Abstract:
Cooling pads, mattresses, and limb-comforming sleeves reduce a person&#39;s temperature by evaporative and/or conducting cooling. An open cell foam pad defines an internal air flow passages proceeding according to serpentine or other desired routing. The pad is wetted, and a blower circulates air through the air flow passage and evaporatively cools the pad by removing warm water vapor. By contacting the cooled structure, the person is conductively cooled. The pad also employs evaporative cooling if water is permitted to seep from the foam pad onto the person&#39;s skin and subsequently evaporate. Another cooling device is a multi-layer evaporative cooling mattress. The mattress comprises an open cell foam structure having a person-receiving side and a base side. At the person-receiving side lies an absorbent layer with internal liquid delivery lines, and optionally having an outer film applied thereto. Beneath the absorbent layer is an air manifold comprising air flow passages defined in a cushion layer, or an open mesh layer interposed between the absorbent layer and the cushion layer. Another cooling device is a thermal cooling sleeve, with a series of multiple elongated, parallel ridges. Pairs of adjacent ridges are separated by intervening channels, and each ridge has a lateral liquid passage through it. When the first and last ridges are brought around to meet each other, the ridges form a continuous sleeve. Within the sleeve&#39;s body, the passages cooperatively define a continuous conduit proceeding from ridge to ridge inside the sleeve.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to devices that utilize evaporative, convective and/or conductive cooling to cool the human body in aid of surgery, medical treatment, therapy, or comfort. Some exemplary cooling structures include various configurations of thermal cooling devices. 
     2. Description of the Related Art 
     Temperature control in humans has important medical consequences. In order to maintain optimum health, the human body must maintain a core temperature within a very narrow range. Core body temperature changes as small as 0.1° Celsius trigger thermoregulatory responses such as vasoconstriction, vasodilation, shivering, or sweating. A narrow temperature range is optimal for human cellular functions, biochemical reactions, and enzymatic reactions. Outside this range of temperatures, the human body experiences hypothermia (excessive cold) or hyperthermia (excessive hot). 
     Hyperthermia can result from illness or environmental heat stress, among other causes. In some cases, healthy people suffer hyperthermia when their natural cooling mechanisms, such as sweating, are overwhelmed during heavy physical work in a hot environment. This situation can become even worse if the person fails to drink enough fluids, and therefore cannot sweat adequately. Heat stress disorders, categorized in ascending order of severity, include: heat cramps, heat syncope, heat exhaustion, and heat stroke. Normally, discomfort causes people choose to stop working before the onset of heat exhaustion, but competitive athletics or military activities sometimes push people beyond the limits of health. 
     Hyperthermia can also result from fever associated with illness. Fever may arise from infection, tumor necrosis, thyroid storm, malignant hyperthermia, brain injury, and other causes. Brain injuries that cause hyperthermia usually involve the hypothalamus, and may be caused by tumors, stroke, head injury, or cardiac arrest (in the case of ischemic brain injury). 
     Some consequences of hyperthermial include fluid and electrolyte imbalances, increased cellular metabolic rates, and cognitive impairment. More serious consequences include motor skill impairment, loss of consciousness, and seizures. Ultimately, hyperthermia can cause irreversible cellular injury (especially of the highly metabolic brain and liver cells), organ failure, and death. Hyperthermia is a condition that, depending on its severity, may require immediate cooling treatment to return the person&#39;s core temperature to normal. 
     Cooling treatment may also have other important uses. In some situations, mild or moderate hypothermia is believed to provide beneficial protection against injury. Moreover, induced hypothermia can be beneficial when the blood flow to some or all of the brain has been interrupted. Brain ischemia due to an interruption of blood flow may occur during cardiac arrest, surgery on the blood vessels of the brain, stroke, traumatic brain injury, or open heart surgery. Cooling the brain before (or in some cases after) these events can protect the brain from injury, or at least decrease the severity of the ultimate brain damage. 
     Physicians have used various devices and techniques to cool the human body, including pharmacological cooling and various types of mechanically induced cooling. Mechanically induced cooling approaches generally fall into one of these categories: conductive, convective, or evaporative. While different implementations have been tried, many are limited by lack of practicality, difficulty of use, ineffectiveness, and/or excessive power consumption. 
     One example of conductive cooling involves packing a hyperthermic person&#39;s body in ice, or immersing the person in cool or cold water. While ice is an effective cooling agent, it is painful to the person, potentially damaging to the skin, difficult to obtain in large quantities, and impractical for long term use. Water baths can be effective, although they are not practical for the comatose or intensive care patient, or for long term use. In one less effective, but common method of conductive cooling, a person may be placed in contact with a cold-water-circulating mattress and/or cover. Water inside the mattress removes heat from the person by conduction wherever the surface of the mattress thermally contacts the person&#39;s skin. Although there is some benefit to such devices, they are often uncomfortable and heavy, and provide inefficient thermal contact because they are not precisely shaped to the body. 
     In contrast to conductive cooling, convective cooling involves blowing air onto a person. Convective cooling is the least effective method of cooling from a thermodynamic point of view. Room temperature air can be blown very inexpensively with a fan. However, its cooling effectiveness is severely limited due to the thermal capacity of air, and related heat transfer coefficients. 
     For more efficient convective cooling, the air can be cooled before being blown onto the person. Air can be cooled, for example, with a traditional compression or heat-pump air conditioner, vortex cooling, or with thermoelectric cooling. Cooled air can also be generated using the “swamp cooler” principle of vaporizing water into the air stream. When water evaporates into the air, it cools the air. Then, the cooled air is applied to a person. 
     After the air is cooled with one of the foregoing techniques, it can be delivered to a person by cooling the air in the person&#39;s room. To save energy, cooling can be confined to the person rather than the whole environment surrounding the person. One technique that uses this approach is the convective thermal device, which has been implemented in a variety of forms. 
     Although convective cooling removes the stress of environmental heat, it is minimally effective in active cooling. This limited thermodynamic effectiveness is particularly evident when trying to cool people with fevers. Generally, in order to be cooled by convection, a feverish person must be anesthetized and paralyzed to prevent the body&#39;s heat-producing shivering response. Further, due to the thermodynamic inefficiency of convective cooling, this method of cooling uses considerable electrical power and generates considerable waste heat, which can be a problem in emergency rooms or intensive care units. 
     Having discussed conductive and convective cooling, the final mechanically induced cooling mechanism is evaporative cooling. Sweating is a principal example of evaporative cooling. Because water has a large heat of vaporization, large amounts of heat can be removed from the body by evaporating relatively small amounts of water. For example, when a gram of water evaporates, it extracts 540 calories of heat (2.26 kJ) from the skin. On hot summer days, many people practice basic evaporative cooling by wetting their skin or clothing with water, and permitting the water evaporate. Medical staff employ evaporative cooling by giving sponge baths to patients, where the unclothed patient is wetted with water and allowed to dry by evaporation. Sometimes a fan is pointed at the person to increase the evaporation rate. While sponge baths are indeed effective, they are labor intensive, messy, demeaning to body-conscious people, and impractical for prolonged cooling. Finally, evaporative cooing has limited effectiveness in high humidity environments. 
     Therefore, as shown above, conductive, convective, and evaporative cooling systems each have certain benefits and limitations. And, although some of the foregoing cooling products have certain advantages and might even enjoy some commercial success, engineers at Augustine Medical, Inc. are continually seeking to improve the performance and efficiency of human cooling systems. Some areas of possible focus include simplifying hardware designs, boosting the effectiveness of cooling systems, and cooling specific body parts. 
     An additional area of focus concerns the management of the liquid source during evaporative cooling. Introducing too much liquid causes liquid to spill over the area of focused cooling (the “cooling field”), and pool under the person. Pooling of contaminated liquids presents hygienic and esthetic problems in the medical environment. On the other hand, if too little liquid is supplied, the cooling field may dry out and stop or reduce cooling effectiveness. 
     SUMMARY OF THE INVENTION 
     Broadly, the present invention introduces a number of improved cooling devices that utilize evaporative and/or conductive cooling to reduce a person&#39;s temperature in aid of surgery, medical treatment, therapy, or comfort. Some exemplary cooling structures include thermal cooling mattresses, pads, and limb-conforming sleeves. 
     One embodiment of the invention involves thermal cooling pads or mattresses that are placed beneath a person, and cool by conduction (and optionally evaporation, as well). According to one such embodiment, a cooling pad is embodied by a foam structure such as an open cell foam pillow or mattress. The pad defines an internal air flow passage proceeding from an air inlet to an air outlet according to a desired routing, such as a serpentine path. The pad may include various recesses shaped to receive certain body parts. The pad is wetted with an evaporation liquid, such as water. Wetting may be conducted by hand, or by routing the liquid through an internal liquid flow passage. When an air blower is coupled to the air inlet, air circulates through the air flow passage, and evaporatively cools the pad by removing warmed water vapor. Through contact with the cooled structure, the person is therefore cooled by conduction. And, depending upon whether the foam pad is covered with a sealant or not, the pad may also employ evaporative cooling if water is permitted to seep from the foam pad onto the person&#39;s skin and subsequently evaporate. 
     Another type of cooling pad is a multi-layer evaporative cooling mattress. The mattress comprises an open cell foam structure having a person-receiving side and a base side. An air manifold abuts the base side. The air manifold may comprise one or more passages defined in the foam mattress, or an open mesh layer. Above the air manifold is an absorbent layer with internal liquid delivery lines. An outer film is applied to the absorbent layer. 
     In contrast to the cooling mattresses and pads, a different embodiment of the invention concerns a cooling sleeve. Such a device is constructed using an open cell foam structure that is configured to provide a series of multiple elongated, parallel ridges of triangular or trapezoidal cross-section. Each pair of adjacent ridges is separated by an intervening channel, and each ridge has a lateral air flow passage through it. When the first and last ridges are brought around to meet each other, the ridges form a contiguous sleeve. Within the body of the sleeve, the air flow passages cooperatively defme a continuous conduit proceeding from ridge to ridge inside the sleeve. The ridges may be interconnected, or they may be separately attached to a common base layer. 
     Accordingly, as discussed above, the invention may be implemented to provide various types of apparatus, such as cooling mattresses, pads, and sleeves. In contrast, certain other embodiments concern methods for utilizing such cooling equipment. 
     The invention affords its users with a number of distinct advantages. By using a blower to induce evaporative cooling, the invention avoids the need for power consuming refrigeration equipment. As another advantage, evaporative cooling is thermally self-limiting, because it will not produce surface temperatures that would freeze skin, as is the case with ice packs. Also, unlike ice and other phase change materials that can only maintain fixed temperatures for a limited time, cooling with this invention can be sustained indefinitely by periodically adding water to the cooling field. 
     As another advantage, the use of materials such as open cell foam enables the cooling devices of this invention to readily conform to the person&#39;s body and thereby boost cooling effectiveness. This provides a marked improvement over prior approaches that practice cooling by placing an inflatable, water-filled mattress under the body. Inflatable, water-filled mattresses can only cool those body parts that support the reclining body and therefore contact the mattress. These body parts include the head, shoulder blades, buttocks, and various locations on the legs. 
     As another advantage, absent from previous approaches, this invention may incorporate a super-absorbent material into thermal cooling mattresses or pads. The super-absorbent material is capable of holding a large volume of water relative to its mass. This material, once wetted, can provide hours of evaporative cooling without the need for a liquid reservoir and piping system to replenish the cooling field. Consequently, cooling devices equipped with super-absorbent material discourage the introduction of too much cooling liquid, and help prevent the cooling liquid from overwhelming the cooling field and spilling over. 
     The invention also provides a number of other advantages and benefits, which should be apparent from the following description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a perspective view of a thermal cooling pad comprising an open cell foam structure employing an internal air flow passage according to the invention. 
     FIG. 1B is a perspective view of a thermal cooling pad shaped to accommodate a person&#39;s limb, according to the invention. 
     FIG. 2 is a perspective view of a thermal cooling mattress according to the invention. 
     FIG. 3 is a partial cross-sectional side view of one type of multi-layer thermal cooling mattress according to the invention. 
     FIG. 4 is a partial cross-sectional side view of a different type of multi-layer thermal cooling mattress according to the invention. 
     FIG. 5 is a perspective view of a limb support cooling structure according to the invention, shown in relaxed state. 
     FIG. 6 is a side view of the limb support cooling structure of FIG.  5 . 
     FIG. 7 is a side view of the limb support cooling structure of FIGS. 5-6, shown in wrapped position. 
     FIG. 8 is a flowchart of an operational sequence for using the cooling systems of FIGS.  1 A- 7 . 
    
    
     DETAILED DESCRIPTION 
     The nature, objectives, and advantages of the invention will become more apparent to those skilled in the art after considering the following detailed description in connection with the accompanying drawings. 
     HARDWARE COMPONENTS &amp; INTERCONNECTIONS 
     Introduction 
     One aspect of the invention concerns a cooling device, which may be implemented in a number of different forms as discussed below. This equipment is used to cool the human body in aid of surgery, medical treatment, therapy, or comfort. The invention utilizes evaporative and/or conductive cooling. Evaporative cooling involves applying a liquid to bodily regions and permitting evaporation to occur naturally or actively encouraging evaporation by directing an evaporating gas to the wetted bodily regions. With conductive cooling, the cooling structure itself is cooled by some means such as evaporation. Since the cooling structure contacts the person, the person is ultimately cooled as well. Some exemplary cooling devices include thermal pads, mattresses, and limb-conforming cooling sleeves. 
     Thermal Cooling Pad 
     FIG. 1A shows one example of thermal cooling pad  100 , in the form of a pillow. The pad  100  comprises a material that readily absorbs water and is amenable to evaporative cooling when air flows as described below. To illustrate some examples, this water absorbent material may comprise open cell foam, natural or synthetic sponge, “super-absorbent material,” etc. So-called “super-absorbent” materials are substances capable of absorbing significantly more water than their own mass and volume, and one example is starch-grafted sodium polyacrylate (SAP), which is present in some types of diapers. SAP material may be processed into a fibrous, cotton-like form and woven into a sheet of gauze-like material. 
     SAP material can absorb more than twice its volume and four-hundred times its mass in water. Thirty grams of SAP (less than the amount in a typical disposable diaper) can absorb approximately 1,000 grams of water. The evaporation of 1,000 grams of water removes 2,400 kilojoules of heat. If a typical seventy kilogram human has a specific heat near the specific heat of water, it would only take 1,470 kilojoules to reduce the mean body temperature by five degrees Celsius. Thus, as discovered by the present inventor(s), and illustrated by the foregoing example, water held by a super-absorbent layer can provide a significant amount of body cooling. The duration of cooling is significant, as well. Namely, while sleeping, the body metabolically generates about one hundred Watts of heat. This heat generation would be canceled by the evaporation of about 1,000 grams of water per hour, neglecting other thermal loads on the system. At this rate, one liter of water would provide about six hours of cooling. 
     Referring to FIG. 1, the pad  100  defines an internal air flow passage  106  proceeding from an air inlet  110  to an air outlet  111 . The passage  106  may assume a straight, serpentine, lattice, or other path shape designed to maximize the exposure of air in the passage to the foam structure, and thereby maximize evaporative cooling of the water-saturated foam. As another example, there may be multiple, separate air flow passages in parallel. Different variations of multiple/single air flow passage(s), inlet(s), and outlet(s) may be use used to best suit the particular application at hand. 
     The pad  100  may also define an internal liquid flow passage (not shown) for the purpose of admitting water or another evaporative cooling liquid into the pad. Although the liquid flow passage may assume any desired shape, serpentine or other paths that thoroughly traverse the pad  100  are especially effective in saturating all areas of the pad  100 . As another example, multiple liquid flow passages (whether interconnected or not) may be used in parallel with each other to increase liquid flow or saturation effectiveness. The liquid flow passage(s) may include a water outlet, but this is unnecessary because the intent of the liquid flow passage is to saturate the pad  100  rather than transport liquid through the pad. The liquid flow passage may comprise a void that is cut or otherwise defined from the foam material. As an alternative or additional feature, the pad  100  may include a perforated tube (not shown) that resides in the liquid flow passage, and distributes water through the perforations, in drip irrigation fashion. Alternatively, the liquid flow passage(s) may be omitted if the pad  100  is soaked in water prior to use, or manually irrigated with a cup, irrigation line, or faucet, etc. In fact, if the pad has a relatively small size, the pad  100  may be capable of achieving sufficiently thorough water saturation through exclusively external, manual irrigation. 
     The foam material of the pad  100  preferably includes a sufficient density to support the intended body parts without collapsing the internal air flow passage(s). If desired, multiple layers of foam may be used, where softer foam is used for surfaces that contact the patient, and stiffer foam is used to maintain the internal passages. 
     The pad  100  includes a person-receiving upper surface  120 , and an opposite, bottom surface  121 . If desired, the bottom surface  121  may be coated, adhered, or temporarily covered with a layer of sealant to prevent moisture from wetting bedding, pillows, or other materials beneath the pad  100  during use. Depending upon the particular application, the person-receiving surface  120  may also be coated, adhered, or temporarily covered with a sealant to prevent the pad  100  from wetting the person. The foregoing sealant layers may be permanently applied to the foam structure, for example, by chemical or heat curing. Alternatively, removable sealant may be used, such as a roll of plastic film or tailored cover that is removed after each use. Applying sealant to the surface  120  forestalls any cooling of the person by evaporation since the person&#39;s skin does not get wet. Nonetheless, the person is still cooled by conduction. Namely, when air runs through the water-laden pad, the pad itself experiences evaporative cooling; in turn, the cooled pad conductively cools the person&#39;s body parts that thermally contact the pad. For this reason, any sealant placed on the person-receiving surface  120  is preferably thermally conductive. 
     The pad  100  may also be cut, molded, or otherwise formed to defme shapes that help receive, prop, or position body parts. As illustrated, the pad  100  includes a recess  104  with adjoining ridges  102  to hold a person&#39;s head and neck in place. FIG. 1B shows a different example  150 , which is shaped to accommodate a limb. This device  150  is cut, molded, or otherwise shaped to form an elongated channel  160  that defines a pair of parallel, outlying ridges  158 - 159 . Dimensions of the channel  160  may be selected to accommodate a desired shape and size of arm, forearm, leg, etc. The structure  150  internally defines a “U-shaped” air flow passage  154 , with an inlet  152  and outlet  153 . Other air flow paths, (e.g. serpentine) are contemplated as well. 
     Thermal Cooling Mattress 
     In addition to the cooling pads discussed above, the invention also includes various cooling mattresses. FIG. 2 shows one example embodied by the cooling mattress  200 . Like the pad  100 , the mattress  200  cools itself by receiving and then evaporating water or some other evaporative medium. Then, through conduction, the cooled mattress cools the person&#39;s body parts that thermally contact the mattress. 
     The mattress  200  comprises open cell foam or other material similar to the pad  100 , although the mattress  200  may be substantially larger so as to accommodate a reclining person. The mattress may be cut, molded, or otherwise formed to define shapes that help receive, prop, or position body parts. The mattress  200  includes a person-receiving upper surface  240  and an opposite, bottom surface  241 . 
     Also resembling the pad  100 , the mattress  200  includes at least one internal air flow passage  202  proceeding from an air inlet  208  to an air outlet  210 . Different variations of multiple/single air flow passage(s), inlet(s), and outlet(s) may be used to best suit the particular application at hand. The mattress  200  also defines an internal liquid flow passage  204  to admit water or another volatile cooling liquid into the mattress  200 . Although the liquid flow passage  202  may assume any desired shape, serpentine or other paths that thoroughly traverse the mattress  200  are especially effective in saturating all areas of the mattress  200 . The liquid flow passage  202  may also include a perforated tube that resides in the passage and distributes water through the perforations, in drip irrigation fashion. Alternatively, the mattress  200  may be soaked in water prior to use, or manually irrigated with a cup, irrigation line, or faucet, etc. In the illustrated embodiment, the mattress  200  receives evaporative cooling liquid from a water source  206 . 
     The mattress  200  may be enhanced with various internal layers, as shown by the mattress sections depicted in FIGS. 3-4. The mattress section  300  (FIG. 3) has a person-receiving surface  340  and an opposite, bottom surface  341 . Between the surfaces  340 - 341  lies a cushion layer  304  of absorbent material, such as open cell foam, natural or synthetic sponge, etc. The cushion layer  304  provides the chief structure of the mattress, and thus establishes the desired level of firmness of the mattress  200 . The cushion layer  304  internally defines an air manifold  302 , which is embodied by various interconnected air flow passages defined in the layer  304 . Above the layer  304  lies an absorbent layer  305 , comprising a material with sufficient liquid absorbency for use as an evaporative cooling layer. As an example, the layer  305  may have more softness than the layer  304  (to better cushion the person&#39;s body), and also have more absorbency than the layer  304  (to better retain water received from the liquid flow passages  303 ). As an example, the absorbent layer  305  may comprise a super-absorbent material. The absorbent layer  305  houses one or more liquid flow passages  303  to distribute water or another evaporative cooling liquid throughout the layer  305 . 
     One or both of the surfaces  340 ,  341  may be coated, adhered, temporarily covered by, or otherwise topped with corresponding sealant layers  301 ,  309 , such as plastic or another water impenetrable substance. The sealant layer  309  prevents moisture in the mattress from wetting bedding, pillows, or other materials beneath the mattress  300  during use. The sealant layer  301  prevents the mattress from wetting the person. 
     The sealant layer  301  forestalls any evaporative cooling of the person since the person&#39;s skin does not get wet. Nonetheless, the person is still cooled by conduction. Namely, when air runs through the water-laden mattress  300 , the mattress  300  itself experiences evaporative cooling; in turn, the cooled mattress conductively cools the person&#39;s body parts that thermally contact the mattress. For this reason, any sealant placed on the person-receiving surface  340  may comprise a thermally conductive material, or a material with sufficient thinness to avoid acting like a thermal insulator. 
     As an alternative to the arrangement of FIG. 3, a different mattress  400  may be constructed as shown by FIG.  4 . The mattress  400  includes a person-receiving surface  440  and an opposite, bottom surface  441 . Between these surfaces, the mattress  400  includes similar layers as in the mattress  300 , including a sealant layers  401 , absorbent layer  404  (with liquid flow passages  405 ), cushion layer  408 , and sealant layer  409 . Unlike the mattress  300 , however, the mattress  400  includes an air manifold  406  that is separate from the cushion layer  408 , instead of being internally defined by voids in the layer  408 . The air manifold  406  comprises a series of parallel tubes, open mesh, fibrous mat, layer of coil springs, or another suitably air permeable structure. 
     Limb-Conforming Cooling Sleeve 
     In contrast to the previously described thermal cooling pads and mattresses, typically used by placing under a reclining person, a different embodiment of the invention concerns a selectively activated thermal cooling sleeve. This device is laid open to accept a person&#39;s limb, then closed to form a limb-supporting sleeve. Generally, this device comprises a block of open cell foam with a series of parallel, elongated channels removed, thereby defining a series of parallel ridges with trapezoidal or triangular cross-section. When the outermost ridges are brought together, all ridges snug together in the spaces formerly occupied by the channels, and the ridges cooperatively form a contiguous limb-supporting sleeve. 
     FIGS. 5-7 show an exemplary cooling sleeve  500  in greater detail. The sleeve  500  comprises a structure of open cell foam, synthetic or natural sponge, or other suitable water-absorbent material. The sleeve  500  has a person-receiving surface  550  and an opposite, bottom surface  551 . The person-receiving surface  550  may be temporarily or permanently covered or coated by a moisture barrier such as plastic or another sealant to prevent water leakage from the absorbent sleeve onto the person. 
     The sleeve  500  is cut, molded, or otherwise shaped to define multiple elongated channels  504 . Each channel  504  defines a pair of outlying ridges or “blocks”  525  of the foam structure. Thus, the sleeve  500  includes a series of parallel ridges  525 . In the illustrated example, the ridges  525  have a trapezoidal lateral cross-section as best seen in FIG.  6 . Alternatively, the ridges may have triangular or other cross-sectional shapes that are narrower toward the person-receiving surface  550  and wider at the bottom surface  551 . 
     The structure  500  may comprise a single, unitary piece. In this case, a wrap layer  502  constitutes a lower layer of foam integral to all ridges  525 . In another embodiment, the ridges  525  are physically distinct from each other, and a separate wrap layer  502  is added to provide a common mounting surface for all ridges. 
     Each ridge has an internal air flow passage  506 . The outermost ridges include an inlet  508  and outlet  509 , which are connected to their respective internal air flow passages  506 . Thus, the ridges  525  and air flow passages  506  are configured such that, when the outermost ridges are brought around to meet each other (FIG.  7 ), the ridges  525  form a contiguous sleeve having a body and a hollow, limb-receiving core  700 . In this arrangement, the air flow passages  506  cooperatively define a continuous conduit proceeding from ridge to ridge inside the sleeve body. 
     OPERATION 
     In addition to the various cooling devices described above, a different aspect of the invention concerns appropriate methods for operating such equipment. FIG. 8 depicts a sequence  800  for operating a thermal cooling pad, mattress, or selectively configurable limb sleeve. These steps  800  may be performed by various people, depending upon the environment where the cooling device is used. For example, the steps  800  may be performed by the subject or a family member at home, by attendants at a nursing facility, medical staff at a hospital, therapists at a treatment center, etc. 
     For ease of explanation, but without any intended limitation, the example of FIG. 8 is described primarily in the context of the cooling pad  100  of FIG.  1 A. In step  802 , the person and/or pad  100  are positioned for operation of the pad  100 . For greatest cooling, the person should be unclothed, or at least those body parts in contact with the pad. The pad  100  is placed on the person&#39;s bed, and the person lies in bed with his/her head in the recess  104 . In the case of the mattress  200 , an operator positions the mattress  200  on a suitable surface and the person reclines atop the mattress  200 . In the case of the limb support sleeve  500 , the operator positions the person&#39;s treating limb upon one of the ridges  525 , and wraps the ridges around the limb to form a circle, such that adjacent ridges come together. Thus, the outermost ridges meet each other, and the all ridges collectively form the contiguous sleeve of FIG. 7 with the person&#39;s limb inside the core  700 . 
     After positioning the person and/or cooling device in step  802 , medical staff moisten the cooling pad in step  804 . The pad may be moistened with water or another wetting agent that is suitably prone to evaporation, hypoallergenic, safe, effective in cooling, nonflammable, etc. An antibacterial agent may be added to the wetting liquid if desired. For explanatory purposes, water is discussed as an exemplary wetting liquid. 
     The cooling pad may be moistened, for example, by pouring water upon the pad  100  (FIG. 1) or sleeve  500  (FIGS.  5 - 6 ), activating a water source  206  (FIG.  2 ), or circulating water through liquid flow passages  303 ,  405  internally provided in a cooling mattress  300 ,  400  (FIG. 3,  4 ). Alternatively, the cooling pad may be pre-moistened by soaking the pad, running water over the pad, utilizing liquid flow passages, immersing the pad, etc. In this case, step  804  is performed before step  802 . The use of internal liquid flow passages is most beneficial in larger foam structures, where manual wetting may not reach all areas of the foam structure. 
     After step  804 , air flow begins in step  806 . This is performed by starting a fan or other air blower. Input air may be room air, filtered air, heated or cooled air, or dehumidified air, depending upon the cooling requirements of the specific application. Air flows into the inlet  110 , continues through the internal air flow passage(s), and ultimately exits from the outlet  111 . As air passes through the moist foam structure, it encourages evaporation of water from the wetted foam, and therefore cools the foam structure. And because the foam structure thermally contacts the person&#39;s skin, the cooled structure cools the person&#39;s skin by conduction. And, depending upon whether the foam structure is covered with a sealant or not, the structure may also employ evaporative cooling if water is permitted to seep from the foam structure onto the person&#39;s skin and subsequently evaporate. 
     In the case of the cooling mattress  300 , cooling may be enhanced by permitting water to seep from the absorbent layer  305  into the cushion layer  304 . Namely, wetting of the cushion layer  304  causes increased evaporative cooling by placing the flowing air (in the manifold  302 ) in proximity to a moist region of greater volume. 
     Next, the operator decides whether to stop the procedure (step  808 ). If the cooling operation is not finished yet, cooling continues in step  810 . At this point, the operator may re-moisten the cooling field as needed to sustain evaporative cooling of the foam structure. Otherwise, when cooling is done, step  808  proceeds to step  812 , where the operator removes the pad  100 . Then, the routine ends in step  814 . At this point, the operator may dispose of the pad  100 . Alternatively, the sealant on the person-receiving surface may be removed and replaced with a new or sanitized cover for convenient reuse of the cooling structure. 
     OTHER EMBODIMENTS 
     While the foregoing disclosure shows a number of illustrative embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, although the present disclosure is described in the context of human persons, the invention additionally contemplates application of cooling techniques described herein to animals and other warm blooded animals. Moreover, ordinarily skilled artisans will recognize that operational sequences must be set forth in some specific order for the purpose of explanation and claiming, but the present invention contemplates various changes beyond such specific order.