Patent Publication Number: US-2007101478-A1

Title: Physiologically based warming gloves

Description:
This application claims the benefit of U.S. Provisional Application Serial No. 60/290,384, file 11 May 2001, which is incorporated herein by reference in its entirety. 
    
    
     STATEMENT OF GOVERNMENT RIGHTS  
      The present invention was made with support from the National Aeronautics and Space Administration (NASA) under NASA Grant No. NAG9-1218. The government may have certain rights in this invention. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to liquid cooling/warming garments. More particularly, the present invention pertains to physiologically based garments and methods/systems for liquid cooling/warming of, for example, a human.  
     BACKGROUND  
      When operating normally, the core temperature of the human body is regulated somewhere between 98° F. and 100° F. The body uses a variety of heat transfer mechanisms in regulating its core temperature. These heat transfer mechanisms include radiation, conduction, convection and evaporation of water from the body.  
      When the environmental temperature is below the body temperature, heat is transferred from the body through one or more heat transfer mechanisms of radiation, conduction, convection and/or evaporation of water from the body. This forces the body to conserve heat and increase heat production. When the environmental temperature is above the body temperature, heat is transferred into the body through one or more heat transfer mechanisms of radiation, conduction, and/or convection. In this situation, for example, the body uses the evaporation of perspiration from the skin and the evaporative cooling from exhaled moisture to maintain the core body temperature.  
      The body takes an active role in regulating the body temperature. The temperature of the body is regulated by neural feedback mechanisms that operate primarily through the hypothalmus. The hypothalmus contains not only the control mechanisms, but also the key temperature sensors. Under control of these mechanisms, sweating begins almost precisely at a skin temperature of 35° C. and increases rapidly as the skin temperature rises above this value. The heat production of the body under these conditions remains almost constant as the skin temperature rises. If the skin temperature drops below 35° C. a variety of responses are initiated to conserve the heat in the body and to increase heat production. These include vasoconstriction to decrease the flow of heat to the skin, cessation of sweating, shivering to increase heat production by the muscles and the secretion of norepinephrine, epinephrine, and thyroxine to increase heat production.  
      Different regions of the body have different abilities to transfer heat. This is based in part on both the surface area of the body region and the relative vascularization of the body region. For example, up to 40% of the body&#39;s heat is lost from the head. This is due to the large blood supply to the head, the extra surface area of the head, and from water evaporating from the nose and mouth. Other areas where there is a large muscle mass also coupled with a large surface area also can lose a significant amount of heat.  
      Clothing is used to help maintain the body core temperature. For example, additional layers of clothing are worn to help maintain body temperature in cold environments. Conversely, fewer layers of clothing are worn to help maintain body temperature in warmer environments. Regulating body temperatures due to a change in a person&#39;s activity level in these conditions is usually as simple as adding or subtracting additional layers of clothing.  
      In some situations, the person is unable to remove or add additional layers of clothing when their activity level changes. For example, people working in very hostile environments are not able to remove or add to their protective clothing and/or suits if they become too hot or cold (e.g., astronauts, fighter pilots, firemen, divers, etc.). In some situations it is also possible that a person can be too warm in one region of their body, while another region is too cold.  
      Garments for controlling the core body temperature have been suggested. These garments typically have a system for circulating temperature controlling fluid into and out of the garments, e.g., via tubes positioned in the garment. The temperature controlling fluid is generally circulated through the entire garment, regardless of whether the body area needs to be heated or cooled. In doing so, the system wastes energy. For example, energy is wasted in pumping temperature controlling fluid that may not be needed in a particular area of the suit. In addition, the efficiency of the system is reduced. Reduced efficiency results when areas that may require more heating or cooling fail to receive sufficient temperature controlling fluid to control the body temperature because a portion of the finite amount of temperature controlling fluid may be circulating in areas that do not require heating or cooling at that time. Furthermore, the garments used to control temperature of the body are generally heavy and cannot be worn for long periods of time.  
     SUMMARY OF THE INVENTION  
      The present invention provides a thermodynamically efficient garment for cooling and/or heating a human body. The thermodynamic efficiency is provided in part by targeting the heat exchange capabilities of the garment to specific areas and/or structures of the human body. The present invention identifies these specific areas and/or structures of the human body based on an evaluation of their effectiveness in transferring heat. These specific areas and/or structures of the human body include not only areas of high blood vessel distribution, but also areas of high tissue conductivity. These areas of high tissue conductivity are also referred to herein as areas of high-density tissue. Recognizing and using these areas of high tissue conductivity for heat transfer allows for a smaller more efficient garment for cooling and heating the human body as compared to other heat exchange garments.  
      The present invention introduces the concept of high density (HD) tissue for use in heat transfer to and from the human body. HD tissue includes discrete areas of the human body that have a higher efficiency in transferring heat to or from the body than other non-HD tissue areas of the body. Generally, HD tissue has been found to have superior blood vessel distribution, heat conductivity, and heat transport capability to and from the blood. The present invention makes use of the HD tissue to allow a lighter, more compact garment for heat transfer than has been known.  
      HD tissues are located in different regions of the body, but all share common major characteristics. These major characteristics include, but are not limited to, discrete areas of the body that have a high cell density or compact mineral content as compared to other body tissues, areas that include more than one of bone, tendon, fascia and muscle tissues types in close proximity to both the skin and to major vascular structures of the body, and that display high coefficients of conductivity. These high coefficients of conductivity are due in part to the body tissues that make up the HD region of the body (e.g., bone, tendon, fascia, muscle).  
      The present invention uses both HD tissue and non-high density tissue in controlling the temperature and comfort of the human body. A heat exchange garment is provided, where the heat exchange garment comprising at least one heat exchange zone and one or more non-heat exchange zones. In one embodiment, the at least one heat exchange zones are configured to correspond to one or more HD tissue areas of the human body. Each of the heat exchange zones further comprises heat exchange elements for use in transferring at least heat to the human body. Preferably, the location of heat exchange elements in the garment are located substantially only in the at least one heat exchange zone.  
      In one embodiment, the heat exchange zones of the heat exchange garment can be positioned to be adjacent one or more HD tissue areas of the body. The areas of the HD tissue preferably include high levels of vascularization. Heat can then be transferred between heat exchange zones of the heat exchange garment and the adjacent HD tissue areas of the body. The heat exchange can include providing cooling or heating to the adjacent HD tissue areas. In one embodiment, one or more adjacent HD tissue areas can be cooled, while one or more additional adjacent high density tissue areas can be heated.  
      In one embodiment, heating and cooling of the HD tissue regions of the body can be in an effort to provide thermal comfort to the person wearing the heat exchange system of the present invention. Thermal comfort can be accomplished by balancing the heating and cooling requirements of different HD tissue regions of the body. In one embodiment, this balancing can be accomplished by using one or more sensed physiological parameters in a feedback control system. Based on the sensed physiological parameters, at least one characteristic of a heat exchange fluid within a heat exchange garment can be controlled based on the sensed one or more physiological parameters. 
    
    
     BRIEF DESCRIPTION OF FIGURES  
       FIG. 1  is a flow chart illustrating a technique for controlling body temperature according to one embodiment of the present invention.  
       FIG. 2  is a flow chart illustrating an additional technique for controlling body temperature according to one embodiment of the present invention.  
       FIG. 3  is a schematic diagram illustrating a front view of a person wearing a heat exchange garment according to one embodiment of the present invention.  
       FIG. 4  is a schematic diagram illustrating a rear view of the person shown in  FIG. 3  wearing a heat exchange garment according to one embodiment of the present invention.  
       FIG. 5  is a schematic diagram illustrating a portion of a heat exchange garment according to one embodiment of the present invention.  
       FIG. 6A, 6B ,  6 C, and  6 D is a schematic diagram illustrating various embodiments of a portion of a heat exchange garment according to one embodiment of the present invention.  
       FIG. 7  is a block diagram of a heat exchange system according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      In the following detailed description of the embodiments, reference is made to drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and processing step/structural changes may be made without departing from the scope of the present invention.  
      The present invention provides a thermodynamically efficient garment for cooling and/or heating a human body. The thermodynamic efficiency is provided in part by targeting the heat exchange capabilities of the garment to specific areas and/or structures of the human body. The present invention identifies these specific areas and/or structures of the human body based on an evaluation of their effectiveness in transferring heat. These specific areas and/or structures of the human body include not only areas of high blood vessel distribution, but also areas of high tissue conductivity. These areas of high tissue conductivity are also referred to herein as areas of high-density tissue, and will be discussed more fully below. Recognizing and using these areas of high tissue conductivity for heat transfer allows for a smaller more efficient garment for cooling and heating the human body as compared to other heat exchange garments.  
      Generally, the garment for cooling and heating of the present invention includes two or more zones for exchanging heat with the human body. In one example, each of the two or more zones includes a closed loop system in which a fluid can be used to exchange heat with the body. The fluid can then exchange the transferred heat with a heat sink reservoir. Each of the two or more zones is specifically tailored to exchange heat with one or more specific areas of high tissue density in the body. Tailoring the zones to these specific areas allows for a smaller heat exchange area for a given quantity of heat transfer as compared to conventional heat exchange garments for the comparable quantity of heat transfer. This is due in part to the recognition that high-density tissue areas have the ability to more efficiently transfer heat as compared to other tissue areas. Less heat exchange surface area results in smaller more efficient heat exchange garments for cooling and heating the human.  
      The more efficient the heat transfer, the smaller the area of the garment that is required to heat and/or cool the body area. These smaller areas result in a heat exchange garment that is lighter and more energy efficient than conventional heat exchange garments. For example, because the heat exchange garment of the present system is smaller than conventional systems due to its increased efficiency, there is less heat exchange fluid and tubing required for heat exchange. This results in a lighter heat exchange garment. In addition, since a smaller volume of fluid can be required for the heat exchange, the amount of heat transferred to or from the body for a given volume of fluid is increased. Thus, the energy to move the fluid in the heat exchange garment is more efficiently used than in conventional methods of heat exchange.  
      The garment of the present invention can also include a shunting system between each of the two or more compartments of the garment. The shunting system provides for controlling a volume of fluid flow in one or more of the compartments of the garment. The shunting system can be used to stop or reduce the volume of fluid moving in one or more compartments of the garment. The shunting system can be activated either manually, and/or through an automatic feedback system of the heat exchange garment. In certain situations, minimal heating or cooling requirements for a person wearing the garment of the present invention can be attained by closing off or reducing the flow to one or more compartments of the garment through the use of the shunts. Adjusting the fluid flow in this way creates an effectively shorter tube pathway that places less of a demand on the heat exchange system of the present invention.  
      The garment of the present invention also allows for body heat to be balanced. Balancing body heat with the garment of the present invention includes providing heating to one or more compartments of the garment, while simultaneously providing cooling to one or more separate compartments of the garment. Balancing body heat can include attempting to maintain a uniform temperature across the body. For example, balancing body heat can include removing heat from the torso of a person&#39;s body, while simultaneously providing heat to the periphery (such as fingers and/or toes) of the person&#39;s body. Other examples will be discussed below.  
      The present invention introduces the concept of high density (HD) tissue for use in heat transfer to and from the human body. HD tissue includes discrete areas of the human body have a higher efficiency in transferring heat to or from the body than other non-HD tissue areas of the body. Generally, HD tissue has been found to have superior blood vessel distribution, heat conductivity, and heat transport capability to and from the blood. The present invention makes use of the HD tissue to allow a lighter, more compact garment for heat transfer than has been known. Examples of the garment for heat transfer are provided below.  
      In one embodiment, HD tissue can be defined based on the density of cells making up the body tissue along with the amount of vascluarization present in the body tissue. Tissues having a HD designation include a threshold number of cells per unit volume of tissue. Examples of HD tissue include, but are not limited to regions of bone, tendon, and/or fascia, positioned proximal to the skin. HD tissues can also include muscle, where the muscle is highly vascularized (intensive circulation). Preferably, the HD tissues are regions of the body that include more than one of these types of tissues (e.g., bone, tendon, fascia, muscle).  
      In addition, HD tissues in general can include high levels of vascularization. For example, areas of HD tissue typically include major arteries and/or veins in or adjacent to the HD tissue. In one embodiment, blood flowing in the major arteries and/or veins in or adjacent to the HD tissue transfers heat to and from the HD tissue. The blood flowing in the major arteries and/or veins in or adjacent to the HD tissue can then be used to transfer heat directly from or into the heat exchange fluid in the garment.  
      Specific areas of the body have been identified as having HD tissue. These areas include, but are not limited to the forearm, wrist, lateral thoracic area (also referred to as the rib cage), upper torso, paraspinal areas, occipital and parietal head areas, gluteal and medial or inner thigh, shoulder, pectoral region, ankle, and groin area. Different combinations of these areas can be used in providing the efficient heat transfer of the present invention.  
      The two or more compartments of the present invention can be targeted to the HD tissue areas of the body. In this way, heat exchange between the compartments of the garment and the body can be accomplished more efficiently. Table 1 provides examples of coefficient of heat conductivity and tissue density for different tissue types, including HD tissues and non-HD tissues.  
                       TABLE 1                           Coefficient           Body tissues with different blood   of conductivity,   Density,       circulation intensity   (W/m*K)   (g/cm 3) )                  Skin (weak circulation)   0.147 ± 34%   1.085 ± 0%       Skin (intensive circulation)   0.314       Fat   0.187 ± 17%    0.92 ± 0%       Muscle (weak circulation)   0.461 ± 27%   1.062 ± 4%       Muscle (normal circulation)   0.533       Muscle (intensive circulation)   0.628       Bone   0.782 ± 46%   1.357 ± 0%                  
 
      As will be noted, bone displays the highest coefficient of heat conductivity of the body tissues listed in Table 1. In addition, bone also displays the highest density of the body tissues listed in Table 1. Both the coefficient of heat conductivity and the density are important factors in the heat transfer characteristics of the HD tissue. In addition, when the HD includes not only bone, but also includes muscle having intensive circulation, such as in the lateral thoracic (rib cage) area and/or shoulder area, there is an increase in the overall coefficient of conductivity, and therefore the ability to exchange heat with the body.  
      The HD tissue areas of the body are also typically highly vascularized. For example, the lateral thoracic (rib cage) area and/or shoulder area include the common carotid artery, the subclavian artery, suprascapular and subscapular artery, and interior, lateral thoracic artery, exterior jugular veins, lower subclavian veins, and the axillary vein including both the brachial and cephalic veins. Other arteries and veins are also useful in heat exchanges with the garment of the present invention, and the foregoing list of arteries is only exemplary, and not intended to be limiting. Thus, it is preferred that the HD tissue also includes sufficient adjacent vascularization that allows for efficient heat transfer to and from the body.  
      Thus, HD tissues are located are different regions of the body, but all share common major characteristics. These major characteristics include, but are not limited to, discrete areas of the body that have a high cell density as compared to other body tissues, areas that include more than one of bone, tendon, fascia and muscle tissue types in close proximity to both the skin and to major vascular structures of the body, and that display high coefficients of conductivity. These high coefficients of conductivity are due in part to the body tissues that make up the HD region of the body (e.g., bone, tendon, fascia, muscle). In one embodiment, the HD tissues preferably have a coefficient of conductivity of at least 0.5 (W/m*K). More preferably, the HD tissues preferably have a coefficient of conductivity of at least 0.8 (W/m*K). It is also possible that the HD tissues have a coefficient of conductivity in a range of 0.5 to approximately 0.8 (W/m*K).  
      Other areas were identified as not exhibiting HD tissue characteristics. These areas include, but are not limited to, areas having large muscle groups with reduced vascularization. Examples of these non-HD tissues include, but are not limited to, those of the thigh (e.g., rectus gemoris, vastus lateralis, gracilis, and biceps muscles), the stomach (e.g., transverses, rectus abdominis, linea alba, and interior and exterior oblique muscles), and buttocks (e.g., gluteus maximus). These areas of the body typically exhibit a larger percentage of the body surface area. Surprisingly, however, these areas have less intensive heat dissipation as compared to HD tissues because of their lower tissue conductivity coefficients. High thermal insulation and low thermal conductivity compared to other body tissues reduce the non-HD tissues effectiveness in transporting heat.  
      These areas of the body can exhibit a combination of features that lead them to being non-HD tissue. For example, the features can include, but are not limited to, exhibiting a high thermal insulation due in part to insufficient vascularization for rapid heat transfer. The high thermal insulation can also be due to the presence of a fat layer over the muscle structure that adds more significantly to the thermal insulation than thermal conductivity of the area, especially in rest conditions. These areas of the body typically have a thicker fat layer as compared to those in the HD tissue area. The presence of the fat layer adds to the high thermal insulation characteristics (e.g., low thermal conductivity) of the non-HD tissue area. Also, blood impregnation of the leg and buttock surface from the deep vessels networks occurs slowly, because the network is not as highly developed for this function as the distal parts of extremities. Therefore, heat is not distributed quickly through blood to the surface of the thigh. Understanding the differences in tissue conductivity and structure between HD and non-HD tissue allows for smaller more efficient heat exchange garments to be created as compared to other heat exchange suits.  
       FIG. 1  provides one example of a method for controlling body temperature according to the present invention. At  10 , a heat exchange garment is provided that includes at least one heat exchange zone configured to correspond to one or more high density tissue areas of a human body. As will be described more fully below, each heat exchange zone comprises heat exchange elements for use in transferring at least heat to the human body.  
      At  20  of  FIG. 1 , the location of heat exchange elements in the garment is limited to substantially only in the at least one heat exchange zone. So, the at least one heat exchange zone of the heat exchange garment is substantially only positioned adjacent one or more HD tissue areas of the body. In one example, each of the heat exchange zones can be located in predetermined regions of the heat exchange garment. When the garment is then worn on the human body, each of the at least one heat exchange zones can be positioned adjacent the HD tissue sites of the human body.  
      In one example, the at least one heat exchange zones can be positioned adjacent the HD tissue sites located in or through any number of body planes. These body planes include, but are not limited to, the superior and/or inferior portions of the transverse plane, and/or the posterior and/or anterior portions of the coronal plane. In addition, the at least one heat exchange zones can be located on bilateral portions, or contralateral portions, of the HD tissue areas of the body. For example, the at least one heat exchange zones can include at least a first heat exchange zone and a second heat exchange zone, where the first heat exchange zone can be located on a left lateral thoracic area and the second heat exchange zone can be located on a right lateral thoracic area when the garment is worn.  
      Additional heat exchange zones (e.g., third heat exchange zone, fourth heat exchange zone, etc) can also be included on the heat exchange garment. These additional heat exchange zones can also be located adjacent HD tissue in any of the above mentioned body planes and bilateral portions of the body. For example, in addition to the first and second heat exchange zones located on the bilateral portions of the lateral thoracic area, additional heat exchange zones (e.g., third and fourth heat exchange zones) can be located adjacent additional HD tissue areas of the body. In one embodiment, the third and fourth heat exchange zones can be located on the left forearm and the right forearm, respectively, of the human body. Alternatively, the third and fourth heat exchange zones could include other bilateral portions of the HD tissue described above. It is also recognized that additional heat exchange zones could be located on any combination of HD tissue areas (bilateral or not bilateral) described for the present invention. As will be discussed more fully below, each of the heat exchange zones located with respect to the garment also includes one or more heat exchange elements.  
      The heat exchange element can be used to exchange heat between the at least one heat exchange zones of the heat exchange garment and the adjacent HD tissue areas of the body. In one example, the heat exchange element is tubing that uses heat exchange fluid to exchange heat between the heat exchange zone and the adjacent HD tissue area of the body. For example, heat exchange fluid can be pumped through the heat exchange element, where depending in part upon a temperature gradient between the heat exchange fluid and the adjacent HD tissue, heat either flows from the heat exchange fluid to the adjacent HD tissue or flows from the adjacent HD tissue to the heat exchange fluid.  
      In one embodiment, the heat exchange element can be used to cool the HD tissue area adjacent a heat exchange zone of the heat exchange garment. In addition, more than one heat exchange zone could be used to cool HD tissue areas of the body. Similarly, the heat exchange element can be used to heat the HD tissue area adjacent a heat exchange zone of the heat exchange garment. In addition, more than one heat exchange zone can also be used to heat HD tissue areas of the body.  
      Alternatively, exchanging heat with the heat exchange elements can include cooling and heating different HD tissue areas. For example, a heat exchange element in the first heat exchange zone can be used in cooling a first adjacent HD tissue area, while a heat exchange element in the second heat exchange zone can be used in heating a second adjacent HD tissue area. The heating and cooling by the heat exchange elements can occur substantially simultaneously during the same time interval or can occur during independent time intervals, e.g., sequentially.  
      Different combinations of heating and cooling multiple HD tissue areas are also possible. For example, first and second heat exchange zones can be positioned adjacent bilateral portions of a first HD tissue area, while third and fourth heat exchange zones can be positioned adjacent bilateral portions of a second HD tissue area. In this situation, the heat exchange elements in the first and second heat exchange zones can be used to cool the bilateral portions of the first HD tissue area, while the heat exchange elements in the third and fourth heat exchange zones can be used to heat the bilateral portions of the second HD tissue area. Adding additional heat exchange zones for combinational heating and/or cooling of additional HD tissue areas is also possible.  
      In addition, substantially simultaneous heating and cooling of different halves of bilateral portions of a HD tissue area is also possible. For example, a bilateral HD tissue area having a first and a second HD tissue area can have the first HD tissue area being cooled with a first heat exchange zone, while the second HD tissue area is being heated with a second heat exchange zone. This option can be useful when the first HD tissue area and the second HD tissue area are experiencing contrasting levels of heat flux. For example, heat flux differences can exist when the first HD tissue area is exposed to a heat source (e.g., facing the sun), while the second HD tissue area is not exposed to the heat source (e.g., shaded from the sun).  
       FIG. 2  shows an additional embodiment of a method for controlling body temperature according to the present invention. At  40 , one or more physiological parameters are sensed, e.g., at a position on a distal extremity of the human body. These physiological parameters can include, but are not limited to, skin temperature, heat flux, blood perfusion and skin wetness data. In one embodiment, the position on the distal extremity of the human body is monitored. This position on the distal extremity can include any number of locations. In one example, one or more fingers are used as the distal extremity from which the physiological parameters are sensed. In an additional example, the ear canal is used as the position on a distal extremity from which the physiological parameters are sensed. Alternatively, additional or alternative physiological parameters can be sensed from the dorsal surface of one or both hands.  
      At  60 , based on one or more of the sensed physiological parameters, at least one characteristic of the heat exchange fluid in the heat exchange garment can be controlled. For example, controlling at least one characteristic of the heat exchange fluid can include controlling a flow rate of the heat exchange fluid within the heat exchange garment based on the sensed physiological parameters. So, for example, when the heat exchange garment includes heat exchange elements located in two or more heat exchange zones, the flow rate of the heat exchange fluid in each of the two or more heat exchange zones can be controlled based on the sensed physiological parameters. Control of the flow rate includes, but is not limited to, independent control of the heat exchange fluid flow rate within each of the individual heat exchange elements.  
      In addition to controlling the heat exchange fluid flow rate, the present invention also includes controlling a temperature of heat exchange fluid within the heat exchange garment. Control of the temperature of the heat exchange fluid can also be based on the sensed physiological parameters. So, for example, when the heat exchange garment includes heat exchange elements located in two or more heat exchange zones, the temperature of the heat exchange fluid in each of the two or more heat exchange zones can be controlled based on the sensed physiological parameters. Control of the temperature includes, but is not limited to, independent control of the heat exchange fluid temperature within each of the individual heat exchange elements. In an additional embodiment, it is also possible to control both the flow rate and the temperature of the heat exchange fluid in each of the heat exchange zones based on the sensed physiological parameters.  
      In one embodiment, the present invention allows for the temperature of the body to be controlled (i.e., regulated) through heat exchange with the HD tissues of the body based on sensed parameters. For example, sensors may be located on one or more locations of the garment or elsewhere for providing temperature measurements to determine whether cooling/heating is needed at one or more locations of the body. By targeting the HD tissue regions for heat exchange, the present invention can provide a smaller, lighter and more efficient heat exchange garment as compared to presently available heat exchange suits. Such feedback control of the heat exchange that can take place between the heat exchange zones of the garment and the HD tissues regions adjacent the heat exchange zones will be further described herein with reference to the system of  FIG. 7 . In the example discussed above, the feedback control can be provided from physiological parameters sensed at a position on a distal extremity of the human body.  
      One particular position on the distal extremity used for controlling the body temperature in the present invention relies on the physiological mechanism of vessel response and blood flow change in one or more fingers under different temperature applications on the body surface and heat deficit in the body. The degree of finger vessel constriction in cold conditions, and vasodilation in warm conditions shows a direct relationship between status of finger blood flow and different levels of developing heat deficit/excess in the body (See Koscheyev et al., “Augmentation of Blood circulation to the fingers by warming distant body areas”, Eur. J. Appl. Physiol (2000) 82:103-111; Koscheyev et al., “Thermoregulation and Heat Exchange in a Nonuniform Thermal Environment During Simulated Extended EVA” Aviat Space Environ Med 2000: 71:579-85; Ducharme M B, Tikuisis p (1994). Role of blood as heat source or sink in human limbs during local cooling and heating. J Appl Physiol 76:2084-2094; Ducharme M B, Van Helder W P, Radomski M W (1991). Tissue temperature profile in the human forearm during thermal stress and thermal stability. (J Appl Physiol 71:1973-1978).  
      This type of information can be used in the feedback control of the heat exchange garment of the present system. For example, when physiological parameters sensed from one or more fingers indicate a drop in temperature and/or heat flux, heat can be transferred to at least one heat exchange zones of the present invention. Heat delivered to the HD tissue region is also known to increase, lower and/or maintain finger temperature. This in turn helps to increase the comfort level of the person using the heat exchange suit of the present invention.  
      Alternatively, physiological parameters sensed from the finger may indicate an increase in temperature and/or heat flux, heat can be transferred from the at least one heat exchange zones of the present invention. Other combinations of heat transfer between the heat exchange zones and the HD tissues, as previously discussed, can also be controlled by the physiological parameters sensed from the finger.  
       FIG. 3  is a schematic illustration of one embodiment of a heat exchange garment  100  according to the present invention.  FIG. 3  shows an example of a front view of the heat exchange garment  100 . The heat exchange garment  100  includes a support material  104 . In one embodiment, the support material  104  is defined to conform to at least a portion of a human body  108 . Examples of suitable material for the garment  100  include, but are not limited to, woven or knitted fabrics. The woven or knitted fabrics can also include a flexible and/or stretchable component to allow the support material  104  to conform closely to the human body  108 . Fabrics that include Lycra® are examples of suitable support materials for the present invention. Other suitable fabrics can include those with various percentages of polyester, cotton, nylon and Lycra®.  
      The heat exchange garment  100  also includes examples of heat exchange elements located in at least one heat exchange zones. For example, the heat exchange garment  100  includes heat exchange zones  110 ,  112 ,  114 ,  116 ,  118 ,  120 , and  122 . The heat exchange zones  110 ,  112 ,  114 ,  116 ,  118 ,  120 , and  122  are located in regions of the support material  104  such that when the heat exchange garment  100  is worn on the human body  108  the heat exchange zones are positioned adjacent high density tissue sites of the human body  108 . Examples of the high density tissue areas shown in  FIG. 3  include a left forearm (zone  118 ) and a right forearm (zone  120 ); a left half of a lateral thoracic area and upper torso (zone  114 ) and a right half of the lateral thoracic area and upper torso (zone  116 ); a left half of an occipital and parietal head area (zone  110 ) and a right half of an occipital and parietal head area (zone  112 ), gluteal and medial inner thigh area and groin area (zone  122 ).  
       FIG. 3  also shows examples of one or more non-heat exchange zones that are defined in the support material  104 . The non-heat exchange zones were previously discussed above. Examples of the non-heat exchange zones include, but are not limited to, areas or regions of the abdominal muscles (e.g., stomach)  123 , deltoid muscle  124 , bicep and triceps muscles  125 , gluteus maximus muscle  126  ( FIG. 4 ), and quadriceps muscle group  127 . Other non-heat exchange zones are also present on the human body.  
      Each of the heat exchange zones  110 ,  112 ,  114 ,  116 ,  118 ,  120 , and  122  also includes at least one heat exchange element  130 ,  132 ,  134 ,  136 ,  138 ,  140  and  142 , respectively. The heat exchange elements (e.g.,  130 ,  132 ,  134 ,  136 ,  138 ,  140  and  142 ) are located primarily only in the at least one heat exchange zones (e.g.,  110 ,  112 ,  114 ,  116 ,  118 ,  120 , and  122 ), where each of the at least one heat exchange zones are defined in regions of the support material  104  such that when the garment  100  is worn on the human body  108  the at least one heat exchange zones are positioned adjacent high density tissue sites of the human body  108 .  
      In one example, each of the heat exchange elements  130 ,  132 ,  134 ,  136 ,  138 ,  140  and  142  is a length of tubing that is secured to the support material  104  of the heat exchange garment  100 . For example the tubing can be secured to the support material  104  by sewing the tubing to an inside surface of the support material  104  of the heat exchange garment  100 . Alternatively, the tubing can be secured to the support material  104  by integrating the tubing into and/or through the support material  104 . Other methods of locating the tubing at positions on the support material are also possible (e.g., gluing).  
      In one embodiment, each of the heat exchange elements  130 ,  132 ,  134 ,  136 ,  138 ,  140  and  142  can include heat exchange fluid. Heat can be transferred between the heat transfer fluid and the high density tissues sites of the human body, as previously discussed. In one embodiment, the heat exchange fluid enters each of the heat exchange elements  130 ,  132 ,  134 ,  136 ,  138 ,  140  and  142  through an inlet port and leaves through an outlet port. In  FIG. 3 , inlet ports  150 ,  154 ,  158 ,  160 , and  164  are shown for heat exchange elements  134 ,  136 ,  138 ,  140  and  142 , respectively. Outlet ports  166 ,  168 ,  170 ,  172 , and  174  are also shown for heat exchange elements  134 ,  136 ,  138 ,  140  and  142 , respectively. Examples of heat exchange fluid include, but are not limited to, water, antifreeze type solutions and/or alcohols.  
      As discussed, each of the heat exchange zones of the present invention are defined to add or remove heat from the adjacent high density tissue. Adding or removing the heat can depend on one or more operating conditions of the present invention, along with the density of the heat exchange element in the heat exchange zone. For example, larger temperature differences between the heat exchange fluid and the adjacent high density tissue can lead to higher heat transfer rates. The temperature difference, however, must not be so large as to cause discomfort to the user. The flow rate of the heat exchange fluid can also be varied to produce different heat transfer rates. Furthermore, the density of the heat exchange elements can be tailored to each heat exchange zone. This can be based on the ability of the high density tissue to transfer heat more or less effectively as compared to other high density tissue areas.  
      The heat exchange garment  100  can further include one or more valves that are operatively coupled to the tubing of the heat exchange elements. For example, valves  180 ,  184  and  188  are shown located in heat exchange zones  114 ,  116 , and  122 , respectively. In one embodiment, valves  180 ,  184  and  188  are incorporated into the length of tubing for the heat exchange elements  134 ,  136  and  142 . The valves can be used to control the flow of the heat transfer fluid in the tubing of the heat exchange elements. For example, the valves can be manually operated to position the valves in any number of positions so as to reduce, increase or stop the flow of the heat exchange fluid in the tubing of the heat exchange elements. Alternatively, the valves can be operated electronically, or by any other actuator that is capable of controlling the valves in any number of positions so as to reduce, increase or stop the flow of the heat exchange fluid in the tubing of the heat exchange elements.  
       FIG. 4  shows an additional schematic illustration of one embodiment of the heat exchange garment  100  according to the present invention. The  FIG. 4  shows an example of a rear view of the heat exchange garment  100 . The rear view of heat exchange garment  100  includes portions of heat exchange zones  110 ,  112 ,  114 ,  116 ,  118 ,  120 , and  122 , as discussed above. In this view, additional high density tissue sites can be see, such as the paraspinal areas  198  of the human body  108 .  FIG. 4  also shows inlet port  200  and outlet port  204  for the heat exchange element  130 , and inlet port  208  and outlet port  212  for the heat exchange element  132 .  
      In addition,  FIG. 4  shows that heat exchange element  142  further includes inlet connection ports  216  and  220 , and outlet connection ports  224  and  228 . Connection ports  216 ,  220 ,  224  and  228  are defined to be connected to a heat exchange zone that can be positioned adjacent high density tissues on and around the left ankle and tibia/shin region  229  and the right ankle and tibia/shin region  230  of the human body  108  as shown, for example, in  FIG. 5 .  
       FIG. 5  shows one example of a supplemental heat exchange zone  234  corresponding to both the ankle and shin (e.g., tibia bone) region for the heat exchange suit  100 . The ankle and shin regions of the leg include HD tissue composed of, but not limited to, the tarsus and tibia bones, the calcaneal tendon, the soleus muscle (among many others), the posterior tibial and peroneal arteries, as well as portions of the great saphenous vein. The heat exchange zone  234  also includes a heat exchange element  236 , which can be similar to those heat exchange elements already described. In addition, the heat exchange element  236  also includes inlet connection ports  240  and  244 , and outlet connection ports  248  and  252 . Note that the tubing is primarily adjacent HD bone structure of the tibia and tarsus along the inner portion of the calf and ankle.  
      In one embodiment, the heat exchange zone  234  is optionally connected to the to become part of the heat exchange garment  100 . In one embodiment, these connection ports  240 ,  244 ,  248  and  252  allow the heat exchange element  236  to be operatively coupled to the heat exchange element  142  through inlet connection ports  216  and  220 , and outlet connection ports  224  and  228 . Heat exchange fluid moving through the heat exchange element  142  can then also be moved through the heat exchange element  236 . Alternatively, the connection ports  240 ,  244 ,  248  and  252  of heat exchange zone  234  can be coupled to other inlet and outlet ports to allow for heat exchange fluid to move through the heat exchange element  236 .  
      The heat exchange elements of the present invention can have any number of shapes and sizes, and can be constructed of any number of materials. For example, the heat exchange element can be tubing through which the heat exchange fluid can be moved. The tubing can have any number of profile shapes, including, but not limited to, round, oval, elliptical, or other shapes that would allow for increase in surface area of tubing. The tubing can also be constructed of any number of flexible polymeric materials, including, but not limited to, polyvinyl chloride, polyethylene, polypropylene, silicon. In one example, Tygon® tubing can be used for the heat exchange elements.  
      The inlet and outlet connections of the heat exchange elements can also be coupled in any number of ways. For example, fluid tight quick connect coupling mechanisms at each end of the inlet and outlet connections for the heat exchange elements can be used to releasably connect the tubing of the heat exchange elements to each other and/or to one or more heat exchange units, as will be discussed below. Other types of fluid tight connection mechanisms are also known.  
       FIGS. 3, 4 , and  5  show only one example of the heat exchange garment  100  of the present invention. Modifications to the structure of the heat exchange garment  100  are certainly possible. For example, valves can be used to interconnect one or more of the heat exchange elements of the various heat exchange zones. In addition, two or more heat exchange zones through any number of planes of the body can share a common heat exchange element. This would reduce the number and complexity of inlet and outlet connections required. In addition, two or more valves could be placed at locations along the heat exchange elements used to heat and cool two or more heat exchange zones such that one or more zones could optionally receive reduced heat exchange fluid flow or be isolated from other heat exchange zones. As will be appreciated, the valves used to accomplish this feature will be bypass valves that will maintain a closed loop in the heat exchange zones such that the heat exchange fluid can continue to be moved through the system.  
       FIGS. 6A, 6B ,  6 C and  6 D show a schematic illustration of one or more configurations for heat exchange gloves defined for use with the heat exchange garment of the present invention. Each of the one or more configurations for the heat exchange gloves can optionally be used in conjunction with the heat exchange garment  100 , described above. In one embodiment, the heat exchange gloves of the present invention are defined to be positioned adjacent high density tissue of a right wrist joint of the hand and a left wrist joint of the hand of the human body.  
      The glove configurations are also intended to function to maintain hand/finger comfort and prevent chilled fingers. The problem of maintaining thermal stability of the hands and fingers can be addressed by the design of the gloves, where the design is based on anatomical and physiological principles of heat transfer by high density tissues and blood flow. Four different configurations of gloves are shown in  FIGS. 6A, 6B ,  6 C, and  6 D. Any one of the different configurations of gloves can be integrated into the heat exchange garment  100  of the present invention.  
       FIGS. 6A and 6B  show a first glove configuration  250  and a second glove configuration  252  defined to fit a human hand, respectively. In one embodiment, the gloves include support material  256  that conforms to the human hand. The first glove configuration  250  and the second glove configuration  252  includes a heat exchange zone  258  that positions a heat exchange element  260  on the wrist and mid-palm area  264  of the human hand.  
      A third glove configuration  270  and a fourth glove configuration  272  are shown in  FIGS. 6C and 6D . The third and fourth glove configurations includes a heat exchange zone  274  that positions a heat exchange element  278  on the proximal/lateral sides of the fingers precisely where there are major blood vessel paths, so the circulating blood can easily absorb heat and transport this heat to the distal phalanges. The glove configurations  250 ,  252 ,  270  and  272  can improve finger comfort and also significantly decrease the length of the heat exchange elements, e.g., tubes. This will decrease energy consumption and enhance the effectiveness of the heating system. Also, there can be less dissipation of heat because the heating elements are in direct contact with the vessel walls. By locating the heat exchange elements between the fingers (proximal/lateral part of phalanges), or strung around three fingers following the vessels paths, the rest of the fingers will be warmed between the heated fingers, therefore shortening the heat exchange elements. In addition, each of the glove configurations  250 ,  252 ,  270  and  272  include an “open” finger design, where at least two or more of the fingers of the person wearing the glove are not covered by the support material or heat exchange element.  
      In one embodiment, the heat exchange elements can be tubing, as described above, that allows heat exchange fluid to move through the heat exchange zones  258  and  274 . Alternatively, the heat exchange elements can be electrical heating elements that are used to heat the heat exchange zones  258  and  274 . When electrical heating elements are used, an electrical energy source can be included for powering the electrical heating elements.  
       FIG. 7  is a block diagram of a heat exchange system  300  according to one embodiment of the present invention. The heat exchange system  300  includes a heat exchange garment  310 , as previously described. The heat exchange garment includes the support material and heat exchange elements, as discussed. At least one heat exchange zones and one or more non-heat exchange zones are shown in  FIG. 7 , where a first heat exchange zone  316  is defined to be positioned on and around the high density tissues of the head and torso, as described above. A second heat exchange zone  320  is also defined to be positioned on and around the high density tissues of the forearms, as described above.  FIG. 7  also shows a third heat exchange zone  324  and a fourth heat exchange zone  328 , where the third heat exchange zone  324  is defined to be positioned on and around the high density tissues of the gluteal and thigh, and the fourth heat exchange zone  328  is defined to be positioned on and around the high density tissues of the ankle and calves, as described above. Use of additional heat exchange zones is also possible, as discussed above.  
      The heat exchange system  300  also includes one inlet  334  and one outlet  338  for the heat exchange fluid moving through the heat exchange elements in the heat exchange zones  316 ,  320 ,  324  and  328 . As previously discussed, the heat exchange elements are located primarily only in the at least one heat exchange zones. Control of the movement of the heat exchange fluid through the various heat exchange zones  320 ,  324  and  328  can be controlled through the use of one or more in-line valves  344 , where each of the valves  344  can be independently controlled to change the flow rate of the heat exchange fluid through the various heat exchange zones  320 ,  324  and  328 .  
      As discussed above, the valves  344  can be used to adjust flow of heat exchange fluid in different zones of suit. The valves  344  can be adjusted by the user through either manually adjusting the valve (e.g., turning a handle of the valve mechanism) or electronically, for example, through the use of one or more solenoids. Electronically adjusting the valves can be accomplished through the use of one or more switches adjacent to or located apart from the valve to adjust the flow of fluid through the valve. Positions for the valve include fully open, fully closed or any number of positions between the fully open and fully closed position. Alternatively, electronic adjustment of the valves may be accomplished through an automatic feedback control mechanism.  
      The heat exchange system  300  further includes at least one heat exchange unit  350  operatively coupled to the heat exchange elements of the heat exchange garment  310 . In one embodiment, the at least one heat exchange unit  350  can be operatively coupled to the heat exchange elements of the heat exchange garment  310  through the inlet  334  and the outlet  338  for the heat exchange fluid. The heat exchange unit  350  may, for example, include a heat exchange conduit and an apparatus to move heat exchange fluid through the heat exchange conduit. In one embodiment, the heat exchange conduit may be a portion of tubing that includes a high thermal conductivity value so as to allow efficient heat exchange in the heat exchange unit  350 . Examples of suitable materials for the heat exchange conduit include metals, such as copper, steel, aluminum, metal alloys, etc.  
      In one embodiment, the apparatus to move heat exchange fluid through the heat exchange conduit includes a pump. In one embodiment, the pump can be a variable speed pump to allow for various heat exchange fluid flow rates to be achieved. In addition, the heat exchange unit  350  can be used to add or remove heat energy from the heat exchange fluid moving through the heat exchange conduit. In one embodiment, the heat exchange unit  350  can include a heating mechanism and a cooling mechanism, where the heat exchange fluid moving through the heat exchange conduit can either add heat energy to or remove heat energy from the cooling source or to heating source, respectively. For example, electrical heating or cooling systems could be used to exchange heat with the heat exchange fluid in the heat exchange conduit. Alternatively, radiator type systems could be used in cooling the heat exchange fluid in the heat exchange conduit. Other cooling and heating source mechanisms are also possible. A power source  352  may also provided to supply electrical energy to the heat exchange unit, and other components of the heat exchange system  300 . The power source  352  can include one or more batteries having one or more electrochemical cells for generating the electrical energy.  
      The heat exchange system  300  further includes at least one sensor. The example of  FIG. 7  shows a single sensor  354 . However, any number of sensors may be used. Preferably, the sensor  354 , or other sensors, is defined to detect one or more physiological parameters from the human body, as previously discussed. However, other parameters other than physiological parameters may be sensed for use in controlling the system, e.g., temperature of surroundings, humidity thereof, etc.  
      As previously discussed, the sensor  354  can detect the one or more physiological parameters from one or more fingers of the human body. As discussed above, monitoring a temperature and a heat flux from the one or more fingers can provide an assessment of overall thermal status of the human body. In one embodiment, the sensor  354  can include a temperature sensor and one or more thermistors to measure the temperature and the heat flux at the finger. In one embodiment, the temperature sensor and the thermistors of the sensor  354  can be embedded in a ring that is worn on the finger.  
      The heat exchange system  300  also includes a feedback system controller  360  operatively coupled to the sensor  354 , and or other sensors, and the heat exchange unit  350 . The feedback system controller  360  may, for example, include a microprocessor and associated memory. In one embodiment, the microprocessor is used to execute executable programs stored in memory. These programs can include those for receiving signals from the sensor  354  and controlling the operation of one or more of the heat exchange units  350  and the valves  344  based on signals received from the sensor  354 . For example, the feedback system controller  360  can be used to control the pump and/or heating and cooling operations of the heat exchange unit  350  to add or remove heat from the heat exchange fluid in the heat exchange conduit as a function of the one or more physiological parameters from the human body.  
      In one example, the feedback signals from the sensor  354  can be used to determine the amount of heat that is either being lost or gained by the body. Based on these amounts of heat, the feedback system controller  360  can be used to control the heating or cooling of the heat exchange fluid in the heat exchange unit  350  along with which combination of heat exchange zones in the heat exchange garment  310  need to be used to transfer the required amount of heating or cooling to the body. Control of the heat exchange zones can be accomplished through use of the valves  344 . In addition, signals initiated from the sensor  354  can be used to indicate a life-threatening situation or minimally a tissue-damaging condition during which the feedback system controller  360  and the heat exchange unit  350  will attempt to balance the body heat of the person wearing the heat exchange garment so as to provide the best possible heating or cooling required during the emergency situation. One approach to balancing the body heat during the emergency situation is to isolate one or move heat exchange zones (i.e., stop or reduce flow of heat exchange fluid to the one or more heat exchange zones). Isolation of these zones effectively shortens the closed loop of the heat exchange fluid, thereby allowing the finite heating and/or cooling abilities of the heat exchange unit  350  to be better utilized in heating or cooling the core body areas.  
      The present invention provides various embodiments of protective heat exchange garments, heat exchange systems and methods for their operation in extreme environments. These include, but are not limited to, those encountered by firefighters, by military personal (especially those wearing biological/chemical/radiation protective suits), by divers wearing a diving suit, by miners, and by astronauts in outer space. Athletes for pre- or post-competition temperature regulation in extreme environments can also use the present invention. The present invention can also be used as a supplemental technology in the rehabilitation of stroke patients and other disabled groups such as those with multiple sclerosis.  
      All references cited herein are incorporated in their entirety as if each were incorporated separately. Documents cited herein, however, are not suggested to be prior art to the present invention. This invention has been described with reference to illustrative embodiments and is not meant to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as additional embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description.