Abstract:
An apparatus is disclosed for convectively and evaporatively cooling a patient. The apparatus comprises an upper sheet and a base sheet that are attached at a plurality of locations to form a convective device. The base sheet includes a plurality of apertures that direct an inflating medium from the convective device toward the patient. The base sheet also supports a fluid delivery apparatus that distributes and delivers a cooling fluid to the patient. The fluid is evaporated from the patient&#39;s skin by the inflating medium exhausted from the convective device. The fluid delivery apparatus may be constructed in a variety of configurations and may circulate a variety of fluids, which may be pressurized or unpressurized. In operation, an air blower, that may also include a compressor for selectively delivering room temperature or cooled air to the appatatus, is connected to the convective device. The blower delivers air, under pressure, to an inlet opening in the convective device. The pressurized air is distributed throughout the convective device and flows to the patient through the apertures in the base sheet. The apparatus is configured to cover one or more portions of a patient&#39;s body. In one construction, the apparatus covers all of the patient&#39;s body except for the head. In an alternative construction, a specially designed apparatus is constructed to cover only the patient&#39;s head.

Description:
This application is a continuation of U.S. patent application Ser. No. 09/176,477, filed Oct. 20, 1998, which is a continuation of U.S. patent application Ser. No. 08/918,308, filed Aug. 26, 1997, now U.S. Pat. No. 5,860,292. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to convective devices such as thermal blankets used in a medical setting to deliver a bath of thermally-controlled gaseous medium, such as air, to a patient. 
     2. Description of the Related Art 
     Thermal blanket prior art is disclosed in commonly-assigned U.S. Pat. No. 4,572,188 entitled “AIRFLOW COVER FOR CONTROLLING BODY TEMPERATURE” and U.S. Pat. No. 5,405,371 entitled “THERMAL BLANKET”. These two patents describe thermal blankets which include a plurality of communicating inflatable chambers. In these blankets, apertures are formed through blanket base sheets. These apertures open through the base sheets into the chambers. When inflated with warmed air, the pressure of the air in the chambers causes the air flow cover to inflate. The apertures exhaust the warmed air through the base sheets, and the warmed air is contained between the base sheets and the patients. Therefore, these thermal blankets create an ambient environment about the patient, the thermal characteristics of which are determined by the temperature and pressure of the gaseous inflating medium. 
     Temperature control in humans has important medical consequences. The human body has evolved over several million years to maintain its core temperature within a very narrow range. Thermoregulatory responses such as vasoconstriction, vasodilatation, shivering or sweating occur in response to core body temperature changes as small as +/−0.1° C. Human cellular functions, biochemical reactions and enzymatic reactions are optimized within this narrow temperature range. 
     The prior art thermal blankets address the problem of warming a patient in order to treat hypothermia (a core temperature that is less than normal) such as might occur operatively or post-operatively. These thermal blankets have proven themselves to be extremely useful and efficient in the treatment of patients whose core body temperatures might otherwise become undesirably low either during or after a medical procedure, such as surgery. 
     However, there are circumstances under which a patient should be cooled rather than warmed in order to treat hyperthermia (a core temperature that is greater than normal). Hyperthermia may result from environmental heat stress or from illness. Otherwise normal individuals may suffer hyperthermia when their natural cooling mechanisms, such as sweating, are overwhelmed during heavy physical work in a hot environment. This is usually associated with relatively inadequate fluid consumption that results in inadequate sweating. Heat stress disorders, categorized in ascending order of severity, include: heat cramps, heat syncope, heat exhaustion and heat stroke. Normally, a person will voluntarily stop working well before the onset of heat exhaustion, but competitive athletes or military personnel may push themselves beyond this limit. 
     Hyperthermia may also be caused by fever associated with illness. Such fever has many causes, including: infection, tumor necrosis, thyroid storm, malignant hyperthermia or brain injury. Brain injuries that cause hyperthermia usually involve the hypothalamus, and may be caused by tumors, stroke, head injury or ischemic brain injury due to cardiac arrest. 
     The physiologic consequences of hyperthermia span a spectrum of severity with fluid and electrolyte imbalances, increased cellular metabolic rates, and cognitive impairment being at the low end. In the mid-spectrum, motor skill impairment, loss of consciousness and seizures occur. At the high end, the individual suffers irreversible cellular injury, especially of the highly metabolic brain and liver cells, and then finally organ failure and death. Hyperthermia is a thus a condition that, depending on its severity, may require immediate cooling treatment to return the patient&#39;s core temperature to normal. 
     Cooling treatment may also have other important uses. There is a growing body of evidence suggesting that in some situations, mild-to-moderate hypothermia may provide beneficial protection against injury. The protective benefit of hypothermia has been shown when the blood flow to all or part of the brain is interrupted. Brain ischemia due to an interruption of the 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 occur seems to be protective, and decreases the severity of the ultimate brain damage. 
     Various apparatus and techniques have been used over the centuries to cool the human body. Cooling technologies can be generally categorized as: conductive, convective, or evaporative. While many technologies have been tried, all are limited in the clinical setting by lack of practicality, difficulty of use, ineffectiveness, and/or excessive power consumption. 
     Conductive cooling is very effective when accomplished by packing a hyperthermic person in ice, or immersing the person in cool, or even cold, water. While ice is an effective cooling agent, it is painful to the patient, can damage the skin, is frequently not available in large quantities, and is not practical for long term use. Water baths are also effective, but not practical for the comatose or intensive care patient, or for long term use. A less effective, but commonly used, method of conductive cooling involves placing the person on, and/or under, a cold water circulating mattress and/or cover. These devices have chambers with circulating water therein. The water cools the surfaces of the device, which in turn removes heat from the patient wherever the surfaces thermally contact the patient&#39;s skin. These devices are generally uncomfortable and heavy, and their thermal contact is frequently inefficient because they are not precisely shaped to the body surface. 
     Convective cooling consists of blowing room temperature air, or cooled air onto the patient. 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 if the patient is not sweating. Cooled air can be made with a traditional compression or heat-pump air conditioner, or with thermoelectric cooling. Cooled air has also been generated for centuries using the so-called “swamp cooler” principle of vaporizing water into the air stream. The water evaporates into the air, thus cooling the air. The cooled air is then applied to a person. 
     An example of such a cooler is shown in U.S. Pat. No. 5,497,633 entitled “EVAPORATIVE COOLING UNIT” by Jones et al. Once the air is cooled by any of these technologies, it can be delivered to a person by generally cooling the environment around the person, such as cooling the air in a room. For more efficient convective cooling utilizing less energy, the cooled air can be delivered to a person more effectively by confining the cooling to only the person. This can be accomplished using a convective thermal blanket such as shown in U.S. Pat. No. 4,572,188 or 5,405,371, referred to above and incorporated herein by reference. Another convective thermal blanket is shown in U.S. Pat. No. 4,777,802 entitled “BLANKET ASSEMBLY AND SELECTIVELY ADJUSTABLE APPARATUS FOR PROVIDING HEATED OR COOLED AIR THERETO” by Feher. Confined convective cooling has also been shown in the form of a jacket-like device in U.S. Pat. No. 5,062,424 entitled “PORTABLE APPARATUS FOR RAPID REDUCTION OF ELEVATED BODY CORE TEMPERATURE” by Hooker. 
     Convective cooling removes the stress of environmental heat, but is minimally effective in active cooling. This limited thermodynamic effectiveness is particularly evident when trying to cool patients with fevers. Generally, in order to be cooled by convection, the patients must be anesthetized and paralyzed to prevent heat producing shivering. Further, the thermodynamic inefficiency of convective cooling causes this method of cooling to use considerable electrical power and generate considerable waste heat, both of which can be a problem in the emergency or intensive care situation. 
     Evaporative cooling is the thermodynamic basis of the highly efficient sweating response. Each gram of water that evaporates extracts 540 calories of heat from the skin of the body being cooled. Because of the very large heat of vaporization of water, large amounts of heat are removed from the body by evaporating relatively small amounts of water. Evaporative cooling has been practiced since the beginning of mankind, simply by wetting the skin or clothing, and letting the wetting agent evaporate. Evaporative cooling is used even today in hospitals, in the form of sponge baths, where the patient is wetted with water, and allowed to dry by evaporation. Sometimes a fan will be blown on the patient to increase the rate of evaporation. While this method of cooling is clearly effective, it is labor intensive, messy, requires the patient to be totally exposed, and is generally not practical for prolonged cooling. Finally, the effectiveness of evaporative cooling is severely limited in high humidity environments. 
     Therefore, there is a need for a temperature control device, and particularly a thermal blanket, that can accommodate a patient who requires treatment for hyperthermia or requires cooling as an injury prevention mechanism. What is required is an inexpensive covering that cools a patient rapidly and efficiently in a clinical setting, yet which may be easily and conveniently used by medical personnel. 
     SUMMARY OF THE INVENTION 
     In accordance with certain objectives of this invention, and to overcome the limitations of the prior art, an apparatus is provided that compounds convection with evaporation to cool a patient The apparatus includes an inflatable thermal blanket including an upper sheet and a base sheet that are attached at a plurality of locations to form an inflatable structure. The base sheet includes a plurality of apertures that exhaust an inflating medium from the inflatable structure toward the patient. An air blower that may also include a compressor for selectively delivering room temperature, or cooled, air to the thermal blanket, delivers air, under pressure, to an inlet opening in the inflatable thermal blanket. The pressurized air is distributed within the inflatable structure, and flows to the patient through the apertures in the base sheet. The base sheet supports a fluid delivery element that directs a cooling fluid onto the patient. The fluid is evaporated by the inflating medium exhausted from the inflatable structure. The fluid delivery element may be constructed in a variety of configurations and may circulate a variety of fluids, which may be pressurized or unpressurized. 
     The inflatable thermal blanket is configured to cover one or more portions of a patient&#39;s body. In a first preferred embodiment, the thermal blanket covers all of the patient&#39;s body except for the head. In an alternative embodiment, a specially designed thermal blanket is constructed to cover only the patient&#39;s head. 
     It is therefore a primary object of the invention to provide a convenient, inexpensive and effective means for rapidly cooling a body (human or animal). 
     It is a further object of the invention to provide a device for cooling a body both convectively and evaporatively. 
     It is a further object to provide such cooling in an inexpensive inflatable thermal blanket which can be used with existing inflatable thermal blanket equipment. 
     The foregoing, together with other objects, features and advantages of this invention, will become more apparent when referring to the following specification, claims and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For a more complete understanding of this invention, reference is now made to the following detailed description of the embodiments as illustrated in the accompanying drawing, wherein: 
     FIG. 1 is a perspective view of a patient and an inflatable thermal blanket according to the invention, deployed with forced-air pump that supplies air to the thermal blanket, and a fluid supply system for delivering an evaporative cooling fluid to the thermal blanket; 
     FIG. 2 is a partial cross-sectional view taken through an inflatable portion of the inflatable thermal blanket of FIG. 1; 
     FIG. 3 is a diagrammatic cross-sectional view of the patient and inflatable thermal blanket of FIG. 1, showing one alternative lateral placement arrangement for components of a fluid delivery apparatus; 
     FIG. 4 is another diagrammatic cross-sectional view of the patient and inflatable thermal blanket of FIG. 1, showing another alternative lateral placement arrangement for components of a fluid delivery apparatus; 
     FIG. 5 is a bottom view of the inflatable thermal blanket of FIG. 1, showing one alternative two-dimensional placement for components of a fluid delivery apparatus and also showing one alternative manifold therefor; 
     FIG. 6 is a bottom view of the inflatable thermal blanket of FIG. 1, showing another alternative two-dimensional placement for components of a fluid delivery apparatus and also showing another alternative manifold therefor; 
     FIG. 7 is a bottom view of the inflatable thermal blanket FIG. 1, showing another alternative two-dimensional placement for components of a fluid delivery apparatus and also showing another alternative manifold therefor; 
     FIG. 8 is another diagrammatic cross-sectional view of the patient and inflatable thermal blanket of FIG. 1, showing additional components which may be used in the inflatable thermal blanket; 
     FIG. 9 is a perspective view of a patient and an inflatable thermal blanket, and also illustrates a forced-air pump for supplying air to the inflatable thermal blanket, and an alternative fluid supply apparatus for delivering an evaporative cooling fluid to the inflatable thermal blanket; 
     FIG. 10 is a side view of a patient and inflatable thermal blanket for convectively and evaporatively cooling a patient&#39;s head; 
     FIG. 11 is a cut-away side view of the inflatable thermal blanket of FIG. 10 showing construction details thereof; and 
     FIG. 12 is a cut-away plan view of the patient and inflatable thermal blanket of FIG. 10 showing additional construction details thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This invention is represented by embodiments set forth in the following description, and illustrated in the figures, in which like numbers represent the same or similar elements. While this invention is described in terms of an exemplary embodiment, it will be appreciated by those skilled in the art that variations may be accomplished in view of these teachings, without deviating from the spirit or scope of the invention. 
     Effective patient cooling in a clinical setting is achieved by providing an inflatable thermal blanket that joins an air delivery system for providing a convective cooling component with a fluid delivery apparatus for providing an evaporative cooling component. It has been found that combining evaporative cooling with convective cooling with an inflatable thermal blanket dramatically increases the cooling effectiveness of the convective cooling, while making the evaporative cooling convenient and practical, even for prolonged use. The inflatable thermal blankets disclosed herein maximize the positive features of convective and evaporative cooling while minimizing the negative features of each. 
     FIG. 1 illustrates a patient  100  in a prone position on an examination or operating table  102 . The table  102  may be in doctor&#39;s office, in an out-patient facility associated with a hospital facility, or any other suitable location. The patient  100  is ill with his head  104  and shoulders  106  lying flat and supported on the table  102  (along with the remainder of the patient&#39;s body). As shown in FIGS. 3 and 4, the patient&#39;s arms  110  lie at the patient&#39;s side. 
     An inflatable thermal blanket indicated by reference numeral  120 , and having convective cooling and evaporative cooling components, is shown covering all of the patient&#39;s body, except for the head  104  and shoulders  106 . The inflatable thermal blanket  120  includes an inflatable section  130  surrounded by a non-inflatable section that includes a foot drape  140  and side edges  150 . A head drape could also be provided, as could one or more non-inflatable recesses in the inflatable portion  130  to facilitate unrestricted viewing of, and access to, selected areas of the patient  100 . 
     Further, FIG. 1 is not meant to suggest limitation of the invention to an inflatable thermal blanket that covers substantially all of a patient&#39;s trunk and limbs. It could also be embodied in an arrangement that uses an inflatable thermal blanket that is shaped and deployed over portions of the patient&#39;s body, as well as over one, or fewer than all of the patient&#39;s limbs. In this regard, for example, reference is given to U.S. Pat. No. 5,405,371, which describes inflatable thermal blankets that cover the outstretched arms and upper chest, and the lower extremities of a person. Other configurations are illustrated in U.S. Pat. Nos. 5,300,101; 5,324,320; 5,336,250; and 5,350,417. 
     Returning to FIG. 1, the inflatable section  130  includes an inlet  160  through which a flow of temperature-controlled air is received to inflate the inflatable thermal blanket. The flow of air is provided by an airhose  162  from a forced-air unit  164 . The forced-air unit  164  minimally includes a blower system powered by an electric motor or the like for delivering a flow of air. The blower system preferably has variable air speed control capability and may have air temperature control capability. Optionally, for additional cooling effectiveness, especially in hot and humid environments, an air cooling unit or dehumidifying unit could be included in the forced-air unit. Alternatively, the air cooling unit or dehumidifying unit may be separate from the forced-air unit, in which case it could be interposed between the forced air-unit and the airhose  162 . Cooled air increases the efficiency of the convective cooling component of the blanket  120 . Dehumidified air increases the efficiency of the evaporative cooling component of the blanket. Cooled, dehumidified air therefore optimizes patient cooling. 
     The inlet  160  in the inflatable section  130  may be provided with a cuff or other conventional connector adapted to receive and retain a nozzle  163  of the airhose  162 . Using this configuration, pressurized air can flow through the airhose  162  into the inflatable section  130 . 
     The inflatable thermal blanket  120  of this invention may be constructed by modifying a commercially available inflatable thermal blanket of the type which is known in the art, including BAIR HUGGER® Thermal Blankets from Augustine Medical, Inc., Eden Prairie Minn. Alternatively, the inflatable thermal blanket  120  could be constructed using methods and materials that are known for making similar products. One example of construction details suitable for making the inflatable thermal blanket of this invention is found in commonly-assigned U.S. Pat. No. 5,405,371. 
     With reference now to FIGS. 1 and 2, the inflatable thermal blanket  120  is assembled from a base sheet  200  having a laminated structure in which a bottom layer  210  comprises a fibrous, preferably non-woven, structure composed of synthetic or natural materials. A top layer  211 , comprising a sheet of synthetic material, is disposed on and laminated to a surface of the bottom layer  210 . For example, the bottom layer  210  may be a non-woven, hydroentangled polyester material and the top layer may include a polypropylene film that is extrusion-coated on to the polyester layer. According to a first alternative, the bottom layer  210  may comprise a non-woven, paper-based material to which a top layer including either a polyethylene or a polypropylene film has been glue laminated. According to a second alternative, the bottom layer may comprise a single layer of fibrous material. To form an inflatable structure that may include one or more inflatable chambers  220 , an upper sheet  215  of material is attached at a plurality of locations to the top layer  211 . Preferably, the upper sheet  215  comprises the same material as the top layer  211  of the base sheet  200 . The upper sheet  215  is attached to the top layer  211  in the preferred embodiment in a continuously-running web process that includes stations at which the upper sheet  215  is heat-bonded to the top layer  211  to form the inflatable and non-inflatable sections of the inflatable thermal blanket  150 . The inflatable chambers  220  are shown in FIGS. 1,  3  and  4  as having a generally elongate tubular shape, although such chambers and shapes are not necessary to the invention The inflatable chambers  220  are formed by discontinuous elongate heat seals extending longitudinally along the blanket  120 . FIGS. 3 and 4 show a cross-sectional view of the elongate heat seals. These heat seals are shown as having sealed portions  221  and unsealed portions  227 . At the sealed portions  221  of the discontinuous elongate heat seals, the top layer  211  of the base sheet  200  is bonded to the upper sheet  215  in an elongate, air impermeable seam. Where the discontinuities  227  occur, air may circulate laterally between the inflatable chambers. These discontinuities provide communication between the inflatable chambers, permitting pressurized air to circulate from the inlet  160  to, and through, the inflatable chambers  220 . It should be understood that the inflatable structure could be formed by a plurality of stake-point seals, or by longer elongate seals. The plurality of apertures  217  that open through the base sheet  200  exhaust pressurized air from the inflatable chambers  220  underneath the inflatable thermal blanket  120  to bathe the patient  100  in a cooling ambient atmosphere. 
     Continuous, air impervious seals  230  are shown in FIGS. 1,  3  and  4  along the sides of the inflatable thermal blanket  120 . Continuous, air impervious seals  232  and  234  also extend transversely at the foot end and the head end of the blanket  120 , respectively. These seals form the one or more uninflatable sections of the inflatable thermal blanket  150 . These uninflatable sections function essentially as drapes that maintain an ambient atmosphere beneath the inflatable thermal blanket. As FIGS. 1,  3  and show, there are two, parallel continuous, air-impervious edge seals  230  that are near the respective sides of the inflatable thermal blanket and two continuous, air-impervious end seals  232  and  234  at either end of the inflatable thermal blanket. The perimeter of the inflatable thermal blanket  120  is therefore sealed by a continuous, air-impervious seal comprising the seals  230 ,  232  and  234 . 
     The invention further includes an evaporative cooling element comprising a fluid distribution apparatus. The fluid distribution apparatus distributes fluid over, and delivers it to, various areas, portions, or limbs of a patient&#39;s body. The fluid distribution apparatus includes one or more fluid delivery channels or conduits  250  mounted to the underside of the base sheet  200 . Preferably, the conduits  250  are attached to the inflatable thermal blanket  120  in areas of the blanket that correspond to areas of the patient&#39;s body that are to be evaporatively cooled. In FIG. 1, the conduits  250  are shown extending from the patient&#39;s chest area to the patient&#39;s lower legs. In FIG. 3, the conduits  250  are attached to the underside of the inflatable thermal blanket  120  below central portions of the inflatable section  130 . In FIG. 4, the conduits  250  are attached to the underside of the inflatable thermal blanket  120  below the discontinuous elongate heat seals. One example of a fluid conduit would be a length of approximately ⅛ inch internal diameter PVC tubing, similar to standard IV (intravenous) tubing. 
     The fluid conduits  250  deliver fluid to the patient  100  through a plurality of orifices  252 , which are formed intermittently along the length of each conduit in the walls thereof. The orifices  252  allow fluid to be delivered to a selected area or areas of the patient  100 . As shown in FIG. 3, the orifices  252  may be holes, or they may be slits, or any other type of perforations that allow the fluid to pass through the wall of the conduits  250 , and be deposited onto the body surface below. Alternatively, as shown in FIG. 4, the orifices may be formed as nozzles  254  that allow the fluid to be sprayed through the wall of the conduits  250 , on the body surface below. Additionally, the orifices  252  may include openings  256  in the ends of the conduits  250 . 
     As shown in FIG. 1, the fluid distribution apparatus includes a fluid reservoir  260  connected to the conduits  250 , via an inlet line  262 , and an inlet manifold  264 . The fluid reservoir  260  is preferably a collapsible plastic bag, identical to the currently-used IV fluid containers. Alternatively, bottled fluid or a continuous supply from a water system could be used. The inlet line  262  is preferably made from fluid supply tubing such as standard IV tubing with standard Luer connectors at each end. A valve  266  is provided in inlet line  262  to allow an operator to control the flow rate of the fluid. The inlet manifold  264 , which distributes fluid among the conduits, can be formed in a variety of ways. 
     FIG. 5 illustrates the inlet manifold as a Y-connection coupler  270  that is attached, at its upstream side, to the end of the inlet line  262 . FIG. 5 also illustrates an alternative pattern for the conduits  250 , in which two conduits  272  and  274  made from small bore plastic tubing are attached to the downstream side of the coupler  270 . These conduits extend from the upper side of the inflatable thermal blanket  120  to the underside thereof through respective holes  276  and  278  that are formed in adjacent ones of the seals that join the upper and base sheets of the inflatable thermal blanket  120 . The conduits  272  and  274  are attached to the underside of the inflatable thermal blanket  120  in a serpentine pattern. In the configuration shown in FIG. 5, the orifices  280  of the conduits are oriented to wet the entire body of the patient  100  except the head area. It should also be understood that the conduits could be oriented to wet only selected parts of the body. As shown in FIG. 5, the numerous air apertures  217  will direct evaporative air to all portions of the patient&#39;s body where fluid is delivered by the conduits. 
     FIG. 6 illustrates an alternative construction for an inlet manifold and fluid delivery conduits. In this construction, the inlet manifold is a linear length of tube  290  mounted to the underside of the blanket  120 . The inlet line  262  extends through a hole formed in a seal, and attaches to a coupler  292  that is centrally located on the linear manifold tube  290 . FIG. 6 also illustrates an alternative pattern for the conduits that deliver fluid for evaporation. In the figure, five conduits  294 ,  295 ,  296 ,  297  and  298 , made from small bore plastic or silicone tubing, are attached at spaced locations on the linear manifold tube  290 . Each of these conduits is attached to the underside of the inflatable thermal blanket  120 . While the conduits are shown in a straight line pattern, it should be understood that other patterns could also be employed. In the configuration shown in FIG. 6, the orifices  300  of the fluid distribution conduits are oriented to wet the entire body of the patient  100 , except the head area It should also be understood that the conduits could be oriented to wet only selected parts of the body. As shown in FIG. 6, the numerous air apertures  217  will direct evaporative air to all portions of the patient&#39;s body where fluid is delivered by the conduits. 
     FIG. 7 illustrates another alternative construction for an inlet manifold and fluid delivery conduits. In this construction, the inlet manifold is a hub member  320  having a central fluid inlet and multiple radially oriented fluid outlets. The inlet line  262  extends through a hole formed in a central seal and attaches to a central inlet of the hub  320 . FIG. 7 also illustrates an alternative pattern for the conduits in which eight conduits  322 ,  323 ,  324 ,  325 ,  326 ,  327 ,  328  and  329  made from small bore plastic or silicon tubing are attached to the radial outlets of the hub  320 . Each of these conduits is attached to the underside of the inflatable thermal blanket  120 . In the configuration shown in FIG. 7, the orifices  330  of the fluid distribution conduits are oriented to wet the entire body of the patient  100  except the head area. It should also be understood that the conduits could be oriented to wet only selected parts of the body. As shown in FIG. 7, the numerous air apertures  217  will direct evaporative air to all portions of the patient&#39;s body where fluid is delivered by the conduits. 
     The inventors contemplate modes of fluid delivery other than the tube-based embodiments that have been presented. For example, strips, or sheets, of hydrophilic material or wicking material could be used. 
     Preferably, the fluid distribution apparatus delivers the cooling fluid by depositing it directly on the skin the patient  100 . However, there may be times when direct application to the skin is disadvantageous. For example, if the fluid flow rate is not adequately controlled or if the contours of the patient&#39;s body allow runoff, some of the fluid can pool under the patient. This pooling of fluid is wasteful, messy and may be harmful to the skin laying in the pooled fluid for a prolonged time. Accordingly, as shown in FIG. 8, a layer of wicking material  350  may be loosely interposed between the underside of the inflatable thermal blanket  120  and its fluid distribution system, and the skin of the patient  100 . The wicking material  350  may be loosely attached to the inflatable thermal blanket  120  by connecting it at the peripheral edges only. The wicking material  350  may be any thin, loosely woven or non-woven material. One example is a single layer of cotton gauze material. The wicking material  350  serves to keep the fluid on the skin area where it is deposited, by minimizing run-off. 
     If a low fluid supply pressure is desirable, the fluid reservoir  260  can be elevated above the level of the inflatable thermal blanket  120  such that fluid pressure is generated by gravity. This configuration is shown in FIG.  1 . If higher fluid supply pressures are desired, a pump  360  may be employed, as shown in FIG.  9 . The pump  360  is interposed in the fluid supply line  262 . It may be provided using one of many IV fluid pumps that are generally available. Other pumps could also be employed. For example, the fluid reservoir  260  could be pressurized. 
     Preferably, the evaporative fluid used in the fluid distribution system is water. However, other volatile fluids may also be used, or mixed with water. For example, in high humidity environments the evaporative cooling effect of water is severely reduced. In these situations, it may be desirable to use a different volatile fluid such as a mixture of alcohol and water. Other volatile, non-toxic fluids could be substituted or mixed with water to provide the desired evaporative characteristics. These fluid combinations may be premixed and supplied in sealed containers for convenience or may be mixed by the therapy provider. 
     In addition to inflatable thermal blankets shaped to various partial portions and combinations of the patient&#39;s trunk and limbs, specialized blanket configurations for various body parts may also be constructed. FIGS. 10,  11  and  12  illustrate an inflatable thermal blanket formed as a thermal helmet  400  constructed to fit over the head  402  of a patient  404 . The helmet  400  is constructed in similar fashion to the inflatable thermal blanket  120 . Thus, it has a base sheet  410  and an upper sheet  412  that are joined together by a continuous air-impervious heat seal at the periphery thereof, and optionally attached at interior portions thereof with heat seals, to define an inflatable structure  414 . The base sheet  410  is provided with a plurality of apertures  416 . The helmet  400  is inflated with air delivered by an airhose  420 . This air is exhausted toward the patient&#39;s head  402  through the apertures  416 . Thus, the helmet  400  has a component for cooling the patient  404  convectively. It also has an evaporative component that includes a conduit  430  made from small bore plastic tubing or the like. The conduit  430  is attached to the underside of the helmet  400 , and is arranged in serpentine fashion. The conduit  430  extends through a hole in the helmet  400 , and connects to an inlet line  432 , via a connector  434 . The inlet line  432  is connected to a fluid supply reservoir (not shown), and delivers a cooling fluid to the conduit  430 . The conduit  430  is provided with multiple orifices  436 , shown in FIG. 12 as spray nozzles. Alternatively, slits or holes could also be used to provide the orifices. 
     Advantageously, the regions of the patient&#39;s body that receive the combined evaporative-convective cooling in accordance with the invention can be selected by the care giver. The volume of fluid delivered can be controlled to either be fully evaporated, or to be in excess, and thus be delivered to body areas which are at various distances from the orifices. Optionally, an incorporated liquid sensing device could be used to determine and control the rate of delivery of the fluid for evaporation. 
     The fluid distribution apparatus thus allows fluid to be distributed and delivered to desired portions of the patient&#39;s body, at a controlled rate, over a prolonged period of time, without requiring the inflatable thermal blanket to be lifted or frequent operator involvement. While the inflatable thermal blankets illustrated herein are shown in particular shapes and sizes, it will be recognized that because different patients have different shapes and sizes, different shapes and sizes of inflatable thermal blankets may be made available to accommodate most patients. 
     Other embodiments and modifications of this invention may occur to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.