GB1604401A - Mattresses - Google Patents

(54) IMPROVEMENTS IN OR RELATING TO MATTRESSES (71) We, DAVID BRUCE NEAL, of 28 North Farm Road, Lancing, West Sussex, and BARRY CHARLES TEASDALE, of 165 Shearwater Road, Bosden Farm, Offerton, Cheshire, both British subjects, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to mattresses and in particular to surgical mattresses.

A common problem in'operating theatres, particularly where relatively lengthy surgery is involved, is that patients tend to develop pressure sores due to uneven distribution of body weight on the operating table mattress.

This problem is particularly acute where, as is frequently the case, the mattress is corrugated to increase the friction between the patient and the mattress and thereby prevent the patient from sliding down the operating table if placed in a Trendelenburg or reverse Trendelenburg position.

A similar problem arises in other departments of hospitals, particularly casulty departments where a patient may be left on a trolley for long periods of time.

According to the present invention there is provided a mattress having good recovery properties comprising a base and side-walls constructed of rigid foam material, the sidewalls being of denser foam material than the base; a layer of resilient soft foam material disposed between the said side-walls; and a stretchable, air-permeable, water-impermeable cover which surrounds the said base, side-walls and resilient soft foam material.

The mattress according to the present invention may be used in particular as a surgical mattress on an operating table or as a trolley mattress. Matresses according to the invention for use in operating theatre serve in use to locate the patient firmly without subjecting the patient to undue shear stresses, even when in the Trendelenburg or reverse Trendelenburg position. and to distribute evenly the weight of the patient whereby pressure sore formation is minimised or avoided.

The mattress according to the present invention has good recovery properties, i.e.

indentations made by a patient located on the mattress recover spontaneously after removal of the patient.

The mattress according to the present invention includes a firm base and side walls which form a channel, the channel being filled with a layer of resilient soft foam material. If desired, the mattress may also include end walls which in combination with the side-walls and base, define a cavity which is filled with the resilient soft foam material.

End-walls are generally desirable in mattresses intended for use on an operating table in order to assist location of a patient laying thereon in the Trendelenburg or reverse Trendelenburg position.

The base and side-walls are constructed of a material having sufficient rigidity to support the structure of the mattress. The sidewalls must be of denser foam material than the base and of sufficient rigidity to prevent bulging of the mattress, to provide support for slide hooks etc and to avoid placing undue strain on seaming especially when a patient is getting onto or off the mattress. It will be understood that the term "side-walls" refers to the walls substantially parallel to a patient lying on the mattress whereas the end-walls are those walls substantially perpendicular to such a patient. The rigidity of the base will depend on the particular resilient soft foam material used and the thickness of layer employed.Thus the base must be of a sufficient rigidity to support the structure of the mattress and to avoid back pressure from the surface on which the mattress is placed being felt by the patient but not so rigid that it may itself be felt by the patient through the layer of resilient soft foam material. One suitable material for both the base and the side-walls is reconstituted chip foam (compressed polyurethane foam pieces) but others include high density latex, closed cell PVC foam, polyurethane and cross-linked polyethylene.

In one embodiment of the present invention. the base is constructed of 3-8, preferably 5 > , Ib/ft3 (48-128, preferably 8F96 kg/m3), reconstituted chip foam, e.g. the foam DR 73 marketed by Dunlop and the side-walls are constructed of W12, preferably 8-10, Ib/ftl (9 < 192, preferably 128 160 kg/m') reconstituted chip foam e.g.

the foam DR 73 marketed by Dunlop.

The side-walls and base are preferably from 4 to 21 inches (12.5 to 63mm) thick, a thickness of approximately I inch (25.4mm) having been found to be particularly suitable. Especially preferred is a base and sidewall thickness of about 1 inch in combination with an about 2 inch thick layer of resilient soft foam material. The end-walls, where present, are preferably of the same thickness as. and of similar material to, the side-walls.

The filling of the mattress, i.e. the resilient soft foam material. is conveniently a soft polyurethane or polyether foam material which readily conforms to the patient's body shape in use and which recovers spontaneously on removal of the patient. Particular foams which may be used with advantage are polyether foams having a density of from 1.7 to 2.2, preferably 1.9 to 2.0 Ib/ft3 (28 to 35, preferably 30.5 to 32.5 kg/m3) and a hardness of 34--45 45 Ib/f (15-200 N), preferably 38--44 lb/f(170--195 N). It is also preferred that when tested according to British Standard 4443, process A, a foam sample of 380 X 380 X 50 mm has about 40% deflection.

Suitable foams include for example, the foam D 39 marketed by Dunlop. Also suitable are polyurethane foams which absorb greater than 80 to, preferably about 90 o of shock and vibration e.g the soft, lightweight polyurethane foam Temper Foam T36 manufactured by Edmund Wilson of Coshockton, Ohio, USA [marketed in the U.K. by Superfine Tapes Co. Ltd. of Watford] but other materials having similar properties may alternatively be used, e.g. low density latex, plastic polyurethane foam or soft PVC foam.

In a further embodiment of the present invention the base is formed from polyurethane foam with a density of 2-31b/ft3 (32w8 kg/m3) preferably about 2.31b/ft3 (36.8 kg/m3) e.g. the foam DP 107 marketed by Dunlop and the base is about lj inches (38mm) thick with a resilient soft foam material layer thickness of about I inches (38mm) such a mattress is particularly advantegeous where X-ray translucency is desired. The side-walls, which may be of any of the materials described above, are preferably about I inch (25.5 mm) thick to avoid impingement on the X-ray picture. Hinges connectingdifferent polyurethane portions of the mattress are also preferably contoured for minimum register on an X-ray picture.

The mattress cover must be air-permeable in order to permit the resilient soft foam material to adapt to the shape of a patient lying on the mattress and to spontaneously recover when the patient is removed from the mattress. The cover must, however, be waterimpermeable to allow the mattress to be cleaned without saturation of the foam materials used in the interior of the mattress.

The mattress cover is preferably neoprene or rubber although other materials such as e.g. PVC and 'iIypalon" [registered Trade Markl may be used if desired. For use in the United Kingdom. the mattress should be antistatic to meet DHSS requirements i.e.

should conform to British Standard 2891 which requires that the material should conduct electricity in the range of from 2.5 x 104 to 10" ohms A preferred material for the mattress cover is neoprene latex sheet material. Preferably the neoprene latex will have an elongation at break of from 600 to 800%, most preferably about 700%; a tensile strength of from 2000 to 3000 lb/in2 (140 to 210 kgf/cm2), most preferably about 2,500 lb/in2 (175 kgf/cm2); a hardness of from 30 to 50, most preferably 40 to 45 on the Shore scale; and, at 65'F, requires from 500 to 700, most preferably about 600 Ib/in2 (35 to 49, most preferably about 42 kgf/cm2) to stretch by 300it and from 1200 to 1400, most preferably about 1300 Ib/in2 (84 to 98, most preferably about 92 kgf/cm2) to stretch by 500%.A particularly preferred material is the neoprene latex sheet obtainable from 4D Research and Development Ltd, Derby and made according to the process described in British Patent Specification No. 1,326,541.

The various components of the mattress according to the invention are secured together by means of suitable adhesives, e.g. a cross-linked resinated adhesive, preferably a polychloroprene elastomer with phenolic resins such as the adhesives supplied by Plus Products, Blaydon-on-Tyne. The Plus Products adhesive AN 175 has been found to be particularly suitable for wide surface areas whereas the Plus Products adhesive AN94 is particularly suitable for seams and hooks etc.

These adhesives, which are preferably used in conjunction with a polyisocyanate accelerator, must be fully cured to ensure a strong weld. The surfaces to be joined by the adhesives are preferably cleaned with a halogenation wipe e.g. Plus Products A1006 halogenation wipe, before application of the adhesive, to ensure adequate cross-linking during subsequent curing of the adhesive According to one embodiment of the present invention, the mattress is formed in segments which may be hinged together, the segments, which may if desired be separable, conforming to segments of the surface on which the mattress is to be placed e.g.

conventional operating tables or trolleys.

Where X-ray translucency is desirable then any hinges are preferably contoured to minimise interference in X-ray pictures of pa tients lying on the mattress. We have found that in general, V-shaped hinges are preferred with the apex of the hinge itself being at the underface of the mattress. In such an embodiment, any end-walls of the segments traversed by the patient's body in use are desirably cut back by approximately half to minimise pressure sore formation resulting from the end-walls of the mattress segments.

In mattresses intended for use on an operating table the extreme end-walls of the head and foot section should not however, be cut back or problems in locating the patient when in the Trendelenburg or reverse Trendelenburg position may arise.

If desired, sections of the side-walls may be cut back to facilitate attachment of ancillary surgical apparatus. Previous suggestions for using foam surgical mattresses have tended to result in relatively thick mattresses if pressure sore formation is to be avoided.

However, the present invention enables pressure sore formation to be avoided with the use of relatively thin mattresses thereby resulting in a cost-saving in materials. Mattresses according to the present invention will in general be from li to 5 inches (38 to 127 mm) thick, thickness of approximately 3 inches (76mm) being preferred.

The length and breadth of the mattress according to the invention will vary depending on the dimensions of the operating table, trolley or other supporting means the mattress is intended to be used in conjunction with.

For a better understanding of the present invention, reference is made to the accompanying drawings, wherein Figure 1 shows, in partially cut-away form, a perspective view of an operating table mattress according to one embodiment of the present invention and Figure 2 shows, in partially cut-away form, a perspective view of a trolley mattress according to a further embodiment of the present invention.

In Figure 1 the mattress comprises a head supporting section 1, two torso supporting sections 2 and 3 connected by a hinge 4 and a leg supporting section 5. The various sections are provided with hooks 6, 7, 8 and 9 for attachment, in use, to an operating table, (The hooks on the leg supporting section are not shown in the drawing).

Each section comprises a base 10, sidewalls 11 and end-walls 12 of a rigid foam material. The side-walls are cut back by approximately half at points 13 traversed by the patient's body when the mattress is in use. Each section is filled with a resilient soft foam material 14 and covered with an antistatic skin 15.

The upper torso-supporting section may if desired be provided with shoulder restraints 16 which assist in preventing movement of the patient whilst in the Trendelenburg or reverse Trendenlenburg position.

In Figure 2, wherein similar features to those shown in Figure 1 are numbered similarly, the mattress is formed as a single unit with a head supporting section I and a section 17 for the remainder ofthe body. The sections 1 and 17 are joined by means of a Vshaped hinge 4, said hinge 4 being contoured for maximum X-ray translucency. The hooks 6 on the head supporting section 1 (only one shown) are slidable to allow mobility of the head supporting section 1 without damage to the mattress.

WHAT WE CLAIM IS: 1. A mattress having good recovery properties comprising a base and side-walls constructed of rigid foam material, the sidewalls being of denser foam material than the base; a layer of resilient soft foam material disposed between said side-walls; and a stretchable, air-permeable, water-impermeable cover which surrounds the said base, side-walls and resilient soft foam material.

2. A mattress as claimed in claim 1 wherein the base and side-walls are of reconstituted chip foam.

3. A mattress as claimed in claim 2 wherein the base is of 5dlb/ft9 foam and the side-walls are of 8-10lb/ft foam.

4. A mattress as claimed in any of the preceding claims wherein the base and the side-walls are about 1 inch thick the layer of resilient soft foam material is about 2 inches thick.

5. A mattress as claimed in claim 1 wherein the base is of a polyurethane foam having a density of about 2.3 Ib/ft3.

6. A mattress as claimed in claim 5 wherein the base is about I i inches thick, the side-walls are about 1 inch thick and the layer of resilient soft foam material is about 1 inches thick.

7. A mattress as claimed in any of the preceding claims wherein the resilient soft foam material is a polyether foam having a density of from 1.9 to 2.0 lb/ft3 and a hardness of from 38 to 44 Ib/f.

8. A mattress as claimed in any of claims I to 6 wherein the resilient soft foam material is a soft, lightweight polyurethane foam.

9. A mattress as claimed in any of the preceding claims wherein the cover is formed from neoprene or rubber.

10. A mattress as claimed in claim 9 wherein the cover is formed from a neoprene latex sheet.

11. A mattress as claimed in claim 10 wherein the neoprene latex sheet conducts electricity in the range of from 2.5 x 104 to 106 ohms.

12. A mattress as claimed in claim 11 wherein the neoprene latex sheet has an elongation at break of about 700%, a tensile

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