AU2005200891B2

AU2005200891B2 - Heat Transfer Devices

Info

Publication number: AU2005200891B2
Application number: AU2005200891A
Authority: AU
Inventors: Simon Andrews; Robert Mcnair; Aws Nashef; Ted Vander Wiede; Stephen Wilson
Original assignee: Omega Critical Care Ltd
Current assignee: Omega Critical Care Ltd
Priority date: 1999-08-26
Filing date: 2005-03-01
Publication date: 2007-02-08
Anticipated expiration: 2020-08-25
Also published as: AU2005200891A1

Description

00 Ci 1 "HEAT TRANSFER DEVICES" 2 3 The present invention relates to improvements for 4 catheters having a heat transfer device at or near their distal end.

6 7 One of the present constraints concerning manufacture 8 of catheters designed to monitor various cardiac 9 output data is the manner and form of the required heat transfer device system. One present form of 11 heat transfer device involves a thermal coil radially 12 disposed about the catheter body to form a generally 13 tubular coil which extends along the outside wall of 24 the catheter. Such a heat transfer device is shown in US 5509424. However, such heat transfer coils 16 require time and effort to wind and form and also 17 restrict the possible miniaturisation of such 18 catheters for use in paediatrics.

19 19 -2-

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N It is an object of the present invention to provide improvements to the manner Oand nature of heat transfer devices for use with catheters.

z Thus, according to the present invention, there is provided a catheter having a heat transfer device at or near its distal end, and a temperature sensing element to measure the ambient blood temperature wherein the heat transfer device is 0 layered or coated onto or into the catheter wall as a flexible film having one or more electrical resistor flow paths thereon or there through, which film is locatable around the catheter wall.

Such films can include flexible metal films on which one or more electrical paths have been etched or otherwise created. Alternatively, one or more electrical paths could be added onto a plastic film backing. The form of addition includes any type of deposition or coating, and the one or more electrical paths could be formed by etching, etc to form the resistor structure.

One or more temperature sensors or sensor leads are included on or within the heat transfer device film to monitor the temperature of the electrical path(s), and thus the temperature of the overall heat transfer device.

-1 Suitable backing materials include PVC, polyurethane, 8 2 silk, synthetic silk, silicon rubber, ElastonT etc, c' 3 possibly about 20-80 microns thick, and suitable thin t 4 high resistant metal films include nickel, chromium 5 or nickel-chromium. These can be deposited on the 6 plastic backing material, and patterned using a 7 photolithography mask to form the resistor structure.

S8 00 C 9 On top of the resistor structure could be located a N' 10 suitable insulator like parylene C, followed by S11 deposition of a suitable temperature sensing means C( 12 e.g. thermistors or platinum. Finally the outer 13 surface may be coated with a silver or gold layer, 14 possibly 5-10 microns thick. This layer assists in averaging heat distribution. Gold and/or silver are 16 suitable as they are conductive and biocompatible.

17 Optionally a further layer of parlyene C or other 18 insulation is added as the outer layer.

19 Possible arrangements for the electrical paths and 21 temperature sensing means across the backing material 22 are shown in Figures 3 and 4 of the accompanying 23 drawings.

24 This form of heat transfer device can be fixed around 26 a catheter at or near its distal end. Preferably the 27 film is about 0.5-2.0 cm long, in order for it to 28 remain within the main pulmonary artery trunk. The 29 film could be fixed around the catheter starting at about 4-5 cm from the tip, and in the case of a PVC 1 catheter body, the PVC film heat transfer device 2 could be bonded by solvent.

3 S4 Such a heat transfer device could be adapted to fit a catheter les than 7F diameter (2.3mm). More 6 preferably the heat transfer device can be 7 incorporated in a catheter of 3-5F (1-1.67mm) 8 diameter. The heat transfer device should not 00 9 increase the outer diameter of the catheter more than

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10 about 0.3F (0.1mm).

C 12 Using the same technique, a similar film could be 13 formed purely for temperature sensing. The 14 temperature sensing material could be deposited on a backing film, followed by parylene (and gold) 16 coatings. Such a temperature sensor could be 17 positioned to 2-4 cm proximal to the heat transfer 18 device. Optionally a further layer of parlyene C or 19 other insulation is added as the outer layer.

21 According to another embodiment of the present 22 invention, the heat transfer device is disposed onto 23 the catheter wall by any known method of deposition, 24 eg plasma deposition, printing, electroplating onto plastic, photo lithography etc. Application by 26 printing uses eg conductive ink, or a conductive 27 layer, with subsequently etching. This method of 28 deposition can use any suitable resistive material.

29 In addition, the temperature sensor material could be similarly applied.

31 1 According to a second aspect of the present 2 invention, there is provided a catheter having a 3 length of its outer wall formed wholly, substantially S4 or partly from doped material able to act as a heat transfer device upon application of power 6 therethrough.

7 OQ 8 This form of heat transfer device could be formed as O 9 an inherent part of the catheter wall, rather than as a separate addition of a heat transfer device to the 11 catheter. The catheter wall is sufficiently doped 12 with a resistive material or ingredient able to pass 13 electrical current therethrough, without affecting 14 its other properties. Any conductive material could be suitable, eg silver, gold.

16 17 According to a third aspect of the present invention, 18 there is provided a catheter wall having one or more 19 metal wires therethrough.

21 By locating the electrical connections within the 22 catheter body wall, separate lumens for electrical 23 connections to its distal end within the catheter 24 interior are no longer required. These wires can also provide the catheter with the desired or 26 required stiffness.

27 28 The wire(s) can be formed from any suitable metal, eg 29 copper. Preferably, each wire is co-extruded within the catheter body.

31 1 More preferably, there are one or more sets of 2 electrical wires in the catheter wall, each set 3 having the required number of wires for the desired 4 operations.

6 In one embodiment of the present invention, the 7 catheter body has three sets of wires, each set 00 8 comprising two wires. One set of wires is for a O 9 heating element, and the other two sets are for each I 10 of two temperature sensing elements located on or 11 along the catheter wall, or one set for measuring 12 ambient blood temperature, and the other set for 13 measuring the temperature of the heat transfer 14 device, or any other suitable combination of measurements.

16 17 The wire or wires inside the catheter wall should be 18 easily exposable and thus connectable to the required 19 electrical units to which they correspond. Any exposed wire could be covered by a suitable insulator 21 such as vinyl adhesive, or urethane potting compound.

22 23 An example of this aspect of the present invention is 24 shown in Figure 2 of the accompanying drawings.

26 According to a preferred embodiment of the present 27 invention, there is provided a catheter combining the 28 first and third aspects described above.

29 One advantage of the use of one or more aspects of 31 the present invention as described above is the 1 ability to reduce the size of the catheter, more 2 particularly for paediatric use. A catheter wherein 3 the electrical wires required for the heat transfer 4 device, etc are co-extruded within the catheter body, means that the catheter may only need a single distal 6 lumen, (possibly 0.5-0.7 mm diameter) for solution 7 infusion and pressure monitoring.

8 00 9 The novel apparatus and methods of the present NI 10 invention could also be used in non-medical fields 11 using heat transfer devices at or near the distal C 12 ends of elongate tubing to be located in remote 13 locations. Such fields include aeronautics, any 14 fluid flow analysis, food and drink processing and monitoring, water and sewerage management, chemical 16 engineering, fuel supply to engines, etc.

17 18 The present invention is also particularly applicable 19 to the paediatric catheter field.

21 Embodiments of the present invention are shown by way 22 of example only in the accompanying diagrammatic 23 drawings in which: 24 Figure 1 is side view of a paediatric catheter; 26 27 Figure 2 is a radial cross-sectional view of a 28 catheter wall having electrical wires located 29 therein; S1 Figure 3 is an example of a heat transfer device film 2 for application around a catheter body; 3 4 Figure 4 is an example of a temperature sensor for application around a catheter body.

6 7 Figure 5 is a longitudinal cross-sectional view of a 8 catheter body having a heat transfer device 00 9 therearound.

11 Figures 6a, b and c show a method of preparing a 12 catheter having a heat transfer device.

13 14 The dimensions referred to in relation to accompanying diagrammatic drawings are illustrative 16 only, and in no way limiting or essential.

17 18 Referring to the drawings, Figure 1 shows the general 19 form of a paediatric pulmonary artery catheter, which may be 70-100 cm long. At one end, such catheters 21 generally have a connection 2, for example, to a 22 TRUCCOMTM, and a distal lumen 4. Such catheters are 23 generally 3-5F size, i.e. approximately 1-1.67mm 24 diameter.

26 For all such catheters, the heat transfer device 27 should preferably be in the range 0.5-2.0 cm long in 28 order to remain within the main pulmonary artery 29 trunk. The catheter body shore hardness should be about 45-55D for proper handling during insertion

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1 into patients. Use of softer materials may be 2 possible, but may require the additional use of a C 3 wire to stiffen the catheter body allowing S4 manoeuvrability during insertion.

6 In the versions of the present invention based on the 7 layering or coating of the transfer device onto or 8 into the catheter wall, the heat transfer device 0 9 should not increase the outer diameter of the c- 10 catheter more than 0.3F (0.1mm) S11 12 Figure 1 shows a schematic representation of a heat 13 transfer device 6 according to the present invention 14 2cm long, and located 4cm from the end of the catheter. Thereafter is located a temperature sensor 16 8, approximately 0.3cm long.

17 18 Figure 2 is a cross-section of a catheter wall 19 wherein six copper wires 12 are co-extruded with the catheter body so as to be located in the catheter 21 wall 10. Of the six wires, two are located for the 22 heating element, and two for each of two temperature 23 sensing elements (not shown). Thus, the catheter 24 only has a single distal lumen 14, 0.5mm diameter for solution infusion and pressure monitoring.

26 27 Figure 3 is an example of a flexible metal film heat 28 transfer device 20 according to the present 29 invention. The film consists of a thin high resistance metal film, e.g. of nickel, chromium or 31 nickel-chromium, deposited on a PVC film 22, e.g. of 1 25-50 microns thick. The resistor wire 24 in Figure 2 3 can be patterned using a photolithography mask.

S3 The device 20 includes temperature sensor leads 26.

t 4 Figure 4 shows a possible pattern for temperature 6 sensor leads 30 on a similar PVC film 32 to act as a 7 temperature sensor as shown in Figure 1. It is 00 8 similarly made to the device in Figure 3, but only 9 the temperature sensing material is deposited followed by Paralyene C and gold coatings.

11 12 Figure 5 shows a longitudinal cross-section of a 13 catheter having a heat transfer device 34 based on 14 that shown in Figure 3. Around the catheter body 36 is a PVC film 0.05mm thick. The resistor and 16 temperature sensor leads are on the PVC film, which 17 is then coated with a suitable insulator such as 18 Parylene C, possibly of 0.005mm thickness. The outer 19 surface is coated with a silver or gold layer (suitably 5-10 microns thick).

21 22 As shown in Figures 6a-6c the overall heat transfer 23 device 34 can be conjoined with the catheter body 36 24 using any suitable means such as a solvent.

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temperature sensor 40 such as that shown in Figure 4 26 is also conjoined with the catheter body 36, e.g. 2-4 27 cm proximal to the device 34. Thereafter, and as 28 shown in Figures 6a-c, the wires 38 inside the 29 catheter wall 36 are then exposed and the heat and temperature sensing wires are then connected and

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covered by a vinyl adhesive or another suitable insulator.

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Claims

2. A catheter for measuring cardiac output data comprising a heat transfer device at or near its distal end and a temperature sensing element to measure the ambient blood temperature, characterised in that the heat transfer device is coated onto the catheter wall (10) as a flexible film having one or more electrical resistor flow path(s) (24) thereon or therethrough and the heat transfer device includes one or more temperature sensors or sensor leads (26,
3. A catheter for measuring cardiac output data comprising a heat transfer device at or near its distal end and a temperature sensing element to measure the ambient blood temperature, characterised in that the heat transfer device is layered into the catheter wall (10) as a flexible film having one or more electrical resistor flow path(s) (24) thereon or therethrough and the heat transfer device includes one or more temperature sensors or sensor leads (26,
4. A catheter for measuring cardiac output data comprising a heat transfer device at or near its distal end and a temperature sensing element to measure the ambient blood temperature, characterised in that the heat transfer device is coated in to the catheter wall (10) as a flexible film having one or more electrical resistor flow path(s) (24) thereon or therethrough and the heat transfer device includes one or more temperature sensors or sensor leads (26, I-13- O O 5. A catheter as claimed in any one of the preceding claims wherein the film is a flexible metal film on which the one or more electrical paths (24) have been O z etched or otherwise created.
6. A catheter as claimed in any one of claims 1 to 4 wherein the one or more electrical paths (24) are added onto a plastic film backing. 00
7. A catheter as claimed in Claim 6 wherein the one or more electrical paths (Ni (24) are added by a deposition process.
8. A catheter as claimed in Claim 6 wherein the one or more electrical paths (24) are added by a coating process.
9. A catheter as claimed in Claim 1 or 2 wherein the heat transfer device is disposed directly onto the catheter wall A catheter as claimed in Claim 9 wherein the heat transfer device is disposed onto the catheter wall by deposition process.
11. A catheter as claimed in Claim 10 wherein the deposition process is a plasma deposition process.
12. A catheter as claimed in Claim 10 wherein the deposition process is a printing process.
13. A catheter as claimed in Claim 12 wherein the printing process uses a conductive ink or a conductive layer, with subsequent etching.
14. A catheter as claimed in any one of Claims 1 to 13 wherein a temperature sensor material is also disposed onto the catheter wall (10) by a deposition process. A catheter as claimed in any one of the preceding claims wherein one or more insulator layers are located over the resistor flow paths (24). -14- \O 0 16. A catheter as claimed in Claim 15 wherein one of the insulator layers is (N parylene C. 0 n 17. A catheter as claimed in any one of the preceding claims wherein the heat transfer device comprises an outer or penultimate outer layer of silver or gold. 00oO S18. A catheter as claimed in any one of Claims 1 to 4 wherein a length of the N outer wall of the catheter is wholly, substantially or partly formed from doped V) Smaterial able to act as a heat transfer device upon application of power N therethrough.
19. A catheter as claimed in Claim 18 wherein the doped material is silver or gold. A catheter as claimed in any preceding claim wherein the catheter wall has one or more metal wires (38) therethrough.
21. A catheter as claimed in Claim 20 wherein the or each wire is copper.
22. A catheter as claimed in Claim 20 or Claim 21 wherein the or each wire is co- extruded within the catheter body.
23. A catheter as claimed in any one of Claims 20 to 21 wherein the catheter wall includes one or more sets of wires (38).
24. A catheter as claimed in Claim 23 wherein the catheter body has three sets of wires each set comprising two wires. A catheter as claimed in any one of Claims 20 to 24 wherein the or each wire (38) inside the catheter wall (36) is easily exposable.
26. A catheter as claimed in any one of the preceding Claims of size O
27. A catheter as claimed in any one of the preceding Claims having a single distal lumen O S28. A catheter as claimed in Claim 27 wherein the lumen has a diameter of approximately 0.5-0.7 mm. 00 on