodiment of the tapered strain relief of FIG. 6A.

[0046] FIG. 7A is a side view of a spatially modulated strain relief.

[0047] FIG. 7B illustrates the spatial modulation pattern of the strain relief of FIG. 7A unwrapped for clarity.

[0048] FIG. 8 is a cross-sectional view of an embodiment of a diametrally-reduced catheter.

[0049] FIGS. 9A-9E illustrate a process for producing a diametrally-reduced catheter.

[0050] FIGS. 10A and 10B illustrate examples of a diametrally-reduced catheter or tubing coupled to a balloon member.

[0051] FIG. 11 is a table of experimental results confirming the efficacy of diametral reduction.

DETAILED DESCRIPTION OF THE INVENTION

[0052] The following illustrations are examples of the invention described herein. It is contemplated that combinations of aspects of specific embodiments or combinations of the specific embodiments themselves are within the scope of this disclosure. The methods, devices, and systems described herein are discussed as being used with a gastric balloon device for convenience for illustrative purposes only. It is intended that the devices, methods, and systems of the present disclosure can be used with other devices where fluid is delivered into/out of the device. For example, such devices can include fluid-inflatable devices that are deployed and inflated with a fluid after insertion into the body. Further, the methods, devices, and system described herein can be used in devices in which a flexible catheter passes through a more rigid barrier.

[0053] The angular strain relief approaches described above reducing the likelihood of catheter kinking by mitigating or smoothing the effects of the inherent discontinuity between the stiff constraining element and the flexible catheter, where this mitigation is achieved by adding a mitigating element to the original catheter. Alternatively, it is possible to modify the structure of the catheter itself to reduce its susceptibility to kinking. Two of these catheter modifications are suggested by equation 3, which states that the critical radius depends on three variables—a constant derived from the catheter's material properties (K), the outer diameter of the catheter (D), and the wall thickness of the catheter (D−d) where d is the inner diameter of the catheter. A third modification of the catheter is not related to equation 3. This third structural modification is to change form of the catheter from a cylindrical tube.

[0054] The first structural modification to consider is to change a material property of the catheter. For the purposes of this specification, K in equation 3 can be thought of as a measure of springiness. A springy material (e.g., one that is elastically resilient) will allow the outer bend of a catheter to stretch and/or the inner bend to compress.

[0055] The second modification suggested by equation 3 is to reduce the catheter's inner and/or outer diameter, creating a “diametrally-reduced” catheter, where an inner diameter and/or an outer diameter of the catheter is reduced relative to another portion of the catheter. This modification is discussed in the next section, Diametral Reduction.

[0056] The third structural modification that will reduce a catheter's susceptibility to kinking is to change its geometric structure from a pure cylindrical tube to a tube in which the walls are not uniform. The critical radius for this geometric structure is not described by equation 3, which only applies to a cylindrical tube.

[0057] Diametral reduction, specifically reduction of the inner diameter (ID), is a method of decreasing the critical radius of a catheter. Additionally, as shown in equation 3, reducing the OD can also decrease the critical radius as long as the wall thickness, equal to ½ (OD−ID) is not reduced so much as to counteract the effect of the diametral reductions. That is, since the critical radius is inversely proportional to the wall thickness it grows rapidly as the wall thickness approaches zero. One variation of a diametrally-reduced catheter is illustrated in cross-section in FIG. 8. In this variation a catheter 110 has been treated to reduce the diameter (both ID and OD) over a section of its length. Reduced diameter section 110D is the section of the catheter intended to pass through, or be held by, the relatively stiffer constraining element 116. Section 110D can be located anywhere along catheter 110 and in some variations of the catheter it may be beneficial to dispose section 110D displaced away from an end of the catheter to leave an unmodified, and therefor stiffer, leading catheter section 110E. This leading section 110E, because it is generally stiffer than reduced diameter section 110D, may be easier than section 110D to thread through the lumen in constraining element 116.

[0058] As shown in FIG. 8, catheter 110 has an initial OD of D1 and initial ID of D3. In reduced diameter section 110D the OD is reduced to D2 while the ID is reduced to D4. Typically, the target value of D4 is determined by the minimum system flow rate requirement while the minimum achievable critical radius is achieved with an experimentally or computer-aided design (CAD) determined target D2.sub.T.

[0059] The efficacy of diametral reduction to decrease the critical radius was demonstrated using a thermal diametral reduction process. In one example, a 0.070-inch OD, 0.054-inch ID catheter was modified to have a target ID of 0.046-inch over an approximately 1-inch section of the catheter. In one variation, the portion of the catheter which passes through the constraining element 116 is located about 1-inch from the end of the catheter. To create a sufficient length to bend as needed, a 1-inch reduced diameter section was created.

[0060] In this variation, an initial step in the diametral reduction process is illustrated in FIG. 9A wherein a Teflon®-coated 304 stainless steel (304SS) 0.045-inch diameter mandrel 305 has been inserted into the 0.054-inch lumen of catheter 110. The diameter of mandrel 305 defines the reduced internal diameter D4 of the diametrally-reduced catheter. Mandrel 305 has a length sufficient to extend into the lumen of catheter 110 approximately 1-inch beyond the planned diametrally-reduced section 110D.

[0061] Another step of the process is shown in FIG. 9B and comprises sliding two segments of 304SS tubing 310 over the exterior of catheter 110, where tubing 310 has an 0.072-inch ID to conveniently fit over the conduit's 0.070-inch initial OD [D1] and a 0.095-inch OD. Tubing segments 310 are thermo-mechanical shields 310 to protect the catheter from diametral reduction outside of section 110D. As shown, one shield is located with its leading edge coincident with the end of catheter 110 while the second shield is located with its leading edge disposed to leave a gap equal to section 110D. In this example the gap is approximately 1-inch.

[0062] FIG. 9C illustrates a third step of the process in which a polyolefin heat shrink tube 320 with 0.10″ ID is slid onto the catheter, over both shields 310, covering section 110D and overlapping both shields 310 slightly. After tube 320 is in place, heat is applied to the polyolefin tube 320 until it shrinks, compressing catheter 110, which is also heated, so that the catheter 110 shrinks inwardly against Teflon-coated mandrel 305, as shown in FIG. 9D. During this example process, the OD of section 110D was reduced to 0.064-inches. It may be noted that shields 310 prevent tube 320 from compressing conduit 110 outside of the intended diametrally-reduced section 110D.

[0063] After allowing time to cool, the polyolefin heat shrink tubing is carefully cut/torn away and shields 310 are removed, as shown in FIG. 9E. As shown, the catheter 110 includes an initial outer diameter D1 and initial inner diameter D3 (in a lumen of the catheter), where the diametrally-reduced section 110D includes an outer diameter D2 and a passage having an inner diameter D4. For this example, the catheter was kept on the mandrel for at least 10 minutes to avoid unwanted additional shrinkage.

[0064] In one experiment, eight sample diametrally-reduced catheters were produced. These catheters and eight control catheters cut from the same stock were installed in a fixture to measure their kink resistance when bent in a small radius. That is, the tests performed provided an estimate the critical radius reduction of the diametrally-reduced catheters relative to the control catheters. More specifically, the test procedure and fixture measured the bend diameter at which flow through the catheter was reduced by a specified percentage, that is, it measured a functional kink diameter. This is a functional measure of kink resistance since flow through the catheter is the primary specification for the catheter.

[0065] The test method performed to assess kink resistance of the heat-shrunk catheters compared to unmodified catheters comprised bending the test object into a decreasing radius arc while water was pumped through the catheter at a constant pressure. Kink resistance was quantified by measuring the arc radius at which flow is reduced by 50% compared to the same catheter segment when not bent. For the usual uses of a catheter, the “50% flow rate radius” measured in this test is more useful than an actual measurement of the critical radius. The 50% flow reduction, while arbitrary, is a valid indication of kink-resistance. The heat-shrunk catheters were made using the process detailed above.

[0066] FIGS. 10A and 10B illustrate examples of a catheter or tubing 110 having a diametrally-reduced region 110D adjacent to a wall 102 of a balloon-device 110. Variations of the configuration can include the diametrally-reduced region 110D extending into the balloon 100, stopping at the wall 102, or stopping in a constraining element 116. The diametrally-reduced region 110D shown is for purposes of illustration and can have a shorter or longer length than shown. FIG. 10B illustrates a catheter 110 having a region 111 of increased internal and/or external diameter 111 at a location spaced from the diametrally—reduced region 110.

[0067] FIG. 11 is a table of results from this assessment. As shown in the table, the thermal diametral reduction technique produced a very consistence reduced inner diameter of 0.046 inches, reduced from the original (and control) ID of 0.053 inches. The outer diameter was also reduced from the original (and control) OD of 0.070 inches to a reduced OD of 0.064 inches. More important than the specific ID and OD reductions is the reduction in the kink diameter. From this assessment we see that these diametrally-reduced catheters have a kink diameter approximately 42% of the control catheters. During testing, it was found that the absolute flow rate of the unkinked reduced diameter catheter was only 4%-5% lower than the unkinked control catheters, indicating that the functional impact of reducing the ID of these catheters was minimal. It is believed the apparent disagreement between the predictions of equation 3 and the kink diameter determined by flow rate is due to the difference between the definition of R.sub.c, which is the radius at which kinking starts, and the kink diameter, which is based on 50% flow reduction.

[0068] It should be noted that the diametrally-reduced catheter described herein can be used in with a region of strain relief, where the region of diametral reduction 110D may coincide with interface region 200 (that is, region 200 may cover all or most of region 110D) or be located to start at or to extend beyond terminus region 210 in the direction of catheter fill end 110B.