NZ728499B2

NZ728499B2 - Mattress

Info

Publication number: NZ728499B2
Application number: NZ728499A
Authority: NZ
Inventors: Jonphysical Lewis
Original assignee: Direct Healthcare Group Limited
Priority date: 2014-07-29
Filing date: 2015-02-18
Publication date: 2021-04-30

Abstract

mattress (100) comprises a first air-holding portion (102) and a second air-holding portion (104). The first air-holding portion comprises the approximate middle section of the mattress and the second air-holding portion comprises the foot portion of the mattress. The second air-holding portion further comprises a plurality of interconnected chambers wherein at least one of the chambers is larger than the other chambers and located closer to the middle section of the mattress than the other chambers, the chambers being in fluid communication such that air may flow in only one direction between the plurality of chambers. The first air-holding portion is connected to the second air-holding portion via a connecting portion (106) arranged with a one-way valve (108) to allow only one-way airflow from the first air-holding portion to the second air-holding portion. The first air-holding portion includes a one-way air inlet valve (112) and the second air-holding portion includes a one-way air outlet valve (114). The mattress assists in the prevention of pressure sores that can develop from external forces on a patient, resulting from direct pressure, shear and friction. This is achieved by relieving pressure on vulnerable areas by changing the patient position without requiring significant carer time or disturbing the patient. rther comprises a plurality of interconnected chambers wherein at least one of the chambers is larger than the other chambers and located closer to the middle section of the mattress than the other chambers, the chambers being in fluid communication such that air may flow in only one direction between the plurality of chambers. The first air-holding portion is connected to the second air-holding portion via a connecting portion (106) arranged with a one-way valve (108) to allow only one-way airflow from the first air-holding portion to the second air-holding portion. The first air-holding portion includes a one-way air inlet valve (112) and the second air-holding portion includes a one-way air outlet valve (114). The mattress assists in the prevention of pressure sores that can develop from external forces on a patient, resulting from direct pressure, shear and friction. This is achieved by relieving pressure on vulnerable areas by changing the patient position without requiring significant carer time or disturbing the patient.

Description

Mattress Field of the Invention The present invention concerns a ss arrangement and mattress. More particularly, but not exclusively, this ion concerns a mattress to assist in the prevention of re sores, and a method of reducing pressure sores.

Background of the Invention In hospitals and other care nments, patients who are bed—bound or spend a long period of time confined to bed can suffer from pressure sores, which are also known as pressure ulcers. These are painful and attending to pressure sores also diverts nurses and carers from other tasks. The cost of attending to re sores can also be high causing a strain on healthcare budgets.

Pressure sores develop as a result of external forces on a patient, resulting from direct pressure, shear, and friction, causing stresses and strain on the tissue. This inhibits circulation and may prevent oxygen and other nutrients from reaching the tissue. Common places for pressure sores include bony protuberances, such as the heels, ankles, hips, bottom, shoulders, elbows, back, and back of the head of a patient. Prolonged pressure n these pressure points and a mattress may result in red skin which, in time, forms a blister, followed by an open sore.

The re sore can be painful for a patient, and also destroy or damage the muscle and/or bone under the skin.

These may also become infected and cause potentially life— threatening blood poisoning or bone infections.

The heels of a patient are particularly vulnerable to pressure sores because of the small amount of flesh present at the heels.

One way to prevent pressure sores is to reduce or relieve the pressure on vulnerable areas. This may be by moving the t and changing the patient position. One way in which this can be achieved, t requiring significant nurse or carer time, and without disturbing the patient more than necessary, is by using special mattresses.

Conventional pressure relief sses include specialised foam mattresses comprising a foam base and a lly contoured foam insert on which the patient body is ted. These mattresses may be known as static mattresses. Although such mattresses may be effective at preventing the development of pressure sores, some ts may require more assistance to keep moving. Alternative mattresses may be provided, such as an inflatable mattress.

These mattresses maybe known as dynamic mattresses. This type of mattress comprises a series of inflated sections.

Such mattresses may be permanently inflated or the inflatable sections may be partially or wholly inflated/deflated using motorised pumps. Where a pump is used, each inflatable section is in fluid communication with the pump, the pump selectively inflating and deflating each inflatable section thereby gently moving the patient supported on the mattress. However, it is not practical to supply every bed in a hospital or care home with an inflatable mattress with a pump due to the significant costs involved.

The present invention seeks to mitigate the above— mentioned problems. atively or additionally, the 2015/050471 present ion seeks to provide an improved mattress and mattress system for use in a hospital and/or care environment.

Summary of the Invention The present invention provides, according to a first aspect, a mattress comprising: a first air—holding portion; a second air—holding n; wherein the first air—holding portion comprises the approximate middle section of the mattress and the second air—holding portion comprises the foot portion of the mattress; the first air—holding portion connected to the second air—holding portion via a connecting portion arranged to allow only y airflow from the first air—holding portion to the second air-holding portion; wherein the first air—holding portion includes a one— way air inlet valve and the second air—holding n includes a one—way air outlet valve.

The skilled person will appreciate that the middle portion of a mattress is the section in which the pelvis of a user lying or sitting on a mattress would usually be placed on, and the foot portion of the ss is the section in which the feet of a user lying or g on a mattress would y be placed on.

Preferably, the mattress is configured to allow passage of air through the mattress in one direction only. The first air—holding portion may take air in through the one— way air inlet valve and push air into the second air—holding 2015/050471 portion, via the connecting portion. The second air—holding portion may take air in from the first air—holding portion and push air out of the one—way air outlet valve.

The one—way air inlet valve may be open to the atmosphere. The one—way air outlet valve may be open to the atmosphere. The mattress may be an “open” system, in that air may be taken into the mattress from the atmosphere and leave the mattress arrangement to the atmosphere.

The connecting portion may comprise a tube and a one— way valve.

The first lding portion and second air—holding portion may be made of an air impermeable material.

Advantageously, the first air—holding portion may be compressible, for example in response to a patient g or lying on the ss. Such compression may increase the pressure within the first air—holding portion and cause the first air—holding portion to pump air into the second air- holding portion. Therefore, airflow through the mattress may be tated using only the movement of a patient, with no motorised pump required.

The first air—holding portion may comprise a r.

The first air-holding portion may comprise a ity of interconnected chambers. The chambers may be interconnected such that the chambers are in fluid communication with each other. The interconnection may be such that air may flow in any direction between the plurality of chambers. atively, the interconnection may be such that air may flow in only one direction between the plurality of chambers. The chamber(s) comprising the first air—holding portion may comprise an air—retaining material. The air— retaining material may be a foam. The air—retaining WO 16602 material may be surrounded by an air impermeable material, such as polyurethane or PVC. The first air—holding portion may be resiliently deformable. The air—retaining material may be resilient, such that under compression the material is biased to return to an uncompressed position. The volume of the first air—holding portion may be reduced under ssion. The volume of the first air—holding portion may be reduced under compression as air is pushed into the second lding portion. The air—retaining material may act to return the first air—holding portion to an uncompressed volume on removal of the compression. The first air—holding portion may take air in through the one- way air inlet valve On removal of ssion.

The second air-holding portion may comprise a chamber.

The second air—holding portion may comprise a plurality of interconnected chambers. At least one of the ity of interconnected chambers may be larger than the other interconnected chambers. The at least one larger interconnected chamber may be located closer to the middle n of the mattress than the other interconnected The chambers may be interconnected such that the chambers are in fluid communication with each other. The interconnection may be such that the air may flow in only one direction between the plurality of chambers. The plurality of interconnected chambers may be interconnected such that air may flow only in one direction between the plurality of chambers, from the smaller chamber or chambers to the larger chamber. The one-way air outlet valve may be ated with the larger chamber.

The direction of airflow in the first air—retaining portion may be opposite to the direction of airflow in the second air—retaining portion. The second air—holding portion may be deformable. The chamber(s) may be substantially free of any air—retaining material. On compression, the volume of the second air—holding n may be reduced. The volume of the second air—holding portion may be reduced under compression as air is pushed out of the one—way air outlet valve. The volume of the second lding portion may remain reduced on removal of the compressive force. The re within the second air- holding portion may reduce to substantially zero pressure under compression. The volume of the second air-holding portion may remain reduced on removal of the compressive force until additional air is moved into the second air— g portion by compression of the first air—holding portion.

The middle section of a mattress may be the n of the mattress which experiences the greatest pressure when the mattress is used on an adjustable bed in a seating position. The foot sectiOn of a mattress is the area of a mattress in which a user of the mattress places their feet in usual stances. As a patient sits or lies on the first air—holding n they may compress the first air- g portion such that air is pushed into the second air— holding portion. The air pushed into the second air—holding portion may increase the pressure within the second air— holding portion. When the pressure within the second air— holding portion increases to a certain level, air passes out of the second air—holding portion via the one—way air output valve. The pressure may increase to such a level due to the passage of air from the first air—holding portion to the second air—holding portion. Alternatively or additionally, the pressure may increase to such a level due to the user adjusting their position on the second air-holding portion or simply the weight of the user acting on the second air— holding portion. The pressure at which air passes out of the second lding portion via the one-way air output value may be in the range from 1mm Hg (millimetre of mercury) to 25mm Hg. The pressure at which air passes out of the second air—holding portion via the one—way air output value may be in the range from 3mm Hg to 10mm Hg. The pressure at which air passes out of the second air—holding portion via the one—way air output valve may be 6mm Hg. The pressure at which the air passes out of the second air— holding portion via the one—way air output valve may be determined by the rating of the air output valve. The one— way air output valve may be rated according to any of the ranges or valves described above.

According to a second aspect, there is provided a method of 2O pumping air through a mattress, the mattress according to the first aspect of the invention, comprising the steps of: compressing the first air—holding portion, y pushing air into the second air—holding portion, and compressing the second air—holding portion, thereby pushing air out of the second air—holding portion into the atmosphere.

According to a third aspect, the invention provides a method of reducing the pressure on the heels of a bed user, the method sing the steps of providing a ss according to the first aspect of the ion, a user lying or sitting on the mattress, with their pelvis d on the first air-holding n and their heels located on the second air—holding portion, nt of the user compressing the first air-holding portion, thereby pusing air into the second air—holding portion, and pressure d by the user on the second air—holding portion compressing the second lding portion,.thereby pushing air out of the second air holding portion into the atmosphere.

The second air—retaining portion may comprise a plurality of interconnected chambers, with a larger chamber located towards the middle of the mattress. The larger chamber may be arranged to support the leg of the user above their heels, for example, around their mid—calf. Supporting the leg of the user above their heels may act to reduce the pressure experienced by the heels of the user, thereby helping to reduce pressure sores on the heels of a user.

The plurality of interconnected chambers may be arranged such that pressure d by the heels of a user on the second air—retaining portion pushes air from the smaller of ‘the interconnected chambers to the larger interconnected chamber. Therefore, the heels of the user may initially sink into the smaller of the interconnected chambers, and the larger of the interconnected chambers may increase in size to support the lower leg of the user. The heels of the user may end up in t with the smaller of the interconnected chambers, but essentially experiencing little or no pressure as a result of the contact, due to the lower leg support offered by the larger of the interconnected chambers. The pressure d on the larger chamber by the lower legs of the user may increase as the volume of air in the larger chamber increases, causing the air outlet valve ated with the larger chamber to release a ty of air. The volume of the larger chamber will then reduce, and the support provided to the lower legs se. As the user moves, more air will be pumped from the first air— retaining portion to the second air—retaining portion. This will increase the pressure in the chamber or chambers supporting the heels of the user. The heels of the user will rise, and the cycle begins again, with the pressure on the heels initially being raised and then reduced as air is pumped into the larger of the interconnected chambers. The ion in pressure on the heels of the user, together with the gentle movement provided by the pumping action, may significantly reduce the risk of re sores developing.

According to a fourth , the invention provides a hospital bed, the hospital bed comprising a mattress as described with s to the first aspect of the invention.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the es described with reference to the mattress of the invention and vice versa.

Description of the Drawings Embodiments of the present invention will now be bed by way of example only with reference to the accompanying schematic drawings of which: Figure 1 shows a schematic View of a mattress arrangement according to a first embodiment of the invention; _lO_ Figure 2 shows a schematic view of a mattress arrangement according to a second embodiment of the invention; Figure 3 shows a mattress according to a third embodiment of the invention comprising a mattress arrangement according to the second embodiment of the ion; Figure 4 shows a cross—sectional view of the first air— holding portion according to the first embodiment of the invention; Figure 5 shows a mattress ing to a fourth embodiment of the invention, and Figure 6 shows a cross-sectional view of the second air— ing portion of the fourth embodiment of the invention.

Detailed Description Figure 1 shows a mattress comprising a ss arrangement 100. The mattress arrangement 100 comprises a first air—holding n 102 and a second air—holding portion 104. The first air holding portion 102 is in fluid communication with the second air—holding portion 104 via a connecting portion comprising a tube 106, which includes a one-way valve 108. The one way valve 108 allows air to flow from the first air—holding portion 102 to the second air— holding portion 104 via the tube 106, but does not allow air flow in the reverse ion. Both the first air—holding portion 102 and second air—holding portion 104 are made of an air impermeable material, in this case thermoplastic polyurethane (TPU) film. Alternative suitable materials may 2015/050471 -11.. be used, as will be appreciated by the skilled person, and may include a number of plastics and/or rubber materials provided the materials are suitably strong, resilient, and air impermeable. The first air-holding portion 102 includes an air—retaining material 110 in the form of a foam material. An example air—retaining al is tion modified high-resilience (CMHR) foam. The air—retaining material 110 is porous and resiliently deformable. When compressed, the air—retaining material 110 is reduced in volume, but when the compressive force is removed, the air— retaining material 110 returns to the al volume.

Figure 4 shows a potential cross—sectional profile of the taining material 110. The profile of the cross—section may be ed depending on the required physicalr teristics for the foam.

The first air—holding portion 102 comprises a one—way air intake valve 112. The oneeway air intake valve 112 is open to the atmosphere and allows air to be drawn into the first air—holding portion 102, but does not allow air to leave the first air—holding portion 102. When the first air—holding portion 102 is compressed, air passes via the tube 106, through the valve 108, and into the second air- holding portion 104. When the compressive force is removed or reduced, the air retaining material 110 decompresses and draws air into the first lding means 102 Via the one- way air inlet valve 112.

The second air-holding portion 104 does not include any air-retaining al. Other than the air impermeable material and any air held within the second air—holding portion 104, the second air—holding portion 104 is substantially empty. If the pressure within the second air— _12_ g n 104 s a n value, in this embodiment 6mm Hg, air will begin to pass through the one— way air outlet valve 114. The pressure within the second air-holding means 104 may be increased due to either the volume of the second air—holding means 104 being reduced by compression, or due to the ingress of air which has been pumped from the first air—holding portion 102. If the second lding portion 104 is compressed, resulting in the egress of air from the second air—holding portion 104, the pressure within the second air—holding portion 104 may reduce to substantially zero. Once compressed, the volume and pressure within the second air—holding portion 104 will not increase until air is pumped into the second lding portion 104 from the first air—holding portion 102.

Figure 2 shows a schematic view of a second embodiment of the invention. A mattress arrangement 200 comprises a first air-holding n 202 and a second air—holding portion 204. The first air—holding portion 202 comprises three chambers 206, 208, and 210. Each of the chambers, 206, 208, 210, comprises a foam air—retaining material as described for the air—holding portion 102 in relation to figure 1. To improve clarity, the foam air—retaining material is not shown in figure 2. The chamber 206 is connected to a one—way air inlet valve 212 arranged to allow air to flow into the chamber 206 but not out of the chamber 206. The chambers 206, 208, 210 are in fluid communication with each other via tubes 214, 216, such that air may flow between the chambers 206, 208, 210, in any ion. The second air—holding means comprises three chambers 218, 220, and 222. The chambers are connected to each other via tubes 224 and 226 which include one way valves. The one—way _l3_ valves are arranged such that air may flow from chamber 218 to chamber 220, but not from chamber 220 to chamber 218.

Also air may flow from chamber 220 to chamber 222, but not chamber 222 to r 220. Chamber 222 is connected to a one—way outlet valve 230 which allows air to flow out of chamber 222 but not into chamber 222. Therefore, airflow through the second lding portion 204 is allowed in one ion only. The chambers 218, 220, and 222, are substantially empty apart from air, as described in relation to the second air—holding portion 104 with reference to figure 1. The first air—holding portion 202 and second air— holding n 204 are connected via a connecting portion comprising a tube 226 running between the chamber 210 and chamber 218. The tube 226 includes a one—way valve 228 which allows air to pass from the first air—holding n 202 to the second air—holding portion 204, but not from the second air—holding pdrtion 204 to the first air—holding portion 202.

Figure 3 shows a mattress according to a third embodiment of the invention. The mattress 300 comprises a foam body 302, into which the mattress arrangement 200 has been integrated. Not all of the features of the mattress arrangement have been shown in figure 3 to e clarity.

The first air—holding portion 202 is located in the approximate middle of the mattress 300. This is where the buttocks of a patient will be d when the patient is lying on the mattress 300. The second air—holding portion 204 is located at the foot of the ss 300. This will be where the heels and feet of a patient will be located when the patient is lying on the mattress 300. The mattress 300 may be placed on an adjustable bed, where the bed is -14— e of being laid fully flat, or in one or more ted sitting positions. Whether the patient is in a fully flat lying position or in a supported position, the principles of operation of the mattress assembly 200 remain the same.

The mattress may be covered by a stretchable fabric cover to t the mattress. The stretchable fabric cover may be chosen to be easily cleaned n patient changeovers.

A significant portion of the weight of a patient will be supported by the first air—holding portion 202. When a patient moves, the first air—holding portion 202 may be compressed. This compression of the first air—holding portion 202 will increase the pressure within the rs 206, 208 and 210 until the one—way valve 228 is opened, and air is pushed into the second air—holding portion 204. When the patient moves again, the compression of the first air— holding portion 202 may be reduced, and the chambers 206, 208, and 210 increase in volume under the action of the air— ing material, drawing air in from the atmosphere via the one—way air inlet valve 212.

The air pushed through the valve 228 enters the chamber 218 of the second air—holding n 204. If and when the pressure inside the chamber 218 increases to the point of g the valve in the tube 224, air will be pushed into the chamber 220. Such a pressure increase may be as a result of the movement of air from the first air—holding portion 202. Alternatively or additionally, the pressure increase may be caused by compression of the chamber 218 via the movement of the feet of a patient, the feet being supported by the second air—holding portion, or simply the WO 16602 _15_ weight of the feet on chamber 218. This compression and resultant w into chamber 220 may reduce the pressure inside the r 218 to substantially nothing. Therefore, the pressure on the heels and feet of a patient may be significantly reduced. The amount of air within the chamber 218 will only increase if the first air—holding portion 202 pushes air through the tube 226. The amount of air within the chamber 220 may be reduced in a similar way, such that air may flow from the chamber 220 to the chamber 222. The amount of air within-the chamber 224 is only reduced by passage of air out of the chamber via the outlet valve 230, open to the atmosphere. Therefore, it can be seen that the first lding portion 202, acts, under the movement of a patient, to pump air into the second air holding portion 204. The movement of a patient then acts to pump air out of the second lding portion 204 into the atmosphere. The movement of a patient over time results in the second air— holding portion being increased and decreased in pressure and volume in a similar way to that found in dynamic pressure relief mattresses, but without requiring a powered pump to be present.

Figure 5 shows a mattress ing to a fourth embodiment of the invention. The mattress 500 ses a first air-retaining portion 502 comprising a plurality of interconnected rs 506, 508, 510, located in the approximate middle of the mattress 500. An air inlet valve is associated with the chamber 506, and each of the chambers 506, 508, and 510, include an air—retaining material as described for the chambers 206, 208, and 210, of figure 3.

The ss 500 also comprises a second air—retaining portion 504 which comprises a plurality of interconnected -16... chambers 518, 520, and 522. The chamber 510 is connected to the chamber 522 via a tube and a one way valve, such that compression of the chambers 506, 508, and 510, pumps air into the chamber 522: The chamber 522 is fluidly connected to the chamber 520 by a one way valve, arranged to allow air to flow from the chamber 522 to the chamber 520. The chamber 520 is connected to the chamber 518 by a one way valve, ed to allow air to flow from the chamber 520 to the chamber 518. The chamber 518 includes a one—way air outlet valve, which is open to the atmosphere. As can be seen in figure 6, the chamber 518 is larger than the chamber 520 and 522. This allows a user to rest their legs on the second air—retaining portion 504 with their heels in contact with one or both of the chambers 520, and also a part of their lower leg, in this case mid—calf, in contact with the r 518. A user may sit or lie on the mattress 500 with their pelvis located over the first air—retaining portion 502. In this position, their heels will be located over the second air—retaining n, as described with reference to figure 6. When a user shifts position, they will ss the first taining portion 502, causing air to be pumped from the chambers 506, 508, and 510, into the chamber 522 of the second air—retaining portion 504. When the pressure in the chamber 522 builds to the required level, air will pass into the chamber 520 via the one-way valve connecting the two chambers. The pressure within the chamber 520 will increase accordingly. The weight of the user’s heels on the r 520 will act to ss the chamber 520, causing air to be pumped from the chamber 520 into the chamber 518 via the one—way valve connecting the two chambers. This will lift the lower legs of the user, -17— reducing pressure on the feels, which with the reduction of re in the r 520 means that the pressure experienced by the heels of the user is much reduced, tending to zero. Once the pressure within chamber 518 increases to a certain level, air will escape through the air outlet valve. Movement of the user will pump air from the first air—retaining portion 502 into the chamber 522, and the cycle will begin again, with the lower legs and heels of the user being moved and the pressure experienced by the heels and lower legs of the user being varied accordingly.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible ions will now be described. In the description above, the second air—holding portion is located at the foot of the mattress. In alternative embodiments, the second air—holding n may be d at any area in which reduced pressure is required or desired. For example, the second air—holding portion may be located at the head of a mattress.

In an alternative ment, the mattress arrangement may be a modular arrangement, thereby allowing the configuration of the mattress to be adjusted according to the ular needs of a patient for which the mattress arrangement is intended. The modular arrangement may provide a ss system which is configurable in dependence on the weight and/or size of a patient. The modular arrangement may comprise a number of connectable and -18— disconnectable tubes, chambers, and valves. The configuration may se adjusting the size or position of the mattress elements in relation to a patient.

Alternatively or additionally, the pressures required to pump air through the mattress arrangement may be adjusted by selection of the als from the first air—holding portion and/or second air holding portion may be made, and the ratings of the valves and tubes included in the ss arrangement.

Where in the foregoing description, integers or ts are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that rs or features of the ion that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may ore be absent, in other embodiments.

Claims

1. A mattress comprising: a first air-holding portion; a second air-holding portion; wherein the first air-holding portion comprises the approximate middle section of the mattress and the second air-holding portion comprises the foot portion of the ss, the first air-holding portion connected to the second air-holding portion via a connecting portion ed to allow only one-way airflow from the first air-holding portion to the second air-holding portion; wherein the first air-holding portion includes a one- way air inlet valve and the second air-holding portion includes a one-way air outlet valve, wherein the second air-holding portion comprises a plurality of interconnected chambers, n at least one of the plurality of interconnected chambers is larger than the other interconnected chambers and the at least one larger chamber is located closer to the middle portion of the mattress than the other interconnected chambers, the chambers being interconnected such that the rs are in fluid communication with each other, and the interconnection is such that the air may flow in only one direction between the plurality of

2. A mattress as claimed in claim 1, wherein the one-way air inlet valve is open to the here.

3. A mattress as claimed in claim 1 or claim 2, wherein the one-way air outlet valve is open to the atmosphere.

4. A mattress as claimed in any preceding claim, wherein the first air-holding portion comprises a plurality of interconnected chambers.

5. A mattress as claimed in claim 4, n the chambers are interconnected such that the chambers are in fluid communication with each other.

6. A mattress as claimed in claim 4 or claim 5, wherein the chambers sing the first lding portion comprise an air-retaining material.

7. A mattress as claimed in claim 1, wherein the chambers are interconnected such that air may flow only in one direction between the ity of chambers, from the smaller chamber or chambers to the larger chamber.

8. A mattress as claimed in claim 7, wherein the one-way air outlet valve is associated with the larger chamber.

9. A mattress as claimed in any preceding claim, n the second air-holding portion is substantially free of any air retaining material.

10. A method of pumping air through a mattress arrangement, the mattress arrangement according to any of claims 1 to 9, sing the steps of: compressing the first lding portion, thereby pushing air into the second airholding n, and compressing the second air-holding portion, thereby pushing air out of the second airholding portion into the atmosphere.

11. A hospital bed comprising a mattress as claimed in any of claims 1 to 9. WO 16602