Abstract:
A flexible thermal pack to be intimately applied to a patient&#39;s body is in the form of a plastic container enclosing a chemical compound capable of an endo- or exo-thermic reaction when intermixed with a catalyst. The plastic container has a vent in one wall covered by a semipermeable membrane for passage of gas but not liquid. Also enclosed in the container is another frangible container housing a suitable catalyst for the compound.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to the medical field and patient care, specifically to thermal dressings intimately conforming to the shape of the patient&#39;s body. For the purposes of this disclosure, heat and cold refer to temperatures above and below the normal body temperature, respectively.  
         BACKGROUND OF THE INVENTION  
         [0002]    The medical use of thermal therapy, both hot and cold, is well known to treat various maladies and traumas. Usually, application of heat is used stimulate the body to increase blood flow in an area in order to dissipate the heat build-up. This acts to prevent stiffness in a traumatized joint or appendage. The application of a cold pack reduces swelling and lessens perceived pain. Both of these standard treatments have a place in caring for a patient.  
           [0003]    In a hospital or office, thermal appliances may be in stock to apply to various portions of the anatomy. However, in emergency medical services where space and/or weight may be limited, hot and cold treatment is generally restricted to simple containers or absorbent pads, having the desired temperature, applied directly to the affected part of the patient&#39;s body. Because of the infinite sizes and shapes of the body, the few thermal devices available do not always conform to the patient in such a way to provide the most effective treatment. To alleviate this problem, small thermal packs have been developed.  
           [0004]    To eliminate the problem of maintaining both hot and cold packs at a predetermined temperature for prolonged periods of time, the use of pliant containers enclosing ingredients which, when combined, create an endo- or exo-thermic reaction are used to apply cold or heat to the desired location on the body. However, a by-product of these endo- or exo-thermic reactions is gas. The gas becomes trapped in the container rendering the thermal pack rigid and lacking in the ability to conform to the anatomy. In the extreme, the container may rupture putting the reacting chemicals in direct contact with the patient&#39;s body.  
         DESCRIPTION OF THE PRIOR ART  
         [0005]    U.S. Pat. No. 6,248,125 issued to Helming discloses a thermal pack for treating the perineal and rectal area with either heat or cold. Both the hot pack and the cold pack have an envelope within which are two separate compartments housing ingredients that cause a thermal reaction when mixed together. To use the device the compartments are ruptured allowing the components to mix. There is no indication of any provision for the volume of ensuing gas that is created inside the fixed volume of the container.  
           [0006]    Dunshee, U.S. Pat. No. 4,953,550, discloses a chemical thermal pack with two compartments and separated ingredients which will create an exo- or endo-thermal reaction when mixed. A portion of the outer container has a wall with capillary tubes formed there-through. The capillary tubes allow for the drainage of water from the interior of the pack. Additionally, the capillaries act as an insulator to prolong the effects of either the hot or cold pack.  
           [0007]    Vakharia and Jessup et al, U.S. Pat. No. 5,171,439 and U.S. Pat. No. 4,203,445, respectively, disclose gas vents for plastic bags. The vents permit gases to migrate into or out of the bags to equalize pressure while preventing liquid from escaping.  
           [0008]    What is needed in the art is a hot or cold pack that allows gas to escape and remains compliant after the initiation of the endo- or exo-thermic reaction so that it can conform intimately with the injured portion of the body.  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, it is an objective of the instant invention to teach a medical device to apply heat or cold to a patient by intimately conforming to the anatomy.  
           [0010]    It is a further objective of the instant invention to teach a medical device that creates a thermic reaction within a compliant container by mixing two or more chemical compounds.  
           [0011]    It is yet another objective of the instant invention to teach a medical device having a vented container which allows escape of gaseous by-products of a thermic reaction and remains compliant during use.  
           [0012]    It is a still further objective of the invention teach a medical device with a vented compliant container which has two compartments separated by a frangible partition with each compartment enclosing an ingredient necessary to create a thermic reaction. By applying pressure to the container, the partition is ruptured allowing the ingredients to mix within the container producing a temperature change, a liquid or gel residue and gases. The gases pass through the vent to the atmosphere.  
           [0013]    Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0014]    [0014]FIG. 1 shows a perspective of the thermal pack of the invention;  
         [0015]    [0015]FIG. 2 shows a cross section of the thermal pack of FIG. 1 including separate compartments;  
         [0016]    [0016]FIG. 3 shows a schematic cross section of the vent;  
         [0017]    [0017]FIG. 4 shows a perspective of another embodiment of the thermal pack;  
         [0018]    [0018]FIG. 5 shows a cross section of the closed vent valve along line A-A of FIG. 4; and  
         [0019]    [0019]FIG. 6 shows a cross section of the open vent valve. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    The thermal pack  10 , shown in FIG. 1, is a generally rectangular container. The container may be made in different shapes as a matter of choice and for special applications. The container  10  is made of supple plastic films forming walls  11  and  12  which have seals  13 ,  14 ,  15  and  16  closing the corresponding edges to form a liquid tight container. The films may be single ply or co-extrusions of different polymers or laminated films having the same properties or different properties. The walls are formed of materials that will be impervious to each of the ingredients and to the resulting combination. The container may be made using a tubular plastic film which is sealed at the opposite ends. The plastic film may be thermoplastic and the seals may be formed by heat and pressure. If other plastic films are used, the seals may be formed by adhesives or solvents. As illustrated, the container  10  encloses, as one ingredient, a chemical compound  21  which will initiate a thermal reaction when mixed with another ingredient, in the form of a catalyst. Preferably, when the chemical compound is mixed with the catalyst a gel-like substance is formed. The gel acts to prolong the thermal effects.  
         [0021]    As shown in FIG. 1 and  2 , the container  10  encloses another tube having opposing walls  17  and  18 . The walls  17  and  18  are preferably continuous plastic film with end seals  19  and  20 . These films and seals may be formed in the same manner as the films and seals in container  10 . Also, the tube may be formed by superimposing film layers and sealing the superposed periphery. The opposing walls  17  and  18  have a structure or are made of material that will rupture before the container  10 , when placed under a compressive load. This insures the integrity of the container  10  and prevents the thermal compound from coming into contact with the user.  
         [0022]    The catalyst  22 , for the thermal reaction, is enclosed within the inner container until the inner container is ruptured. Once the thermal compound and catalyst come into contact with each other, the outer container is kneaded to thoroughly mix the ingredients.  
         [0023]    As the thermal reaction progresses, there is generated a gaseous by-product. The volume of the gas is released from the interior of the container through aperture  23  and porous membrane  24 . The porous membrane is made from a material that will allow passage of gas, including any air trapped in the interior, but not liquid. The membrane spans the aperture  23  and has a continuous edge seal  25  joining the membrane to the container. The edge seal  25  may be formed by heat and pressure, solvent or adhesives. The material of the membrane may be in the nature of a semipermeable membrane or it can be a microporous nonwoven material.  
         [0024]    The thermal pack  40 , shown in FIG. 4, is substantially similar to the thermal pack  10  of FIG. 1. The thermal pack  40  has a peripheral seal  41  and encloses a catalyst  43  inside the bag in separated from the thermal composition  44  by a frangible wall. The thermal pack has a manual one-way valve  45  which has an annular valve  48  on the internal end of a valve body that reciprocates through a collar  46  sealed into an aperture in the thermal pack wall  42 . The annular valve is seated into an annular recess  49 .  
         [0025]    As shown in FIG. 5, the gas by-product of the thermal reaction caused by mixing the catalyst and the thermal composition will act against the annular valve  48  to seat the valve in the recess  49  closing the valve. The gas pressure closing the valve may be overcome by manually depressing valve actuator  47 . The valve body moves displacing the annular valve  48  and opening a vent passageway  50 . The gaseous by-product and any other trapped gases are released through the passageway.  
         [0026]    As an example of the thermal pack, the outer container may be fabricated from polyethylene film, alone, or laminated with other materials, the thermal compound may be ammonium nitrate, either alone or mixed with other chemicals, disposed inside the outer container. The ammonium nitrate is in the form of dry particles.  
         [0027]    The inner container may be made of the same plastic composition as the outer container. The inner container may have a weakened portion of a wall or the container may be of a thinner film. The catalyst, enclosed in the inner container, is water.  
         [0028]    The vent may be a hydrophobic microporous nonwoven plastic material such as TYVEK made by DuPont Co. The vent material will allow gas to pass through while repelling liquid.  
         [0029]    In use, the thermal pack may be stored indefinitely until the ingredients are mixed. To provide a cold treatment to a patient, the compliant envelope is squeezed or put under compressive pressure to rupture the inner tube. The container is then kneaded to thoroughly mix the chemicals and produce a temperature change. As the chemical endothermic reaction proceeds, gas evolves and escapes from the container through the semipermeable vent leaving the gel. The cold compliant container is then intimately wrapped about the injured part of the patient&#39;s body.  
         [0030]    It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and drawings.