Patent Publication Number: US-2018042762-A1

Title: Thermal system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional patent application Ser. No. 62/373,564 filed Aug. 11, 2016, by inventor and entitled THERMAL SYSTEM, the complete disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a thermal control system for controlling the temperature of circulating fluid that is delivered to one or more thermal pads positioned in contact with a patient. 
     Thermal control systems are known in the art for controlling the temperature of a patient by providing a thermal control unit that supplies temperature controlled fluid to one or more thermal pads positioned in contact with a patient. The thermal control unit includes one or more heat exchangers for controlling the temperature of the fluid and a pump that pumps the temperature controlled fluid to the pad(s). After passing through the pad(s), the fluid is returned to the thermal control unit where any necessary adjustments to the temperature of the returning fluid are made before being pumped back to the pad(s). In some instances, the temperature of the fluid is controlled to a target temperature, while in other instances the temperature of the fluid is varied as necessary in order to automatically effectuate a target patient temperature. The thermal control unit can therefore be used to warm or cool a patient. 
     The pads are placed in close contact with the patient in order to facilitate heat exchange between the patient and the pad. In one common arrangement, three pads are applied to the patient: one applied around the patient&#39;s torso, one applied around the patient&#39;s right leg, and one applied around the patient&#39;s left leg. 
     SUMMARY 
     The present disclosure provides various improved aspects to a thermal control system, including the thermal control unit and the thermal pads. These improved aspects include improved thermal transfer between the pads and the patient; improved control of the patient&#39;s temperature; improved sensing of the temperature environment at the patient; and improved targeting of the temperature controlled fluid to one or more areas of the patient. Other improved aspects of the present disclosure are described in more detail below. 
     According to one embodiment of the present disclosure, a thermal pad for controlling a patient&#39;s temperature is provided that includes a body, a first temperature sensor, a second temperature sensor, and a temperature output. The body is adapted to be placed in contact with the patient and defines an interior in which fluid circulates. The body includes a fluid inlet adapted to receive fluid from a thermal control unit adapted to control a temperature of the fluid, and a fluid outlet adapted to return the fluid to the thermal control unit. The first temperature sensor is positioned adjacent the fluid outlet and adapted to detect a temperature of the fluid exiting the thermal pad. The second temperature sensor is positioned adjacent the fluid inlet and adapted to detect a temperature of the fluid entering the thermal pad. The temperature output reports the temperature of the first and second temperature sensors to the thermal control unit. 
     According to other aspects of the disclosure, the thermal pad includes a second fluid inlet and a second fluid outlet that are in communication with a fluid channel inside of the thermal pad that is fluidly separated from a fluid channel that receives fluid from the first inlet. The fluid in the channels therefore does not mix while inside the thermal pad. Third and fourth temperature sensors may also be included that detect temperature of the fluid entering and exiting the thermal pad via the second fluid inlet and outlet, respectively. 
     In some embodiments, the thermal pad includes an interior surface adapted to contact the patient and an exterior surface adapted to face away from the patient wherein the interior surface includes a plurality of craters. The craters create suction when the interior surface is applied to a skin of the patient and the suction releasably retains the interior surface against the patient&#39;s skin. The suction allows the thermal pad to be retained against the skin of the patient without using an adhesive. 
     Alternatively, the interior surface may include a gel layer adapted to directly contact a skin of the patient and to have inherent adhesive properties for releasably adhering to the patient&#39;s skin. 
     According to another embodiment, a thermal pad for controlling a patient&#39;s temperature is provided. The thermal pad includes a body, at least one channel, and a valve. The body is adapted to be placed in contact with the patient and includes an interior in which fluid circulates. The body further includes an inlet adapted to receive temperature controlled fluid from a thermal control unit and an outlet adapted to return the fluid to the thermal control unit. The channel is in the body and in fluid communication with the inlet and outlet. The valve is adapted to control an amount of fluid flowing through the channel. 
     According to other aspects of the disclosure, a port is included that is adapted to receive a control signal for controlling the valve. 
     The pad may further include a plurality of channels wherein a first one of the channels is associated with a first zone of the thermal pad and a second one of the channels is associated with a second zone of the thermal pad. In such cases, the valve controls what proportion of the fluid from the fluid inlet is directed to the first zone versus the second zone. 
     In some embodiments, the valve is positioned at the fluid inlet and controls the amount of fluid flowing through the channel. 
     The valve is a pressure operated valve controlled by a pressure of the fluid in some embodiments. In other embodiments, the valve is controlled by signals that are based upon, either wholly or partially, a fluid flow rate and/or volume. 
     According to another embodiment, a thermal control unit is provided for supplying fluid controlled temperature to one or more thermal pads. The thermal control unit includes a fluid outlet, a fluid inlet, a heat exchanger, a pump, and a controller. The fluid outlet couples to a fluid supply line and the fluid inlet couples to a fluid return line. The pump circulates fluid from the fluid inlet through the heat exchanger and to the fluid outlet. The controller receives a first temperature reading from a first temperature sensor positioned remote from the thermal control unit and adapted to measure a temperature of the fluid delivered by the fluid supply line to a thermal pad. The controller also receives a second temperature reading from a second temperature sensor positioned remote from the thermal control unit and adapted to measure a temperature of the fluid returned from the thermal pad by the fluid return line. The controller controls the heat exchanger based upon the first and second temperature readings. 
     According to other aspects, the controller receives third and fourth temperature readings from third and fourth temperature sensors that are positioned remotely from the thermal control unit. The third temperature sensor measures a temperature of the fluid delivered by a second fluid supply line to the thermal pad and the fourth temperature sensor measures a temperature of the fluid returned from the thermal pad to a second fluid return line. The controller controls the heat exchanger based upon the third and fourth temperature readings. 
     The thermal control unit includes, in some embodiments, one or more valves that control the amount of fluid flowing to the one or more fluid supply lines. The controller is adapted to control the valves based upon temperature readings from the multiple temperature sensors. 
     In some embodiments, the controller determines a first difference between the first and second temperature readings and a second difference between the third and fourth temperature readings. The controller controls at least one valve based upon the first and second differences. The controller may also or alternatively control a speed of the pump based upon one or more of the temperature differences. 
     According to another embodiment, a thermal control unit is provided that includes first and second fluid inlets, first and second fluid outlets, a heat exchanger, a pump, a temperature sensor, a valve, and a controller. The pump circulates fluid from the first and second fluid inlets through the heat exchanger and to the first and second fluid outlets. The temperature sensor detects a temperature of fluid returning from one of the first or second fluid inlets. The valve controls an amount of fluid flowing to the first fluid outlet. The controller controls the valve based at least in part upon the temperature sensed by the temperature sensor. 
     In some embodiments, the thermal control unit further includes a second valve for controlling an amount of fluid flowing to the second fluid outlet. The controller controls the second valve based at least in part upon the temperature sensed by one or more of the temperature sensors. 
     The controller may also, or alternatively, control one or more of the valves based upon one or more temperature readings from temperature sensors positioned remote from the thermal control unit. 
     The first fluid supply line and first fluid return line are coupled to a first zone of a thermal pad, in some embodiments, and the second fluid supply line and the second fluid return line are coupled to a second zone of the thermal pad. 
     According to another embodiment, a thermal control system is provided that includes a thermal control unit, a thermal pad, first, second, third, and fourth hoses, and a thermocouple. The thermal control unit includes first and second fluid outlets and first and second fluid inlets, a heat exchanger, a pump, and a controller. The thermal pad is adapted to receive fluid from the thermal control unit. The first and second hoses couple the first and second fluid outlets, respectively, to a first zone of the thermal pad. The third and fourth hoses couple the first and second fluid inlets, respectively, to a second zone of the thermal pad. The thermocouple has a first and second conductor coupled to a first location of the first zone. The thermocouple communicates with the controller of the thermal control unit. 
     According to other aspects, the controller controls the heat exchanger based upon at least an output of the thermocouple. The controller may also or alternatively control a speed of the pump and/or a valve based upon outputs from the thermocouple. 
     Before the various embodiments disclosed herein are explained in detail, it is to be understood that the claims are not to be limited to the details of operation or to the details of construction, nor to the arrangement of the components set forth in the following description or illustrated in the drawings. The embodiments described herein are capable of being practiced or being carried out in alternative ways not expressly disclosed herein. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the claims to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the claims any additional steps or components that might be combined with or into the enumerated steps or components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a thermal control system according to one aspect of the present disclosure shown applied to a patient on a patient support apparatus; 
         FIG. 2  is block diagram of the thermal control system of  FIG. 1 ; 
         FIG. 3  is a plan view of a first embodiment of a thermal pad usable with the thermal control system of  FIG. 1 ; 
         FIG. 4  is an exploded perspective view of the thermal pad of  FIG. 3 ; 
         FIG. 5  is a diagram of an illustrative flow channel layout that may be incorporated into the inside of the thermal pad of  FIG. 3 ; 
         FIG. 6  is a plan view of a second embodiment of a thermal pad usable with the thermal control system of  FIG. 1 ; 
         FIG. 7  is a plan view of a third embodiment of a thermal pad usable with the thermal control system of  FIG. 1 ; 
         FIG. 8  is a diagram of an illustrative flow channel layout that may be incorporated into the inside of the thermal pads of  FIG. 3 or 7 ; 
         FIG. 9  is a plan view of a fourth embodiment of a thermal pad usable with the thermal control system of  FIG. 1 ; 
         FIG. 10  is an exploded perspective view of the thermal pad of  FIG. 9 ; 
         FIG. 11  is a side sectional view of the thermal pad of  FIG. 9 ; and 
         FIG. 12  is a side view of an illustrative thermal pad interior layer that may be incorporated into any of the thermal pads disclosed herein. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A thermal control system  20  according to one embodiment of the present disclosure is shown in  FIG. 1 . Thermal control system  20  is adapted to control the temperature of a patient  30 , which may involve raising, lowering, or maintaining the patient&#39;s temperature, or combinations thereof. Thermal control system  20  includes a thermal control unit  22  coupled to one or more thermal therapy devices  24 . The thermal therapy devices  24  are illustrated in  FIG. 1  to be thermal pads, but it will be understood that thermal therapy devices  24  may take on other forms, such as, but not limited to, blankets, vests, patches, caps, or other structure. For purposes of the following written description, thermal therapy devices  24  will be referred to as thermal pads  24 , but it will be understood by those skilled in the art that this terminology is used merely for convenience and that the phrase “thermal pad” is intended to cover all of the different variations of thermal therapy devices  24  mentioned above (e.g. blankets, vests, patches, caps, etc.). 
     Thermal control unit  22  is coupled to thermal pads  24  via a plurality of hoses  26 . Each hose includes one or more lines  28 . In the embodiment shown in  FIG. 1 , each hose  26  includes a fluid supply line  28   a , a fluid return line  28   b , and one or more control lines  28   c . Thermal control unit  22  delivers temperature controlled fluid (such as, but not limited to, water) to the thermal pads  24  via the fluid supply lines  28   a . After the temperature controlled fluid has passed through thermal pads  24 , thermal control unit  22  receives the temperature controlled fluid back from thermal pads  24  via the return lines  28   b . Control lines  28   c  are used by thermal control unit  22  in different manners, depending upon the capabilities of thermal control unit  22 , the construction of one or more of the thermal pads  24 , and/or the desired treatment to be applied to the patient  30 . As will be discussed in greater detail below, in some instances thermal control unit  22  uses a control line  28   c  to take one or more temperature readings from a location adjacent to, or inside of, thermal pad  24 . In other instances, thermal control unit  22  uses a control line  28   c  to control one or more valves incorporated into thermal pad  24 . In still other instances, thermal control unit  22  uses control lines  28   c  to both take temperature readings and control one or more valves inside of thermal pads  24 . Still other uses are discussed below. 
     In the embodiment of thermal control system  20  shown in  FIG. 1 , three thermal pads  24  are used in the treatment of patient  30 . A first thermal pad  24  is wrapped around a patient&#39;s torso, while second and third thermal pads  24  are wrapped, respectively, around the patient&#39;s right and left legs. Other configurations can be used and different numbers of thermal pads  24  may be used with thermal control unit  22 , depending upon the number of inlet and outlet ports that are included with thermal control unit  22 . By controlling the temperature of the fluid delivered to thermal pads  24  via supply lines  28   a , the temperature of the patient  30  can be controlled via the close contact of the pads  24  with the patient  30  and the resultant heat transfer therebetween. 
     Thermal control unit  22  is adapted to raise or lower the temperature of the fluid supplied to thermal pads  24  via supply lines  28   a . As shown in  FIG. 2 , thermal control unit  22  includes a pump  32  for circulating fluid through a circulation channel  34 . Pump  32 , when activated, circulates the fluid through circulation channel  34  in the direction of arrows  36  (clockwise in  FIG. 2 ). Starting at pump  32  the circulating fluid first passes through a heat exchanger  38  where it is delivered to an outlet manifold  40  having an outlet temperature sensor  42 , a plurality of valves  44 , and a plurality of outlet ports  46 . Temperature sensor  42  is adapted to detect a temperature of the fluid inside of outlet manifold  40  and report it to a controller  48 . Valves  44  are adapted to move between open and closed positions (and in some embodiments, one or more positions therebetween) under the control of controller  48 . Outlet ports  46  are adapted to be coupled to supply lines  28   a  of thermal control system  20  and deliver temperature controlled fluid thereto. Valves  44  control how much fluid flows from outlet manifold  40  to each of the supply lines  28   a , as will be discussed in greater detail below. Supply lines  28   a  are, in turn, coupled to a thermal load  70 . Thermal load  70  includes one or more thermal pads  24  that are used to control the temperature of a patient  30 . 
     Control unit  22  also includes a bypass line  50  fluidly coupled to outlet manifold  40  and an inlet manifold  52 . Bypass line  50  allows fluid to circulate through circulation channel  34  even in the absence of any thermal pads  24  or lines  28   a  being coupled to any of outlet ports  46 . In the illustrated embodiment, bypass line  50  includes an optional filter  54  that is adapted to filter the circulating fluid. If included, filter  54  may be a particle filter adapted to filter out particles within the circulating fluid that exceed a size threshold, or filter  54  may be a biological filter adapted to purify or sanitize the circulating fluid, or it may be a combination of both. 
     Inlet manifold  52  includes the plurality of inlet ports  56  that receive fluid returning from the one or more connected thermal pads  24 . The incoming fluid from inlet ports  56 , as well as the fluid passing through bypass line  50 , travels back toward the pump  32  into an air separator  58 . Air separator  58  includes any structure in which the flow of fluid slows down sufficiently to allow air bubbles contained within the circulating fluid to float upwardly and escape to the ambient surrounding. In some embodiments, air separator  58  is constructed in accordance with any of the configurations disclosed in commonly assigned U.S. patent application Ser. No. 62/361,124 filed Jul. 12, 2016, by inventor Gregory S. Taylor and entitled THERMAL CONTROL SYSTEM, the complete disclosure of which is hereby incorporated herein by reference. After passing through air separator  58 , the circulating fluid flows past a valve  60  positioned beneath a fluid reservoir  62  that supplies fluid to thermal control unit  22 . After passing by valve  60 , the circulating fluid travels to pump  32  and the circuit is repeated. 
     Controller  48  of thermal control unit  22  is contained within a main body of thermal control unit  22  and is in electrical communication with a variety of different sensors and/or actuators. More specifically, controller  48  is in electrical communication with pump  32 , heat exchanger  38 , a control panel  64  ( FIG. 1 ), outlet temperature sensor  42 , valves  44 , a plurality of inlet temperature sensors  66 , and a plurality of control ports  68 . 
     Inlet temperature sensors  66  are positioned inside of inlet manifold  52  and measure the temperature of the fluid returning through each of inlet ports  56 . That is, each temperature sensor  66  measures the temperature of fluid entering one of the inlet ports  56 . One or more of the inlet ports  56 , in turn, are coupled to return lines  28   b  that return fluid from thermal load  70  to thermal control unit  22 . 
     Control panel  64  allows a user to operate thermal control unit  22 , including setting a desired fluid target temperature and/or a desired patient target temperature, and/or to control other aspects of thermal control unit  22 . Control panel  64  communicates with controller  48  and includes controls enabling a user to turn control unit  22  on and off, as well as one or more controls enabling the user to select a target temperature for the fluid delivered to thermal pads  24 . In some embodiments, control panel  64  also allows a user to select a target temperature for the patient being treated, rather than a specific target temperature for the fluid. When this feature is present, controller  48  makes automatic adjustments to the temperature of the fluid in order to bring the patient&#39;s temperature to the desired patient target temperature. In addition, control panel  64  allows a user to configure how thermal control unit  22  controls the thermal pads in light of temperature and/or flow information received by thermal control unit  22 , as will be discussed more below. Control panel  64  also allows a user to configure how thermal control unit  22  controls one or more valves that may be positioned inside of one or more thermal pads and/or inside of thermal control unit  22 . 
     Both the outlet temperature sensor  42  and one or more of the inlet temperature sensors  66  may be used to provide feedback to controller  48 , depending upon the embodiment of thermal control unit  22 , so that controller  48  can adjust heat exchanger  38 , as appropriate, in order to effectuate closed-loop control of the temperature of the circulating fluid. 
     Each control port  68  couples to a control line  28   c . In other embodiments discussed below, control ports  68  received temperature readings via control lines  28   c  from one or more locations within one or more thermal pads  24 , as will be discussed below. In other embodiments, control ports  68  output one or more control signals to one or more valves positioned inside of one or more thermal pads  24 . In still other embodiments, control ports  68  are used for both receiving temperature readings and for controlling valves. 
     Controller  48  includes any and all electrical circuitry and components necessary to carry out the functions and algorithms described herein, as would be known to one of ordinary skill in the art. Generally speaking, controller  48  may include one or more microcontrollers, microprocessors, and/or other programmable electronics that are programmed to carry out the functions described herein. It will be understood that controller  48  may also include other electronic components that are programmed to carry out the functions described herein, or that support the microcontrollers, microprocessors, and/or other electronics. The other electronic components include, but are not limited to, one or more field programmable gate arrays, systems on a chip, volatile or nonvolatile memory, discrete circuitry, integrated circuits, application specific integrated circuits (ASICs) and/or other hardware, software, or firmware, as would be known to one of ordinary skill in the art. Such components can be physically configured in any suitable manner, such as by mounting them to one or more circuit boards, or arranging them in other manners, whether combined into a single unit or distributed across multiple units. Such components may be physically distributed in different positions in thermal control unit  22 , or they may reside in a common location within thermal control unit  22 . When physically distributed, the components may communicate using any suitable serial or parallel communication protocol, such as, but not limited to, CAN, LIN, Firewire, I-squared-C, RS-232, RS-485, universal serial bus (USB), etc. 
     Controller  48  uses the outputs of outlet temperature sensor  42  and the outputs from one or more of the inlet temperature sensors  66  and/or one or more thermal pad temperature sensors (which are communicated via control lines  28   c  and control ports  68 ) to control heat exchanger  38  and/or pump  32 . Controller  48  controls the heat exchanger and/or pump  32  such that the temperature of the circulating fluid has its temperature adjusted (or maintained) in accordance with the operating mode (manual or automatic) selected by the user of thermal control unit  22 . Controller  48  may control the temperature of the fluid using a closed-loop proportional-integral (PI) controller, a closed-loop proportional-integral-derivative (PID), controller, or some other type of closed-loop controller. 
     Control unit  22  may also be modified to include one or more flow sensors that measure the rate of fluid flow and report this information to controller  48 . In such modified embodiments, controller  48  uses the flow rate in determining what control signals to send to heat exchanger  38 , valves  44 , pump  32 , and/or one or more thermal pads via control ports  68 . 
     It will be understood by those skilled in the art that the particular order of the components along circulation channel  34  of control unit  22  may be varied from what is shown in  FIG. 2 . For example, although  FIG. 2  depicts pump  32  as being upstream of heat exchanger  38  and air separator  58  as being downstream of heat exchanger  38 , this order may be changed. Air separator  58 , pump  32 , heat exchanger  38  and reservoir  62  may be positioned at any suitable location along circulation channel  34 . Indeed, in some embodiments, reservoir  62  is moved so as to be in line with and part of circulation channel  34 , rather than external to circulation channel  34  as shown in  FIG. 2 . 
     Further details regarding the construction and operation of one embodiment of thermal control unit  22  that are not described herein are found in commonly assigned U.S. patent application Ser. No. 14/282,383 filed May 20, 2014, inventors Christopher Hopper et al. and entitled THERMAL CONTROL SYSTEM, the complete disclosure of which is incorporated herein by reference. 
       FIG. 3  illustrates in greater detail one embodiment of a thermal pad  24  that may be used with the thermal control system  20  of  FIG. 1 . Thermal pad  24  includes a top  72 , a bottom  74 , a first side  76   a  and a second side  76   b  that collectively define a perimeter of thermal pad  24 . Thermal pad  24  also includes a fluid inlet hose  78   a , a fluid outlet hose  78   b , and a control line  80 . Fluid inlet hose  78   a  is adapted to couple to fluid supply line  28   a  from thermal control unit  22 . Fluid outlet hose  78   b  is adapted to couple to fluid return line  28   b  from thermal control unit  22 . Control line  80  is adapted to couple to control line  28   c  from thermal control unit  22 . 
     Although not shown, thermal pad  24  may also include one or more straps that are used to secure thermal pad  24  to patient  30  when in use. Each strap may be adapted to releasably attach to another strap after thermal pad  24  has been wrapped around the patient  30 . In some embodiments, the straps include hook and loop type fasteners, such as those sold under the tradename Velcro, while in other embodiments, the straps include one or more repositionable tapes. In other embodiments, the straps include other types of fasteners for securing themselves to each other in order to maintain pad  24  in a wrapped stated around the patient&#39;s leg or torso. 
     Although thermal pad  24  of  FIG. 3  is shown as having a generally rectangular shape, it will be understood by those skilled in the art that this may be varied greatly. That is, thermal pad  24  may take on any shape that is conducive to being wrapped around one or more portions of patient  30 . In some embodiments, those thermal pads  24  that are intended to be wrapped around the patient&#39;s torso have a different shape than those intended to be wrapped around the patient&#39;s legs. Those adapted to be wrapped around the patient&#39;s legs may include one or more cutouts or contours that allow the patient to bend his or her knees while thermal pads  24  are wrapped around his or her legs. 
       FIGS. 4 and 5  illustrate in greater detail the internal construction of thermal pad  24  of  FIG. 3 . As shown more clearly in  FIG. 4 , thermal pad  24  includes an interior layer  82 , an exterior layer  84 , a first intermediate layer  86 , and a second intermediate layer  88 . In some embodiments, one or both of interior layer  82  and exterior layer  84  are omitted. Interior layer  82  is designed to face toward the patient  30  while exterior layer  84  is designed to face away from the patient  30 . Interior layer  82 , first and second intermediate layers  86  and  88 , and exterior layer  84  are all bonded to each other around their perimeters. Exterior layer  84  is an insulating layer that is bonded to second intermediate layer  88  over substantially the entire exterior surface of exterior layer  84 . Interior layer  82  and intermediate layers  86  and  88  may all be constructed from any suitable plastic material that is flexible enough to conform to the patient&#39;s body and that provides good thermal conductivity. In some embodiments, interior layer  82  and intermediate layers  86  and  88  are constructed from a polyester and/or nylon composite. Other materials, however, may be used. Exterior layer  84  is constructed from any suitably flexible material that has relatively poor thermal conductivity properties so as to thermally insulate the other layers (and the fluid contained therein) from the temperature of the ambient surroundings. In some embodiments, exterior layer  84  is constructed from material that includes a polyester foam, or other type of foam. Still other constructions are possible. 
     The bonding of interior layer  82 , exterior layer  84 , and intermediate layers  86  and  88  to each other about their periphery may be accomplished in any suitable manner. In some embodiments, the bonding is carried out using welds. Such welds may be implemented via heat welding, ultrasonic welding, Radio Frequency (RF) welding, or by other types of welding. In addition to being bonded to each other around their perimeters, first intermediate layer  86  and second intermediate layer  88  are bonded to each other at a plurality of internal locations  90  ( FIG. 3 ). The space between first intermediate layer  86  and second intermediate layer  88  where they are not bonded to each other defines a fluid chamber in which the temperature controlled fluid supplied by thermal control unit  22  (via supply line  28   a ) circulates. 
     In some regions of thermal pad  24 , bonding locations  90  are contiguous with each other to create one or more fluid channel walls  92  within thermal pad  24 . One such wall  92   a  extends contiguously from top  72  to bottom  74  to thereby separate thermal pad  24  into a first zone  94   a  and a second zone  94   b . First zone  94   a  is fluidly isolated from second zone  94   b . That is, fluid that is supplied to first zone  94   a  by the left inlet hose  78   a  in  FIG. 3  does not mix inside of pad  24  with the fluid that is supplied to second zone  94   b  by the right inlet hose  78   a  in  FIG. 78 b   . Instead, all of the temperature controlled fluid that is supplied to thermal pad  24  by the left inlet hose  78   a  ( FIG. 3 ) circulates through first zone  94   a  and eventually exits pad  24  via the left hose  78   b  ( FIG. 3 ). Likewise, all of the temperature controlled fluid that is supplied to thermal pad  24  by the right inlet hose  78   a  ( FIG. 3 ) circulates through second zone  94   b  and eventually exits pad  24  via the right hose  78   b  ( FIG. 3 ). 
     Although  FIG. 3  illustrates first and second zone  94   a  and  94   b  as both being rectangular and substantially the same size, it will be understood that this is merely one manner of implementing zones  94   a  and  94   b . In other embodiments, zones  94   a  and  94   b  are not symmetrical and/or are not of equal size. In some embodiments, one or more of zones  94   a  and  94   b  have shapes, sizes, and/or locations that are defined with reference to their intended anatomical placement on the patient. For example, first zone  94   a  may be sized, shaped, and positioned on thermal pad  24  such that it will contact a first particular anatomical location of the patient and second zone  94   b  may be sized, shaped, and/or positioned on thermal pad  24  such that it will contact a second anatomical location of the patient when thermal pad  24  is placed in contact with the patient. 
     The paths followed by the temperature controlled fluid while it circulates inside of thermal pad  24  may vary.  FIG. 5  illustrates one illustrative layout of a first fluid channel  96   a  and a second fluid channel  96   b . Fluid flows in channels  96   a  and  96   b  in the directions indicated by arrows  98 . First fluid channel  96   a  is defined in first zone  94   a  and second fluid channel  96   b  is defined in second zone  94   b . First and second fluid channels  96   a  and  96   b  are each defined essentially as an inverted “U” in  FIG. 5 . It will be understood by those skilled in the art that different shapes of fluid channels  96   a  and  96   b  can be used. Further, it will be understood by those skilled in the art that, in some embodiments, fluid channel  96   a  has a shape and/or layout that is different from the shape and/or layout of fluid channel  96   b . Still further, in some embodiments, first zone  94   a  and/or second zone  94   b  can be comprised of multiple fluid channels  96  that may be arranged in series or parallel, or any combination or sequence of channels arranged in parallel or serial fashion. 
     As shown in  FIG. 3 , thermal pad  24  further includes two control lines  80   a  and  80   b . In this embodiment, a first one of the control lines  80   a  is coupled to a first temperature sensor  100   a  and a second one of the control lines  80   b  is coupled to a second temperature sensor  100   b . Temperature sensors  100   a  and  100   b  are thermocouples, in at least one embodiment. In other embodiments, temperature sensors  100   a  and/or  100   b  are thermistors. In still other embodiments, temperature sensors  100   a  and/or  100   b  are implemented as still other types of temperature sensors. 
     First temperature sensor  100   a  is integrated into thermal pad  24  at a first location that, in at least one embodiment, is positioned close to fluid outlet hose  78   b  coupled to first zone  94   a . First temperature sensor  100   a  therefore provides a temperature reading of the temperature controlled fluid after it has circulated through substantially all of the first zone  94   a  of thermal pad  24 . Second temperature sensor  100   b  is integrated into thermal pad  24  at a second location that, in at least one embodiment, is positioned close to fluid outlet hose  78   b  coupled to second zone  94   b . Second temperature sensor  100   b  therefore provides a temperature reading of the temperature controlled fluid after it has circulated through substantially all of the second zone  94   b  of thermal pad  24 . 
     In other embodiments, temperature sensors  100   a  and/or  100   b  may be positioned at other locations inside of thermal pad  24 . For example, temperature sensors  100   a  and/or  100   b  may be positioned at any location along fluid channels  96   a  and  96   b , respectively. Regardless of the position of temperature sensors  100   a  and  100   b , they are secured inside of thermal pad  24  such that their location does not change. Any conventional manner of securing them inside of thermal pads  24  may be used, such as, but not limited to, the use of adhesive, fasteners, welding, etc. 
     When temperature sensors  100   a  and  100   b  are positioned close to fluid outlet hoses  78   b  of their respective zones  94   a  and  94   b , temperature sensors  100   a  and  100   b  report temperature readings back to thermal control unit  22  (via control ports  68 ) that are indicative of how much thermal energy has been transferred to or from the patient. In some embodiments, thermal control unit  22  is constructed to include a flow meter coupled to each of inlet ports  56  or each of outlet ports  46  so that controller  48  can calculate how much fluid is circulating through each zone  94  and/or pad  24 . By knowing the amount of fluid returning from a zone  94  and/or pad  24 , the temperature of the returning fluid (measured by temperatures sensors  100   a  and  100   b ), and the temperature delivered to each pad or zone  94  (measured by outlet temperature sensor  42 ), controller  48  is able to calculate how much thermal energy has been delivered or absorbed by each zone  94  and/or pad  24 . In some embodiments of thermal control unit  22 , controller  48  calculates this thermal energy and displays it to the user. In still other embodiments, one or more flow meters may be incorporated into the thermal pad  24  and/or one or more of the hoses  26  that couple thermal pad  24  to thermal control unit  22 . 
     In other embodiments of thermal control unit  22 , controller  48  calculates this thermal energy, compares the calculated thermal energies of each zone  94  and/or pad  24  to each other, and determines if any discrepancies exist that exceed one or more thresholds. Such discrepancies may be indicative of poor contact of a zone or pad with the patient, or poor circulation of fluid through one or more zones or pads  24 . For example, if controller  48  determines that a first thermal pad  24  coupled to one of the patient&#39;s legs is absorbing X amount of kilocalories per hour and a second thermal pad  24  coupled to the patient&#39;s other leg is absorbing Y amount of kilocalories per hour, and X is significantly different from Y, there is likely an issue with one of the thermal pads  24 . This is because there typically is not a large difference between the patient&#39;s right and left legs in terms of the amount of heat they can deliver or absorb. As noted, the issue may be due to one of the thermal pads  24  not being wrapped properly around the patient&#39;s leg, or it may be due to reduced fluid flow, such as from a constricted fluid line, or it may be due to other reasons. By notifying the user of the potential issue, thermal control unit  22  is able to prompt the user to take investigative action in order to address and correct the issue. 
     In some embodiments, thermal control unit  22  does not include flow meters for each individual inlet port  56  and therefore does not calculate how much thermal energy is being delivered or absorbed by a thermal pad  24  and/or its individual zones  94 . In such embodiments, controller  48  still monitors differences in temperatures sensed by temperature sensors  100   a  and  100   b  and issues an alert if those temperature differences exceed one or more predefined thresholds. Thus, for example, if fluid if being delivered to both zones  94   a  and  94   b  that is at approximately the same temperature, yet temperature sensor  100   a  is sensing a temperature that differs from the temperature sensed by temperature sensor  100   b  that is greater than a threshold, controller  48  issues an alert to the user to investigate the possible cause of this greater-than-normal temperature difference. 
     In still other embodiments, thermal control unit  22  is configured to monitor the flow rates associated with different thermal pads  24  and/or different zones of one or more thermal pads  24  and determine if any of the monitored flow rates differ from each other by more than one or more thresholds. This monitoring is carried out independently of the temperature monitoring. Thus, for example, if thermal control unit  22  detects that the temperature of the returning fluid from first and second pads  24  is the same (or has very little difference), yet one of the pads has a markedly higher or lower flow rate, this may be an indication that one or both of the thermal pads  24  are not properly positioned on the patient. Consequently, if thermal control unit  22  detects differences in flow rates that exceed one or more predetermined thresholds, it provides notification to the user to investigate the source of such differences. 
     By positioning temperature sensors  100   a  and  100   b  inside of thermal pad  24 , more accurate indications of the temperature of the fluid at the local region where the heat transfer is occurring between pad  24  and the patient  30  are able to be obtained. That is, measurements of the temperature of the fluid inside thermal control unit  22 , either after it has returned from the thermal pad or when it is inside outlet manifold  40  and ready to be delivered to the pads, are not necessarily accurate indications of the temperature of the fluid at the thermal pad  24 . Differences in these temperatures can exist due to thermal loss or gain that occurs as the fluid flows through lines  28   a  and  28   b , and/or while flowing through hoses  78   a  and  78   b . By providing temperature readings at the thermal pads  24 , temperature sensors  100   a  and  100   b  allow the thermal control unit  22  to have more accurate knowledge of the state of thermal pad  24  and its thermal characteristics. 
     In some embodiments of thermal control unit  22 , controller  48  is configured to take one or more automatic actions in response to the detection of discrepancies between temperature readings from temperature sensors  100   a  and  100   b  that exceed one or more thresholds. Such automatic actions may be in addition to, or in lieu of, a notification to the user of the detection of such discrepancies. In one such embodiment, controller  48  is adapted to change the fluid pressure and/or fluid volume supplied to one or more of supply lines  28   a  in response to the detection of such a temperature discrepancy. Controller  48  may achieve this by opening, closing, or otherwise adjusting one or more of valves  44  inside of thermal control unit  22 . Alternatively, some thermal pad embodiments (which will be discussed in greater detail below), include one or more valves that are controllable by thermal control unit  22  via control ports  68 . When thermal control unit  22  is used with such thermal pads, control unit  22  sends a signal to the appropriate control port  68  instructing one or more valves positioned inside of the thermal pad to change their state (e.g. to open, close, or move to some position in between). 
     Still further, in some embodiments, thermal control unit  22  is constructed to be able to deliver fluid to zones  94  and/or thermal pads  24  that is at different temperatures. In such embodiments, controller  48  is adapted to react to detected temperature discrepancies (from sensors  100 ) that exceed a threshold by adjusting the temperature of the fluid supplied to one or both of the zones whose sensed temperatures are different by more than the threshold. Thus, for example, if a thermal pad  24  is being used to cool a patient and the temperature inside of first zone  94   a  is much cooler than the temperature inside of second zone  94   b , controller  48  may lower the temperature of the fluid supplied to second zone  94   b . Alternatively, controller  48  may take other actions. Such actions may vary depending upon not only the magnitude of the temperature difference between sensors  100   a  and  100   b , but also the operational mode of thermal control unit  22 , the temperature of the patient, the absolute temperature of the fluid (as measured at one or more locations), and one or more user-configured settings of thermal control unit  22 . 
     Thermal control unit  22  is also constructed in some embodiments to allow a user to designate a priority level for one or more of the thermal pads  24 . Based upon temperature and/or flow readings associated with the one or more high priority pads  24 , thermal control unit  22  automatically adjusts its resources from the low priority pad(s) to the high priority pad(s)  24  if an undesired condition occurs with respect to the high priority pad(s). Such an undesired condition may include flow volume and/or temperature readings that are outside of desired ranges. The shifting of the resources includes, but is not limited to, reducing flow volumes to the low priority pad(s) via valves  44  and/or  102  (discussed below), adjusting the heat exchanger  38 , pump  32 , and/or other components of thermal control unit  22  based upon the readings from the high priority pad(s) instead of readings from the low priority pad(s), and/or shutting off fluid flow to the low priority pads until the desired state of the high priority pad(s) is attained. In some such embodiments, the user is able to specify how thermal control unit  22  reacts to deviations from target conditions in the one or more high priority pad(s). Still further, thermal control unit  22  is configured to allow the same priority designations discussed herein to be applied to individual zones of one or more thermal pads  24 . When applied to individual zones, thermal control unit  22  is able to take the same actions discussed above when the high priority zone deviates from one or more target conditions. 
       FIG. 6  illustrates an alternative embodiment of a thermal pad  124  that may be used with thermal control system  20 . Thermal pad  124  includes a number of components and/or features that are the same as thermal pad  24 . Those components or features that are common are labeled with the same reference numbers used to describe thermal pad  24  and, unless otherwise explicitly stated below, operate in the same manner or provide the same function as previously described. Those components or features that are different from thermal pad  24  are provided with a new reference number and described in more detail below. 
     Thermal pad  124  differs from thermal pad  24  in two respects. First, thermal pad  124  includes only a single zone, and thus has only one inlet hose  78   a  and one outlet hose  78   b . Second, thermal pad  124  includes two temperature sensors  100   a  and  100   b  that are contained within the same (single) zone. In one embodiment of thermal pad  124 , first temperature sensor  100   a  is positioned generally adjacent fluid outlet hose  78   b  so as to sense the temperature of the fluid as it exits, or is about to exit, thermal pad  124 . Second temperature sensor  100   b  is positioned generally adjacent fluid inlet hose  78   a  so as to sense the temperature of the fluid that is entering, or has just entered, thermal pad  124 . Each temperature sensor  100   a  and  100   b  is coupled to a control line  80   a  and  80   b  that are, in turn, coupled to a pair of control ports  68  on thermal control unit  22 . 
     Thermal control unit  22  uses the temperature readings from sensors  100   a  and  100   b  of thermal pad  124  to calculate the change in fluid temperature across the thermal pad  124 . That is, controller  48  calculates how much the fluid temperature changes from when the fluid first enters thermal pad  124  to when the fluid exits thermal pad  124 . This provides an indication to thermal control unit  22  of how much thermal energy is being transferred to, or delivered by, thermal pad  124  (assuming a relatively steady flow rate). As noted previously, in some embodiments, thermal control unit  22  is configured to determine the flow rates for each thermal pad or zone. In such embodiments, control unit  22  uses the readings from temperature sensors  100   a  and  100   b  of thermal pad  124  to calculate how much thermal energy is being delivered to the patient, or absorbed from the patient. The calculation can either be an absolute quantity over a period of time, or it can be a rate at which the thermal energy is transferred. In some embodiments, control unit  22  displays this thermal energy transfer amount to the user. 
     Thermal control unit  22 , in some embodiments, takes similar actions as described above with respect to thermal pad  24 , if thermal control unit  22  senses that a temperature difference between sensors  100   a  and  100   b  of a first pad  124  are significantly (more than a threshold) different from the temperature difference between sensors  100   a  and  100   b  of a second pad  124 . As noted above, such actions include any one or more of the following: notifying the user, adjusting a target temperature of the temperature controlled fluid, adjusting a fluid pressure and/or flow volume of the temperature controlled fluid delivered to one or both of the thermal pads  124  (such as, but not limited to, the adjustment of one or more valves), and/or other actions. 
     Thermal pad  124  may be used with other thermal pads  124  of similar construction, or it may be used with one or more thermal pad  24 . Indeed, control system  20  is configured so that it can be used with a mixture of one or more thermal pads  24  and/or  124  (and/or one of the other thermal pad embodiments discussed below) and/or with other thermal pads. Regardless of the homogeneity or heterogeneity of the types of thermal pads coupled to thermal control unit  22 , thermal control unit  22  is adapted, in some embodiments, to individually control one or more of the pads, or one or more of the zones of the pads. That is, thermal control unit  22  controls any one or more of the following characteristics of a thermal control pad or zone in a manner that may be different from the other pads or zones coupled to thermal control unit  22 : the temperature of the fluid delivered to the pad or zone by thermal control unit  22 , the flow rate of the fluid delivered to the pad or zone, and/or one or more valves associate with the pad or zone. Thermal control unit  22  therefore gives the users the ability to individually, and uniquely (if desired), control the thermal therapy that is delivered to the patient at each zone and/or at each thermal pad. 
       FIG. 7  illustrates an alternative embodiment of a thermal pad  224  that may be used with thermal control system  20 . Thermal pad  224  includes a number of components and/or features that are the same as thermal pad  24  and/or  124 . Those components or features that are common are labeled with the same reference numbers used to describe thermal pads  24  and/or  124 , and unless otherwise explicitly stated below, operate in the same manner or provide the same function as previously described. Those components or features that are different from thermal pad  24  and/or  124  are provided with a new reference number and described in more detail below. 
     Thermal pad  224  is similar to thermal pad  124  but includes multiple zones  94   a  and  94   b . Each zone  94  includes a pair of temperature sensors  100 . Specifically, zone  94   a  includes temperature sensors  100   a  and  100   b , and zone  94   b  includes temperature sensors  100   c  and  100   d . Temperature sensors  100   a  and  100   b  operate in the same manner, and may be constructed in the same manner, as temperature sensors  100   a  and  100   b  of thermal pad  124 , except that temperature sensors  100   a  and  100   b  of thermal pad  224  measure fluid temperatures for a particular zone ( 94   a ) of thermal pad  224  (rather than for the entire pad, as with thermal pad  124 ). Further, thermal control unit  22  uses the outputs from temperature sensors  100   a  and  100   b  of thermal pad  224  in any of the same manners discussed above that it uses the outputs from temperature sensors  100   a  and  100   b  of thermal pad  124 . 
     Temperature sensors  100   c  and  100   d  operate in the same manner, and may be constructed in the same manner, as temperature sensors  100   a  and  100   b  of thermal pad  124 , except that temperature sensors  100   c  and  100   d  of thermal pad  224  measure fluid temperatures for a particular zone ( 94   b ) of thermal pad  224  (rather than for the entire pad, as with temperature sensors  100   a  and  100   b  of thermal pad  124 ). Each temperature sensor  100   a, b, c,  and  d  of thermal pad  224  is coupled to a corresponding control line  80   a, b, c,  and  d,  respectively. Controls lines  80   a - d,  in turn, are coupled to four of the control ports  68  of thermal control unit  22 . Thermal pad  224  may be used in a thermal control system  20  that also utilizes one or more different types of thermal pads when controlling the temperature of a patient (e.g. thermal pads  24 ,  124 , and/or others), or it may be used in a thermal control system  20  that utilizes only similar thermal pads  224 . Of course, in some embodiments, thermal control system  20  only includes a single thermal pad. 
       FIG. 8  illustrates another alternative embodiment of a thermal pad  324  that may be used with thermal control system  20 . Thermal pad  324  includes a number of components and/or features that are the same as thermal pads  24 ,  124 , and/or  224 . Those components or features that are common are labeled with the same reference numbers used to describe thermal pads  24 ,  124 , and/or  224 , and unless otherwise explicitly stated below, operate in the same manner or provide the same function as previously described. Those components or features that are different from thermal pads  24 ,  124 , and/or  224  are provided with a new reference number and described in more detail below. 
     As seen in  FIG. 8 , thermal pad  324  includes two zones  94   a  and  94   b . Each zone  94  includes a plurality of internal walls  92  that define a plurality of fluid channels  96   a - h.  First zone  94   a  includes fluid channels  96   a - d  and second zone  94   b  includes fluid channel  96   e - h.  Fluid flows in channels  96   a - h  in the directions indicated by arrows  98 . It will be understood by those skilled in the art that different shapes of fluid channels  96   a - h  can be used. Further, it will be understood by those skilled in the art that in some embodiments, one or more of fluid channels  96   a - h  may have a shape that is different from one or more of the other fluid channels  96   a - h.    
     In addition to multiple fluid channels  96 , thermal pad  324  also includes a plurality of valves  102 . Valves  102  control the flow of fluid through one or more of the fluid channels  96 , as will be described in more detail below. Each valve  102  includes an associated control port  104 . Control ports  104  are coupled to wires, cables, or other similar structures that are in communication with thermal control unit  22  via control ports  68 . In some embodiments, control ports  104  may be wireless transceivers that wirelessly communicate with wireless transceivers on thermal control unit  22 . Regardless of the media used to communicate between thermal pad  324  and thermal control unit  22 , thermal control unit  22  sends control signals to thermal pad  324  that control the position of valves  102 . 
     As shown in  FIG. 8 , a first valve  102   a  is positioned in first zone  94   a  generally adjacent outlet hose  78   b . First valve  102   a  controls the relative amount of fluid that exits from pad  324  via channels  96   a  and  96   b . First valve  102   a  is movable between a first blocking position that completely stops fluid flow through first channel  96   a  and a second blocking position that completely stops fluid flow through second channel  96   b , as well as a plurality of intermediate positions that allow varying amounts of fluid to flow through first and second channels  96   a  and  96   b . First valve  102   a  is controlled by signals received at first control port  104   a.    
     A second valve  102   b  is positioned in second zone  94   b  generally adjacent inlet hose  78   a . Second valve  102   b  controls the relative amount of fluid that enters zone  94   b  of pad  324  via channels  96   g  and  96   h . Second valve  102   b  is movable between a first blocking position that completely stops fluid from entering fluid channel  96   g  and a second blocking position that completely stops fluid from entering fluid channel  96   h , as well as a plurality of intermediate positions that allow varying amounts of fluid to flow into channels  96   g  and  96   h . Second valve  102   b  is controlled by signals received at second control port  104   b.    
     Thermal pad  324  also includes a third valve  102   c  that is an inter-zone valve. That is, third valve  102  controls the amount of fluid that is able to pass between first zone  94   a  and second zone  94   b . Third valve  102   c  is movable between a blocking position that maintains fluid isolation between zones  94   a  and  94   b  and an open position in which valve  102   c  is completely open to allow fluid to freely flow therethrough between zones  94   a  and  94   b . Third valve  102   c  is also movable to a plurality of intermediate positions that partially restrict fluid flow between zones  94   a  and  94   b . Third valve  102   c  is controlled by signals received at third control port  104   c.    
     It will be understood by those skilled in the art that the number of valves  102  and their position within thermal pad  324  may be varied widely from that illustrated in  FIG. 8 . For example, in some modified embodiments, thermal pad  324  includes valves  102   a  and  102   b  that are both positioned adjacent inlet hoses  78   a  of each zone, or that are both positioned near outlet hoses  78   b  of each zone, rather than in the locations shown in  FIG. 8  wherein valve  102   a  is positioned adjacent outlet hose  78   b  of one zone and valve  102   b  is positioned adjacent inlet hose  78   a  of the other zone. In other modified embodiments, thermal pad  324  eliminates inter-zone valve  102   c , or includes more than one inter-zone valve  102   c . In yet another alternative, thermal pad  324  includes fewer valves  102  than the three shown in  FIG. 8 . Thermal pad  324  may also be modified to include only a single zone or more than the two zones shown in  FIG. 8 . 
     Still further, thermal pad  324  may be modified to include one or more valves  102  that, instead of controlling a relative amount of fluid flowing through two or more channels, such as is illustrated in  FIG. 8 , are configured to control the amount of fluid flowing through a single channel. In such a modified embodiment, the valve  102   b  shown in  FIG. 8 , for example, could be replaced by a pair of valves  102 , one of which controls how much fluid flows through channel  96   g  independent of the other one which controls how much fluid flows through channel  96   h . As yet another alternative, thermal pad  324  may be constructed such that one or more of the zones  94   a, b  has more channels  94  and/or valves  102  than what are illustrated in  FIG. 8 , or has fewer channels  96  and/or valves  102  than what are illustrated in  FIG. 8 . 
     Additionally, although not illustrated in  FIG. 8 , thermal pad  324  may include one or more temperature sensors  100 . In some embodiments, thermal pad  324  includes a single temperature sensor  100  for each zone  94   a  and  94   b , similar to thermal pad  24 . In other embodiments, thermal pad  324  includes both an inlet temperature sensor  100  and an outlet temperature sensor  100  for each zone, similar to thermal pad  224 . In still other embodiments, still other numbers and/or locations of temperature sensors  100  may be implemented. 
     Regardless of the specific number and position of valves  102  and zones  94 , thermal control unit  22  controls the valves based upon temperature readings from the temperature sensors  100 , the flow rates to each zone (if thermal control unit  22  includes flow meters for individual zones), the temperature difference between one or more of the temperature sensors  100  and/or temperature sensors  42  and/or  66 , the target fluid temperature, the target patient temperature, and/or one or more user-configurable settings of thermal control unit  22 . 
       FIGS. 9-11  illustrate another alternative embodiment of a thermal pad  424  that may be used with thermal control system  20 . Thermal pad  424  includes a number of components and/or features that are the same as thermal pads  24 ,  124 ,  224 , and/or  324 . Those components or features that are common are labeled with the same reference numbers used to describe thermal pads  24 ,  124 ,  224 , and/or  324 , and unless otherwise explicitly stated below, operate in the same manner or provide the same function as previously described. Those components or features that are different from thermal pads  24 ,  124 ,  224 , and/or  324  are provided with a new reference number and described in more detail below. 
     As shown more clearly in  FIGS. 10 and 11 , thermal pad  424  includes an interior layer  82 , an exterior layer  84 , and first and second intermediate layers  86  and  88 . As with thermal pad  24 , first intermediate layer  86  and second intermediate layer  88  are bonded at their perimeter (and potentially one or more interior locations  90 ). The space between intermediate layers  86  and  88  defines a chamber for the temperature controlled fluid to flow. The chamber may include one or more walls  92  defining one or more fluid channels  96 . Further, although not illustrated in  FIGS. 9-11 , thermal pad  424  may include one or more valves  102  and/or one or more temperature sensors  100  incorporated therein in any of the manners previously described. 
     Interior layer  82  of thermal pad  424  is made of a gel material having higher thermal conductivity than air. The gel material is adapted to releasably adhere to the skin of a patient in order to provide and maintain close physical contact of thermal pad  424  with the patient. The particular gel material used for interior layer  82  may vary. In some embodiments, the gel is a urethane gel. The specific chemical composition of the urethane gel can be adjusted to change the adhesive properties of the side of interior layer  82  that contacts the patient&#39;s skin. Gel layer  82  may be secured to first intermediate layer  86  by RF welding, lamination, by being poured thereon, or by other means. Regardless of the specific gel used and the specific manner it is secured to first intermediate layer  86 , the gel should provide suitable adhesion to the surface of the patient&#39;s skin in order to resist physical separation between the pad  424  and the patient, yet not be so resistant to physical separation so as to cause discomfort to the patient when the pad  424  is subsequently removed. Gel layer  82  of thermal pad  424  includes an exterior surface that contacts the patient and that, in some embodiments, is cleanable with water and/or mild surfactants, thereby allowing the thermal pad  424  to be re-used, if desired. In some embodiments, one or more antibacterial materials are incorporated into the gel in order to resist the growth of bacteria on the patient&#39;s skin where the pad  424  is placed. Alternatively, or additionally, the gel layer may include a skin conditioner (e.g. lanolin, aloe, etc.) that helps prevent chapping, chafing, or other types of skin degradation. 
       FIG. 12  illustrates an alternative interior layer  82  that may be used on thermal pad  424  in place of gel layer  82  and/or that may be used on any of thermal pads disclosed herein in place of the other interior layers  82  described herein. Interior layer  82  of  FIG. 12  includes an interior surface  106  and an exterior surface  108 . Interior surface  106  faces toward the patient while exterior surface  108  faces away from the patient. Exterior surface  108  is bonded to a first intermediate layer  86  (not shown in  FIG. 12 ). Interior surface  106  includes a plurality of craters  110  defined on it that act as suctions cups when contacting the skin of the patients. Craters  110  therefore releasably adhere to the patient and help maintain physical contact between the patient&#39;s skin and the thermal pad (of which interior layer  82  is a part). 
     The shape, size, and number of craters  110  may vary. In general, craters  110  act in a similar manner to the craters found on many conventional shower or bath mats that releasably stick the mat to the floor of the shower or bath. That is, craters  110  are defined by resiliently flexibly material that, when engaged with the person&#39;s skin, are designed to maintain a negative gauge pressure therein. The negative gauge pressure urges the patient&#39;s skin and craters together. Craters  110  are made from any material that has suitable characteristics for creating negative gauge pressure or suction between the layer  82  and the patient&#39;s skin and that has good thermal transfer properties for transferring thermal energy between the patient&#39;s skin and the thermal pad. 
     It will be understood by those skilled in the art that many variations may be made to the thermal pads described herein beyond the specific modifications described above. For example, and not by way of limitation, the temperatures sensors  100  have been primarily described herein as being inside of thermal pads  24  where they may come into direct contact with the circulating fluid, but it will be understood that they may be placed elsewhere, such as on an exterior surface of the thermal pads. In some of these modified embodiments, the temperature sensors  100  are used to measure the patient&#39;s temperature. Still further, some thermal pads may include both internal and external temperature sensors wherein the internal temperature sensors measure the temperature of the circulating fluid and the external temperature sensors measure the temperature of the patient and/or the ambient surroundings of the thermal pad. In other embodiments, any one or more of the valves  102  used in the thermal pads may be replaced with pressure operated valves that are not controlled by signals received through a corresponding control port  104 . In such embodiments, the thermal pads may omit control ports  104  for the pressure operated valves. 
     It will also be understood by those skilled in the art that although the thermal pads described herein have been described as being used in conjunction with thermal control unit  22 , and vice versa, that the thermal control unit  22  can be used with other types of thermal pads than those described herein and that the thermal pads can be used with other types of thermal control units than the thermal control unit  22  described herein. As one example, if thermal pads  24  include one or more temperature sensors  100 , they may be used with, in some embodiments, a thermal control unit that does not include one or more of the temperature sensors  42  and/or  66 . In such embodiments, the controller uses the temperature readings from the thermal pads to control the heat exchanger  38  and/or pump  32 . Still other modifications are possible. 
     Still further, it will be understood that although the flow of fluid to the thermal pads described herein has been described herein as being controlled by valves  44  positioned in thermal control unit  22  and/or valves  102  positioned inside of the thermal pads, the flow of fluid can also be controlled by one or more valves positioned between thermal control unit  22  and the attached thermal pads, such as by one or more valves coupled to hoses  26 , or to one or more structures positioned intermediate control unit  22  and the thermal pads. 
     Various additional alterations and changes beyond those already mentioned herein can be made to the above-described embodiments. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described embodiments may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.