GB2290960A

GB2290960A - Mattress

Info

Publication number: GB2290960A
Application number: GB9414052A
Authority: GB
Inventors: Robert John Dudley Welch
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-07-12
Filing date: 1994-07-12
Publication date: 1996-01-17
Anticipated expiration: 2014-07-12
Also published as: GB9414052D0; GB2290960B

Abstract

A patient support mattress 1 comprises a generally rectangular block of open-cell foam. The invention is characterized in that the longitudinal edge portion 3 are formed with a longitudinally extending wedge portion 4 to give the mattress a concave configuration. <IMAGE>

Description

WEDGED PATIENT SUPPORT MATTRESS The present invention relates to patient support mattresses and particularly to improvements therein incorporating wedges and/or arrangements to reduce hammocking due to interaction between mattress covers and the mattress foam material itself.

The recent introduction of fire resistant furniture foams occurred essentially before the technology was ready and this has contributed to an increased instance in pressure sores in hospitalised patients. The new foams have tended to exhibit early wet compression set and foam fatigue especially when lain on as intensively as in a hospital. The result of this is that the mattresses taken as a whole tend to fail after a while to properly redistribute pressure away from bony prominences such as the sacrum.

Hospital mattresses are now often covered with a vapour permeable yet moisture resistant cover. These allow perspiration to enter the foam but provide no easy escape for the moisture thus acquired. Under such warm moist conditions the foam tends to loose its pressure redistributing capacity and makes pressure sores more likely. The present invention is directed to an alleviation of these problems.

These problems have been addressed inter alia in my co-pending UK patent application number GB-A-2 274 054 which claims inter alia a patient support mattress comprising a plurality of layers of open cell foam synthetic plastics material, said mattress being provided with air passages extending therethrough for the dissipation of moisture; wherein there are provided a plurality of longitudinal channels each extending from one longitudinal edge of the mattress to the other longitudinal edge. Such mattresses may be provided with a pair of opposed longitudinally extending foam wedges, the narrow portions of each wedge being juxtaposed. The juxtaposed narrower portions of the wedges may be spaced apart to define a longitudinal channel.

The inventor has now found inter alia that this arrangement may equally be applied to foam mattresses for hospital use without longitudinal channels.

The standard hospital mattress comprises a 150 mm open cell foam of a synthetic plastics material enclosed in a close fitting vapour permeable but moisture resistant cover. This simple form of mattress is of course reverable but this reversibility confers on the mattress no other technical effect.

According therefore to a first aspect of the present invention there is provided a patient support mattress comprising a generally rectangular block of open cell foam, characterised in that the longitudinal edge portions are each formed with a longitudinally extending wedge portion, said wedge portion being either formed of said open cell foam or formed of a second material in a wedge shape thereby to confer on the mattress a concave configuration in use.

The longitudinal edge portions may be formed of a harder foam to support the longitudinal edges of a softer open cell foam from which the main body of the mattress is formed. Wedge portions may be formed of a second material which may be a solid, a rigid hollow member or members, or a harder foam material. The harder foam material may have the same hardness as or be harder than, the foam material utilised to support the longitudinal edges as described above.

The wedge portion may be formed at about one half of the depth of the foam block to confer reversibility on the mattress.

In accordance with prior art provisions the upper and lower surfaces of the mattress may also be provided with a chequer board or egg box configuration surface.

The wedge portions may be of any convenient configuration such as triangular in vertical cross section. Other possible configurations in vertical cross section are rectangular, ovoid, or asymmetric combinations of all of these.

The pressure signature of the foregoing arrangement tends to be improved because relatively more of the patients weight is borne in use by more of the patients skin surface. Also the concave configuration tends to move the patient axially of the mattress even if the degree of concavity is relatively small.

This has beneficial effects both when the mattress is used as a patient support by itself, or when used in conjunction with other mattress aids.

It will be appreciated that where the wedges are inserted intermediate the depth of the longitudinal edges of the mattress both larger upper and lower surface areas will have a generally concave configuration in the longitudinal sense.

When a patient lies upon such a mattress the central axial portion of the mattress is depressed thereby increasing the concave effect. For this reason only relatively small wedges are required since the effect of providing for reversibility also has the effect of increasing the effectiveness of the mattress.

Such an arrangement is not really suited to the close fitting vapour permeable but moisture resistant covers in accordance with the prior art. These tend to be close fitting so as to avoid wrinkles etc appearing in use. Because of this when the mattress deforms there is a hammocking effect which tends to reduce the effectiveness of the mattress in preventing bed sores.

This is occasioned in part because of the close fitting nature of the cover and in part because in order to provide a cover of sufficient strength it necessary to provide it upon a woven base. The open cell foam mattress provides a high friction surface which tends to bind to the underside of the mattress cover and hence induce friction.

The present invention in a second aspect provides a low friction interlayer disposed about the longitudinal and preferably also the transverse edge portions of the mattress and secured inboard of the edges so that the cover can readily slide over the longitudinal (or transverse) edges relative to the mattress.

Therefore to a further aspect of the present invention there is provided a patient support mattress comprising a generally rectangular block of open cell foam provided with a moisture resistant vapour permeable cover; characterised in that the longitudinal edges of the foam block are provided with a low friction interlayer. The interlayer may be formed of a low friction flexible material such as a silky material optionally the longitudinal edges of the foam block may be chamfered. Similar arrangements may be made for the transverse edge portions of the mattress.

The longitudinal edges of the silky material may be secured within the body of the mattress adjacent to, but spaced from, the longitudinal edge.

In both the foregoing aspects of the invention a standard chequer board or egg box configuration upper layer may be incorporated. In such arrangements the inner core of the mattress may be formed of a foam having a density of 45 to 55 kgs/m3 and a hardness of 190 to 240 newtons. In such a case the wedges and the longitudinal edges may be made of the same foam and may have a density of 70 to 100 kgs/m3 with a hardness of 300 to 600 newtons. The chequer board or egg box configuration layer may be made of a foam having a density of 35 to 45 kg/m3. The density is measured by BSS 4413 part method to 1988 whereas hardness is measured by BSS 4993 part 2 method 7 1988.

The invention will now be described, by way of illustration only, with reference to figures 1 to 4 of the accompanying drawings, wherein Figure 1 shows a transfer section through the first standard concave mattress in accordance with the present invention, Figure 2 shows a transverse cross section through a concave mattress with chequer board inserts in accordance with the present invention, Figure 3 shows a transverse section through an edge portion of a mattress showing the silky interlayer and Figure 4 shows a bar graph showing the effects of wedge insertion.

With reference to Figure 1 a standard concave mattress 1 in accordance with the present invention is provided with an inner core layer 2 of synthetic foam having a density of 48 to 52 kgs/m3 and a hardness of 195 to 235 newtons. The longitudinal edges of the standard mattress 1 are formed of a harder foam material having a density of about 95 kgs/m3 with a hardness of 300 to 600 newtons.

Wedges 4 formed of the same material as that which forms the longitudinal edges, extend inwardly approximately on the mid line towards each other from either longitudinal edge. The effect of the wedges 4 is to thicken the outer edges of the support mattress thereby leaving the central portions 8 with a narrower vertical configuration. It will be appreciated that when the patients weight falls upon the central portion 8 of the mattress the mattress will deform so that the lower surface 8 will press upon the ground. The effect of this is to deform the wedges 4 downwardly towards the central portion and thereby provide a greater patient support area on the upper surface.

In Figure 2 an arrangement similar to that shown in Figure 1 is shown, but in Figure 2 a soft foam chequer board insert 6 is utilized said chequer board insert having a density of 38 to 48 kgs/m3 and a hardness of 140 to 180 newtons. At regular intervals throughout the chequer board surface cuts are made so that the chequer board comprises a plurality of upstanding independently pressure absorbing areas the better to absorb patient discontinuities. Figure 2 is also provided with a central channel 5 which runs the length of the mattress to provide a measure of ventilation when the mattress is in its at rest condition.

It will be observed that both the mattress of Figures 1 and 2 are reversible as shown and accordingly both have the advantage of utilizing the patients weight to decrease the pressure signature.

In the improvement of the present invention the arrangement of Figure 3 provides a standard foam mattress 11 terminating at its longitudinal edges in a longitudinal harder edge material 13. In this arrangement, the longitudinal edges of the longitudinal harder edge portion 13 are chamfered at 17 so as to provide a lower friction aspect to a vapour permeable, moisture resistant cover 14. Further and perhaps more importantly, the longitudinal harder edge portion 13 is covered by a silk interlayer 15 which extends about the edge portion 13 and is secured below the chequer board layer 12 adhesively or by other means. Alternatively, the silk interlayer may be secured within the chequer board layer itself.

The vapour permeable moisture resistant cover 14 is formed of two layers, an outer layer to confer vapour permeability and moisture resistance, an inner layer to provide strength and permeability. The inner layer is of a woven material which tends to be rough. The effect of the silky interlayer 15 is to provide a low friction interlayer between the cover 14 and the portion of the foam which normally provides high friction interference during relative movement between the cover and the foam mattress. This arrangement significantly reduces hammocking.

The efficiency of the present arrangement is shown in Figure 4. In Figure 4 the pressure signature expressed as a percentage pressure reduction over a standard hospital mattress provided with a close fitting cover and with 150 mm deep open cell foam is shown. In said Figure 4 bar graph A relates to an arrangement shown in Figure 3 and 4 of co pending UK patent application number GB-A-2 274 054, while bar graph B shows the results obtained from an arrangement in accordance with Figures 1 and 2 of the said co pending UK patent application. It will be observed that the effect of wedges is to reduce the pressure signature by some 14% at the sacrum, and some 10% at the heels.

Claims

1. A patient support mattress comprising a generally rectangular block of open cell foam; characterised in that the longitudinal edge portions are each formed with a longitudinally extending wedge portion, said wedge portion being either formed of said open cell foam or formed of a second material in a wedge shape thereby to confer on the mattress a concave configuration in use.

2. A mattress according to claim 1 wherein the longitudinal edge portions are formed of a harder foam to support the longitudinal edges of the generally rectangular block of open cell foam.

3. A mattress according to either claims 1 or 2 wherein the wedge portions are formed of a second material which may be a rigid hollow or solid member or members, or a harder foam material.

4. A mattress according to any preceding claim wherein the wedge portion is formed generally intermediate the depth of the foam blocked to confer to reversibility on the mattress.

5. A mattress according to any preceding claim wherein at least one of the upper and lower surfaces of the mattress is provided with a chequer board or egg box configuration foam layer.

6. A mattress according to any preceding claim wherein the wedge portions have a configuration in cross section which is generally triangular, ovoid, rectangular or an asymmetric combination thereof.

7. A patient support mattress comprising a generally rectangular block of open cell foam provided with a moisture resistant vapour permeable cover; characterised in that the longitudinal edges of the foam block are provided with a low friction interlayer.

8. A mattress according to claim 7 wherein the interlayer is formed of a silky material.

9. A mattress according to any preceding claim wherein the longitudinal edges at least of the foam block are chamfered.

10. A mattress according to any one of claims 7 to 9 wherein the longitudinal edges of the silky material are secured within the body of the mattress.

11. A mattress according to any one of claims 7 to 10 wherein the low friction inter layer extends along the transverse edges of the foam as well as the longitudinal edges.