This invention is directed to a hypothermia management system for injured persons and more particularly, to a shell for receiving an injured person having a powered heater internally to maintain, but not exceed, a predetermined temperature inside the shell.
Based upon studies performed by the United State military, the number one cause for preventable combat death is one or more extremity hemorrhage. In fact, extremity hemorrhage accounts for approximately 60% of studied preventable combat deaths. When an injured person hemorrhages, hypothermia prevention and management is of critical importance. Hypothermia can lead to cardiac arrhythmias, decreased cardiac output, increased systemic vascular resistance, and most importantly, induced coagulopathy by inhibition of the clotting cascade. If hypothermia is not prevented in this casualty demographic, the potential exists that the injured person will not be able to form a clot due to the disruption of the clotting cascade and may potentially bleed to death from an otherwise survivable wounding.
The prior art discloses various means for treating and protecting against hypothermia including emergency blankets, insulated apparel, and heating devices, such as air activated heating pads. For example, U.S. Patent Publication No. 2005/0044602 discloses self-heating apparel having air activated heating elements sealed between layers of fabric and disposed throughout the apparel for providing a heating effect for the wearer. Another example is provided by U.S. Pat. No. 5,386,604, which discloses a patient rescue bag having top and bottom layers of insulated weatherproof material joined by releasable fasteners for adjusting the size of the bag to adapt to the size of the patient, while also keeping the patient warm and protected from the weather. Yet another example is provided by U.S. Pat. No. 4,998,296, which discloses a hypothermia protection suit having an integrated hood to be worn by a person in an emergency situation to provide extra warmth and protection from the weather. Another example is U.S. Pat. No. 7,766,950 which discloses hypothermia treatment sack having a plurality of self-activating heating pads carried in the top sheet for producing heat when exposed to air.
When dealing with the rigors of combat and the treatment and prevention of hypothermia in wounded patients, the prior art devices do not provide a sufficient solution to the unique problems encountered by medics on the battlefield. For example, the current practice by medics on the battlefield treating a patient with hypothermia is to first wrap the patient in a blanket containing air activated heating elements. These blankets are not heat reflective or weatherproof and are susceptible to rips and tears, and thus have been difficult to use in the field due to their fragility. Next, the medic will wrap the patient in a weatherproof heat reflective blanket, typically one made of lightweight aluminized polyester commonly referred to as a space blanket, around the first heating blanket to reflect the patient's body heat and heat from the blanket back against the patient. Finally, the medic will apply a heat reflective cap to the patient's head. The individual application of each of these items takes an unnecessarily long time. Worse, however, is the fact that by wrapping the patient in the heat reflective blanket, the air activated heating blanket does not get a sufficient supply of oxygen to sustain an acceptable level of heating capacity for extended time periods. Additionally, once the patient is wrapped in the blankets, the medic cannot easily check on the patient's wounds without unwrapping the patient, which exposes the patient and reduces the heat buildup around the patient intended to manage or prevent hypothermia.
Further, the heating devices that are air activated have little or no temperature control devices so that these heating devices provide heat in uncontrollable temperatures. Typically, these types of heating pads only provide for 8 to 12 hours of heating and generate temperatures between 122° F. to 131° F. (50° C. to 55° C.). However, it is medically recommended that heat applied to an injured person be approximately 104° F. (40° C.) to avoid further injury to the person.
Accordingly, it is an object of the present invention to provide a single use lightweight durable hypothermia treatment device having a controllable heat source.
It is another object of the present invention to provide a hypothermia treatment apparatus that can be powered by a variety of power sources eternal to the outer shell.
The objects of the invention are accomplished by providing a hypothermia management apparatus comprising: a receiving cavity defined by an outer shell arranged and sealable to encircle an injured person; an internal layer attached to the outer shell wherein the internal layer includes a bottom sheet disposed generally under the injured person when the injured person is placed in the receiving cavity and a top sheet disposed generally on top of the injured person when the injured person is placed in the receiving cavity; an inner liner attached to the bottom sheet of the internal layer forming an internal cavity; and, an absorption layer attached to the inner liner disposed generally under the injured person when the injured person is placed in the outer shell; and, a heater assembly disposed in the internal cavity comprising: a heating substrate layer, a heating element adjacent the heating substrate layer, a power supply electrically connected to the heating element, a thermostat included in the electrical circuit for regulating the temperature produced by the heating element to a predetermined temperature, an electrical circuit defined by the heating element, the power supply and the thermostat, and a heater dissipating layer disposed adjacent the heating element for radiating heat into the outer shell at approximately 40° C.
The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown and wherein:
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The outer shell includes a top sheet 14 and a bottom sheet 16 which can have corresponding rectangular shapes so that when the bottom sheet and top sheet are engaged, a receiving cavity 18 is formed. Top sheet 14 and bottom sheet 16 each have a weatherproof exterior side, designated generally as 20a and 20b, respectively, for repelling wind and water from entering patient receiving cavity 18. Further, top sheet 14 and bottom sheet 16 each have a heat reflective interior layer, designated generally as 22a and 22b, respectively, for preventing heat from escaping patient receiving cavity 18. In one embodiment, top sheet 14 and bottom sheet 16 comprise aluminized polyester which is capable of both repelling wind and water and reflecting heat. In this arrangement, only one sheet of materials is required to form each of top sheet 14 and bottom sheet 16, which reduces bulk and weight for storage and transport in the field. Further, aluminized polyester is extremely durable and well suited to the rigors of extreme field conditions, such on a battlefield.
In a further advantageous embodiment, weatherproof exterior sides 20a and 20b of top and bottom sheets 14 and 16, respectively, are a generally dark green color, such as olive drab, for camouflaging injured patients on a battlefield. In order to reduce manufacturing costs, heat reflective interior layer 22a and 22b may be the standard reflective finish common to aluminized polyester, which can be used to attract attention of rescuers if required.
When top sheet 14 and bottom sheet 16 are engaged to form patient receiving cavity 18, releasable connectors 24a and 24b are carried along a perimeter portion of top sheet 14 and bottom sheet 16 for releasably connecting the top and bottom sheets. This provides patient access from any location around the perimeter of the sheets when connected together. In a preferable embodiment, releasable connectors 24a and 24b comprise cooperating hook and loop fasteners, such as Velcro®. The receiving cavity can include a head area 26a, a chest area 26b, a torso area 26c, and a leg area 26d.
In one embodiment, a hood 34 is carried by bottom sheet 16 for covering a patient's head when placed in the receiving cavity. In a further embodiment, hood 34 includes a weatherproof exterior side for repelling wind and water from a patient's head. Further, hood 34 can include a heat reflective internal layer for preventing heat from escaping through the hood. As with top sheet 14 and bottom sheet 16, hood 34 may be constructed from aluminized polyester to provide lightweight durable wind and water resistance while also providing heat reflective capability.
In one embodiment, a neck closure, designated generally as 36, is carried by hood 34 and adapted for surrounding a patient's neck. Preferably, the neck closure includes a weatherproof exterior side for repelling wind and water from the patient's neck, and a heat reflective interior liner for reducing heat loss from the patient's neck. Neck closure 36 can include a first flap 38a including a first portion of hook and loop fastener, and a second flap 38b including a second portion of cooperating hook and loop fastener for engaging hook and loop fastener of first flap, wherein first flap and second flap overlap each other around a patient's neck.
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In one embodiment, heater substrate layer and heating dissipation layer are non-woven materials such as felt. Further, the heater substrate material can be of 12 oz density and the heating dissipation layer can be a 4 oz density. The heating elements can generate temperatures which are dissipated by the dissipating layer. For example, if the heating elements produce temperatures in the range of 55° C. to 65° C., the heat will be dissipated after passing through the dissipation layer to a range including 35° C. and 45° C. Therefore, the optimal temperature for the receiving cavity of 40° C. can be maintained by the dissipating layer.
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In one particular embodiment, the heating element is a thin-film consisting of a relatively thin polyamide, or polyester film impregnated with a resistive carbon layer onto which conductive busses (leads) are printed. The leads can be comprised of low resistance, highly conductive materials such as silver, copper or gold. The film of the heater element itself is less than 0.5 mm thick with strength, flexibility and reliability. In one particular embodiment the heater is laminated with a 0.1 mm layer of Teflon™ to allow for forming heater into a wave pattern. Critically, this heater technology draws far less power than competitive alternatives allowing for extended battery life and lightweight, highly portable designs. In one exemplary embodiment, the heater material of the heater elements may be directly applied to the housing members using a spray and/or deposition technique. In one alternate embodiment, it is possible to use a single layer carbon-based resistive film that is directly applied to the outer surface of the inner housing.
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The invention can be packaged within a vacuum sealed pliable container capable of maintaining a high gas barrier while sealed.
While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.