Patent Publication Number: US-2020297528-A1

Title: Heat Exchange Catheters With Bi-Directional Fluid Flow and their Methods of Manufacture and Use

Description:
RELATED APPLICATION 
     This patent application is a continuation of U.S. patent application Ser. No. 15/495,800, filed on Apr. 24, 2017, which is a continuation of U.S. patent application Ser. No. 13/631,076, filed Sep. 28, 2012, which claims priority to U.S. Provisional Patent Application No. 61/542,024 filed Sep. 30, 2011, the entire disclosure of each such application being expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to medicine and biomedical engineering and more particularly to heat exchange catheter devices and their methods of manufacture and use. 
     BACKGROUND OF THE INVENTION 
     Pursuant to 37 CFR 1.71(e), this patent document contains material which is subject to copyright protection. The copyright owner has no objection to facsimile reproduction of the entire patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     Hypothermia can be induced in humans and some animals for the purpose of protecting various organs and tissues (e.g., hear, brain, kidneys) against the effects of ischemic, anoxic or toxic insult. For example, animal studies and/or clinical trials suggest that mild hypothermia can have neuroprotective and/or cardioprotective effects in animals or humans who suffer from ischemic cardiac events (e.g., myocardial infract, acute coronary syndromes, etc.), postanoxic coma after cardiopulmonary resuscitation. traumatic brain injury, stroke, subarachnoid hemorrhage, fever and neurological injury. Also, studies have shown that whole body hypothermia can ameliorate the toxic effects of radiographic contrast media on the kidneys (e.g., radiocontrast nephropathy) of patients with pre-existing renal impairment who undergo angiography procedures. 
     One method for inducing hypothermia is by endovascular temperature management (ETM) wherein a heat exchange catheter is inserted into a blood vessel and a thermal exchange fluid is circulated through a heat exchanger positioned on the portion of the catheter that is inserted in the blood vessel. As the thermal exchange fluid circulates through the catheter&#39;s heat exchanger, it exchanges heat with blood flowing past the heat exchange in the blood vessel. Such technique can be used to cool the subject&#39;s flowing blood thereby resulting in a lowering of the subject&#39;s core body temperature to some desired target temperature. ETM is also capable of warming the body and/or of controlling body temperature to maintain a monitored body temperature at some selected temperature. If a controlled rate of re-warming or re-cooling from the selected target temperature is desired, that too can be accomplished by carefully controlling the amount of heat added or removed from the body and thereby controlling the temperature change of the patient. 
     In most if not all commercially available heat exchange catheters, the heat exchange fluid flows through an inflow lumen of the catheter shaft, then enters one end of the catheter&#39;s heat exchanger, then flows through the heat exchanger, then exits from the heat exchanger into an outflow lumen located within the catheter shaft. In general, greater heat exchange efficiency is accomplished when the heat exchange fluid flows through the catheter&#39;s heat exchanger in a direction that is opposite the direction in which the blood is flowing through the blood vessel in which the heat exchanger is positioned. Thus, the type of catheter used and/or the selection of which port(s) of the catheter should be used for inflow and outflow, respectively, is sometimes dictated by the intended sites of entry and positioning of the catheter. For example, in some cases, a heat exchange catheter is inserted into a femoral vein and advanced to a position where its heat exchanger is within the subject&#39;s vena cava. In such cases, the blood flowing normally through the vena cava will progress from the proximal end of the heat exchanger toward the distal end of the heat exchanger. Thus, in those cases, it will generally be desirable for the heat exchange fluid to enter the catheter&#39;s heat exchanger at its distal end and flow back toward the proximal end of the heat exchanger (i.e., counter to the direction of blood flow). If, however, the heat exchanger catheter were inserted into a femoral artery and advanced to a position where its heat exchanger is within the descending aorta, blood flowing normally through the descending aorta would progress from the distal end of the heat exchanger toward the proximal end of the heat exchanger. Thus, in those cases, it would generally be desirable for the heat exchange fluid to enter the catheter&#39;s heat exchanger at its proximal end and flow distally toward the distal end of the heat exchanger (i.e., again counter to the direction of blood flow). 
     Also, in heat exchange catheters where the heat exchange fluid flows in only a single direction through the catheter&#39;s heat exchanger, the heat exchange fluid typically is shunted to one or the other end of the heat exchanger through an internal lumen of the catheter. While traveling though that internal lumen the heat exchange fluid is exchanging only minimal if any heat with the flowing blood. 
     The following U.S. patents, the entire disclosures of which are expressly incorporated herein by reference, disclose various intravascular catheters/systems/methods useable for altering or maintaining a subject&#39;s body temperature: U.S. Pat. Nos. 6,881,551 and 6,585,692 (tri-lobe catheter), U.S. Pat. Nos. 6,551,349 and 6,554,797 (metal catheter with bellows), U.S. Pat. Nos. 6,749,625 and 6,796,995 (catheters with non-straight, non-helical heat exchange elements), U.S. Pat. Nos. 6,126,684, 6,299,599, 6,368,304, and 6,338,727 (catheters with multiple heat exchange balloons), U.S. Pat. Nos. 6,146,411, 6,019,783, 6,581,403, 7,287,398, and 5,837,003 (heat exchange systems for catheter), U.S. Pat. No. 7,857,781 (various heat exchange catheters). 
     There remains a need in the art for the development of new heat exchanger catheters and methods which offer improved heat exchange efficiency and/or ease of use. 
     SUMMARY OF THE INVENTIONS 
     In accordance with the present invention, there are provided heat exchange catheter devices having bi-directional flow of heat exchange fluid though a heat exchange region of the catheter. 
     Further in accordance with the present invention, there are provided methods for modifying or controlling a body temperature of a human or animal subject by inserting a bi-directional flow heat exchange catheter of the present invention and circulating heat exchange medium through the catheter to bring about the desired modification of control of a body temperature of the subject. In some embodiments the catheter may comprise a catheter shaft and tubular conduit(s) that is/are arranged on or connected to the catheter shaft to define a heat exchange region having a heat exchange medium supply flow path and a heat exchange medium return flow path. As explained in detail herein, the tubular conduit(s) may be passed (e.g., laced) through bores in the catheter shaft such that loops of the tubular conduit(s) protrude from the catheter shaft or they may be attached to but positioned entirely outboard of the catheter shaft. The tubular conduit(s) may be formed of non-expanding tubing or, in some embodiments, the tubular conduit(s) may comprise balloons or collapsible tubing (e.g., compliant or non-compliant material) that alternately expands and collapses in accordance with the pressure of heat exchange medium currently within the tubular conduit(s). 
     Still further aspects and details of the present invention will be understood upon reading of the detailed description and examples set forth herebelow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an endovascular temperature management system of the present invention. 
         FIG. 2A  is a partial perspective view of a portion of a catheter body having a plurality of transverse bores formed therein during manufacture of a catheter device of the present invention. 
         FIG. 2B  is a partial perspective view of the catheter body portion of  FIG. 2  having a tube passed in alternating directions through the transverse bores such that loops of the tube protrude on opposite sides of the catheter thereby forming a supply flow path for heat exchange fluid. 
         FIG. 2C  shows the catheter body of  FIG. 2B  with the tube being further passed in alternating directions through intervening transverse bores such that additional loops of the tube protrude on opposite sides of the catheter thereby forming a return flow path for heat exchange fluid. 
         FIG. 2D  is a partial perspective view of one example of a bi-directional flow heat exchange catheter of the present invention. 
         FIG. 2E  is a partial perspective view of another example of a bi-directional flow heat exchange catheter of the present invention. 
         FIG. 3  is a transverse cross sectional view through line  3 - 3  of  FIG. 2E . 
         FIG. 4  is a side view of one embodiment of a fully assembled catheter device of the present invention having a heat exchange region as shown in  FIG. 2E . 
         FIG. 5  is a side view of an alternative bi-directional flow heat exchange device useable on heat exchange catheters of the present invention, wherein the heat exchange fluid return flow path is shorter than the heat exchange fluid supply flow path. 
         FIG. 5A  is a distal end view of the alternative bi-directional flow heat exchange device of  FIG. 5 . 
         FIG. 6  is a partial side view of yet another example of a bi-directional flow heat exchange catheter of the present invention, in which the heat exchange region has a heat exchange fluid return flow path that is shorter than the heat exchange fluid supply flow path. 
         FIG. 7  is a partial side view of yet another example of a bi-directional flow heat exchange catheter of the present invention, in which the heat exchange region has a heat exchange fluid return flow path that is shorter than the heat exchange fluid supply flow path. 
         FIGS. 8A through 8G  are schematic diagrams that show various alternative ways in which tubing may be deployed on and/or in catheters of the present invention to form heat exchange regions having bi-directional heat exchange fluid flow paths. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description and the accompanying drawings to which it refers are intended to describe some, but not necessarily all, examples or embodiments of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The contents of this detailed description and the accompanying drawings do not limit the scope of the invention in any way. 
     In typical heat exchange catheter systems of the prior art, a heat exchange medium (e.g., heated or cooled saline solution) is circulated though a heat exchanger located on a flexible heat exchange catheter while the catheter is inserted within a blood vessel of the subject whose body temperature is to be warmed, cooled or maintained. Typically, the heat exchange fluid flows in one direction through the catheter&#39;s heat exchanger (i.e., either the distal (outbound) direction or the proximal (inbound) direction. This results in either co-current or counter-current heat exchange, respectively. In co-current heat exchange, the heat exchange fluid is flowing through the catheter&#39;s heat exchanger in the same direction as the subject&#39;s blood is flowing past the heat exchanger. In counter-current heat exchange, the heat exchange fluid is flowing through the catheter&#39;s heat exchanger in a direction that is opposite the direction in which the subject&#39;s blood is flowing past the heat exchanger. The present invention provides heat exchange catheters and systems wherein the catheter&#39;s heat exchanger has both a distal (i.e., outbound) flow path and a proximal (i.e., inbound) flow path so that heat exchange fluid flows through the catheter&#39;s heat exchanger in both co-current and counter-current fashion. As explained more fully herebelow, this bi-directions flow of heat exchange fluid through the catheter&#39;s heat exchanger minimizes the time the heat exchange fluid spends within the catheter shaft and maximizes the time in which the heat exchange fluid is flowing through the catheter&#39;s heat exchanger and effectively exchanging heat with the subject&#39;s blood. Additionally, this bi-directional flow of heat exchange fluid allows the heat exchange fluid to enter and exit the same end (e.g., the proximal end) of the catheter&#39;s heat exchanger, thereby avoiding any need to provide a distal lumen to shuttle heat exchange fluid through the catheter shaft to or from the distal end of the heat exchanger. This allows for use of a catheter shaft that is relatively thick walled which does not support high heat transfer rates and also allows for the inflow and outflow lumens in the proximal catheter shaft to be shorter in length. Compared to the heat exchange tube, the inflow and outflow lumens are relatively small in diameter. Therefore, shortening their length will reduce the amount of pressure required to drive saline through the catheter, and/or increase the rate of saline flow thereby increasing the rate of heat exchange. 
       FIG. 1  is a schematic diagram of an endovascular temperature management system  10  which comprises a heat exchange catheter  12  of a type having heat exchange tubing loops  14 , an extracorporeal control console C and at least one body temperature sensor TS. In this example, the extracorporeal console C contains a controller (e.g., a microprocessor controller), a user interface UI for inputting data to the controller, a heater/cooler for adjusting the temperature of a thermal exchange medium (e.g., 0.9% sodium chloride solution) and a pump for pumping the thermal exchange medium. 
     The catheter  12  is connected to the extracorporeal console C by way of an inflow line IL and an outflow line OL so that the pump within the console C will circulate temperature-controlled thermal exchange medium through a heat exchange tube  14  that is mounted or laced onto the catheter such that a first segment of the heat exchange tube runs in the distal (outbound) direction and a second segment of the tube  14  returns in the proximal (inbound) direction. As shown, the heat exchange tube  14  may be configured in a series of loops that protrude outwardly from the catheter body so that the flowing through the subject&#39;s vasculature will pass over and in proximity with the heat exchange tubing  14 , thereby allowing heat to be exchanged between the circulating thermal exchange medium and the subject&#39;s flowing blood. Warming or cooling of the subject&#39;s flowing blood then results in warming or cooling of all or a desired portion of the subject&#39;s body. In the particular non-limiting example shown in  FIG. 1 , the distal portion of the catheter  12  is positioned so that the heat exchange tubing loops  14  reside within the subject&#39;s inferior vena cava IVC, such catheter positioning being suitable for applications wherein whole body temperature management is desired. 
     The temperature sensor(s) TS may be positioned on or in the subject&#39;s body to measure the temperature of all or part of the body where it is desired to effect temperature modification or control. The controller within the console C receives signals from the temperature sensor(s) TS indicating the currently sensed body temperature. A desired target temperature may be input via the user interface UI and the controller will then issue control signals to the heater cooler and/or pump to adjust the temperature and/or the flowrate of the heat exchange medium in an effort to attain and/or maintain the target body temperature. A control console of the type shown in  FIG. 1  and described in this example is commercially available as the Thermogard XP™ Temperature Management System from ZOLL Circulation of Sunnyvale, Calif. 
     The catheter  12  of this example may be constructed and manufactured in the manner shown in  FIGS. 2A through 4 . In this example, the catheter  12  generally comprises an elongate catheter body  11  and a heat exchange tube  14 . The catheter body  11  has at least an inflow lumen  18  and an outflow lumen  19  which extend through at least a proximal portion of the catheter body  11 . Optionally, in any catheter of the present invention, a through lumen  16  may extend through the entire length of the catheter body  11 , terminating distally in an opening in the distal end of the catheter  12  so as to be useable as a distal infusion or guidewire lumen. Also, optionally, in any catheter of the present invention, the catheter body may include one or more additional lumens and ports, such as an optional medial infusion lumen (not shown) terminating in a medial infusion port (item  46  on  FIG. 4 ) and/or a proximal infusion lumen (not shown) terminating in a proximal infusion port (item  44  on  FIG. 4 ). The individual lumens of the catheter  12  may be integrally formed (e.g., extruded) within the catheter body  11  or may comprise one or more separate tube(s) that are passed through a lumen of the catheter body  11 . 
     As seen in  FIG. 2A , at the time of manufacture, a series of transverse bores  13  are formed through the catheter body  12 . These transverse bores  13  may be formed at any suitable angle relative to the longitudinal axis LA of the catheter body  11 . Also, a first window  20  leading into the inflow lumen  18  is skived or otherwise formed at a first location in a wall of the catheter body  11 , at a location that is proximal to the bores  13 . A second window  22  leading into the outflow lumen  19  is skived or otherwise formed at a second location in a wall of the catheter body  11 , also proximal to the bores  13 . 
     As shown in  FIG. 2B , a first (outbound) segment of the heat exchange tube  14  is advanced toward the distal end of the catheter  12  traversing through though every other bore  13  such that loops of that first segment of the heat exchange tube  14  remain protruding outboard of the catheter body  11 . 
     Thereafter, as seen in  FIG. 2C , a second (inbound) segment of the heat exchange tube  14  is advanced back toward the proximal end of the catheter  12 , traversing through the remaining bores  13 , thereby forming loops in that second segment of the tube  14 , as shown. It is to be appreciated that the manner in which the tube  14  is laced, threaded or otherwise disposed may vary. Appended hereto as Appendix A are a number of sketches showing alternative ways in which the tube  14  may be laced, threaded or otherwise disposed and/or other alternative modes for construction of bi-directional flow catheters of the present invention. 
     A first end of the heat exchange tube  14  is inserted through window  20  into inflow lumen  18  and secured to the wall of the inflow lumen  18 . This forms a sealed connection through which inflowing thermal exchange medium will flow from the inflow lumen  18  into the first (e.g., distal) end of the heat exchange tube  14 . Sealing attachment of the heat exchange tube  14  to the luminal wall of the inflow lumen  18  may be accomplished by any suitable means such as heat sealing or by adhesive bonding. Examples of adhesives that are useable for this purpose include but are not necessarily limited to cyanoacrylate adhesives (e.g. Loctite 4011 available from the Henkel Corporate, Westlake, Ohio, UV curing acrylic adhesives (e.g. Loctite 3311 available from Henkel Corporate, Westlake, Ohio, and epoxy adhesives (e.g. Loctite 3981 available from Henkel Corporate, Westlake, Ohio). The other end of the heat exchange tube  14  is inserted through window  22  into outflow lumen  19  and secured to the wall of the outflow lumen  19  in the same manner as described above. 
     This construction allows thermal exchange medium to flow into the catheter  12  through the inflow lumen  18 , then into the first end of the heat exchange tube  14 , through the first segment of the heat exchange tube (in the distal direction), then back through the second segment of the heat exchange tube  14  (in the proximal direction), into the outflow lumen  19  and then out of the catheter  12 . In this manner, thermal exchange medium flows through the heat exchange tube in both the distal direction and proximal directions. 
     In the particular example shown, the bores  13  are oval or ovoid shaped bores formed by advancing an oval or ovoid shaped punch through the catheter body  12  on a predetermined trajectory or by suitable alternative means such as laser cutting or water jet cutting. Such bores  13  extend through the catheter body  12  substantially at right angles relative to the longitudinal axis LA of the catheter body  12 . The trajectory of the bores  13  will avoid obliteration of the through lumen  16  such that the wall of that lumen  16  remains in tact. In embodiments that have optional lumens in the proximal portion of the catheter body  11  (e.g., a proximal and/or medial infusion lumen), such proximal lumens may terminate or be terminally sealed to proximal and medial infusion lumen outlet openings  44 ,  46  (seen on  FIG. 4 ) at locations proximal to where the bores  13  are formed. Therefore, the optional medial and proximal infusion lumens (if present) are nonfunctional in the region where the bores  13  are formed. 
     The catheter body  11  may be appropriately sized and formed of any material(s) suitable for the intended applications of the catheter device. For example, in many applications, it will be desirable for the catheter body  12  to have enough rigidity and wall thickness to contain working pressures of up to about 100 psi while being sufficiently flexible to navigate through the intended blood vessels or other body lumens to the desired location within a subject&#39;s body. Typically, this may be accomplished by a catheter body that has an outer diameter of 6 Fr (0.080°) to 14 Fr (0.180°) and is formed of a biocompatible polyurethane (e.g., Elastollan™ available from BASF Corporation, Florham Park, N.J. or Tecothane™ available from The Lubrizol Corporation, Wickliffe, Ohio) or polyether block amide (e.g., Pebax™ available from Arkema, Inc., Philadelphia, Pa.). 
     The heat exchange tube  14  may be appropriately sized and formed of any material(s) suitable for the intended applications of the catheter device. For example, in many applications, it will be desirable for the heat exchange tube  14  to a) have a thin wall thickness (typically around 0.001″) to best facilitate heat transfer, b) have sufficient tensile strength to withstand pressures of up to about 100 psi and c) be sufficiently rigid or semi-rigid so as not to expand uncontrollably under pressure. Thus, it will be desirable for the tube  14  to be formed of a material capable of being extruded and/or blown into a tube having such wall thickness and properties. Examples of materials that may be suitable for forming the tube  14  include polyethylene terephthalates (PETs) available from a variety of sources or polyether block amide (e.g., Pebax™ available from Arkema, Inc., Philadelphia, Pa.). 
     In some embodiments, it will be desirable to form the protruding loops of heat exchange tube  14  into desired shapes by thermosetting or other suitable forming techniques. 
     Also, as shown in  FIG. 4 , when fully assembled, the catheter device  12  of this example includes a hub  30  on its proximal end, with an outflow lumen connector  32  (connected to outflow lumen  19 ), inflow lumen connector  34  (connected to inflow lumen  18 ), optional medial infusion lumen connector  36  (connected to an optional medial infusion lumen), through lumen connector  36  (connected to the through lumen  16  useable as a distal infusion or guidewire lumen) and an optional proximal infusion lumen connector  36  (connected to an optional proximal infusion lumen). 
     Additionally, graduated distance markings  42  may optionally be formed on a proximal region of the catheter body  11  to indicate the length of catheter that is indwelling in the body at any particular time. Also, an optional proximal radiographic marker  48  and an optional distal radiographic marker  50  are located on the catheter body to facilitate radiographic determination of the location of the heat exchanging region (e.g., the protruding tube loops  14 ) within a subject&#39;s body. 
       FIGS. 5 through 7  show an alternative embodiment wherein the heat exchange region  60  comprises a tubular conduit  62  that is arranged in a first series of loops  66  of diameter or cross-dimension D 1  forming the heat exchange fluid supply path  62   a  and a returning second series of loops  64  of diameter or cross-dimension D 2  forming the return flow path  62   b . D 2  is smaller than D 1 . Thus, in this embodiment, the return flow path  62   b  is configured to be radially smaller than the supply flow path  62   a . Also, in this embodiment, the overall length of the tubular conduit that forms the return flow path  62   b  is shorter than that which forms the supply flow path  62   a.    
     Providing a return flow path  62   b  that is radially smaller and/or shorter in overall tubular conduit length than the supply flow path  62   a  has been found to substantially increase heat exchange efficiency with blood or body fluid that flows in heat exchange proximity to the heat exchange region  60 . 
     The portion of the tubular conduit forming the supply flow path  62   a  receives heat exchange fluid from the inflow lumen of the catheter shaft. The heat exchange fluid then flows from the proximal end of the through the coiled supply flow path  62   a  to its distal end, where it then circulates into the distal end of the tubular conduit that forms the return flow path  62   b  and then returns in the proximal direction through return flow path  62   b . The return flow path is connected to the return lumen of the catheter shaft such that the returning heat exchange fluid will circulate back to the extracorporeal portions of the system as described above. The supply and return conduits  62   a ,  62   b  of this heat exchange region  60  may be spaced from each other except at the distal location, such that blood can flow between and around the surfaces of the conduits when the catheter is positioned in a blood vessel of a subject. 
     The loops or other convolutions  64 ,  66  of the supply and return flow paths  62   a ,  62   b  may or may not be coaxial and they may be of various shapes other than the round shape shown in  FIGS. 5 and 5A . For example,  FIGS. 6 and 7  show examples of bi-directional flow heat exchange catheters that are similar in construction and design to those shown in  FIGS. 2D and 2E , but wherein the tubular conduit that forms the return flow path  62   a  is arranged in loops that are smaller in cross-dimension than those of the supply flow path  62   a.    
     In any embodiments of the invention, the tubular conduit(s)  14 ,  62  that form the heat exchange region need not necessarily be laced or passed through transverse bores in the catheter shaft  12 , as in the above described examples. Rather, in some embodiments, the heat exchange region  60  may be disposed on the exterior of, or may be apart from, the catheter shaft and only the inlet and outlet ends of the supply and return flow paths need be connected to the catheter shaft so as to receive and exhaust circulating heat exchange medium from the inflow and return lumens of the catheter shaft. Also, as explained above, the tubular conduit(s) that form the supply and return flow paths may be coiled of looped in various shapes or configurations.  FIGS. 8A through 8G  show a series of non-exhaustive, non-limiting examples of alternative designs and configurations that are possible in accordance with the present invention. In  FIG. 8A , the tubular conduit  14  is passed through bores in the catheter shaft  12  in different transverse planes to form generally sinusoidal loops that protrude in different planes from the catheter shaft  12 . In  FIG. 8B , the tubular conduit  14  is passed through bores formed in the catheter body to form a helix with the supply and return flow paths passing through alternating side by side convolutions of the helix. In  FIG. 8C  the tubular conduit  14  is laced through grouped bores in the catheter shaft  12  in a double cloverleaf pattern, as shown. In  FIG. 8D  the tubular conduit  14  is passed through bores in the catheter shaft  12  such that separate helical supply and return flow paths are formed. In  FIG. 8E , the tubular conduit  14  is not passed or laced through bores in the catheter shaft  12  but, rather, is formed in separate coiled supply and return flow paths which are connected to inflow and outflow lumens of the catheter and which protrudes beyond the distal end of the catheter shaft. Optionally, as indicated by dotted lines on  FIG. 12 , the catheter shaft could extend to or beyond the distal end of the heat exchange region formed by the tubular conduit  14  and the tubular conduit  14  could optionally be mounted on or supported by such distal extension of the catheter shaft  12 .  FIG. 8F  shows a configuration similar to that of  FIG. 8E  but wherein the tubular conduit  14  passes through the interior of the catheter shaft  12  thereby itself forming inflow and outflow lumens through the proximal catheter shaft  12 . Although the examples of  FIGS. 8A through 8F  show the return and supply portions of the tubular conduit  14  being coiled in loops of substantially the same size, it is to be appreciated that the loops may differ in size. For example, the loops of the return flow path may be smaller in diameter or cross-dimension that those of the supply flow path or vice versa and/or the actual length of the tubular conduit forming the return flow path may be shorter than that which forms the supply flow path or vice versa. Varying size of the loops in the supply and return flow paths is again illustrated by the additional non-limiting example of  FIG. 8G . In the example of  FIG. 8G , a tubular conduit  14  that is substantially the same as that shown in  FIG. 5  is attached to and extends distally from a catheter shaft  12  thereby forming a catheter device having a heat exchange region on the distal end of the catheter wherein the heat exchange region comprises a coiled supply flow path and a coiled return flow path with the supply flow path being coiled in loops that are larger in diameter or cross-dimension than the coiled loops of the return flow path. Also, in the embodiment of  FIG. 8G , the length of the tubing  14  forming the return flow path  14  is shorter than the length of the tubing  14  that forms the supply flow path. 
     It is to be appreciated that the invention has been described hereabove with reference to certain examples or embodiments of the invention but that various additions, deletions, alterations and modifications may be made to those examples and embodiments without departing from the intended spirit and scope of the invention. For example, any element or attribute of one embodiment or example may be incorporated into or used with another embodiment or example, unless otherwise specified of if to do so would render the embodiment or example unsuitable for its intended use. Also, where the steps of a method or process have been described or listed in a particular order, the order of such steps may be changed unless otherwise specified or unless doing so would render the method or process unworkable for its intended purpose. All reasonable additions, deletions, modifications and alterations are to be considered equivalents of the described examples and embodiments and are to be included within the scope of the following claims.