Field-deployable stretcher with forced air warming system

Abstract: A portable, forced air apparatus for warming a hypothermia victim in the field includes a stretcher (2,3), strips (24) of material extending across the stretcher (2,3) for supporting the torso of the victim above the stretcher bottom (7), a canopy (25) for covering the victim's torso, a blower operated heater (51,55) in a compartment in the stretcher (2,3) beneath the victim's legs for delivering hot air to the canopy (25) in the area of the torso for warming the victim's body, a heated head and neck support (13) for controlled warming of the victim's head and neck, and sleeves (41,76) for covering the victim'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 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'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. DISCUSSION OF THE PRIOR ART Warming apparatuses, some of which are portable, are disclosed by United States Patents Nos. 5,300,101, which issued to S.D. Augustine et al on April 5, 1994; 5,304,213, which issued to L.D. Berke et al on April 19, 1994; 5,336,249, which issued to I. Mahawili on August 9, 1994; 5,350,417, which issued to S.D. Augustine on September 27, 1994; 5,975,081, which issued to D.D. Hood et al on November 2, 1999 representing the closest prior art, and 6,001,057, which issued to R.A. Bongiovanni et al on December 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'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'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's body. Another object of the invention is to provide a portable warming apparatus which can be used to warm a victim'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'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 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 spaced apart from said bottom wall and extending between said side walls for supporting the torso of a hypothermia victim above and spaced apart from the bottom wall of the stretcher; openings in said support permitting the circulation of warm air completely around the torso of a victim, a canopy for covering the torso of a victim and together with said stretcher defining a heating chamber completely around the torso of a victim; heating ducts in said chamber above and below said support for discharging warm air simultaneously against the front and back of the torso of a victim on said support, 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 ducts, wherein said stretcher includes first and second shells; and hinges pivotally interconnecting said first and second shells for rotation between a compact closed position and an open use position, said support being located in said first shell. 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: Figure 1 is a perspective view of a portable warming apparatus in accordance with the present invention in the closed condition; Figure 2 is a side view of the warming apparatus of Fig. 1 in the open, use condition; Figure 3 is a perspective view of one end of the apparatus of Figs. 1 and 2 in the use condition; Figure 4 is an end view of a housing used in the apparatus of Figs. 1 and 2; Figure 5 is a perspective view of a head and neck support platform use in the apparatus of Figs. 1 to 3; Figure 6 is a perspective view of a sleeve used in the apparatus of Figs. 1 to 3; Figure 7 is a schematic top view of a shell used in the apparatus of Figs. 1 to 3; Figure 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; Figure 9 is a top view of the shell of Fig. 8; Figure 10 is a perspective view of the shell of Fig. 7; and Figure 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 5 on one shell 2, and a notched arm 6, 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, the stretcher including bottom walls 7, side walls 8 and outer end walls 9 contiguous with the bottom and side walls. To facilitate manual lifting and carrying of the housing in the open or use condition, tubular handles 10 are provided in the housing. The handles 10 (Figs. 2 and 3) are slidably mounted in sockets 11 in the corners of the outer free end walls 9 of the shells 2 and 3 for movement between retracted positions (not shown) in the housing 1, and extended, use positions. The handles 10 are retained in the retracted, non-use positions by small latches 12, 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 10. The patient's head and neck are supported by a headrest generally indicated at 13. The headrest 13 is defined by a platform 14 carrying a cushion 15. The platform 14 is a thin, metal, generally L-shaped panel. A short arm 16 at one end of the platform 14 includes keyhole slots 17 for releasably mounting the platform 14 on pins 18 extending outwardly from a plate 20 (Figs. 4 and 5) on one end wall 9 of the shell 2. The sides of the patient's head are covered by a hood 23, which is integral with the cushion 15. 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 side walls 8 of the shell 2. The spaced apart strips 24 promote air flow around the patient'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'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's arm. A zipper 49 extends longitudinally of the sleeve 41 permitting access to a patient'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 the inner end of the shell 3. The air is circulated between the shells 2 and 3. Air exhausted from one end of the shell 2 through an opening (not shown) flows through the opening 52 into the shell 3. The opening 52 and the opening of 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 ends of the ducts 60 are anchored to the inner 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 8 and the free end 9 of the shell 3. Referring to Fig. 11, an insulated bag 76 is used to cover the legs of a patient. The bag 76 is tubular with a closed bottom end 86 and an open top end 87 for receiving the patient'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 76 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'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.

Claims: A portable apparatus for warming a hypothermia victim comprising a stretcher, said stretcher (2,3) including a bottom wall (7), side walls (8) and end walls (9) contiguous with each other; a support (24) spaced apart from said bottom wall (7) and extending between said side walls (8) for supporting the torso of a hypothermia victim above and spaced apart from the bottom wall (9) of the stretcher (2,3); openings in said support (24) permitting the circulation of warm air completely around the torso of a victim, a canopy (25) for covering the torso of a victim and together with said stretcher (2,3) defining a heating chamber completely around the torso of a victim; heating ducts (62, 67) in said chamber above and below said support (24) for discharging warm air simultaneously against the front and back of the torso of a victim on said support (24), whereby the warm air circulates through said openings around the torso; and a forced air heater (55) for warming ambient air, and delivering the warm air to the heating ducts (62,67), characterised in that said stretcher (2,3) includes first and second shells (2,3); and hinges (4) pivotally interconnecting said first and second shells (2,3) for rotation between a compact closed position and an open use position, said support (24) being located in said first shell (2). The apparatus of claim 1, wherein each said first and second shell (2,3) includes a bottom wall (7), side walls (8), end walls (9) and an open top end. The apparatus of claim 2, wherein said support (24) includes a plurality of spaced apart strips (24) extending across the open top end of said first shell (2) for supporting the torso of a victim. The apparatus of claim 1, wherein said canopy (25) includes an inflatable, semicylindrical body having first and second closed ends (29,30), a first semicircular opening (38) in said first end (29) for receiving the neck of a victim, and a second semicircular opening (39) in said second end (30) for receiving the bottom of the body of a victim. The apparatus of claim 4, wherein said canopy (25) is inflatable. The apparatus of claim 1, including a heated headrest (13) for supporting the head and neck of a victim. The apparatus of claim 6, wherein said headrest (13) includes a platform (14) for removable connection to one end of said stretcher (24), a heated cushion (15) for supporting the head of a victim of hypothermia, and a hood (23) for covering the sides of the head of the victim. The apparatus of claim 1, wherein said forced air heater (55) includes a blower (51) in said second shell (3) for receiving ambient air, a heater (55) in fluid communication with said blower (51) for warming ambient air, a first manifold (60) in one end of said first shell (2) for receiving warm air from said heater; a second manifold (66) in said canopy (25) for receiving warm air from said heater (55), said first and second manifolds (60,66) being connected to said heating ducts (62,67) for distributing warm air thereto. The apparatus of claim 8, wherein said first manifold (60) extends transversely of said one end of said first shell (2), said second manifold (66) extends transversely of one end of said canopy (25), and said heating ducts (62, 67) extend longitudinally of said first shell (2) and said canopy (25). The apparatus of claim 1, including a panel (79) in said second shell (3) for supporting the legs of a victim, and a collapsible leg (81) on said panel (79) for supporting the panel and the legs of a victim in an inclined position. The apparatus of claim 10, including a bag (85) for covering the legs of a victim during warming of the torso to prevent heat loss by the legs. The apparatus of claim 11, including sleeves (41) for covering the arms of a victim during warming of the torso to prevent heat loss by the arms.

Inventors: DUCHARME MICHEL B, FRIM JOHN, DUCHARME, MICHEL B., FRIM, JOHN
Applicants: CANADA MINISTER DEFENCE, HER MAJESTY THE QUEEN AS REPRESENTED BY THE MINISTER OF NATIONAL DEFENCE
Application year: 2001
Main classification: A61F7
IPC codes: A61G10, A61F7, A61G1