Abstract:
A portable, forced air apparatus for warming a hypothermia victim in the field includes a stretcher, strips of material extending across the stretcher for supporting the torso of the victim above the stretcher bottom, a canopy for covering the victim&#39;s torso, a blower operated heater in a compartment in the stretcher beneath the victim&#39;s legs for delivering hot air to the canopy in the area of the torso for warming the victim&#39;s body while the legs and arms are covered to prevent heat loss, a heated head and neck support for controlled warming of the victim&#39;s head and neck, and sleeves for covering the victim&#39;s arms and legs to prevent heat loss therefrom during torso warming. The heating system is complemented by warm IV infusion and warm oxygen delivery to the victim.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a portable forced air warming apparatus for warming victims of hypothermia. 
     Severe hypothermia is a surprisingly common occurrence in cold areas of the world. Hypothermia is considered to be severe when there is a significant risk of spontaneous ventricular fibrillation, which can result in death of the victim. The risk of ventricular fibrillation increases significantly when the victim&#39;s core or deep body temperature is below 28° C. At such low core temperatures, the victim should be handled carefully because of his/her unstable condition. A severe hypothermia victim who has been cooled rapidly, e.g. during immersion in water, is preferably rewarmed rapidly. A severe hypothermia victim who has been cooled slowly, e.g. by exposure to cold air, is preferably rewarmed slowly. In any event, it is imperative to stop heat loss and to initiate rewarming of victims of hypothermia as soon as possible to optimize the chances of survival. During rescue operations in remote areas, it may take several hours to transport casualties from the rescue site to a hospital for treatment. 
     2. Discussion of the Prior Art 
     Warming apparatuses, some of which are portable, are disclosed by U.S. Pat. No. 5,300,101, which issued to S. D. Augustine et al on Apr. 5, 1994; U.S. Pat. No. 5,304,213, which issued to L. D. Berke et al on Apr. 19, 1994; U.S. Pat. No. 5,336,249, which issued to I. Mahawili on Aug. 9, 1994; U.S. Pat. No. 5,350,417, which issued to S. D. Augustine on Sep. 27, 1994 and U.S. Pat. No. 6,001,057, which issued to R. A. Bongiovanni et al on Dec. 14, 1999. 
     The inventors have determined that when rewarming a hypothermia victim, it is preferable to heat the torso only while preventing heat loss from the extremities. Heating of the victim&#39;s limbs causes the return of cold blood to the torso which contributes to a core temperature drop that can decrease the chances of survival. 
     Very few warming apparatuses are available in the marketplace, and those that do exist consist of heated blankets or bags for heating a victim&#39;s entire body and extremities, and devices for providing warm air for inhalation by the victim. A need exists for a system for eliminating heat loss and initiating rewarming of a hypothermia victim in the field. 
     GENERAL DESCRIPTION OF THE INVENTION 
     An object of the present invention is to meet the above need by providing a relatively simple, portable, forced air warming apparatus, which is easily transported to the field, and which can be used for controlled heating of a victim&#39;s body. 
     Another object of the invention is to provide a portable warming apparatus which can be used to warm a victim&#39;s body only while preventing heat loss from the extremities. 
     Yet another object of the invention is to provide a warming apparatus which can be used to effect controlled warming of the victim&#39;s head and neck which contributes to warming of the central nervous system, and helps a victim to regain normal respiratory and cardiovascular functions. 
     In its simplest form, the invention relates to a portable warming apparatus for warming a hypothermia victim comprising a stretcher, said stretcher including a bottom wall, side walls and end walls contiguous with each other; a support extending between said side walls for supporting the body of a hypothermia victim, openings in said support permitting the circulation of warm air around the torso of the victim, a canopy for covering the torso of the victim and defining a heating chamber around the torso with said stretcher; at least one heating duct in said chamber for discharging warm air against the torso of the victim, whereby the warm air circulates through said openings around the torso; and a forced air heater for warming ambient air, and delivering the warm air to the heating duct. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described below in greater detail with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention, and wherein: 
     FIG. 1 is a perspective view of a portable warming apparatus in accordance with the present invention in the closed condition; 
     FIG. 2 is a side view of the warming apparatus of FIG. 1 in the open, use condition; 
     FIG. 3 is a perspective view of one end of the apparatus of FIGS. 1 and 2 in the use condition; 
     FIG. 4 is an end view of a housing used in the apparatus of FIGS. 1 and 2; 
     FIG. 5 is a perspective view of a head and neck support platform use in the apparatus of FIGS. 1 to  3 ; 
     FIG. 6 is a perspective view of a sleeve used in the apparatus of FIGS. 1 to  3 ; 
     FIG. 7 is a schematic top view of a shell used in the apparatus of FIGS. 1 to  3 ; 
     FIG. 8 is a perspective view of a second shell and canopy used in the apparatus of FIGS. 1 to  3  in the open, use condition; 
     FIG. 9 is a top view of the shell of FIG. 8; 
     FIG. 10 is a perspective view of the shell of FIG. 7; and 
     FIG. 11 is a perspective view of a leg bag used in the apparatus of FIGS. 1 to  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 to  3 , the warming system of the present invention includes a housing generally indicated  1  defined by two rectangular shells  2  and  3 , which are connected together by hinges  4  (FIGS. 8 and 9) to define a generally rectangular box, which can be easily carried into the field on a vehicle such as a snowmobile, an all terrain vehicle or a trailer. The housing  1  is releasably locked in the open position by a latch mechanism defined by a pin  6  on one shell  2 , and a notched arm  7 , which is pivotally mounted on the other shell  3  of the housing. In the fully open position (FIG.  2 ), the housing shells  2  and  3  define an elongated stretcher for receiving and transporting a patient. To facilitate manual lifting and carrying of the housing in the open or use condition, tubular handles  8  are provided in the housing. The handles  8  (FIGS. 2 and 3) are slidably mounted in sockets  9  in the corners of the outer free ends of the shells  2  and  3  for movement between retracted positions (not shown) in the housing  1 , and extended, use positions. The handles  8  are retained in the retracted, non-use positions by small latches  11 , which are pivotally mounted on the ends of the shells  2  and  3  for rotation into and out of the path of travel of the handles  8 . 
     The patient&#39;s head and neck are supported by a headrest generally indicated at  12 . The headrest  12  is defined by a platform  13  carrying a cushion  14 . The platform  13  is a thin, metal, generally L-shaped panel. A short arm  16  at one end of the platform  13  includes keyhole slots  17  for releasably mounting the platform  13  on pins  18  extending outwardly from a plate  20  (FIGS. 4 and 5) on one end  21  of the shell  2 . The sides of the patient&#39;s head are covered by a hood  23 , which is integral with the cushion  14 . 
     The shell  2  contains a plurality of spaced apart strips  24  (in this case nylon) for supporting the torso of a patient. The strips  24  extend transversely of the housing between the sides of the shell  2 . The spaced apart strips  24  promote air flow around the patient&#39;s torso. However, other supports with openings permitting air circulation around the patient can be used. For example, the strips  24  can be replaced by a perforated sheet or panel. 
     An inflatable, semicylindrical canopy generally indicated at  25  is mounted on the open top of the shell  2 . The canopy  25  is defined by outer and inner shells  26  and  27 , respectively, and arcuate end walls  29  and  30 . The canopy  25  is stored in the shell  3  when the housing  1  is closed, i.e. not in use. After the housing  1  is opened, the canopy is removed and inflated using CO 2  cartridges  31  carried by the canopy. In order to inflate the canopy  25 , an actuation cord  32  is pulled to open a valve  33  on one of the cartridges  31 , admitting CO 2  to the canopy through the valve. Excess pressure in the canopy  25  is released using hose  35  containing a one-way exhaust valve. The canopy  25  is attached to flanges  36  on the periphery of the shell  2  to surround the top and sides of the torso of the patient. The head and neck of the patient extend through a generally semicircular notch  38  in one end wall  29 , and the hips and legs of the patient extend through a similar notch  39  in the other end wall  30  (FIG. 8) of the canopy  25 . Notches  40  in the bottom side edges of the canopy  25  receive the arms of the patient, so that the arms extend out of the canopy. 
     The arms of the patient are covered by insulated sleeves  41 . Each sleeve  41  is attached to the canopy  25  by a flap  42  sewn to the sleeve  41 , straps  43  and buckles  44 . With the buckle  44  released, the sleeve  41  can be moved to accept a patient&#39;s arm. Once the arm is positioned in the sleeve  41 , the buckle  44  is closed to secure the arm in position against the canopy  25 . As best shown in FIG. 6, the sleeve  41  is tubular with a closed end  46  and an open end  47  for receiving a patient&#39;s arm. A zipper  49  extends longitudinally of the sleeve  41  permitting access to a patient&#39;s arm for connecting an IV line or for administering medicine. 
     With the canopy  25  closed, the torso of the patient is warmed using a hot air system. Referring to FIG. 7, the hot air heating system includes a blower  51  mounted in the shell  3 . The blower  51  receives air via an opening  52  in one end of the shell  3 . The air is circulated between the shells  2  and  3 . Air exhausted from one end of the sheet  2  through an opening (not shown) flows through the opening  52  into the shell  3 . The opening  52  and the opening the shell  2  are closed when the apparatus is not in use, i.e. during storage or transport. The air discharged from the blower  51  passes through a duct  54  containing a pair of heating elements and a heat exchanger (illustrated schematically at  55 ), and then through a flexible tube  56  and an opening (not shown) in the shell  3 . The warm air passes through plastic connectors  57  at the ends of the shells  2  and  3 . The holes in the shells  2  and  3  are plugged by canopies (not shown) fixed to the shells when the system is not in use. The warm air enters into one end of a box  59  in one end of the shell  2 . A manifold  60  (FIG.  9 ), defined by a plastic tube with a closed outer free end (not shown) extends out of the box  59  across the end of the shell  2 . A pair of plastic tubes or ducts  62  extend out of the manifold  60  longitudinally of the shell  2 . The closed outer to ends of the ducts  60  are anchored to the end wall of the shell  2 . Perforations  63  in the manifold  60  and the ducts  62  discharge warm air into the shell  2  beneath the strips  24 . 
     A flexible tube  64  extending out of the top of the box  59  carries warm air to a manifold  66  (FIG. 8) extending transversely of one end of the canopy  25 . Ducts  67  carry air from the manifold  66 , the length of the canopy. The free ends of the manifold  66  and of the ducts  67  are closed. Perforations  68  in the manifold  66  and in the ducts  67  discharge warm air into the top of the chamber defined by the shell  2  and the canopy  25 . 
     Referring again to FIG. 7, the interior of the shell  3  is divided by a partition  70  into a compartment  71  containing the blower  51 , the duct  54 , the heaters and heat exchangers  55  and the tube  56 , and a storage compartment  72  containing a control box  74 . The controls (not shown) for the blower  51 , heater  55  and the heater in the cushion  12  are located on a control panel  75  (FIG. 2) which forms the outer wall of the control box  74  and is accessible from outside of the shell. The control box has preset controls for the speed of the blower  51  and the intensities of the heaters to provide different levels of heating power to the torso of a victim. The storage compartment  72  is used to store the canopy  25  and the head supporting elements during storage or transporting. 
     When the apparatus is not in use, the storage compartment  72  is closed by a panel  79 , which is also used as a support for the legs of a patient during use of the apparatus. The cover/leg support panel  79  supports the legs of the patient in an inclined position. For such purpose, a leg  81  is connected to one end of the panel  79  by a piano hinge  82 . The bottom end of the leg  81  is maintained in position by a flange  84  extending around the two sides and the free end of the shell  3 . 
     Referring to FIG. 11, an insulated bag  85  is used to cover the legs of a patient. The bag  85  is tubular with a closed bottom end  86  and an open top end  87  for receiving the patient&#39;s legs. A longitudinally extending zipper  89  facilitates insertion of the legs into the bag. A second zipper (not shown) extends across the closed end  86  of the bag  85  to facilitate access to the feet of a patient, without opening the zipper  89 . The bag  76  is made snug around the legs of a patient by straps  90  and buckles  91 . During storage or transporting of the apparatus, the bag  76  for the patient&#39;s legs remains on the panel  79 . 
     Thus, in its simplest form the apparatus described above includes a stretcher for supporting a hypothermia victim while warm air is circulated around the torso of the victim. The invention can be incorporated in a modified, commercially available stokes litter. Such a device would be admirably suited to certain search and rescue operations, e.g. ground search and rescue. 
     It should also be noted that the apparatus described herein can be used for complete treatment of hypothermia victims in the field, including the administering of warm IV fluid to correct dehydration and improve circulation, and warm oxygen to assist in the oxygenation of tissues and decrease the risk of infection. An IV fluid bag and an O 2  tank are carried in the stretcher beneath a victim. The containers are warmed by activating the heating system before placing a patient on the stretcher.