Patent Publication Number: US-6701558-B2

Title: Patient support surface

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. Ser. No. 09/537,037 filed Mar. 28, 2000 now U.S. Pat. No. 6,516,483. U.S. Ser. No. 09/537,037 is assigned to the same assignee as this application. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to patient support surfaces and positioners and more particularly to pressure management and skin shear-reducing surfaces and positioners. 
     Care providers are well aware that patient support surfaces and positioners can play a significant role in the creation or prevention of pressure ulcers. Patients undergoing surgical procedures, medical procedures, or recovery from the same, have their entire body and/or portions of their body supported by patient support surfaces and positioners. Portions of the patient&#39;s skin may be subjected to very high pressures and shear forces exerted by the material underlining skin resulting in tissue loads that restrict blood flow to a particular area of the skin resulting in tissue damage or necrosis. This is a major cause of pressure ulcers. 
     The described invention reduces the risk of skin shear and decreases tissue load. The disclosed surfaces and positioners distribute the patient&#39;s weight more evenly across the surface to significantly decrease pressure on the body&#39;s bony prominences. The disclosed surfaces are designed to cradle the patient and reduce pressure on the bony prominences, thus reducing patient interface pressure. This facilitates effective distribution of the patient&#39;s tissue load evenly over the surface. This is accomplished in certain preferred embodiments by using a highly stretchable cover overlying the patient supporting surface of a cushion adapted to more evenly distribute the patient&#39;s weight. The cushion may be an air cushion, a foam pad, or a combination of foam pads having different densities and recovery ratings, an air impregnated gel, or any combination of these cushioning materials. 
     Decreasing interface pressure between the support surface and the patient does not necessarily reduce skin shear. Similarly, it is known that common gel overlays which significantly reduce skin shear can actually increase interface pressure. The present invention comprises an anti-shear liner or layer which combines the four-way stretch cover material with a friction-reducing and anti-shear layer. 
     A patient support surface or positioner according to the present invention includes an anti-shear liner, a cover, and a cushion layer. The anti-shear liner is disposed in selected areas between the cover and the cushion layer to allow the cover to slip in such selected areas relative to the cushion layer. The cover is preferably configured to be highly stretchable. The cover preferably may be a rubber-like material which is characterized by its stretchability in one direction being greater than its stretchability in an orthogonal direction. When the patient support is longitudinally extending with a foot end and a head end, a stretchable cover may be positioned on the support so that it is more stretchable in the longitudinal direction. 
     The cushion may be formed by a plurality of air cavities, a plurality of foam layers, gel material, or any combination thereof. The foam layers may be selected from a group of slow recovery foam, low density foam, high density foam, reduced density foam, medium density foam, and closed cell foam. The air cushion may include a plurality of sealed air bladders in combination with inflatable bladders. Foam layers may be used in different combinations in different areas of the support, to support different areas of the patient&#39;s body differently. Likewise sealed air bladders and inflatable air bladders may be used in different combinations and in different areas of the surface, to support different parts of the patient&#39;s body differently. The anti-shear layer may be disposed under the entire patient supporting surface of the cover or under selected portions of the cover, depending upon the surface characteristics desired. 
     A process of distributing patient weight and minimizing shear on the patient&#39;s skin includes the steps of providing a cover, providing a cushion, and providing an anti-shear layer over selected portions of the cushion. The combination of the cover, anti-shear layer, and cushion, with the anti-shear layer disposed between the cover and the cushion, is placed on a patient support such as a surgery table, bed or stretcher. The anti-shear layer is preferably selectively positioned under the cover to provide an area having less resistance to cover stretching and movement relative to the cushion. 
     According to another aspect of the disclosed invention. A patient support includes air bladders made of anti-shear material and a stretchable cover placed over the air bladders. 
     According to still another aspect of the disclosed invention, a surface for a patient support or part thereof includes a series of inflatable air bladders made from anti-shear material which are disposed to provide a cushion under the patient with the highly stretchable cover over the air bladders. A viscoelastic foam layer may be disposed between the cover and the air bladder. At least one of the plurality of inflatable air bladders may be disposed within a permanently sealed and inflated bladder. 
     In some embodiments of the present invention a cover may not be highly stretchable as that term is hereinafter defined. Thus, in this specification and particularly in the claims, unless the cover is specified as “highly stretchable”, it shall not be limited to such characteristics. 
     Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In describing the disclosed invention reference will be made to the following drawings in which: 
     FIG. 1 is an exploded view of a first embodiment of a patient support in accordance with the present invention showing a cover over an anti-shear layer which is to be adhered to a cushion and a bottom coverlet; 
     FIG. 2 is a sectional view of the support surface of FIG. 1 showing the cover disposed over the anti-shear layer adhered to the cushion in a central region of the patient supporting surface with the cover directly contacting the cushion along a side edge of the patient supporting surface, and also showing a seam coupling the cover to a bottom coverlet which is located along the side of the support surface; 
     FIG. 3 is a perspective view of another embodiment of the patient support of the present invention showing a torso pad having a cover made entirely of highly stretchable material under which a viscoelastic foam layer lies on top of a plurality of sealed arching air bladders having inflatable air bladders disposed therein which are inflated by the pressure controller coupled to the torso pad, and a foot pad having a cover made entirely of highly stretchable material, a viscoelastic foam layer disposed between the patient supporting surface of the foot pad, and plurality of inflatable arching air bladders; 
     FIG. 4 is a perspective view of a foam cushion embodiment of a patient support according to the present invention showing a head pad, a torso pad, and a foot pad, each pad including a foam cushion and anti-shear layer overlying a portion of the patient supporting surface of the foam cushion, a cover extending over the patient supporting surface which is coupled to a bottom coverlet by a seam extending along the side of the support; 
     FIG. 5 is an exploded view of one embodiment of the anti-shear layer and cushion for use in the multi-segmented foam cushion of FIG. 4, showing the cushion formed from multiple sections of slow recovery foam, low density foam, and high density foam; 
     FIG. 6 is an exploded view of an embodiment of the anti-shear layer and cushion for use in the multi-segmented foam cushion of FIG. 4 showing the cushion including several sections made from slow recovery foam, low density foam, high density foam, and reduced density foam; 
     FIG. 7 is an exploded view of an embodiment of the anti-shear layer and foam cushion for use in the multi-segmented foam cushion of FIG. 4, showing the foam cushion made from segments of slow recovery foam, low density foam, and high density foam; 
     FIG. 8 is an exploded view of an embodiment of the anti-shear layer and foam cushion of FIG. 4, showing the foam cushion made of segments of slow recovery foam, medium density foam, and closed cell foam; 
     FIG. 9 is a sectional view of a positioner according to the present invention showing a highly stretchable cover enclosing an anti-shear layer enclosing a gel cushion; 
     FIG. 10 is a partial sectional view of a support surface in accordance with the present invention slightly depressed under a load (not shown) showing a highly stretchable cover partially stretched to conform to the depression in the cushion; 
     FIG. 11 is a sectional view similar to FIG. 10 showing the surface subjected to a heavier load (not shown); 
     FIG. 12 is a plain view of a highly stretchable material used to form a stretchable cover; and 
     FIG. 13 is a sectional view taken along line  13 — 13  of FIG. 12 of the highly stretchable material. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Patient support surfaces and positioners for distributing loads and minimizing the shear on a patient&#39;s skin according to the present invention preferably comprise a resilient cushion and a highly stretchable cover extending across the supporting surface of the cushion or positioner and an anti-shear layer disposed to permit the cover to slide freely with respect to the cushion on at least a portion of the patient support surface. For convenience herein, including in the claims, unless otherwise specified, the term “patient support surface” shall include a support surface such as abed, stretcher, or surgery table or a portion thereof or a positioner or pad used on or in connection with a bed, stretcher, or surgery table. The preferred highly stretchable cover and cushion cooperate to distribute the patient&#39;s weight more evenly across the surface to significantly decrease pressure on the body&#39;s bony prominences. The material forming the preferred highly stretchable cover and a friction reducing anti-shear layer allow the cover to slide with respect to the underlying cushion thereby reducing shear forces on the patient&#39;s skin. In illustrative embodiments, the highly stretchable cover is a rubber-like material such as a neoprene material, for example 1490 Dura neoprene which is available from RUBATEX Corporation, 5223 ValleyPark Drive, Roanoke, Va. 24019. 
     As shown, for example, in FIG. 13, 1490 Dura neoprene includes a cloth material weave  90  bonded to a foam rubber base  92 . Due to the orientation of the weave, 1490 Dura neoprene is stretchable from its unstressed configuration by 64% in one direction, shown by arrows  94  in FIG. 12, (referred to herein as its “stretch length  94 ” not to be confused with its actually length which is a function of its shape) and by 40% in an orthogonal direction, shown by arrow  96  in FIG. 12, (referred to herein as its “stretch width  96 ” not to be confused with its actually width which is a function of its shape). 
     Another example of highly stretchable material is PO 88 Penn-Nyla which is stretchable by 106% along its stretch length  94  and 40% along its stretch width  96 . PO 88 Penn-Nyla is available from Penn-Nyla, Acton Road, Long Eaton, GB-Nottingham, NG10, 1FX, United Kingdom. While some sheet materials may be available which will stretch more than, for example, 120% or more in length and 60% or more in width, and return over time to their normal unstretched dimension, it is important for patient surfaces to have surface integrity against fluid leakage. The 1490 Dura neoprene from RUBATEX Corporation, and PO 88 Penn-Nyla materials are examples of materials which are able when stretched within their respective limits to have suitable integrity against fluid leakage. (The stretchability of a material may be determined by taking a strip which is 2″ wide and 8″ long and placing a four pound weight on the strip to measure its elongation and potential to return to its unstretched condition in a reasonable time.) The present invention, therefore, contemplates a highly stretchable material which will stretch substantially beyond the stretch capability of conventional patient support covers and still maintain its surface integrity against leakage of fluid. It is believed that highly stretchable material, as compared to conventional cover materials, will preferably stretch 20% or more in length and 8 to 10% or more in width, although materials which will stretch substantially more than conventional cover materials to reduce shear contact with the patient may be considered highly stretchable in accordance with the present invention. The preferred material will stretch an amount sufficient to reduce significantly the shear stress on the patient&#39;s skin. 
     It will be appreciated that a preferred material may stretch 60-106% in length and 40% in width and still maintain its surface integrity against fluid leakage. Preferred materials with less stretchability may be satisfactory. 
     As used herein, the term “highly stretchable” shall mean a sheet-like material which is suitable as a cover for a patient support and which is rubber-like to be stretchable to a greater extent than conventional patient surface cover materials. The term “highly stretchable” shall also include, as an example, a material which is stretchable 120% or more along its stretch length  94  and 60% or more along its stretch width  96  and still have surface integrity against fluid leakage suitable for a patient support surface. The term “highly stretchable” also means that, when stretched within its elastic limit, it will tend to return to its normal dimension when released, at least over time. The “highly stretchable” material is also preferably a four-way stretch material which is stretchable along a diagonal and is stretchable and compressible through its thickness. 
     The anti-shear layer of the present invention is a friction reducing layer disposed between the highly stretchable cover and portions of the cushion. The anti-shear layer permits the highly stretchable cover to slide with respect to portions of the underlying cushion. The anti-shear layer also permits the highly stretchable cover to stretch without the stretch being inhibited by the underlying cushion. In the illustrated embodiments, the anti-shear layer is polyethylene material, but may be any other suitable material with suitable surface properties, such as nylon or “parachute” material, to permit the highly stretchable layer to slide and stretch with respect to the underlying cushion. 
     Referring to FIG. 1, an exploded view of a foam cushion embodiment  12  of a patient support surface  10  is shown. Each embodiment of patient support  10  includes a head end  14  spaced apart from a foot end  16  in a longitudinal direction shown by longitudinal axis  18 , a first side  20  and a second side  22  spaced apart in a lateral direction shown by lateral axis  24 , and an upwardly facing patient supporting surface  26  shown illustratively in FIG. 1 as the upwardly facing surface disposed between head end  14 , foot end  16 , first side  20 , and second side  22 . 
     As shown, for example, in FIG. 1, foam cushion patient support surface  12  includes a cover  28  preferably, but not necessarily, formed from highly stretchable material  29 , an anti-shear layer or liner  30 , a cushion or cushion layer  32 , and a bottom coverlet  34 . In the illustrated embodiment of foam cushion patient support surface  12 , anti-shear layer  30  has a surface area smaller than surface area of patient supporting surface  26 . Glue  36  is sprayed in a central portion  38  of patient supporting surface  26  of cushion  32  in an area substantially equal to the area of the anti-shear layer  30 . Anti-shear layer  30  is bonded to central portion  38  of cushion  32 , as shown for example, in FIG.  2 . Cover  28  is placed over combined cushion  32  and anti-shear layer  30  and is connected to bottom coverlet  34  by a seam  40  extending peripherally around sidewall  42  in a position spaced apart from patient supporting surface  26  and bottom surface  44  of patient support surface  10  as shown, for example, in FIG.  2 . 
     Although illustrated as rectangular, anti-shear layer  30  and central portion  38  may have other shapes. For example, an hour glass-shaped anti-shear layer and central portion positioned so that the wider areas underlie the shoulders and hips of a patient on the support surface  10  are contemplated as being within the scope of the invention as presently perceived. Glue  36  may be applied over the entire central portion  38  or over any portion thereof sufficient to adhere or bond anti-shear layer  30  to central portion. Alternatively, glue  36  may be applied to anti-shear layer  30 , or anti-shear layer  30  may be adhered to central portion  38  in any conventional manner. 
     As shown, for example, in FIGS. 1 and 2, cover  28  directly engages cushion  32  along sidewalls  42  and along peripheral portions  46  of patient supporting surface  26 . Frictional engagement between cover  28  and cushion  32  helps to maintain cover  28  properly positioned with respect to patient support  10 . Without this frictional engagement, cover  28  can rotate around foam cushion  32 , or bunch up at one end when made from highly stretchable material  29 , when the support on which patient support surface  10  is placed is inclined. Patient movement on support surface  26  might also induce cover  28  to bunch or gather when cover is made from highly stretchable material  29 . In central portion  38  of patient support surface  26  cover  28  engages anti-shear layer  30  which is disposed over cushion  32 . In this area, cover  28  is free to slide, and to stretch when cover is made from highly stretchable material  29 , without being inhibited by frictional forces. Central portion  38  is the area of support surface  26  on which patient is likely to be supported. 
     In the illustrated embodiment, cover  28  is preferably made from highly stretchable material  29  such as 1490 Dura Neoprene as previously disclosed. Bottom coverlet  34  is made from Lectrolite light material which stretches very little. Seam  40  between cover  28  and bottom coverlet  34  is located on sidewall  42  away from where fluids collect and pool in a healthcare environment. This facilitates maintaining patient support surface  10  in a properly sterile state. 
     Referring to FIG. 3, an air mattress cushion embodiment  50  of patient support surface  10  is illustrated. Air mattress cushion patient support surface  50  includes a torso pad  52  and a foot pad  54 . Torso pad  52  and foot pad  54  each include a unitary highly stretchable cover  56 , a viscoelastic foam layer  58 , and an air mattress cushion  60  with air bladders  64 , 66 , 68  formed from anti-shear material. An inflation controller  62  controls the pressure in inflatable bladders in torso pad  52 , and foot pad  54  by inflating and deflating the bladders. Air mattress cushion  60  of torso pad  52  includes a plurality of longitudinally spaced, laterally extending sealed arching upper cells  64  which are filled to a desired pressure with air and sealed by the manufacturer. Extending laterally within an opening of each sealed arching upper cell  64  is an inflatable inner cell  66  coupled to inflation controller  62 . Air mattress cushion  60  of foot pad  54  includes a plurality of laterally extending inflatable arching cells  68  coupled to inflation controller  62 . Illustrated air mattress cushion  60  is a Carital Air-float system available from Carital Ltd., P.O. Box 1 70, 04300 Tuusula, Finland. It should be understood that other air mattress systems, are within the teaching of the scope of this disclosure. 
     Illustratively, viscoelastic foam layer  58  is ½″ thick viscoelastic foam. Viscoelastic foam is stretchable, and will stretch along with highly stretchable cover  56 . Therefore, highly stretchable cover  56  and viscoelastic foam layer  58  may stretch and slide freely relative to the anti-shear material forming arched cells  64 ,  68 . Inflation controller  62  dynamically alters the pressure of inflatable bladder  66 , and inflatable bladders  68  to optimize patient interface pressure. These bladders will not become permanently compressed or become permanently deformed over time as many static surfaces can. 
     Referring to FIG. 4 there is shown a multi-segmented foam cushion embodiment  70  of patient support surface  10 . Multi-segmented foam cushion patient support surface  70  includes a head pad  72 , a torso pad  74 , and a foot pad  76 . Each pad  72 ,  74 ,  76  includes a cover  28  preferably made from highly stretchable material  29 , an anti-shear layer  30 , a cushion  32 , and a bottom coverlet  34 . In each of pad  72 ,  74 ,  76 , anti-shear layer  30  is adhered by glue  36  to at least a central portion  38  of cushion  32  as described earlier with regard to foam cushion patient support surface  12 . Likewise, cover  28  is joined by a seam  40  peripherally extending around sidewall  42  of each of pads  72 ,  74 ,  76  to bottom coverlet  34 , made for example from Lectrolite material. Several different embodiments of cushion  32  are used in multi-segmented foam cushion embodiment  70  as described hereafter. 
     Referring to FIG. 5, there is shown an exploded view of a first embodiment of a segmented multi-layer cushion  132  and anti-shear layers  130  for use in a multi-segmented foam cushion patient support surface  70 . The cushion segment  132  for use in head pad  72  includes an upper slow recovery foam layer  100 , a medial low density foam layer  102 , and a bottom high density foam layer  104 . 
     Throughout the application the terms slow recovery foam, low density foam, high density foam, reduced density foam, and closed cell foam will be used. Each of these foams is formed from a foam rubber material such as urethane foam, although any suitable material providing similar support and firmness characteristics to those described below for the particular foam can be used without exceeding the scope of the invention as presently perceived. The firmness and support characteristics provided by each of these types of foam depend in part upon indentation load deflection (ILD) of the foam from which each layer is made. The ILD is a well-known industry accepted index indicating the “firmness” of materials such as urethane foam and other foam rubber materials. The ILD indicates the amount of deflection exhibited by a block of foam when subjected to a specified force distributed over a specified area of foam. 
     It is within the scope of the invention as presently perceived to provide foam cushion  32  wherein each segment or layer has the same ILD or to provide foam cushion  32  wherein the ILD of at least one layer is different from the ILD of at least one other layer. 
     In referring to layers or zones described as slow recovery foam, the layer or zone is a foam material that easily conforms to the contour of the patient when weight is applied and slowly returns to its uncompressed state after the weight is removed. Slow recovery foam is typically not characterized by its ILD. Slow recovery foam having the characteristics described herein is available from EAR Specialty Composites, 7911 Zionsville Road, Indianapolis, Ind. 46268 as CF-40 Foam (Sofcare). 
     When referring to a foam section or zone as formed from low density foam, the foam portion or zone primarily facilitates pressure reduction and provides very little support. Such foam is typically used in the heel portion, scapula portion, and seat portion of a patient support. Low density foam having the characteristics described herein is available from Keystone Foam, P.O. Box 355, Loyalhanna, Pa. 15661 as part no. 1820 foam which has a pounds per cubic foot rating of about 18 and an ILD of about 20. 
     When referring to a section or zone as being made from high density foam, the foam primarily serves a support function and contributes, when used alone, only incidentally to pressure reduction, but, when used in conjunction with overlying, underlying, or adjacent lower density foam, substantially improves pressure reduction. High density foam having the characteristics described herein is available from Keystone Foam, P.O. Box 355, Loyalhanna, Pa. 15661 as part no. 2860 foam which has a pounds per cubic foot rating of about 28 and an ILD of about 60. 
     When referring to a section or zone as being made from reduced density foam, the foam contributes primarily to pressure reduction while providing additional firmness and support characteristics to areas of the cushion. Reduced density foam is typically used in cushion areas supporting the shoulders in conjunction with slow recovery foam. Reduce density foam having the characteristics described herein is available Keystone Foam, P.O. Box 355, Loyalhanna, Pa. 15661 as part no. 1845 foam which has a pounds per cubic foot rating of about 18 and an ILD of about 45. 
     When referring to a section or zone as being formed from medium density foam, the foam material contributes both to support and pressure reduction. Medium density foam having the characteristics described herein is available from Keystone Foam, P.O. Box 355, Loyalhanna, Pa. 15661 as part no. 1845 foam which has a pounds per cubic foot rating of about 18 and an ILD of about 45. 
     When referring to a section or zone as being made from closed cell foam, the portion or section is made from a foam that contributes almost exclusively to support. Closed cell foam is typically used as an underlayment in layered cushions to prevent bottoming out of the patient against an underlying rigid surface of a support such as an OR table. Closed cell foam having the characteristics described herein is available from RUBATEX Corporation, 5223 ValleyPark Drive, Roanoke, Va. 24019 as part no. R-341 Nytril. 
     While slow recovery, high density, low density, medium density, reduced density, and closed cell foam have been specifically identified by vendor and part number, other foams having characteristics similar to the specifically identified foams may be used in a patient support surface within the teachings of the invention. Other examples of ILDs for foam cushions adapted to provide adequate support and pressure reduction for various areas of the body are disclosed in U.S. Pat. No. 5,802,646 to Stolpmann et al. which is incorporated herein by reference. 
     Foam cushion  132  of head pad  72  is formed by bonding lower high density foam layer  104  to middle low density foam layer  102  and then bonding upper slow recovery foam layer  100  to middle low density foam layer  102 . Anti-shear layer  130  is then bonded to upper slow recovery foam layer  100  and the entire unit is received within cover  28  and bottom coverlet  34  joined together by seam  40  extending around sidewall  42  of head pad  72 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Foam cushion  132  of torso pad  74  includes an upper slow recovery foam layer  108 , an intermediate low density foam layer  110 , an upper intermediate multi-zone layer  112 , a middle intermediate multi-zone layer  120 , a lower intermediate multi-zone layer  126 , and a lower high density cradle and lumbar bolster layer  138 . Upper intermediate multi-zone layer  112  includes a low density foam scapula/shoulder zone  114 , a high density foam cradle and lumbar bolster zone  116 , and a low density foam sacral/trochanter zone  118 . Middle intermediate multi-zone layer  120  includes a high density foam cradle zone  122  and a low density foam vertebral zone  124 . Lower intermediate multi-zone layer  126  includes a high density foam zone  128  and a low density foam sacral/trochanter zone  136 . 
     Lower high density cradle and lumbar bolster layer  138  is bonded to the bottom of lower intermediate multi-zone layer  126 . The top of lower intermediate multi-zone layer  126  is bonded to the bottom of middle intermediate multi-zone layer  120 . The top of middle intermediate multi-zone layer  120  is bonded to the bottom of upper intermediate multi-zone layer  112 . The top of upper intermediate multi-zone layer  112  is bonded to the bottom of intermediate low density foam layer  110 . The top of intermediate low density foam layer  110  is bonded to the bottom of upper slow recovery foam layer  108 . Thus foam cushion  132  of torso pad  74  includes the bonded assembly of upper slow recovery foam layer  108 , intermediate low density foam layer  110 , upper intermediate multi-zone layer  112 , middle intermediate multi-zone layer  120 , lower intermediate multi-zone layer  126 , and lower high density foam cradle and lumbar bolster layer  138 . Anti-shear layer  130  is glued to the top of upper slow recovery foam layer  108  of foam cushion  132  and the entire assembly is enclosed by cover  28  and bottom coverlet  34  which are joined together by seam  40  extending peripherally around sidewall  42  of torso pad  74 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Foam cushion  132  and anti-shear layer  130  of foot pad  76  are shown to the right in FIG.  5 . Foam cushion  132  of foot pad  76  includes an upper slow recovery foam layer  140 , an intermediate multi-zone layer  142 , and a lower high density foam layer  148 . Intermediate multi-zone layer  142  includes a high density foam zone  144  and a low density foam heel zone  146 . Lower high density foam layer  148  is bonded to the bottom of intermediate multi-zone layer  142 . The top of intermediate multi-zone layer is bonded to the bottom of upper slow recovery foam layer  140 . Thus foam cushion  132  of foot pad  76  includes the bonded upper slow recovery foam layer  140 , intermediate multi-zone layer  142 , and lower high density foam layer  148 . Anti-shear layer  130  is glued to the top of upper slow recovery foam layer  140  of foam cushion  132  and the entire assembly is enclosed in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around the sidewall  42  of foot pad  76 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Referring to FIG. 6, there is shown an exploded view of a second embodiment of an anti-shear layer  230  and foam cushion  232  for use with multi-segmented foam cushion patient support system  70  of FIG.  4 . Foam cushion  232  of head pad  72  is formed by bonding lower high density foam layer  204  to middle low density foam layer  202  and then bonding upper slow recovery foam layer  200  to middle low density foam layer  202 . Anti-shear layer  230  is then bonded to upper slow recovery foam layer  200  and the entire unit is received within cover  28  and bottom coverlet  34  joined together by seam  40  extending around sidewall  42  of head pad  72 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     The anti-shear layer  230  and foam cushion  232  of torso pad  74  are shown as the middle sections in FIG.  6 . Foam cushion  232  of torso pad  74  includes upper slow recovery foam layer  206 , intermediate multi-portion layer  208 , and lower high density foam cradle and lumbar bolster layer  218 . Intermediate multi-portion layer  208  includes multi-zone portion  210  and reduced density foam lateral shoulder portion  212 , as shown, for example, in FIG.  6 . Multi-zone portion  210  includes high density foam lumbar bolster zone  214  and low density foam sacral/trochanter zone  216 . Foam cushion  232  of torso pad  74  is formed by bonding the top of lower high density foam cradle and lumbar bolster layer  218  to the bottom of multi-zone portion  210  of intermediate multi-portion layer  208 , and bonding the tops of multi-zone portion  210  and reduced density foam lateral shoulder portion  212  of intermediate multi-portion layer  208  to the bottom of upper slow recover foam layer  206 . Anti-shear layer  230  is glued to the top of upper slow recovery foam layer  206  of foam cushion  232  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of torso pad  74 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Anti-shear layer  230  and foam cushion  232  of foot pad  76  of multi-segmented foam cushion patient support surface  70  are shown to the right in FIG.  6 . Foam cushion  232  of foot pad  76  includes upper slow recovery foam layer  220 , intermediate multi-zone layer  222  and lower high density foam layer  228 . Intermediate multi-zone layer  222  includes high density foam zone  224  and low density foam heel zone  226 . Foam cushion  232  of foot pad  76  is formed by bonding the top of lower high density foam layer  228  to the bottom of intermediate multi-zone layer  222  and the top of intermediate multi-zone layer  222  to the bottom of upper slow recovery foam layer  220 . Anti-shear layer  230  is glued to the top of upper slow recovery foam layer  220  of foam cushion  232  of foot pad  76  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of foot pad  76 , in the manner described above with regard to FIGS. 1 and 2. 
     The third embodiment of a foam cushion  332  and anti-shear layer  330  for use in multi-segmented foam cushion patient support surface  70  is shown in FIG.  7 . Foam cushion  132  of head pad  72  is formed by bonding lower high density foam layer  304  to middle low density foam layer  302  and then bonding upper slow recovery foam layer  300  to middle low density foam layer  302 . Anti-shear layer  130  is then bonded to upper slow recovery foam layer  300  and the entire unit is received within cover  28  and bottom coverlet  34  joined together by seam  40  extending around sidewall  42  of head pad  72 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Foam cushion  332  and anti-shear layer  330  for torso pad  74  is shown in the middle of FIG.  7 . Foam cushion  332  for torso pad  74  includes upper slow recovery foam layer  306 , intermediate high density foam layer  308 , and high density foam cradle and lumbar bolster layer  310 . Foam cushion  332  for torso pad  74  is formed by bonding the top of high density foam cradle and lumbar bolster layer to the bottom of intermediate high density foam layer  308  and the top of intermediate high density foam layer  308  to the bottom of upper slow recovery foam layer  306  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of torso pad  74 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Anti-shear layer  330  and foam cushion  332  of foot pad  76  of multi-segmented foam cushion patient support surface  70  is shown to the right in FIG.  6 . Foam cushion  332  of foot pad  76  includes upper slow recovery foam layer  320 , intermediate multi-zone layer  322 , and lower high density foam layer  328 . Intermediate multi-zone layer  322  includes high density foam zone  324  and low density foam heel zone  326 . Foam cushion  332  of foot pad  76  is formed by bonding the top of lower high density foam layer  328  to the bottom of intermediate multi-zone layer  322  and the top of intermediate multi-zone layer  322  to the bottom of upper slow recovery foam layer  320 . Anti-shear layer  330  is glued to the top of upper slow recovery foam layer  320  of foam cushion  332  of foot pad  76  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of foot pad  76 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     A fourth embodiment of foam cushion  432  and anti-shear layer  430  for use in multi-segmented foam cushion patient support surface  70  is shown in FIG.  8 . 
     Foam cushion  432  and anti-shear layer  430  for head pad  72  are shown to the left in FIG.  8 . Foam cushion  432  for head pad  72  includes upper slow recovery foam layer  400 , intermediate medium density foam layer  402 , and lower closed cell foam layer  404 . Foam cushion  432  for head pad  72  is formed by bonding top of lower closed cell foam layer  404  to the bottom of intermediate medium density foam layer  402  and bonding the top of intermediate density foam layer  402  to the bottom of slow recovery foam layer  400 . Anti-shear layer  430  is bonded to the top of slow recovery foam layer  400  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of head pad  72 , in the same manner as described with reference to FIGS. 1 and 2 above. 
     Foam cushion  432  and anti-shear layer  430  of torso pad  74  are shown in the middle of FIG.  8 . Foam cushion  432  of torso pad  74  includes an upper slow recovery foam layer  406 , an intermediate medium density form layer  408  and a lower closed cell foam layer  410 . Foam cushion  432  of torso pad  74  is formed by bonding the top of closed cell foam layer  410  to the bottom of intermediate medium density form layer  408  and bonding the top of intermediate medium density form layer  408  to the bottom of upper slow recovery foam layer  406 . Anti-shear layer  430  is bonded to the top of upper slow recovery foam layer  406  of foam cushion  432  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of torso pad  74 , in the manner described above with regard to FIGS. 1 and 2. 
     Foam cushion  432  and anti-shear layer  430  of foot pad  76  of multi-segmented foam cushion patient support surface  70  are shown to the right in FIG.  8 . Foam cushion  432  of foot pad  76  includes an upper slow recovery foam layer  412 , an intermediate medium density foam layer  414 , and a lower closed cell foam layer  416 . Foam cushion  432  of foot pad  76  is formed by bonding the top of lower closed cell foam layer  416  to the bottom of intermediate medium density foam layer  414  and bonding the top of intermediate medium density foam layer  414  to the bottom of slow recovery foam layer  412 . Anti-shear layer  430  is glued to the top of upper slow recovery foam layer  412  to form an assembly. This assembly is received in cover  28  and bottom coverlet  34  which are joined together by a seam  40  extending peripherally around sidewall  42  of foot pad  76 , in the manner disclosed above with regard to FIGS. 1 and 2. 
     Each embodiment of cushion  132 ,  232 ,  332 ,  432  for multi-segmented foam cushion patient support surface  70  is described as being formed by bonding various layers and zones together. Nevertheless, it is within the teaching of the present invention, for the layers and zones to be positioned relative to each other without bonding the layers and zones together. Those skilled in the art will recognize that other arrangements of cushioning elements, such as sealed and inflatable air bladders, foam pads, air impregnated gels, or any combination of these or other cushioning elements, are within the teachings of the invention. 
     In each of the embodiments described above of patient support surfaces  10 ,  50  and  70 , the surface includes a longitudinal axis  18  extending between head end  14  and foot end  16  and a lateral axis  24  extending between first side  30  and second side  22 . Unitary highly stretchable cover  56  and the preferred embodiment of cover  28  are formed from a highly stretchable material  29  such as 1490 Dura Neoprene which is stretchable along its stretch length  94  by 64% and orthogonally along its stretch width  96  by 40% (as the terms “stretch length” and “stretch width” are defined above). The 1490 Dura Neoprene highly stretchable material  29  is formed into cover  28  and unitary highly stretchable cover  56  so that its stretch length  94  lies along or parallel to longitudinal axis  18  and its stretch width  96  lies along or parallel to lateral axis  24 . Other highly stretchable materials  29  which may be used to form covers  28 ,  56  are similarly oriented with respect to longitudinal axis  18  and lateral axis  24 . While in the preferred embodiment the highly stretchable material  29  is oriented in cover  28 ,  56  so that its stretch length  94  is parallel to longitudinal axis  18  of surface  10 ,  50 ,  70  and its stretch width  96  is oriented parallel to lateral axis  24  of surface  10 ,  50 ,  70 , other orientations of highly stretchable material  29  are within the teachings of this invention. 
     FIG. 9 discloses, a sectional view of a positioner  80  with a highly stretchable cover  82  in accordance with the present invention. While the illustrated positioner  80  is a chest roll, other positioners and surfaces such as head donuts, horseshoes, arm boards, heel protectors, or “sandbag positioners” are within the teachings of the present disclosure. In the illustrated chest roll positioner  80 , a unitary highly stretchable cover  82  forms a complete enclosure around an anti-shear layer  84  which forms a complete enclosure around a gel cushion  86 . Highly stretchable cover  82  when subjected to loads and shears by a patient is able to slide and stretch along anti-shear layer  84  without being inhibited by gel cushion  86 . While patient support  10  and  70  disclose an anti-shear layer positioned only over portions of, or the entire, patient supporting surface  69 , it is within the teaching of the invention for the entire foam cushion  32 ,  132 ,  232 ,  332 ,  432  to be completely enclosed in an anti-shear layer in the same manner as positioner  80 . 
     As illustrated, anti-shear layers  130 ,  230 ,  330 ,  430  cover the entire patient supporting surface of foam cushions  132 ,  232 ,  332 ,  432 . However, as shown in FIGS. 1,  2 , and  4 , it is within the teaching of the invention to have an anti-shear layer placed between cover  28  and foam cushion  32  in only a portion of the patient supporting surface  26 . FIGS. 10 and 11 show one advantage that is obtained by leaving peripheral portions  46  of cushion  32  in engagement with cover  28 . As a load (not shown) is placed on patient supporting surface  69 , cover  28  in the area of the load (shown by the depression) stretches, when cover  28  is made from highly stretchable material  29  (as shown by the increased spacing between the cross hatches) and narrows (as shown by the narrowing of the width between the surface lines). The central portion  38  of cover  28  is free to slide in the direction of double headed arrow  86  over anti-shear layer  30  as shown in FIG.  10 . Friction between cover  28  and foam cushion  32  in peripheral portions  46  of patient supporting surface  69  prohibits cover  28  from slipping, and stretching when cover  28  is made from highly stretchable material  29 , in peripheral portions  46  (as shown by the uniform thickness of the surface lines and the uniform spacing of cross hatchings of cover  28 ). 
     As an even greater weight is applied, as shown, for example, in FIG. 11, the central portion  38  of cover  28  stretches even further (as shown by the increased spacing between cross hatches) in the area of the higher pressure and continues to slide in the direction of arrow  88  relative to anti-shear layer  30  (as shown by the alteration of the location of cross hatches between FIGS.  10  and  11 ). Nevertheless the highly stretchable cover in peripheral portions  46  continues to remain substantially unstretched (as shown by the uniform spacing of the cross hatchings) and in the same location as before (as shown by the uniform location of the cross hatchings in FIGS.  10  and  11 ). This prevents highly stretchable material  29  from bunching up at one end or edge of the surface when the patient support is inclined during a surgical procedure or recovery. 
     It will be appreciated that, in some embodiments of the present invention, a suitable and novel patient support surface  10  may be provided which does not have a cover made of highly stretchable material  29  even though its skin shear protection characteristics may be further enhanced with a cover made form highly stretchable material  29 . 
     Although the invention has been described in detail with reference to certain preferred embodiments, additional variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.