DEVICE FOR HYPOTHERMIA THERAPY

Abstract

A device to change the temperature of a localized volume of material. A workable device includes at least one heat transfer mechanism having an external surface for direct contact with an exposed surface of the material. A working fluid is directed by input and output conduits to contact an internal surface of the heat transfer mechanism. The heat transfer mechanism exchanges heat between the working fluid and the material. Temperature of the working fluid may be regulated by a thermal system disposed at a remote location. An optional temperature sensing element may monitor a local temperature of the heat transfer mechanism or otherwise infer a temperature of a portion of the material. Sometimes, a device includes a cooperating anchoring arrangement to facilitate holding the heat transfer mechanism in a desired spot. Certain devices may be plastically deformed to a desired device shape.

Claims

1. An apparatus, comprising: a heat transfer mechanism comprising an external surface to contact a portion of an exposed surface of a material; an input conduit in fluid communication with the heat transfer mechanism to direct a working fluid toward an internal surface of the heat transfer mechanism; and an output conduit in fluid communication with the heat transfer mechanism to direct the working fluid away from the internal surface of the heat transfer mechanism, wherein: the heat transfer mechanism comprises a gap between heat transfer contact loci, the gap cooperating with the loci to impart a multi-trough cooling temperature profile to the surface of the material, the temperature profile being disposed at a cross-section taken through the gap.

2. The apparatus according to claim 1, further comprising: a plastically deformable element associated with a portion of the apparatus to permit a user to impart a desired deformed shape to the apparatus.

3. The apparatus according to claim 1, wherein: a body portion of the apparatus comprises a bonded stack of thin film polymer layers comprising a top layer; a channel layer; and a bottom layer; portions of an input channel and an output channel being disposed in the channel layer and between the top and bottom layers.

4. The apparatus according to claim 3, wherein: the body portion further comprises an outer encapsulating layer comprising a biocompatible material.

5. The apparatus according to claim 1, wherein: the gap has a size between 0.02 inches and 0.32 inches.

6. The apparatus according to claim 1, wherein: the gap is associated with an aperture having a length axis and extending through a thickness of the heat transfer mechanism.

7. The apparatus according to claim 6, wherein: the aperture defines a complete perimeter boundary for a temperature-controlled work area.

8. The apparatus according to claim 6, wherein: the aperture defines an incomplete perimeter boundary for a temperature-controlled work area, the incomplete perimeter comprising a side opening.

9. The apparatus according to claim 1, wherein: the heat transfer mechanism is transversely flexible to conform to the surface.

10. The apparatus according to claim 1, further comprising: a temperature sensing element associated with the heat transfer mechanism to infer the temperature of a local portion of the material.

11. The apparatus according to claim 1, further comprising: a catch element to cooperate with a latching anchor to hold the heat transfer mechanism in a desired operable position.

12. An apparatus, comprising: a body comprising a top layer, a channel layer, and a bottom layer; a heat transfer mechanism coupled to the body; an input channel with an input channel length axis disposed in the channel layer, the input channel being defined in part by walls provided by the channel layer, the top layer, and the bottom layer; and an output channel with an output channel length axis disposed in the channel layer, the output channel being defined in part by walls provided by the channel layer, the top layer, and the bottom layer; wherein the heat transfer mechanism comprises an aperture to form a gap between heat transferring elements to impart a multi-trough cooling profile to an object that is cooled by the heat transfer mechanism.

13. The apparatus according to claim 12, wherein: the aperture comprises a closed perimeter to define a fully bounded conduit extending in a transverse direction through the thickness of the heat transfer mechanism.

14. The apparatus according to claim 12, wherein: the aperture comprises a side opening to define a partially bounded conduit extending in a transverse direction through the thickness of the heat transfer mechanism.

15. The apparatus according to claim 12, further comprising: an outer encapsulating layer disposed to cover a portion of the body, the encapsulating layer comprising a biocompatible material.

16. The apparatus according to claim 12, further comprising: a thermal sensor disposed to indicate a temperature associated with the heat transfer mechanism.

17. The apparatus according to claim 12, further comprising: a catch element to facilitate holding the heat transfer mechanism in a desired location.

18. The apparatus according to claim 12, further comprising: a plastically deformable member associated with the body to permit a user to modify a shape of the body.

19. A method to perform hypothermia therapy on a mammal, comprising: exposing a surface of tissue; providing a heat transfer mechanism comprising a bonded stack of thin film layers comprising a top layer, a channel layer, and a bottom layer, an input channel and an output channel with length axes disposed in the channel layer to convey a thermal fluid from a remote fluid temperature management device for wetted contact between the thermal fluid and a heat transfer element; applying the heat transfer mechanism to the surface of tissue to impose a multi-trough cooling profile on the surface of tissue; passing a medical device through an aperture extending through a thickness of the heat transfer mechanism to install the medical device in registration with respect to the tissue; and removing the heat transfer mechanism from the surface.

20. The method according to 19, further comprising: removing the heat transfer mechanism by displacing the aperture in a transverse direction relative to the length axis of a wire connected on one end to the medical device to cause the wire to pass through a side opening in the perimeter of the aperture and thereby free the wire from disposition inside the aperture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the drawings, which illustrate what are currently considered to be the best modes for carrying out the invention:

[0017] FIG. 1 is a view in perspective of an embodiment according to certain principles of the invention;

[0018] FIG. 2 is a plan view of the embodiment of FIG. 1;

[0019] FIG. 3 is a cross-section view indicated at section 3-3 in FIG. 2, and looking in the direction of the arrows, when the device is disposed in operable registration on a tissue surface;

[0020] FIG. 4 is an XY plot illustrating a representative surface temperature that may be caused by the embodiment in FIG. 3;

[0021] FIG. 5 is a top plan view of a device constructed according to certain principles of the invention;

[0022] FIG. 6 is a side view in elevation of the device in FIG. 5;

[0023] FIG. 7 is a top view of the device in FIG. 5, partially assembled with the top layer removed;

[0024] FIG. 8 is a side view of the embodiment in FIG. 7;

[0025] FIG. 9 is a bottom plan view of the embodiment in FIG. 7;

[0026] FIG. 10 is an exploded view in perspective of a portion of the embodiment in FIG. 5, partially assembled;

[0027] FIG. 11 is a top view of the embodiment in FIG. 10, at a further stage of assembly;

[0028] FIG. 12 is a cross-section view indicated at section 12-12 in FIG. 11 and looking in the direction of the arrows;

[0029] FIG. 13 is a plan view of the embodiment in FIG. 11, at a further stage of assembly;

[0030] FIG. 14 is a plan view of the embodiment in FIG. 13, at a further stage of assembly;

[0031] FIG. 15 is a cross-section view indicated at section 15-15 in FIG. 14 and looking in the direction of the arrows;

[0032] FIG. 16 is a view in perspective of the embodiment in FIG. 5 disposed for connection to ancillary equipment and use in thermal therapy;

[0033] FIG. 17 is a view in perspective of an embodiment coupled to ancillary equipment and ready for deployment as a thermal device;

[0034] FIG. 18 is a view in perspective of an embodiment associated with an implantable array of electrodes;

[0035] FIG. 19 is a close-up view of a portion of the embodiment in FIG. 18;

[0036] FIG. 20 is a top plan view of an embodiment;

[0037] FIG. 21 is a side view of the embodiment in FIG. 20;

[0038] FIG. 22 is an exploded view in perspective of a portion of the embodiment in FIG. 20, partially assembled;

[0039] FIG. 23 is a bottom plan view of the embodiment in FIG. 20;

[0040] FIG. 24 is a plan view of the embodiment in FIG. 20 at a stage of partial assembly;

[0041] FIG. 25 is a side view of the embodiment in FIG. 24; and

[0042] FIG. 26 is a bottom plan view of the embodiment in FIG. 24.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0043] Reference will now be made to the drawings in which the various elements of the illustrated embodiments will be given numerical designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood that the following description is only exemplary of certain principles of the present invention, and should not be viewed as narrowing the claims which follow.

[0044] An embodiment according to certain principles of the invention is illustrated generally at 100 in FIG. 1. Embodiment 100 is a device to change and desirably regulate the temperature of a local volume of material. For purpose of this disclosure, a device such as thermal device 100 will generally be made reference to as a cooling device. However, it is to be understood that a device, such as illustrated at 100, may find equal utility as a heating device. Other workable devices may be regarded as thermal regulating devices, and may be capable of heating or cooling, or alternating between the two. Certain currently preferred devices described herein are applied to cooling local volumes of tissue, including living animal tissue. Consequently, this disclosure will generally make reference to the thermally regulated material as tissue. It is to be understood that thermal devices according to certain principles of the invention may be applied as well to alternative substrates.

[0045] Device 100 includes an input conduit 104 to deliver thermal transfer fluid from a source toward a heat transfer area, generally 108. An output conduit 112 delivers the thermal transfer fluid to a sink. Workable conduits 104, 112 may be formed from sections of fluid-holding tubing, such as medical grade silicone tubing, polymeric tubing, or other suitable hose structure. An exemplary source and sink are indicated generally at 116, and may include a commercially available remote chiller (or heater) to place the thermal fluid at a desired temperature prior to circulation.

[0046] Illustrated heat transfer area 108 includes a first heat transfer element 120, and a second heat transfer element 124 that are coupled in fluid communication to conduits 104, 112 such that circulation 128 of the thermal fluid is permitted without leaking. Desirably, a heat transfer element 120, 124 provides a relatively larger thermal conductivity than provided by the delivery conduits 104, 112. A workable heat transfer element 120, 124 may be formed from or include a metal, or metallic material, disposed between the circulating thermal fluid and a tissue or other material.

[0047] The preferred arrangement of thermally conductive materials tends to focus any increase in temperature of the circulating thermal fluid to be as a consequence of heat transfer from the desired volume of tissue that is operated on by the device 100. That is, preferred devices extract heat from the tissue for which temperature regulation by heat transfer area 108 is desired. Various ways to infer temperature of the cooled tissue volume are facilitated by selection of desirable constituent materials of a device, such as device 100.

[0048] With reference to FIGS. 1 and 2, device 100 includes a connector, generally 132, to form a circulating loop, or aperture 136, for disposition in the heat transfer area 108. Of note, aperture 136 has a length axis 138 that is disposed in penetration through a thickness of the device 100. Also, connectors 140, 144 may be provided for routing thermal fluid conduits to a remote source/sink device 116.

[0049] Reference will now be made to FIGS. 2 and 3. A plurality of plumbing connections may be envisioned to place heat transfer elements 120, 124 in leak-tight registration with thermal fluid conduits 104, 112. It has been found workable to make an adhesive butt joint connection between lengths of copper tube and silicone tube. A workable adhesive includes cyanoacrylate. An alternative fluid-tight joint between elements may be welded, molded, adapted for a plug-fit, or in alternative well known ways.

[0050] Materials of construction for any constituent element of an embodiment of a device may be selected for reasons of serviceability or compatibility of a thermal device, e.g., device 100, when employed in a particular environment. For example, a thermal element, fluid conduit and/or connector may be formed from a suitable, e.g., inherently biocompatible, material. A biocompatible surface treatment may sometimes be applied to portions of a device. For example, a gold film was applied to exterior contact surfaces of the copper thermal elements 120, 124 of an embodiment used during brain surgery performed on an animal. As one alternative example, a portion of a thermal device may be encapsulated within a biocompatible material, such as is illustrated in e.g., FIG. 5.

[0051] In the case particularly illustrated in FIG. 3, thermal fluid may directly contact the inner surface 148 of e.g., a heat transfer element 120. Further, an external surface 152 of a heat transfer element 120 may come into direct contact with a surface 156 of tissue 160 when a device is deployed. As referenced above, the relatively low thermal resistance of a metal heat transfer element facilitates heat transfer from tissue 160, through heat transfer elements, and into thermal fluid 168 circulating 128 in the device 100.

[0052] A distance or gap 164 may be defined by a spacing between heat transfer elements (such as elements 120 and 124 in FIGS. 1-3), with the thermal elements being disposed on opposite sides of the aperture 136 in the case illustrated in FIG. 3. It is preferred for the gap 164 to provide a suitably-sized work area of hypothermic tissue surface on which to perform some sort of therapy, invasive interrogation, medical procedure, or the like. A workable gap 164 may be between about 0.020 in-0.315 in [0.5 mm -8 mm], although much larger gaps 164 are within contemplation. The work area provided by the gap 164 in a thermal device such as device 100 may be round, rectangular, or any other convenient shape.

[0053] The X-Y plot illustrated in FIG. 4 is representative of a surface temperature profile that might be caused by the embodiment and frame of visual reference in FIG. 3. A distance axis X is defined in FIG. 3, and temperature of the surface 156 of the tissue 160 is shown as a cartoon line plot in FIG. 4. The surface temperature permits one to infer the reduced temperature (below the baseline temperature BT) of a local volume of tissue 160 near the device 100. (A similar plot would be expected for the device illustrated in FIG. 23, and indicated by section 4′-4′). In either case, the surface temperature profile is disposed at a cross-section taken through a gap between heat transferring elements.

[0054] FIG. 4 illustrates a hypothetical thermal profile of surface temperature at a section through the device 100 operating in a cooling mode. In FIG. 4, temperature at the locus of contact for heat transfer element 120 is generally indicated at 192, and defines a first trough. Similarly, temperature at the locus of contact for heat transfer element 124 is generally indicated at 196, and defines a second trough. The peak generally indicated at 200 represents the maximum surface temperature in the gap 164 (FIG. 3) between the heat transfer element loci. Temperature of material in a volume proximate the device 100 may be inferred from the surface temperature closest to a point of interest inside the volume. That is, one would expect the temperature of tissue to trend toward an undisturbed (e.g., normal or baseline) value with increased distance inside the material and away from a surface-contacting heat transfer element.

[0055] FIG. 4 illustrates the general thermal profile of surface temperature expected at a section through the device 100, in which a pair of troughs 192, 196 separated by a peak 200 are illustrated. In contrast, a heat transfer device providing essentially a point source for heat removal (e.g., no gap 164 or aperture corresponding to aperture 136) would be properly illustrated by a curve of surface temperature having a single trough and no separating peak corresponding to peak 200 shown in FIG. 4.

[0056] An embodiment according to certain principles of the invention is illustrated generally at 220 in FIG. 5. FIGS. 6-16 illustrate details of construction for the embodiment in FIG. 5 and certain related devices. Certain of the latter group of FIGs. may illustrate one or more optional element that may be added to, or redacted from, other embodiments. FIGS. 17-19 illustrate deployment for a preferred use of an embodiment according to certain principles of the invention. FIGS. 20-26 illustrate structural details of another embodiment. Similar elements in different FIGs. are generally annotated with the same, or a modified version of the same, numeral to avoid redundancy of disclosure. Because a preferred use of certain embodiments is to apply hypothermia therapy to living tissue, a device may be made reference to in this disclosure as a thermal- or thermal therapy device.

[0057] With reference again to FIG. 5, thermal therapy device 220 includes a body 224 with a portion defining a through-hole or aperture 136. In the illustrated top view, it may be visualized that aperture 136 forms a complete boundary extending around a perimeter of a temperature-controlled work surface, where the work surface can be accessed through the aperture 136.

[0058] One or more catch element 228 may sometimes be provided to facilitate holding the aperture 136 in registration at a desired position. Desirably, a catch element cooperates with a latch element to hold a heat transferring portion of a thermal therapy device in operable registration to apply a localized thermal therapy to a portion of tissue. An exemplary latch element may include a screw affixed to bone. The screw may be essentially lassoed by a catch 228. One alternative includes a suture placed in cooperation through a catch loop and adjacent tissue to hold a heat transfer area in registration with respect to tissue. Other cooperating catch and latch structures will occur to one of ordinary skill in the art.

[0059] As illustrated in FIG. 6, sometimes a thermal device may be configured to permit a user to plastically deform a portion of the device from a first configuration (e.g., the solid line portion 224 in FIG. 6) to a second configuration (e.g., dashed line portion 224′ in FIG. 6). One construction to accomplish a plastically deformable portion includes length extensions of one or more catch element along the length of a device. As best illustrated in FIGS. 13, 14, and 16, a workable catch element 228 may include a length of malleable wire including a length extending along a length axis of body 224. A similar functionality may be provided by a dedicated deformable element, e.g., a fully or partially embedded malleable length of wire lacking a catch portion or other functionality. A workable deformable element may be composed of, or include stainless steel, titanium, other metals, and the like. It is within contemplation that a shaped memory alloy may also be incorporated in a system to deform a thermal device, such as device 220, as a function of temperature.

[0060] Connector elements 140, 144 are provided to couple thermal fluid from a source 116 to internal fluid channels or conduit elements defined within the body 224. Channels or conduit elements may conveniently be formed inside a body 224 formed from a plurality of layers of membrane sheets or films. Workable membrane material includes polymer membranes, such as thin sheets or films of polypropylene, Mylar, and the like. Layer thickness for each layer in a laminate style thermal therapy device 220 may range from 0.001 in -0.010 in [0.025 mm -0.254 mm]. Such materials are inherently flexible in a direction transverse to the planar width and length axes.

[0061] Certain layers may inherently carry surface adhesive, or sometimes, adhesive may be applied as separate layers between film layers. Layers may be transparent or opaque. Certain layers may be metallized or metallic. Portions of a layer may be formed from different materials, and constituent materials of a layer may be overlapped at an edge, or butt jointed. Therefore, a layer may not be uniform in thickness throughout. Desirably, a multilayer body retains a certain amount of transverse flexibility to permit conformability of a heat transfer surface to a surface of tissue undergoing therapy.

[0062] Different portions may be selectively removed from certain layers to form a built-up stack of layers having internal structures, including the aforementioned fluid conduits. For example, individual film layers may be die- or laser-cut, and stacked to form a composite multilayer body. This can be performed in a reel-to-reel process, with portions of individual bodies 224 being extracted from formed and bonded layers of a multilayer ribbon of material that defines a series of bodies, or portions thereof. Alternative manufacturing methods to create bodies having internal structures nonexclusively include: photolithography; etching, and machining including micromachining.

[0063] With reference to FIG. 12, a body 224 may include a cap sheet or layer 232 bonded to a channel layer 236, which is in turn bonded to a floor sheet or layer 240. The input lumen 244 of an input conduit, generally 104, is bounded by top sheet 232, walls in channel layer 236, and a floor provided by floor layer 240. The narrowed-down portion 244′ of input lumen 244 is located at one side of aperture 136 (see FIG. 11). Similarly, output lumen 248 of an output conduit, generally 112, is bounded by top sheet 232, walls in channel layer 236, and a floor provided by floor layer 240. The narrowed-down portion 248′ of output lumen 248 is located at the other side of aperture 136.

[0064] FIG. 7 illustrates an embodiment 220 in a state of partial assembly. As illustrated, top layer 232 is removed, and internal features of the body, generally indicated at 224, are visible. It may be seen that channel layer 236 forms side walls for input lumen 244 and output lumen 248, as well as a fluid resistant wall around a portion of aperture 136. While optional, a thermal indication element or sensor 252 is desirably included, and is preferably placed in contact with a heat transfer element 256. A workable thermal sensor 252 nonexclusively includes a thermistor, thermocouple, and the like. Heat transfer element 256 is illustrated as being butt-joined with a portion of polymeric film to form part of a multi-component floor layer 240. As previously mentioned, it is preferred for a heat transfer element, such as floor portion 256, to possess high thermal transmission capability.

[0065] Sometimes, it is helpful to measure the temperature of floor portion 256 (e.g., the heat transfer element that is expected to be in contact with tissue). Accurate knowledge of the floor temperature lends accuracy to the surface temperature of the tissue at the contact loci, and consequently improves accuracy of the inferred temperature in a local volume of tissue. In an alternative arrangement, temperature of the returning thermal fluid may be used to provide estimated floor temperature.

[0066] As illustrated between FIGS. 13-15, sometimes, an embodiment may include an encapsulating coating or layer 264. In that case, it is typically desirable to pull the edge of the layer 264 back from the edges of certain structures, such as aperture 136 and connector structures 140 and 144, as illustrated in e.g., FIG. 14. Another example is illustrated in FIG. 19, where perimeter boundary 266 is pulled back from a heat transferring portion 256 of floor 240. It should be noted that a body may extend by any desired distance in a length direction, as also indicated in FIG. 14.

[0067] FIG. 16 illustrates a thermal device 220 in position to couple with ancillary equipment, such as a source/sink 116 and a temperature display system 268. As illustrated, a connector/manager element, generally 272, is coupled to a body 224. Connector/manager element 272 may include coupling structure to cooperate with elements 140 and 144 to place source/sink 116 into fluid communication with input lumen 244 and output lumen 248. Further, manager element 272 may couple leads, generally indicated at 276, from a temperature sensor 252 or other device carried on-board a body 224.

[0068] FIGS. 17-19 illustrate details of use of a currently preferred embodiment in an exemplary application to apply controlled hypothermia therapy during installation of an individually addressable multi-electrode assembly 280 into brain tissue of a mammal. The thermal device 220 is first used to cool a small volume of a local exposed surface portion of brain tissue, and the electrode array 280 is stabbed through aperture 136 and into registration on the exposed surface of the brain tissue. The temperature of the small local volume of brain tissue is regulated to remain at a reduced temperature (e.g., below a baseline or normal temperature), for a period of time to reduce trauma to the tissue. Wires may be attached to one or more electrode of the electrode array 280, and the brain may be probed while the local volume of brain tissue remains at a reduced temperature. Sometimes, the thermal device 220 is removed, but brain probing may continue. Wires passing through the aperture 136 can be problematic, and may need to be temporarily disconnected to remove the thermal device 220.

[0069] The embodiment generally indicated at 220′ in FIG. 20 provides an aperture 136′ having a side opening 304 to avoid the issue of penetrating wires passing through a closed aperture and connected at a distal end to one or more electrode. Stated another way: aperture 136′ defines an incomplete boundary around the temperature-controlled work area, and includes a side opening 304. In different words, aperture 136′ includes a side opening 304 to define a partially bounded conduit extending in a transverse direction through the thickness of the heat transfer mechanism formed in body 224′. Removal of device 220′ from an installed position in which temperature of brain tissue is regulated and an installed probe is wired may be effected without cumbersome length-wise wire extraction through the aperture or disconnection of wire distal end(s) from one or more electrode. The device 220′ may simply be transversely displaced to pass the connected wire through the side opening.

[0070] Device 220′ can be manufactured in substantially the same way as device 220, and the constituent parts are numbered accordingly. Constituent parts that are sufficiently distinguished may be designated with a prime to alert the reader. For example, the surface 308 of encapsulating layer 264 of embodiment 220′ is also desirably pulled back from fluid connection structure 140 and 144, and also to resist covering an exposed surface of a heat transfer element 256 (FIG. 26).

[0071] While aspects of the invention have been described in particular with reference to certain illustrated embodiments, such is not intended to limit the scope of the invention. The invention for which a monopoly position is currently desired is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0072] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For one example, one or more element may be extracted from one described or illustrated embodiment and used separately or in combination with one or more element extracted from one or more other described or illustrated embodiment(s), or in combination with other known structure. The described embodiments are to be considered as illustrative and not restrictive. Obvious changes within the capability of one of ordinary skill are encompassed within the present invention.