Patent Publication Number: US-2021177677-A1

Title: Rapid evacuation sled for patients and victims

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part (CIP) application of U.S. application Ser. No. 15/392,792, filed on Dec. 28, 2016, which herein is incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a rapid evacuation device and method for patients and victims, and more particularly to a fold-up, wheeled, patient-enclosing sled for rapid evacuation during emergency and non-emergency situations. More particularly, the invention relates to such a compact device that folds up for stowage, but can be quickly deployed and used to evacuate an individual. 
     2. Background Art 
     Evacuation sleds are used by hospitals, assisted living facilities, emergency services, etc., to rapidly and safely evacuate patients from danger zones, such as flood areas, fires, explosions, etc., or to transport patients from one location to another. The patient is typically transferred from a bed into the r sled, lowered to the floor, and then evacuated by pulling or dragging a tow strap affixed to the sled. An efficient evacuation sled can be deployed and used by a single nurse or other caregiver. An evacuation mattress is disclosed in International Application Number PCT/NL 86/00015, published Dec. 18, 1986 under No. WO 86/07253, based on a Netherlands application filed Jun. 12, 1985. The mattress is characterized by belts or ropes to be put around the patient, which are permanently fastened to the sled. Such a mattress, while very useful, may be relatively expensive to buy, store, and maintain. 
     While many sled-type patient evacuation devices are known (such as the evacuation sled disclosed in U.S. Patent Publication No. 2007/0278754 to Walkingshaw), these sleds require several caregivers to transfer the patient into the sled for evacuation, and typically comprise one thin sheet of semi-flexible plastic. The sleds are then dragged through the hospital, down numerous flights of stairs, and then to an evacuation center where the patient waits (often for hours) for transportation to a hospital, where the patient must be removed from the sled and placed in a bed (again requiring several caregivers). This leads to problems such as contusions in the patient from being bounced down steps, patient hypothermia, and the necessity for many caregivers to perform the multiple patient-transfer steps. 
     Other known structures for evacuating non-ambulatory persons include boards or mats to support the patient. For example, U.S. Pat. No. 4,793,008 to Johansson discloses rigid mats with straps, respectively placed beneath the patient&#39;s chest and thighs. A relatively complicated Rescue Transportation Mattress is disclosed in U.S. Pat. No. 4,736,474 to Moran et al., wherein an inflatable support member and crossed straps are used to secure the person being transported. Again, such solutions do little for a quick, safe, and warm evacuation of a patient from a facility during an emergency. 
     A commercially successful evacuation sled is the Evacusled™. This is a tough plastic sheath, which surrounds the patient while the patient is still in his/her mattress. See, for example, U.S. Pat. No. 8,713,731. Wheels on the bottom provide enhanced mobility, and pull straps on front and back allow easy maneuvering. A drawback to this design is that the sheath must be positioned underneath the patient&#39;s mattress, and the entire mattress is evacuated together with the patient. See also, U.S. Pat. Nos. 8,938,828; 8,898,839; 8,881,327; 8,672,842; 8,615,829; 8,365,326; 8,316,487; 8,122,543; 8,006,334; and 7,774,877. 
     There are numerous other patents and patent applications employing rigid or semi-rigid supports and belts or straps to secure the person transported to the support. One apparent disadvantage to this use of straps or belts is that they could exert undue or excessive pressure on particular locations on the bodies of some evacuees, such as in the case of recent-surgery patients. Further, such sleds are often hard on the patient-support surface, and provide little cushioning to the patient as he/she is transported (often) over rough surfaces. 
     Thus, what is needed is an economical emergency evacuation sled for evacuating patients from hospitals, subways, homes, high rises, etc., that is capable of operation by a single care-giver, may be folded-up to fit within a compact space, provides a warm and secure cocoon for the patient, allows easy transport over any type of surface (e.g., up and down stairs), provides proper support for all of the patient&#39;s body, allows the patient to feel a high degree of comfort in what is otherwise a very stressful situation, and provides securing means (e.g., straps) to firmly hold the patient in place during transit. 
     SUMMARY 
     The present disclosure endeavors to provide an economical fold-up mattress for patients that overcomes certain of the problems noted above. 
     According to a first aspect of the present invention, a foldup patient-evacuation sled has a bottom sheet having a head end and a foot end. A foam mattress is disposed above the bottom sheet, and a patient support sheet is disposed above the mattress. The bottom sheet, the mattress, and the patient support sheet form a sandwiched bottom, a sandwiched left side, and a sandwiched right side. The sandwiched left side and the sandwiched right side are preferably dimensioned to respectively enclose at least portions of left and right sides of a patient lying on the sandwiched bottom. The bottom sheet and the patient support sheet preferably form a sandwiched margin left side and a sandwiched margin right side. A foot section is coupled to the bottom sheet and is dimensioned to substantially enclose the patient&#39;s feet and calves when the foot section is folded upward over the calves of the patient. The foot section is configured to fit beneath the sandwiched left side and the sandwiched right side when the patient is strapped within the sled. A plurality of spinal boards is disposed substantially perpendicular to a longitudinal axis of the sled, each spinal board being disposed above the bottom sheet and spaced apart from each other so that the sled may be folded in the direction of the longitudinal axis. The plurality of spinal boards is disposed more toward a head end of the sled than a foot end of the sled. At least one anti-wear surface is disposed on a bottom surface of the bottom sheet, the at least one anti-wear surface being disposed more toward the head end of the sled than the foot end of the sled. A plurality of wheel assemblies is mounted on each spinal board, each wheel assembly having a wheel portion extending through respective holes in the bottom sheet. 
     According to a second aspect of the present invention, a patient-evacuation sleds has a flexible bottom plastic sheet having a head end and a foot end. A foam mattress is disposed above the bottom sheet. A flexible plastic patient support sheet is disposed above the foam mattress. A semi-rigid plastic sheet is disposed below the bottom sheet. At least three spinal boards are disposed between the bottom sheet and the foam mattress, each spinal board extending in a direction substantially perpendicular to a longitudinal axis of the patient-evacuation mattress and having at least five wheel assemblies coupled to a bottom surface thereof. The bottom sheet and the semi-rigid plastic sheet each have at least one opening therein configured so that the spinal board wheel assemblies extend therethrough. The at least three spinal boards are disposed more toward the head end than the foot end of the bottom sheet. The bottom sheet and the patient support sheet are preferably sewn together around at least a majority of a periphery thereof, to form a margin zone, which has substantially no foam mattress between the bottom sheet and the patient support sheet. At least chest, waist, and knee straps are coupled to the margin zone and are disposed substantially perpendicular to a longitudinal axis of the sled. The chest, waist, and knee straps are configured to enclose a patient lying on the patient support surface such that at least a portion of the foam mattress encloses at least a portion of the patient. 
     According to a third aspect of the present invention, a patient evacuation sled has a bottom flexible plastic sheet, a foam layer disposed above the bottom sheet, and at least one rigid spinal board disposed between the bottom sheet and the foam layer. A patient support plastic sheet is disposed above the foam layer. The bottom sheet, the foam layer, and the patient support sheet form a sandwiched portion configured to underlie a patient lying on the patient support sheet. Peripheral edge portions of the bottom sheet and the patient support sheet are coupled together with substantially no foam layer therebetween. A plurality of substantially horizontal straps is disposed substantially perpendicular to a longitudinal axis of the sled, and is coupled to the peripheral edge portions, and configured to, when tightened, at least partially enclose said patient in a cylindrically shaped cocoon. A plurality of wheel assemblies is coupled to each of the at least one spinal boards, at least a portion of each wheel assembly extending through corresponding holes in the bottom sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a patient cocooned in the foldup patient evacuation sled according to a first embodiment of the present invention. 
         FIG. 2  is a front view of the  FIG. 1  embodiment. 
         FIG. 3  is a bottom perspective view of the  FIG. 1  embodiment. 
         FIG. 4  is a cross-section of a portion of the  FIG. 1  embodiment. 
         FIGS. 5-6  are perspective front views of the bariatric version of foldup evacuation sled according to an embodiment of the present invention. 
         FIG. 7  is a perspective rear view of the bariatric version of foldup evacuation sled according to an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of the cross section A-A′ of the bariatric version of fold up evacuation sled shown in  FIG. 7 . 
         FIGS. 9A-9C  show perspective views of the bariatric version of the foldup evacuation sled while the sled is being rolled up, folded, and stored in a pouch or bag, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. 
     As to nomenclature (and with reference to  FIG. 1 ), each evacuation sled  10  has a “head” or “top” end  12  (where the head of a patient  1  will be positioned), a “foot” end  14 , a “left” side  16  (when viewed from the supine patient&#39;s position), and a “right” side  18 . With the patient  1  lying in the sled positioned on the ground, as in  FIG. 1 , “above” will refer to the direction in which the patient looks, and “below” will refer to the opposite direction. The mattress has a longitudinal axis from the head end  12  to the foot end  14 . As can be seen, a portion  161  of the left side of the sled is configured to at least partially enclose the left side of the patient when the various straps are tightened. This provides a comforting cocoon for the patient in the sled, and also adds to the structural strength of the partially-cylindrically-shaped patient-and-sled combination. A portion  181  of the right side of the sled is also configured to enclose at least a portion of the patient in the sled similar to the portion  161 . As will be described further below, at least a portion of the portions  161  and  181  will include foam mattress to further comfort and cushion the patient. 
       FIG. 1  is a front perspective view of the patient evacuation sled  10  according to a first embodiment of the present invention. The sled can be folded up in a direction of the longitudinal axis, generally in about three, four, or five folds. Preferably, the folded-up mattress is approximately 20-36 inches long, 20-36 inches wide, 3-6 inches thick, and weighs approximately 14-18 pounds. An optional label pouch may comprises a clear plastic envelope which may contain information such as patient information, mattress information, hospital information, or a blank sheet which may be used by triage personnel. The unfolded sled may be approximately 35.5 inches wide×80 inches long×1.5 inches thick, but may be larger or smaller depending on the size of the individual being carried. For example, in bariatric situations, the mattress may be substantially wider in order to accommodate the girth of the patient. 
     As will be described in more detail below with respect to  FIG. 4 , each sled has a bottom sheet  50  of flexible plastic (e.g., Vintex), a wear sheet  94  of semi-rigid PVC plastic disposed below at least a portion of the bottom sheet, and wheel assemblies  64  affixed to rigid (plastic or wood) spinal boards  60 ,  62 , and  63 . Above the spinal boards may be an intermediate sheet  92  of flexible or semi-flexible plastic. A foam mattress  90  is disposed above the spinal boards to support the patient in comfort and give some cushioning to the relatively hard surface of the spinal boards. Above the foam mattress is preferably a PVC stiffening layer  80   a.  A patient support flexible plastic sheet  80  is provided above the stiffening layer  80   a  and is the uppermost sheet upon which the patient will lie. 
     The sled  10  has numerous straps to both secure the patient in place and provide towing of the sled. For example, towing straps  141  and  142  are affixed (by sewing, and/or gluing, and/or heat welding, etc.) at the foot end and are preferably “T”-ed or “V”-ed to a single towing strap. In the preferred embodiment, the head strap is “T”-ed while the foot tow strap is “V”-ed. With these towing straps, a single caregiver can tow the patient and sled to safety, from either the head end or the foot end. The towing is made easier by the provision of the wheel assemblies on the bottom surface, as will be described in further detail below. Similar towing straps  121  and  122  are provided at the head end  12  where towing can be performed in conjunction with or in alternative to use of the straps  141  and  142 . 
     Also at the foot end  14  are, preferably, angled foot end straps  111  and  112 . Each strap has a strap portion  1121  and a connector portion  1122 . Preferably, the strap portions are affixed to the bottom surface of the bottom sheet, while the connector portions are affixed to a top surface of a foot flap  13 , which is affixed to the sled foot end  14  and folds upward over the feet and knees of the patient. When connected and tightened, these angled foot straps provide additional support to the patient and ensure that the corners of the sled-patient combination have no extended corners, which could catch on obstructions during an evacuation. While the preferred embodiment features click-together plastic connectors  1123  and  1124 , any convenient means of connecting the strap portions, such a hook-and-fastener, Velcro, tying, may be adopted. 
     Above the angled foot straps is a horizontal knee strap  120 , preferably comprising a strap portion  1221 , a strap connector portion  1222 , and a connector  1223  (similar to that described above). The knee strap preferably overlies the foot flap  13 , and is preferably affixed to bottom surface of the bottom sheet at the left and right sides  16  and  18 , at points between the ends of loop handles  191  and  192  (to be described further below). The knee strap  120 , when connected together and tightened, further ads to the structural rigidity of the patient-sled combination. A vertical foot strap  190  has a strap connector portion  192  affixed to the foot end  14 , a connector  193 , and a strap portion  191  which is configured to loop up and around the knee strap  120 . When connected and tightened, this vertical foot strap also enhances the integrity of the sled and minimizes any exposed parts during towing. 
     Above the horizontal knee strap  120  are two angled thigh straps  130  and  131 . Like the above-described straps, each angled thigh strap comprises a strap portion  1311 , a strap connector portion  1312 , and a connector  1313 . Preferably, the connector portions  1312  are affixed to the top surface of the foot flap  13  at a substantially forty-five degree angle with respect to the sled longitudinal axis. Of course, the angle may be varied from approximately fifteen degrees through approximately seventy-five degrees. Preferably, the strap portions  1311  are affixed to the bottom surface of the bottom sheet at the same angle as the strap connector portions. When connected and tightened, these angled thigh straps pull the foot flap  13  upward and outward, and ensure that the patient&#39;s thighs are fully covered and not exposed. 
     Also above the horizontal knee strap  120  is a horizontal thigh strap  140 . Like the horizontal knee strap  120 , it comprises a strap portion  1411 , a strap connector portion  1412 , and a connector  1413 . Preferably, the strap portion  1411  is affixed to the bottom sheet at the left side  16 , while the strap connector portion is affixed to the bottom sheet at the right side  18 . When connected and tightened, the horizontal thigh strap  140  also pulls the sandwiched portion (the sandwich comprising the patient support sheet, the stiffening layer, the foam mattress, and the bottom sheet) of the left and right sides up and about at least a portion of the left and right sides of the patient. This tightening also adds to the structural rigidity of the patient-sled combination, and also brings the sandwiched cushioning upward from the bottom of the sled to cushion at least the patient&#39;s sides. 
     Above the horizontal knee strap  140  is, preferably, a horizontal waist strap  150 . This waist strap comprises a strap portion  1511 , a strap connector portion  1512 , and a connector  1513 . Preferably, the strap portion  1511  is affixed to the bottom sheet at the left side  16 , while the strap connector portion  1512  is affixed to the bottom sheet at the right side  18 . When connected and tightened, the horizontal waist strap  150  also pulls the sandwiched portion of the left and right sides up and about at least a portion of the left and right sides of the patient. 
     Above the horizontal waist strap  150  is, preferably, a horizontal chest strap  160 . The chest strap  160  preferably comprises a strap portion  1611 , a strap connector portion  1612 , and a connector  1613 . Preferably, the strap portion  1611  is affixed to the bottom sheet at the left side  16 , while the strap connector portion  1612  is affixed to the bottom sheet at the right side  18 . When connected and tightened, the horizontal chest strap  160  also pulls the sandwiched portion of the left and right sides up and about at least a portion of the left and right sides of the patient, and adds to the structural rigidity of the patient-sled combination. 
     Above the horizontal chest strap  160 , and preferably also above the head of the patient, are two angled head straps  171  and  172 . Each strap preferably comprises a strap portion  1711  affixed to an upper surface of the patient support sheet  80 , a strap connector portion  1712  affixed to the bottom surface of the bottom sheet  50 , and a connector  1713 . Again, tightening these two angled head straps enhances structural integrity and keeps all portions of the patient and sled in one compact bundle. 
     Notable in the current embodiment is that the various straps are color coded to make connections/disconnections quick and easy. For example, the two angled foot straps and the vertical foot strap are preferably black; the horizontal knee strap is preferably green; the angled thigh straps are preferably green; the horizontal thigh strap is preferably yellow; the horizontal waist strap is preferably black; the horizontal chest strap is preferably orange; the angled head straps are preferably orange; the head and foot tow straps are preferably orange; and the loop handles are preferably red. The bottom sheet, the patient support sheet, and the anti-wear sheet are all preferably yellow. Of course, the color scheme(s) can vary, so long as a caregiver can quickly and easily strap/unstrap a patient in a high stress environment. Not also that it is possible to cross-connect the various straps to provide more secure fastening of patients of different dimensions. For example, small-dimensioned patients may benefit by cross-strapping one or more of the horizontal thigh strap, the horizontal waist strap, and the horizontal chest strap. 
     Also in  FIG. 1  are shown head handles  1011  and  1012 , chest handles  1013  and  1014 , waist handles  1015  and  1016 , and knee handles  191  and  192 . Preferably, each handle is a loop handle with the ends thereof affixed to a bottom surface of the bottom sheet  50 . As can be seen, the handles are preferably disposed more toward the head end than the foot end, to support the patient weight, which is typically similarly disposed. 
       FIG. 2  shows a top view of the sled  10  without the patient, where the left and right sides  16  and  18  are opened. As can be seen, the patient support surface  80  extends all the way to the edges of the left and right sides. Notably, the foam mattress does not extend so far. In particular, as mentioned earlier, the “sandwich” portion comprises the patient support sheet  80 , the stiffening layer  80   a,  the foam mattress  90 , and the bottom sheet  50 . This sandwich provides the comfort, protection, safety, and structural stability to the patient-sled. This sandwich portion underlies the patient and encompasses at least portions of the patient&#39;s left and right sides, as shown in  FIG. 1 . However, at peripheral portions of at least the left and right sides  16  and  18  is one or more margin sandwich portions ( 2015  in  FIG. 2 ). In these margin portions, the sandwich comprises all except for the foam mattress. This gives a flatter surface on which to affix (e.g., stitch) the various straps and handles. In order to provide further structural rigidity to these margin portions, however, the preferred embodiment includes a reinforcing strap  2017  running longitudinally around the margin portions. Thus, the preferred margin sandwich portion also includes this reinforcing strap. In the preferred embodiments, this reinforcing strap, the handles, the horizontal and vertical straps all comprise nylon webbing similar in material and dimensions to that used in auto seat belts. 
       FIG. 3  is a perspective bottom view of the sled  10  showing the bottom surface of the bottom sheet  50  and the PVC ant-wear sheet  94  affixed (e.g., stitched) thereto. This anti-wear sheet is semi-rigid PVD several centimeters thick, and adds durability to the bottom of the sled in instances where multiple evacuations or extended evacuations are needed. Notably, the openings  941  in the sheet  94  are not affixed to the bottom sheet adjacent these openings. This allows the ant-wear sheet  94  to offer flexibility (give and take in shear) as the sled is moved. Three optional anti-skid strips  31 ,  32 , and  33  are also affixed to the bottom of the bottom sheet  50 , in embodiments where a braking function may be desirable. 
       FIG. 4  has been described above. Note that it is a partial cross-section; in the preferred embodiment there are four spinal boards disposed substantially perpendicular to the sled longitudinal axis. In  FIG. 4 , the bottom sheet  50  is shown, with overlying, rigid spinal boards  60 ,  62 ,  63 . Fixed to each spinal board are at least two (preferably five) wheel assemblies  64  which have wheel portions protruding through openings in the bottom sheet  50  and the anti-wear sheet  94 . Preferably, fabric wear strips  31 ,  32 ,  33  can be affixed to the bottom sheet  50  and/or the anti-wear sheet  94 , to protect the bottom sheet  50  when the mattress  10  is dragged along a surface. These wear strips may comprise Kevlar (which has an excellent co-efficient factor), ballistic nylon (which is a thick, tough, synthetic nylon fabric), or other suitable fabric. 
     In  FIG. 4 , the patient support sheet  80  preferably lies under the patient, and an optional second layer of SoffTICK™  80   a  may be sewn, glued, stapled, and/or welded underneath the patient support sheet  80 . Beneath this sheet is the foam mattress  90 , which is used as a cushion and to conserve warmth for the patient. The foam mattress  90  may be ½ inch thick and be dimensioned slightly smaller than the patient support sheet  80 . The foam material may comprise a fire-retardant, anti-fungal, open-cell material such as Vita B2721T1N urethane foam, available from Vitafoam Canada. Beneath the foam mattress  90  is, optionally, a reinforcing plastic sheet  92 , preferably fixed to the foam mattress  90  by gluing, stapling, sewing, or welding. The reinforcing plastic sheet  92  preferably comprises two parallel sheets of rigid or semi-rigid plastic connected together by a series of orthogonal connecting walls running substantially perpendicular to the mattress longitudinal axis. A preferred reinforcing plastic sheet is Polyethylene Plastic which can be made by Modern Age Plastics Inc. of Toronto, Canada. The reinforcing plastic sheet  92  is preferably 1/16 to ½ inch thick, most preferably ⅛ inch thick, and dimensioned substantially to be ⅛ to ½ inches (preferably ¼ inches) wider/longer than the foam mattress  90 . The reinforcing plastic sheet  92  provides structural stability to the foam mattress  90 , and further shields the patient from the ground and the spinal boards. This sheet may be provided above and/or below the foam mattress. 
     The main role of the spinal boards  60 ,  62 ,  63  (and  64 , not shown) is to provide additional support in the back and spinal regions. This support is particularly important when transporting an injured person (e.g., when lowering from a window, up or down a flight of stairs, etc.) because, not only will the person require additional back support, but the caregiver will require that the mattress stay somewhat planar when the person is being transported. The spinal boards provide substantial rigidity transverse to the longitudinal axis while the patient would provide needed rigidity to the longitudinal axis. 
     Also in  FIG. 4 , the spinal boards  60 ,  62 , and  63  are shown disposed between the plastic reinforcing sheet  92  and the bottom sheet  50 . Each spinal board is typically constructed from a plastic material (e.g., Polystyrene, PVC, Nylon, or other polymers, including high performance polymers) and has dimensions approximately 0.5×7.5×15.75 inches. While a 15.75 inch board is sufficient for a majority of people, in bariatric cases, the width may be increased to accommodate a larger body type. Alternately, the spinal boards may be placed side by side to increase the overall width. Preferably, the spinal board is a high density polyethylene or HDPE. A preferred plastic is made by Modern Age Plastics Inc., Canada. 
     Each spinal board may include a plurality (e.g., 3, 4, 5, or 6) of square openings, each approximately 1 inch×1 inch, where each is capable of receiving a wheel assembly  64  or other wheel structure. A wheel assembly  64  may be snapped, or clipped, into each square opening. Using replaceable wheel assemblies  64  that may be snapped into and out of the spinal board, as opposed to those that are permanently attached or integrated therein (which are also within the scope of the invention), allows for easy replacement should a wheel break or otherwise malfunction. This configuration also allows for interchanging the wheels for different sizes/weights/surfaces. Each wheel may be generally comprised of a single wheel within a housing, typically with an axle. The housing is configured to fit snugly within the square opening in the spinal board, and may include side pressure clips, which snap the wheel assembly in place once in the spinal board. However, it should be appreciated that the roll-up mattress is not limited to this type of wheel assembly. If the mattress is used in a snowy region, for example, it may be advantageous to completely omit casters all together and/or to use small skid plates. 
     In a preferred embodiment, little-to-none of the materials used to fabricate the spinal board would be metallic or any other material that may interfere with an X-ray machine. This is important because the foldup mattress  10  may stay with the patient even during X-ray procedures, particularly when the patient is in a delicate state and should not be moved until X-rays are complete. Suitable materials would include, for example, various plastics, Polystyrene, PVC, Nylon, or other polymers, including high performance polymers. Each spinal board preferably has plural wheel assemblies  64 , which provide proper rolling support for the patient. Preferably, the plural wheel assemblies are respectively disposed along three axes substantially perpendicular to the mattress longitudinal axis. The wheel assemblies may comprise individual wheels mounted on individual axles, but may comprise cylindrical rollers extending all or part way across the length of the spinal board, and/or ball-bearings, and/or any known and convenient means to support the patient&#39;s movement along a surface. The most preferred embodiment has five individual wheel assemblies  64  fixed to the bottom of each spinal board, with one wheel assembly near each of the four corners of the spinal board, and one wheel assembly disposed substantially in the center of the spinal board. 
     Further in  FIG. 4 , the bottom sheet  50  has one or more holes or openings therein for the wheels to extend through so that the wheels contact the surface. In a preferred embodiment, a wheel bracket which holds the wheel axle is used to fix the spinal board to the bottom sheet  50 . Beneath the bottom sheet  50  is, preferably, the anti-wear plastic sheet  94 , which may be similar to the optional reinforcing plastic sheet  92 , but serves not only to reinforce the structural integrity of the mattress  10 , but serves as a skid/wear/slip plate to keep the bottom sheet  50  from being anti-wear reinforcing plastic sheet  94  has one or more opening therein so that the wheel assemblies  64  may be exposed to the surface, as shown schematically in  FIG. 3 . Each wheel assembly preferably comprises a wheel, axle, and bracket/housing, which are all preferably visible from the bottom of the mattress  10 . 
     In the preferred embodiments, the patient support sheet  80  and the bottom sheet  50  are preferably constructed from a material that meets infection control measures, but may also contain microclimate features. In a preferred embodiment, the skin may be constructed from SoffTICK™ Standard Institutional Fabric Ultra 53-14, available from Vintex Inc. at www.vintex.com. Ultra 53-14 is advantageous because it is soft, flame retardant, durable, resistant to bacteria/fungal growth, self-deodorizing, hypo-allergenic, non-irritating and foam compatible, plastic sheet material. The entire bottom sheet  50  may be made from the Ultra 53-14 or from a more durable material. Suitable materials include, for example, Kevlar, or ballistic nylon, which may cover only a portion of the bottom sheet  50 . Forming the entire lower sheet from a single durable material, although typically more expensive than regular skin, would eliminate the need to cut and bond a second material to the lower skin thereby reducing labor and some material costs. 
     An alternative solution to maintaining an anti-fungal and anti-bacterial mattress surface  80  may be to coat the mattress skin with spray-on liquid glass (also referred to as “SiO2 ultra-thin layering”). Spray-on liquid glass is transparent, non-toxic, and can protect virtually any surface against almost any damage from hazards such as water, UV radiation, dirt, heat, and bacterial infections. Liquid glass coating is also flexible and breathable, making it suitable for use on both traditional mattresses and evacuation mattress (e.g., the roll up mattress). 
     The straps may be constructed from a strong fabric woven as flat strips and/or tubes. The flat type of material is more commonly known as webbing. The webbing may be woven from, for example, nylon, polypropylene, polyester, high-modulus polyethylene (e.g., Dyneema®), para-aramid synthetic fiber (e.g., Kevlar®), cotton, flax, and combinations thereof. While the webbing used to form the straps may be flat, for added strength, the webbing may partially encircle a core material, or be folded lengthwise around the core material. To seal the core material within the webbing, the edges of the webbing may be stitched, fused, or otherwise sealed along portions of the length of the strap portion or portions having a core, thereby preventing the core material from becoming disassociated with the webbing. The core material may be, for example, rope, hollow tube, cabling, etc. To the extent that communications or patient-monitoring electronics are incorporated into the evaluation mattress  10 , wires, fiber optics, or other conductors may be embedded within the core (e.g., within a tube or conduit) to communicate signals from end to end. 
     With reference to  FIGS. 5-6 , shown are perspective front views of an embodiment of bariatric version of foldup evacuation sled  3000  of the disclosed invention. With reference to  FIG. 7 , shown is a perspective rear view of an embodiment of bariatric version of foldup evacuation sled  3000  of the disclosed invention. With reference to  FIG. 8 , shown is a cross-sectional view of the cross section A-A′ of the foldup evacuation sled  3000  shown in  FIG. 7 . With reference to  FIGS. 9A-9C , shown are perspective views of the foldup evacuation sled  3000  while the sled  3000  is being rolled up, folded, and stored in a pouch or bag  3600 , respectively. 
     The bariatric version of foldup evacuation sled  3000  of the disclosed invention has a similar structure to the foldup patient evacuation sled  10  shown in  FIGS. 1-4 . However, the bariatric version of the foldup evacuation sled  3000  has double head roll/tow straps and double foot roll/tow straps for pulling, while the foldup patient evacuation sled  10  shown in  FIGS. 1-4  has single head roll/tow strap and foot roll/tow strap. Unlike the sled  10 , the leg/torso cover  3200  of the sled  3000  is no longer simply a foot cover but is more a torso cover that is attached at foot end  3002  of the sled  3000 , given body shape of most bariatrics. This leg/torso cover  3200  is secured with two sets of angled straps  3341 ,  3342 ,  3371 ,  3372  securing strapping: one set of the angled straps  3341 ,  3342  near upper portion of the leg/torso cover  3200  and the other set of the angled straps  3371 ,  3372  near lower portion (near foot end) of the leg/torso cover  3200 . The angled straps  3341 ,  3342 ,  3371 ,  3372  may have black color for easy recognition. The sled  3000  is also reinforced with strap webbing to strengthen the foot end so as to be able to take weight of a person vertically down stairs. These features will be described in detail referring to figures. For compact storage, the bariatric version foldup evacuation sled  3000  is designed to be rolled up from the head end or foot end along the longitudinal direction L ( FIG. 9A ). The folded evacuation sled  3000  ( FIG. 9B ) may be stored in a pouch or bag  3600  ( FIG. 9C ) and conveniently carried by a user. 
     Referring to  FIGS. 5-8 , the bariatric version of foldup evacuation sled  3000  of the disclosed invention includes a bottom sheet  3101 , a first foam mattress  3102  disposed above the bottom sheet  3101 , a second foam mattress  3103  disposed above the first foam mattress  3102 , support sheet  3104  disposed above the second foam mattress  3103 . These bottom sheet  3101 , foam mattresses  3102 ,  3103  and the support sheet  3104  may form a base stack that supports a person (patient, victim, rescue, etc.) lying on the support sheet  3104 . The foam mattresses  3102 ,  3103  are used as a cushion and to conserve warmth for the person. Each foam mattress  3102 ,  3103  may be ½ inch thick and be dimensioned slightly smaller than the support sheet  3104 . The foam material may comprise a fire-retardant, anti-fungal, open-cell material. For example, the foam material may be Vita B2721T1N urethane foam, available from Vitafoam Canada. However, the foam material is not limited to this brand, but may be any fire-retardant, anti-fungal, open-cell material. 
     The foldup evacuation sled  3000  further includes one or more spinal boards  3108  disposed between the bottom sheet  3101  and the second foam mattress  3103 . The first foam mattress  3102  has one or more openings  3102   a  to house the one or more spinal boards  3108 . The spinal boards  3108  are disposed inside the openings of  3102   a  of the first foam mattress  3102 . In the embodiment of the foldup evacuation sled  3000 , the spinal boards  3108  may be placed closer to the head end  3001  than the foot end  3002  to support weight of a person lying on the support sheet  3104 . When the sled  3000  includes two or more spinal boards  3108 , the spinal boards may be spaced apart from each other and may be arranged along the longitudinal direction L. In the embodiment of the disclosed invention, the sled  3000  preferably has four spinal boards  3108  arranged along the longitudinal direction L. The spinal boards  3108  may be placed in the first section  3003  that is a section closer to the head end  3001  than the foot end  3002 . The spinal boards  3108  substantially support a torso of a person when the person is lying on the support sheet  3104 . The spinal boards provide substantial rigidity transverse to the longitudinal axis while the person would provide needed rigidity to the longitudinal axis. 
     The foldup evacuation sled  3000  further includes first internal stiffener sheet  3109  for torso support, and second internal stiffener sheet  3110  for foot/ankle support. These internal stiffener sheets provide additional spinal support. The first stiffener sheet  3109  may be disposed between the spinal board  3018  and the second foal mattress  3103 . The first stiffener sheet  3109  may be placed substantially in the middle of the plurality of the spinal boards  3108  as shown in  FIGS. 7-8 . The second stiffener sheet  3110  may be disposed between the bottom sheet  3101  and the first foam mattress  3102 . The second stiffener sheet  3110  may be placed on a location that substantially corresponds to foot/ankle portion of a person lying on the support sheet  3104 . The second stiffener sheet  3110  may be placed in the second section  3004  where the spinal boards  3108  are not placed. The second foam mattress  3103  may not extend to the portion where the second stiffener sheet  3110  is placed. The internal stiffener sheet  3109 ,  3110  may have a size, for example, 16 inches by 12 inches. 
     Anti-wear sheet  3105  may be affixed to a bottom surface of the bottom sheet  3101 , substantially covering the first section  3003 . The anti-wear sheet  3105  provides durability to the bottom of the sled  3000 . Anti-wear sheet  3105  may be sewn on the bottom sheet  3101 . The anti-wear sheet  3105  is semi-rigid PVD several centimeters thick, and adds durability to the bottom of the sled in instances where multiple evacuations or extended evacuations are needed. A heavy-duty sheet  3106  may be affixed to a bottom surface of the bottom sheet  3101 , substantially covering the second section  3004 . The heavy duty sheet  3106  is coated with anti-fungal, anti-bacterial and fire-retardant materials, and may be sewn on the bottom sheet  3101 . The heavy duty sheet  3106  may have capability to control foot end braking area as well as increasing durability and limited wear and tear. Alternatively, three optional anti-skid strips (see strips  31 ,  32 , and  33  in  FIG. 3 ) may be affixed to the bottom surface of the bottom sheet  3101 , extending through the second section  3004  in embodiments where a braking function may be desirable. 
     The foldup evacuation sled  3000  further includes wheel assemblies  3107  affixed to the rigid spinal board  3108 . The bottom sheet  3101  and anti-wear sheet  3105  may have openings  3107   a  to make the wheels of the wheel assemblies  3107  protrude out of the bottom sheet  3101  and anti-wear sheet  3105 . The wheel assemblies  3107  make the rolling or towing easier when the sled  3000  with a person lying on the support sheet  3104  is rolled or towed on a floor. In the embodiment of the disclosed invention, each spinal board has five (5) wheel assemblies. 
     Optionally, a stiffening layer may be sewn, glued, stapled, and/or welded underneath the support sheet  3104  (see stiffening layer  80   a  in  FIG. 4 ). A reinforcing plastic sheet may be fixed to the foam mattress  3103  by gluing, stapling, sewing, or welding (see reinforcing sheet  92  in  FIG. 4 ). The reinforcing plastic sheet provides structural stability to the foam mattress  3103 , and further shields the person from the ground and the spinal boards. This sheet may be provided above and/or below the foam mattress. 
     At the left and right side peripheral portions  3005 ,  3006  of the sled  3000 , sandwiched margin left side  3111  and sandwiched margin right side  3112  are formed. The support sheet  3104  and the bottom sheet  3101  extends all the way to the edges of the left and right sides of the sled  3000 , while the foam mattresses  3102 ,  3103  may not extend so far. These sandwiched margin left and right sides  3111 ,  3112  may be formed of a margin stack that includes peripheral portions of the bottom sheet  3101  and the support sheet  3104 . The foam mattresses  3102 ,  3103  may not be included in the sandwiched margin left and right sides  3111 ,  3112  to provide flatter surfaces to affix various straps and handles to the sandwiched margin left and right sides  3111 ,  3112 . 
     The foldup evacuation sled  3000  includes a plurality of horizontal straps and angled straps. When connected, the horizontal straps extend along a direction substantially perpendicular to the longitudinal direction L. The horizontal straps may include chest strap  3320 , waist strap  3330 , thigh strap  3350 , and knee straps  3360 . These horizontal straps are color coded to make connections/disconnections quick and easy for healthcare worker as well as lay rescuers. Color coding is for user friendliness so that any lay person can easily deploy the sled, without training, as intuitive matching colors as well as any healthcare trained emergency responder. For example, the chest strap  3320  is preferably orange, the waist strap  3330  is preferably green, thigh strap  3350  is preferably yellow, and knee straps  3360  is preferably blue. However, the color codes are not limited to these colors. 
     When the horizontal straps are tightened, the horizontal straps may pull up left and right peripheral portions of the base stack, which includes the bottom sheet  3101 , foam mattresses  3102 ,  3103  and the support sheet  3104 , to at least partially enclose or cover the left and right sides of a person lying on the support sheet  3104 . These peripheral left and right portions of the base stack, which may be pulled up by the tightened horizontal straps, are referred to as sandwiched left and right sides (or portions)  3113 ,  3114 . This sandwiched sides provides the comfort, protection, safety, and structural stability to the person-sled. This sandwiched portions partially overlie the person lying on the support sheet  3104  and encompasses at least portions of the person&#39;s left and right sides as shown in  FIG. 1 . For example, when the leg/torso cover  3200  is folded upward over the person and the horizontal straps are tightened, the sandwiched left and right sides  3113 ,  3114  may overlie peripheral portions of the leg/torso cover  3200  as shown in  FIGS. 5-6 . When the leg/torso cover  3200  is secured with horizontal straps, the entire sled  3000  becomes fully rigid like a padded backboard with wheels. Essentially, it becomes a fully rigid padded backboard with the leg/torso cover and underside rolling wheel assemblies and built in foot underside braking system. When folded for the storage position (see  FIG. 9B ), the sled becomes compact and rigid to be conveniently stored in a pouch (see  FIG. 9C ). 
     The chest strap  3320  includes a strap portion  3321 , a strap connector portion  3322 , and a connector  3323  that couples the strap portion to the strap connector portion. Preferably, the strap portion  3321  may be affixed to the sandwiched margin left side  3111  and the strap connector portion  3322  may be affixed to the sandwiched margin right side  3112 . The chest strap  3320  is configured to be disposed substantially over chest portion of an adult person lying on the support sheet  3104 . When connected and tightened, the horizontal chest strap  3320  may pull up the sandwiched margin left and right sides  3111 ,  3112  and also sandwiched left and right sides  3113 ,  3114  to at least partially enclose or cover the left and right sides of chest portion of the person. 
     The waist strap  3330  includes a strap portion  3331 , a strap connector portion  3332 , and a connector  3333  that couples the strap portion to the strap connector portion. Preferably, the strap portion  3331  may be affixed to the sandwiched margin left side  3111  and the strap connector portion  3332  may be affixed to the sandwiched margin right side  3112 . The waist strap  3330  is configured to be disposed substantially over waist portion of an adult person lying on the support sheet  3104 . When connected and tightened, the horizontal waist strap  3330  may pull up the sandwiched margin left and right sides  3111 ,  3112  and also sandwiched left and right sides  3113 ,  3114  to at least partially enclose or cover the left and right sides of chest portion of the person. 
     The thigh strap  3350  includes a strap portion  3351 , a strap connector portion  3352 , and a connector  3353  that couples the strap portion to the strap connector portion. Preferably, the strap portion  3351  may be affixed to the sandwiched margin left side  3111  and the strap connector portion  3352  may be affixed to the sandwiched margin right side  3112 . The thigh strap  3350  is configured to be disposed substantially over thigh portion of an adult person lying on the support sheet  3104 . When connected and tightened, the horizontal thigh strap  3350  may pull up the sandwiched margin left and right sides  3111 ,  3112  and also sandwiched left and right sides  3113 ,  3114  to at least partially enclose or cover the left and right sides of chest portion of the person. 
     The knee strap  3360  includes a strap portion  3361 , a strap connector portion  3362 , and a connector  3363  that couples the strap portion to the strap connector portion. Preferably, the strap portion  3361  may be affixed to the sandwiched margin left side  3111  and the strap connector portion  3362  may be affixed to the sandwiched margin right side  3112 . The knee strap  3360  is configured to be disposed substantially over knee portion of an adult person lying on the support sheet  3104 . When connected and tightened, the horizontal knee strap  3360  may pull up the sandwiched margin left and right sides  3111 ,  3112  and also sandwiched left and right sides  3113 ,  3114  to at least partially enclose or cover the left and right sides of chest portion of the person.  FIG. 5  exemplarily shows the chest strap  3320 , waist strap  3330 , thigh straps  3350 , and knee strap  3360 . However, the straps are not limited to these straps, and additional straps may be affixed to the sandwiched margin left and right sides  3111 ,  3112  of the sled  3000 . 
     The bariatric version of the foldup evacuation sled  3000  includes a leg/torso cover  3200 . A lower side of the leg/torso cover  3200  is affixed at the foot end  3002  of the sled  3000 . The leg/torso cover  3200  is designed to fold upward over legs and lower torso portion of an adult person lying on the support sheet  3104 . When folded upward, the leg/torso cover  3200  may substantially cover legs and waist of a person lying on the support sheet  3104 . In order to secure the leg/torso cover  3200 , the knee strap  3360  and thigh strap  3350 , when connected and tightened, overlie the leg/torso cover  3200 . The waist strap  3330 , when connected and tightened, may overlie upper peripheral portion of the leg/torso cover  3200 . 
     The angled straps include left upper angled strap  3341  and right upper angled strap  3342  which are coupled to the leg/torso cover  3200  near upper portion of the leg/torso cover  3200 , left lower angled strap  3371  and right lower angled strap  3372  which are coupled to the leg/torso cover  3200  near lower portion of the leg/torso cover  3200 , left head angled strap  3311  placed at left side near the head end  3001 , and right head angled strap  3312  placed at right side near the head end  3001 . 
     The left upper angled strap  3341  includes strap portion  3341   a,  strap connector portion  3341   b,  and connector  3341   c  that couples the strap portion to the strap connector portion. The right upper angled strap  3342  includes strap portion  3342   a,  strap connector portion  3342   b,  and connector  3342   c  that couples the strap portion to the strap connector portion. Preferably, the strap portions  3341   a,    3342   a  are affixed to sandwiched margin left and right sides  3111 ,  3112 , respectively, and the connector portions  3341   b,    3342   b  are affixed to the top surface of the leg/torso cover  3200 . The strap portions  3341   a,    3342   a  may be affixed to portions of the sandwiched margin left and right sides  3111 ,  3112  between the chest strap  3320  and the waist strap  3330 . The strap portions  3341   a,    3342   a  may be affixed to bottom surfaces of the sandwiched margin left and right sides  3111 ,  3112 . When the strap portions  3341   a,    3342   a  and the connector portions  3341   b,    3342   b  are connected via respective connectors  3341   c,    3342   c,  each of the upper angled straps  3341 ,  3342  extends at a substantially forty-five degree angle with respect to the longitudinal direction L. However, the angle may be varied from approximately fifteen degrees through approximately seventy-five degrees. When connected and tightened, these upper angled straps  3341 ,  3342  pull the leg/torso cover  3200  upward and outward, and ensure that the person&#39;s legs and lower torso are fully covered and not exposed. 
     The left lower angled strap  3371  includes strap portion  3371   a,  strap connector portion  3371   b,  and connector  3371   c  that couples the strap portion to the strap connector portion. The right lower angled strap  3372  includes strap portion  3372   a,  strap connector portion  3372   b,  and connector  3372   c  that couples the strap portion to the strap connector portion. Preferably, the strap portions  3371   a,    3372   a  are affixed to sandwiched margin left and right sides  3111 ,  3112 , respectively, between the foot end  3002  and the knee strap  3360 , and the connector portions  3371   b,    3372   b  are affixed to the top surface of the leg/torso cover  3200 . The strap portions  3371   a,    3372   a  may be affixed to bottom surfaces of the sandwiched margin left and right sides  3111 ,  3112 . When the strap portions  3371   a,    3372   a  and the connector portions  3371   b,    3372   b  are connected via respective connectors  3371   c,    3372   c,  each of the lower angled straps  3371 ,  3372  extends at a substantially forty-five degree angle with respect to the longitudinal direction L. However, the angle may be varied from approximately fifteen degrees through approximately seventy-five degrees. When connected and tightened, these lower angled straps  3371 ,  3372  provide additional support to the person lying on the support sheet  3104  and ensure that the corners of the sled-person combination have no extended corners, which could catch on obstructions during an evacuation. While the preferred embodiment features click-together plastic connectors  3341   c,    3342   c,    3371   c,    3372   c,  any convenient means of connecting the strap portions, such a hook-and-fastener, Velcro, tying, may be adopted. 
     The left head angled strap  3311  includes strap portion  3311   a,  strap connector portion  3311   b,  and connector  3311   c  that couples the strap portion to the strap connector portion. The right head angled strap  3312  includes strap portion  3312   a,  strap connector portion  3312   b,  and connector  3312   c  that couples the strap portion to the strap connector portion. Preferably, the strap portions  3311   a,    3312   a  are affixed to sandwiched margin left and right sides  3111 ,  3112 , respectively, and the connector portions  3311   b,    3312   b  are affixed to the top surface of the support sheet  3104 . When connected and tightened, the head angled straps  3311 ,  3312  enhances structural integrity and keeps all portions of the person and sled in one compact bundle. 
     The foldup evacuation sled  3000  further includes a plurality of loop/side carrying handles. For example, the loop/side carrying handles may include left and right head loop/side carrying handle  3401 ,  3402  near head/neck portion of a person, left and right chest loop/side carrying handles  3403 ,  3404  near the waist strap  3330 , left and right waist loop/side carrying handles  3405 ,  3406  placed between the waist strap  3330  and thigh strap  3350 , and left and right knee loop/side carrying handles  3407 ,  3408  placed near the knee strap  3360 . The left and right loop/side carrying handles may be affixed to the sandwiched margin left and right sides  3111 ,  3112 , respectively. As shown in  FIG. 5 , the loop/side carrying handles are preferably disposed more toward the head end  3001  than the foot end  3002 , to support the person&#39;s weight, which is typically similarly disposed.  FIG. 5  exemplarily shows the four left and four right loop/side carrying handles. However, the number of the loop/side carrying handles is not limited to these numbers. There may be more loop/side carrying handles. The positions of the loop/side carrying handles are not limited to these positions as shown in  FIG. 5 . 
     The foldup evacuation sled  3000  further includes double head roll/tow straps  3511 ,  3512  affixed to the head end portion of the sled  3000  and double foot roll/tow straps  3521 ,  3522  affixed to foot end portion of the sled  3000 . The head roll/tow straps  3511 ,  3512  may be affixed to head end portion of the bottom sheet  3101 , and the foot roll/tow straps  3521 ,  3522  may be affixed to foot end portion of the bottom sheet  3101 . By providing double head and foot roll/tow straps, two caregivers or rescuers may conveniently pull the sled  3000  from the head end or from the foot end, while a person is lying on the support sheet  3104 . The foot roll/tow straps  3521 ,  3522  are designed for one or more rescuers to roll or tow the sled  3000  on underside wheel assemblies to safety from the foot end while a person is lying on the sled. One or more rescuers at foot end are lead rescuers and second rescuers may be at head end; alternatively, lead rescuers may roll or tow the sled  3000  without the assistance of a second rescuer. The sled  3000  can be rolled or towed from either head end or foot end horizontally. However, when the sled  3000  is rolled or towed in a downward direction such as a slope or downstairs, the sled  3000  is designed to be only rolled or towed from the foot end, because the sled  3000  is designed such that underside foot end area is the built-in braking system area for control during substantially vertical or downward evacuation. The towing is made easier by the provision of the wheel assemblies  3107  on the bottom surface of the sled  3000 . 
     The individual components shown in outline or designated by blocks in the attached drawings are all well-known in the sled and mattress arts, and their specific construction and operation are not critical to the operation or best mode for carrying out the invention. 
     While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. All U.S. and foreign patent documents, all articles, brochures, and all other published documents discussed above are hereby incorporated by reference into the Detailed Description.