Patent Publication Number: US-2006005942-A1

Title: Vacuum activated thermal covering

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates generally to thermal coverings, more specifically, to thermal coverings adapted to reduce the incidence of hypothermia. As such, the invention is particularly well suited in medical environments for use as a surgical drape, gown, or blanket. The invention is also suitable for campers, rescue workers, and the like for use in emergency, rescue, and survival conditions. Other uses of course would be evident to those skilled in the art.  
      In many emergency situations, it is critical for a patient to receive prompt and proper attention to his/her injuries in order to avoid exacerbating those injuries that may have already occurred. Often, the first rescuers to arrive on the scene are emergency medical staff who are responsible for preparing the patient for transportation to the nearest medical facility where the individual&#39;s injuries are to be treated. Depending upon the particular circumstances surrounding the patient&#39;s injuries and the location of an accident scene, these rescuers may typically be emergency medical squads who are employed with either a fire department, a local hospital, a law enforcement agency, rescue patrols and the like. In most situations, the patient is transported to the most appropriate medical facility by a ground ambulance, but air ambulances are also employed when circumstances dictate that this would be most efficient.  
      One of the many concerns of certified rescue workers during their preliminary treatment of a patient is to provide, to the extent possible, the most comfortable surroundings for the individual. This can both place the patient at ease and can be vital to the success or failure of initial medical treatment, particularly in instances where weather conditions are severe or where the patient is in shock. For instance, rescues that take place in cold or wet weather conditions, such as those often encountered by ski patrols, require that the patient be adequately insulated from the cold to avoid further reduction in body temperature, while rescues occurring in windy or rainy climates require that the patient be covered with a material repellant to these elements. Therefore, it is vital that the emergency rescue personnel be adequately equipped so that they can quickly and properly adapt to the specific situation at hand.  
      The patient may remain at the medical facility and require continued thermal protection to provide heat to his/her body. In addition, the patient may be required to undergo a surgical procedure. It is well known that a patient under general anesthesia undergoes several physiological changes that inhibit the body&#39;s normal thermo-regulatory capabilities. General anesthesia depresses the function of thermoregulating centers in the hypothalamus, thus resulting in the body&#39;s diminished ability to self-regulate body temperature. Infusion of intravenous fluid may contribute to cooling body temperature during surgery because such intravenous fluids absorb heat from the body when they are at a temperature below body temperature. Inspiration of dry anesthesia gases during surgery may also contribute to body temperature cooling during surgery because the dry gas both absorbs heat from the body and because of the cooling action created when water from the body is absorbed by the dry gas. Moreover, during surgery the body cavity may be exposed, which increases the effective surface area of the body and also cools body parts that are normally not exposed to the environment. The incidence of hypothermia occurring after surgery has been estimated to be as great as 60% to 90%.  
      To prevent hypothermia from occurring in many situations, including rescue, emergency surgery, and/or many elective surgeries, it is necessary to provide active heating to the patient. As such, to minimize any potential complication in the description detailed in this disclosure, the remainder of the disclosure will refer to coverings for use in surgical settings. This is meant to serve as a simplification of the disclosure only and is not intended to exclude other thermal coverings including those more appropriately adapted for use in emergency, survival, or rescue situations.  
      One requirement appropriate for use in a surgical setting is that the heating system or method used to heat the patient during surgery be capable of maintaining a sterile surgical field. Another important requirement for any active heating system or method is that it delivers sufficient heat to the body to lessen the likelihood of the onset of hypothermia. Although many devices exist that may be used to provide heat or to provide a sterile environment, none of these devices are capable of utilizing thermogenic materials contained within the covering to generate heat without requiring a rupturable membrane or continued circulation of the thermogenic material.  
     SUMMARY OF THE INVENTION  
      Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.  
      The present invention provides a chemically activated thermal covering that has two main components. The first component is a thermogenic system which is associated with the second component, a carrier containing or otherwise supporting the thermogenic system. The thermogenic system contains at least one, and often more than one compartment which contains a first reagent. The first reagent is maintained at a first pressure. The system also contains an actuator for controllably isolating a second reagent from the first reagent. The second reagent is maintained at a second pressure which is higher than that of the first reagent. A channel, and often a plurality of such channels are provided for connecting the compartment or compartments to the actuator. In some embodiments, a plurality of individually controllable actuators are provided. Each actuator controls a bank of such channels and compartments. In any event, the system works upon the principle that the pressure differential between the first and second reagents draws the second reagent into the compartment where the first reagent is located thereby initiating the thermal reaction. The carrier portion of the system typically is fashioned into a foldable, conformable, generally planar carrier material for carrying the thermogenic system in the form of a covering including a nonwoven fabric and/or a film material. The covering may be in numerous forms, including a surgical drape or a blanket.  
      In another aspect, the present invention the second reagent is contained within a dedicated reservoir. The reservoir may be volumetrically changeable and may include an expandable bladder. The second reagent may be obtained from an environment within which the covering is located, including utilizing the oxygen contained within the air itself and as such may not include a dedicated reservoir component. In some embodiments the compartments containing the first reagent may be maintained under a vacuum until the actuator is actuated at which time the second reagent is drawn into the compartment initiating the thermal reaction.  
      In yet another aspect of the present invention the compartments and channels of the thermogenic system may be configured as a plurality of compartments and channels thereby forming at least one conduit system. As such, each conduit system may contain at least one channel leading to a plurality of compartments. The channels and/or compartments may be made of reversibly collapsible materials, be formed from a film or other fluid tight substrate, and may be formed from aspects of the carrier material itself. Moreover, the thermogenic system may include a bank of independently controllable actuators each capable of introducing a second reagent into a conduit system containing a channel connected to a compartment containing the first reagent. The thermogenic system may be affixed to an exterior surface of the carrier, may be internal to the carrier or may have internal as well as external components.  
      In still another aspect of the present invention, the thermal covering may include the first reagent impregnated within a foam or other sponge-like material. Embodiments of the thermal covering according to the invention are described below in greater detail with reference to the appended figures. As such, these and other objects are achieved by the apparatus disclosed and claimed herein. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  is a plan view of an embodiment of a thermal covering according to the present invention;  
       FIG. 2  is a cross-sectional view of another embodiment of a thermal covering according to the present invention;  
       FIG. 3  is a cross-sectional view of still another embodiment of a thermal covering according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Reference will now be made in detail to one or more examples of the invention depicted in the FIGs. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield still a different embodiment.  
      Other modifications and variations to the described embodiments are also contemplated within the scope and spirit of the invention.  
      As such, turning in detail to  FIG. 1 , a chemically activated thermal covering  10  in accordance with the present invention is depicted. The chemically activated thermal covering  10  is generally configured to be in the form of a flat, foldable, conformable, relatively planar material. In the  FIG. 1  embodiment, it may be seen that in one of its simplest forms the covering  10  comprises a thermogenic system  12  associated with a carrier  14  of some type, such as a sheet material.  
      Such a structure in the form of the covering  10  may be provided with edges  16  as shown on  FIG. 1 . The thermogenic system  12  comprises a plurality of interconnected compartments  18  affixed to or otherwise carried by the carrier  14 . The location of the compartments  18  may be on either side of; on both sides of; and in some embodiments even within the structure of the carrier  14  itself. In any event, the compartments are each interconnected one to another via tubing or channels  20 . The tubing may actually be constructed of a tubing material, however, channels or passages created within the material comprising the carrier  14  are contemplated as well. For ease of description, dedicated tubing, passages, or channels are referred to as channels  20 , and the compartments  18  together with the channels  20  are referred to as a conduit system  22 .  
      Within each compartment  18  may be found some quantity of a first reagent  24 . The first reagent would be capable of generating heat or otherwise exhibiting thermogenic properties when exposed to a second reagent  26 . In many embodiments the second reagent  26  may comprise a fluid. The fluid itself may comprise a gas such as air or a liquid such as water. In other embodiments more complex arrangements of additional reagents may be used.  
      Specific reagents capable of forming such a thermogenic reaction are known in the art and as such are not individually identified herein. Moreover, though the description is drawn to the creation of an exothermic reaction, reagents capable of inducing a cooling effect may also be selected. It should be understood that the reagents selected should be chosen so that the desired effect heating or cooling effect is induced. For ease of description, the remainder of the disclosure addresses a heating effect though the claims are drawn to both heating and cooling.  
      In any event, the second reagent  26  must be kept separate from the first reagent  24  until such time that the exothermic reaction designed to provide heat to the patient is desired. One such construction provides a reservoir  28  that may be placed in fluid communication with the conduit system  22 . Once the second reagent  26  is introduced into the conduit system  22 , the reaction may progress from compartment to compartment via the channels, or otherwise, depending upon the actual design of delivery of the second reagent  26  to the first reagent  24 .  
      The principle behind the operation of the present invention is that the second reagent  26  is drawn into the conduit system  22  by a pressure differential maintained between the conduit system  22  and the reservoir  28 . To accommodate this, the conduit system  22  is maintained under a lower pressure with respect to the reservoir  28 . In some instances this lower pressure may actually be a vacuum, that is, a pressure less than 1 atmosphere. Under most normal surgical and emergency conditions a slight vacuum would be sufficient, however the covering  10  may also be used in an environment that may differ from 1 atmosphere. Examples of this might be at high altitudes where pressures are lower than 1 atmosphere, and within a decompression chamber or a hyperbaric oxygen therapy chamber where pressures are higher than 1 atmosphere. Therefore it is important to note that the conduit system  22  is at a lower pressure with respect to the reservoir at the time when the reaction is initiated.  
      As stated, until such time that it is desirous for the reaction to take place, the reservoir  28  must be separately maintained or otherwise isolated from the conduit system  22 . As such an actuator  30  of some form is provided that when actuated enables flow of the second reagent into the conduit system  22 . The actuator  30  may be located anywhere on or otherwise associated with the covering  10 , such as at an edge  16 . The form that the actuator  30  takes may vary based upon the system design; some embodiments may be, but are not limited to: providing a rupturable membrane or valve between the reservoir and the remainder of the system, keeping a physical separation between the conduit system  22  and the reservoir  28  until such time that the reaction is desired, as well as other possibilities. In any form, the actuator serves the purpose of keeping the reagents separate from one another until such time that it is desired to initiate the exothermic reaction. Once actuation occurs, the second reagent  26  is drawn into the conduit system  22  through the channels  20  and into the compartments  18  due to the pressure differential, thereby reacting with the first reagent  24 , generating the exothermic reaction and heating the patient.  
      In certain embodiments, connecting the reservoir  28  containing the second reagent  26  to the conduit system  22  does not alter the fact that the thermogenic system  12  remains a closed system. As such, a sufficient quantity of reagent  26  should be contained within the reservoir  28  to enable a complete reaction to occur within the thermogenic system  12  once the reagent  26  is introduced into the conduit system  22 . One construction capable of enabling fluid flow from the reservoir  28  to the conduit system  22  within such a closed system is to provide the reservoir with some way with which to change its volume. Some possible methods suitable to accomplish this include but are not limited to providing a collapsible reservoir, a syringe-type reservoir having a plunger or other moveable component that accommodates a volumetric change in the reservoir  28 , or a bladder within the reservoir that expands to fill the void left within the reservoir  28  as the reagent  26  is drawn into the conduit system  22 .  
      In certain embodiments, the reservoir  28  may comprise the external environment within which the covering  10  itself is located. An example of this is when the second reagent  26  comprises oxygen contained within air. Actuation of the actuator  30  would allow air to be drawn into the conduit system  22 . As such, it should be understood that the reservoir  28  may not exist as a specific component within the thermogenic system  12 , but may comprise the external environment itself. In other embodiments, the reservoir  28  may be attached to the system  12  coincident with manufacture or may be provided as a separate component attached only when it is desirous for the reaction to be initiated.  
      A number of possibilities exist that enable the conduit system  22  to be maintained at a lower pressure with respect to the reservoir  28 . The conduit system  22  could simply be kept at a negative pressure by placing it under a vacuum. Alternatively, the conduit system  22  could be made of a reversibly collapsible material so that the compartments  18  and/or the channels  20  are initially in a collapsed condition and would expand upon transfer of reagent  26  from the reservoir  28  through the actuator  30 . This could be handled by maintaining the conduit system  22  in a collapsed state until the pressure in the thermogenic system  12  is equalized. Equalization occurs when the second reagent  26  is drawn into the conduit system  22  at which time all or part of the conduit system  22  returns to an uncollapsed state. One possible embodiment of such a conduit system may comprise channels that are made of soft rubberized or flexible tubing such as surgical tubing.  
      Looking to  FIG. 2 , a cross section of an alternative embodiment is depicted. In this embodiment the reservoirs  18  are contained within an interior aspect of the covering  14 . Moreover, a large quantity of compartments  18  may be provided. This embodiment may best be described as being reminiscent of a material commonly referred to as “bubble-pack.” Bubble-pack typically consists of two layers of a thin plastic material, such as polyethylene or vinyl formed with periodic bubbles between the layers. In this embodiment, the covering  14  may comprise a multilayer construct having a first layer  32  and a second layer  34 . Between the two layers  32 ,  34  are situated reservoirs  18  and channels  20  together forming the conduit system  22 . One manner with which to form the reservoirs  18  is to utilize film layers  36  to create them in the same manner as one would form bubble-pack. The use of film  36  to create bubble-pack would be understood by those skilled in the art and no further description is considered necessary to address the formation of reservoirs  18 .  
      As in the  FIG. 1  embodiment described above, a quantity of the first reagent  24  would be contained within the compartments  18 . The channel  20  may simply comprise a void space within the covering  14  to connect to the reservoirs  18 . The channel  20  is depicted in  FIG. 2  as being vertically offset from the reservoirs  18  for clarity. It should be understood that the channel  20  may also tangentially impinge upon the reservoirs  18  so as to eliminate the vertical sections of channel  20  depicted in  FIG. 2 . Moreover, since  FIG. 2  is a cross sectional view it is not readily apparent that a plurality of such channels  20  may be provided. Any number of such channels  20  may be independently controlled by the use of individual actuators  30 , as shown in  FIG. 1 , thereby forming a bank of individually controllable reactions. A foam  38 , sponge-like material, or other spacer as depicted in  FIG. 2  may be provided as well. Though such a material is not necessary, it may provide added insulative effects to the covering  10  among other things.  
      In fact,  FIG. 3  depicts an alternative embodiment of a carrier  10 . In this embodiment, a foam  38  is impregnated with the first reagent  24 . Upon actuation, the second reagent  26  is introduced into the conduit system through the channel or channels  20 . An embodiment, such as that shown in  FIG. 3  eliminates the need for dedicated compartments. In essence the entire covering may be made to encase and act as the thermogenic system.  
      In any of the embodiments, the carrier  14  may comprise clothlike, liquid-impervious, barrier material, which itself possesses a unique balance of performance characteristics and features making the material suitable for use in forming surgical drapes, thermal blankets, as well as other emergency thermal coverings. The carrier  14  may be a woven material, a nonwoven material or combinations of the same. In some embodiments a single layer nonwoven material, a laminate of like materials, a laminate of nonwoven polymers combined with film layers or any combination may be provided. In the event that a laminate is selected, the individual layers of the laminate comprising the carrier  14  may themselves be laminated, bonded or attached together by known means, including thermal-mechanical bonding, ultrasonic bonding, adhesives, stitching and the like.  
      In use, for example in a surgical setting, the thermal covering  10  may be provided in the configuration of a sterile surgical-thermal drape of a nonwoven laminate as described above. Medical personnel would remove the drape from its packaging and then place it on the desired patient surface so that the thermal effect is transferred to the patient. The reagents are allowed to intermix by initiating the reaction in a manner that prevents the sterile drape from contacting any unsterilized surface or objects so as to maintain the sterility of the drape. After this has been done, surgical procedures may then be performed on exposed portions of the patient or through a fenestration in the drape (not explicitly shown) without risking inadvertent contamination of medical instruments or devices by contact with the drape. One skilled in the art will recognize that the specific description of the surgical drape is exemplary and other embodiments may incorporate additional features such as fenestration reinforcement materials, pouches, clips, tape, as well as other features found on various embodiments of surgical drapes.  
      Accordingly, while this invention has been described by reference to certain specific embodiments and examples, it will be understood that this invention is capable of further modifications. This application is, therefore, intended to cover any variations, uses or adaptations of the invention following the general principles thereof, and including such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and fall within the limits of the appended claims.