GB2619263A

GB2619263A - A mattress and a method for its operation

Info

Publication number: GB2619263A
Application number: GB2205000.9A
Authority: GB
Inventors: John Baker Gary; John Baker Richard; David Silman Graham; Anne Dearden Jacqueline
Original assignee: SQUIRREL MEDICAL Ltd
Current assignee: SQUIRREL MEDICAL Ltd
Priority date: 2022-04-05
Filing date: 2022-04-05
Publication date: 2023-12-06
Also published as: GB202205000D0

Abstract

An inflatable cell mattress comprising a first set of transversely extending inflatable cells 6 and a second set of transversely extending inflatable cells 12 overlying the first set wherein the ratio of height of the cells of the second layer to the cells of the first layer is between 1:1.9 and 1:2.1. The first layer of cells 6 may have an elongate cross section with a length to width ratio of 1.1:1 to 1.5:1. The first layer may have extended cells which pass up through the second layer. The cells of the second layer 12 may be circular and may be separated from the first cells 6 by a common gas impermeable membrane. Also disclosed is an arrangement with a first layer between 9.5 and 10 cm and a second between 4.5 and 5.5 cm. Also disclosed is an an alternating pressure approach for groups of cells in first and second layers.

Description

A MATTRESS AND A METHOD FOR ITS OPERATION

The present invention relates to a mattress, in particular to a mattress having therapeutic and/or orthopaedic applications. The present invention especially relates to a mattress comprising a plurality of inflatable cells. The present invention further relates to a method of operating a mattress of the aforementioned kind.

It is known to provide mattresses comprising a plurality of inflatable cells. For example, GB 1 595 417 discloses an inflatable mattress or pad comprising inflatable and deflatable flexible tubes laid side by side across the mattress or pad. Alternative tubes are periodically inflated and deflated.

An alternating pressure pad is described and shown in GB 2 197 192 A. The pad comprises two or more layers, each layer having two sets of cells. The cells of each set of cells are inflatable independently of the cells of the other set of cells.

GB 2 327 874 A discloses an inflatable support, such as an air loss mattress. The support comprises an upper layer of inflatable cells and a separate lower layer of inflatable cells. In use, the lower layer of cells is always maintained at a constant pressure higher than the pressure of the upper layer of cells. In this way, a person lying on the support is prevented from contacting the underlying support surface on which the support is resting.

Mattresses of this general type are widely used in hospitals and clinics, in particular for patients with long term illnesses and difficulties requiring them to remain in bed for extended periods of time. It is known to provide such mattresses with suitable pumps and control means to selectively inflate and deflate the cells with air. In this way, the form and contours of the mattress may be varied beneath the patient, so as to avoid the patient developing pressure sores and other conditions symptomatic of extended periods reclining in bed. The mattress may be provided with cells that are permanently inflated and/or cells that may be selectively partially or wholly inflated and deflated. In addition, the mattress may be provided with cells that are provided with air-permeable portions, for example by way of laser perforations, designed to allow air to leak or bleed from the cell at a predetermined rate.

One mattress produced by the present Applicant comprises a base of expanded foam, in particular an open-cell polyurethane foam, a first layer of transverse cells permanently inflated to a predetermined pressure with air, and an upper layer of transverse air-filled cells. The total number of cells in the mattress is 84, divided between the first and upper layers. The cells in the upper layer are of two forms. First, the upper layer is provided with a region of cells of the aforementioned perforated variety, means being provided to supply air at a constant rate and pressure to replace air leaving the cells through the perforations and maintain the cells at a predetermined inflation pressure. Second, the upper layer is provided with a region having cells that io are selectively inflated and deflated, as described hereinbefore. The mattress of this type has proven to be particularly successful in forming a bed for patients that are bedridden or required to spend extended periods of time in bed in a prone position. A mattress of this general type is herein referred to as 'an inflatable cell mattress'.

GB 2 473 661 of the present Applicant discloses an inflatable cell mattress is comprising a base layer, a first layer of cells on the base layer and a second layer of cells overlying the first layer of cells. The layers of the mattress are arranged to provide the mattress with an overall thickness of no greater than 150 mm. The cells of the first layer may have a diameter of from 3 to 6 cm, preferably about 4.75 cm. The cells of the second layer may have a diameter of from 3 to 6 cm, again preferably zo about 4.75 cm.

When a person lies on a mattress, the weight of their body results in capillaries in the region of contact between the body and the mattress being compressed and occluded. This reduces or stops localised blood flow. This effect, if unrelieved, can lead to the formation of pressure sores and ulcers. Generally, humans respond to such discomfort and will naturally move to reposition their body every 11 to 12 minutes.

Elderly people have aged blood vessels, which can have reduced strength. If the flow of blood to the blood vessels of an elderly person is restored too rapidly, blood vessels, such as capillaries, can rupture leading to a reperfusion injury. Conversely, if pressure is applied to the blood vessel too rapidly the blood vessels can become trapped and stasis can occur. The normal response of an elderly person changing position in response to discomfort arising from the pressure of lying on a mattress can result in injuries of this kind.

Inflatable cell mattresses are employed with the intention of reducing or avoiding the formation of pressure ulcers on the bodies of users, in particular patients who are bed-ridden or spend extended periods of time in bed. However, there is a need for an improved inflatable cell mattress and a method for the operation of an inflatable cell mattress that reduce or avoid the aforementioned injuries occurring to elderly patients.

In a first aspect, the present invention provides an inflatable cell mattress, the mattress comprising: a first layer comprising a first set of transversely extending inflatable cells; and a second layer comprising a second set of transversely extending inflatable cells, the second layer of cells overlying at least a portion of the first layer of cells; wherein the ratio of the height of the cells of the second layer of cells to the height of the cells of the first layer of cells is from 1:1.9 to 1:2.1.

There is also provided an inflatable cell mattress, the mattress comprising: a first layer comprising a first set of transversely extending inflatable cells, each cell of the first layer of cells having a height of from 9.5 to 10.5 cm; and a second layer comprising a second set of transversely extending inflatable cells, the second layer of cells overlying at least a portion of the first layer of cells, each cell of the second layer of cells having a height of from 4.5 to 5.5 cm.

In a further aspect, the present invention provides a method for operating an inflatable cell mattress, the mattress comprising: a first layer of cells comprising a plurality of inflatable cells; and a second layer of inflatable cells overlying at least a portion of the first layer of cells, the second layer of cells comprising one or more first groups of cells and one or more second groups of cells, each of the first and second groups of cells comprising at least one inflatable cell, the first groups of cells alternating with the second groups of cells along the length of the mattress; the method comprising: inflating and deflating the cells of the first groups of cells and the cells of the second groups of cells using an inflation regime, the inflation regime comprising: an inflation period during which the cell is inflated from a deflated condition to an inflated condition during a period of from 1 to 2 minutes; an inflated period during which the cell is held in the inflated condition for a period of from 4 to 5 minutes; a deflation period during which the cell is deflated from the inflated condition to the deflated condition during a period of from 1 to 2 minutes; and a deflated period, during which the cell is held in the deflated condition for a period of from 3 to 4 minutes; wherein the inflation regime is applied to the cells of the first groups of cells and the second groups of cells such that as the cells of one of the first and second groups of cells is inflating the cells of the other of the first and second groups of cells are deflating, whereby at no time are all the cells of both the first and second groups of cells fully deflated.

There is also provided an inflatable cell mattress, the mattress comprising: a first layer of cells comprising a plurality of inflatable cells; and a second layer of inflatable cells overlying at least a portion of the first layer of cells, the second layer of cells comprising one or more first groups of cells and one or more second groups of cells, each of the first and second groups of cells comprising at least one inflatable cell, the first groups of cells alternating with the second groups of cells along the length of the mattress; a gas supply system for supplying a gas to the cells of the second layer of cells; and a processor for controlling the pump and configured to operate the gas supply system to inflate and deflate the cells of the first groups of cells and the cells of the second groups of cells using an inflation regime, the inflation regime comprising: an inflation period during which the cell is inflated from a deflated condition to an inflated condition during a period of from 1 to 2 minutes; an inflated period during which the cell is held in the inflated condition for a period of from 4 to 5 minutes; a deflation period during which the cell is deflated from the inflated condition to the deflated condition during a period of from 1 to 2 minutes; and a deflated period, during which the cell is held in the deflated condition for a period of from 3 to 4 minutes; wherein the processor operates the gas supply system to apply the inflation regime to the cells of the first groups of cells and the second groups of cells such that as the cells of one of the first and second groups of cells is inflating the cells of the other of the first and second groups of cells are deflating, whereby at no time are all the cells of both the first and second groups of cells fully deflated.

The inflatable cell mattress and the method of operating an inflatable cell mattress of the present invention provide significant advantages. First, use of the mattress and method results in a significant reduction in pressure sores and ulcers. In addition, they provide advantages for elderly patients or other patients with damaged or delicate blood vessels, in particular by reducing the incidences of reperfusion injuries and stasis.

Further, the mattress and method have been found to stimulate the endothelium of the patient. This in turn results in improved blood flow in the blood vessels of the stimulated region and surrounding regions of the body of the patient. Such improved stimulation leads to improvements in the body's protection against the effects of abnormal durations or intensities of pressure, improved thermal regulation and improved healing and regenerative properties of the skin and other organs.

The inflatable cell mattress of the present invention is used in a conventional manner, in particular resting on a support, such as a bed. The mattress comprises a first layer of inflatable cells and a second layer of inflatable cells. In normal use, the mattress is oriented with the first layer of cells disposed below the second layer of 113 cells. References herein to terms such as 'upper' and 'lower' are references to the mattress and its components when in this orientation of normal use.

During use of the mattress, the cells of both the first and second layers of cells are inflated with a gas. References to the 'height' of the first and/or second layers of cells is a reference to the depth of the layer when the cells of that layer are inflated to their normal operating pressure, in the case of static cells, or inflated to their maximum pressure during normal operation.

The mattress comprises a first layer of inflatable cells. The cells in the first layer of cells extend transversely, that is laterally across the mattress, substantially perpendicular to the longitudinal axis of the mattress. Preferably, each cell of the first layer of cells extends laterally across the entire width of the mattress.

The cells of the first layer of cells may have any suitable shape and form. The cells of the first layer of cells are preferably of a uniform shape along their length. It is also preferred that the cells of the first layer of cells are all of the same shape.

The cells of the first layer of cells may have any suitable cross-sectional shape.

In one embodiment, the cells have a regular cross-section, that is the width of the cross-section is the same as the length of the cross-section, for example circular or square. More preferably each cell of the first layer of cells has a cross-section that is elongate, that is the cross-section has a length that is greater than its width.

Preferably, the cells are arranged with the lengthwise dimension of the cross-section extending substantially vertically in use. In one embodiment, the cells of the first layer of cells each have an elongate cross-section, with the ratio of the length of the cross-section to the width of the cross-section being from 1.1:1 to 1.5:1, preferably from 1.15:1 to 1.4:1, more preferably from 1.2:1 to 1.3:1, with a ratio of about 1.25:1 being preferred for many embodiments. The cells of the first layer of cells may have any suitable elongate cross-section, for example rectangular or elliptical. In one preferred embodiment, the cells of the first layer of cells have an elongate cross-section that is a truncated ellipse, preferably in use the truncated portion of the cross-section lying uppermost.

Preferably, the cells in the first layer of cells are arranged so as to provide a continuous layer of cells, that is adjacent cells in the layer are touching or abut each other.

The cells are formed with a cell wall of flexible, gas-impermeable material.

Suitable materials are known in the art and are commercially available. Preferred materials for forming the cell wall include known polymers, in particular polyurethane.

Preferably, the cells of the first layer have the relevant dimension to provide the first layer with a height with the cells inflated to their normal operating pressure of from 8 to 12 cm, more preferably from 9 to 11 cm, still more preferably from 9.5 to 10.5 cm.

A preferred height of the first layer of cells is about 10 cm.

As noted above, the cells are prepared from a suitable gas-impermeable material. The thickness of the cell wall is selected according to the material of construction to provide sufficient strength to the cell wall to resist the internal gas pressure and retain the shape and form of the cell when the mattress is in use. A typical thickness of the cell wall is from 0.2 to 1.0 mm, more preferably from 0.25 to 0.6 mm, still more preferably from 0.3 to 0.5 mm. A wall thickness of about 0.35 mm has been found particularly suitable for cells formed from polyurethane and having a height of about 10 cm.

If desired, the first layer may be provided with one or more cells of different shapes and sizes, so as to accommodate the needs of the patient.

For example, the first layer of cells may comprise one or a plurality of extended cells, which cells extend from the first layer through to the upper surface of the second layer, that is provide a portion of the mattress with just a single layer of extended cells. The one or more extended cells may be used to provide a headrest portion at one end of the mattress, on which the patient rests their head in normal use. The headrest portion of the mattress may comprise a single extended cell or, more preferably a plurality of extended cells, for example from 2 to 8, more preferably from 3 to 7, still more preferably from 4 to 6, especially 5 extended cells. Similarly, one or more extended cells may be used to provide a heelrest portion at one end of the mattress, on which the patient rests their heels in normal use. The heelrest portion of the mattress may comprise one or a plurality of extended cells, for example a single extended cell or a plurality of extended cells, for example from 2 to 8, more preferably from 3 to 7, still more preferably from 4 to 6, especially 5 extended cells. In one preferred embodiment, the heelrest portion comprises one or more extended cells having a first height at their end portions and a second height in a middle portion, with the first height being greater than the second height. For example, the first height may be from 12 to 18 cm, more preferably from 13 to 17, still more preferably from 14 to 16 cm, especially about 15 cm, while the second height may be from 11.5 to 15.5 cm, preferably from 12.5 to 14.5 cm, more preferably about 13.5 cm.

The number of cells in the first layer will be determined by the overall length of the mattress and the dimensions of the cells in the layer. Preferably, the individual cells and the mattress are sized to provide the first layer with from 20 to 40 cells, more preferably from 25 to 35 cells. It has been found that providing the first layer with from 28 to 32 cells is a particularly effective arrangement.

The mattress of the present invention further comprises a second layer of inflatable cells. The second layer of cells extends across the upper surface of the first layer of cells, with the mattress in use. The cells in the second layer of cells extend parallel to the cells in the first layer and transversely, that is laterally across the mattress, substantially perpendicular to the longitudinal axis of the mattress.

Preferably, each cell of the second layer of cells extends laterally across the entire width of the mattress.

The cells of the second layer of cells may have any suitable shape and form. The cells of the second layer of cells are preferably of a uniform shape along their length. It is also preferred that the cells of the second layer of cells are all of the same shape. The cells of the second layer of cells may have any suitable cross-sectional shape. In one embodiment, the cells have a regular cross-section, that is the width of the cross-section is the same as the length of the cross-section, for example circular or square. Preferably, the cells of the second layer of cells are generally cylindrical. In one preferred embodiment, the cells of the second layer of cells have a regular cross-section that is truncated. For example, the cells may have a generally truncated cylindrical form, that is with a cross-section in the shape of a segment of a circle.

The cells of the second layer of cells are formed with a cell wall of flexible, gas-impermeable material. Suitable materials are known in the art and are commercially available. Preferred materials for forming the cell wall include known polymers, in particular polyurethane.

Preferably, the cells in the second layer of cells are arranged so as to provide a continuous layer of cells, that is adjacent cells in the layer are touching or abut each other.

Preferably, the cells of the second layer of cells have the relevant dimension (for example a diameter in the case of the preferred cylindrical cells) to provide the second layer with a height when the cells are fully inflated to their normal operating pressure of from 3 to 7 cm, more preferably from 3.5 to 6.5 cm, still more preferably from 4 to 6 cm, especially from 4.5 to 5.5 cm. A preferred height of the second layer of cells is about 5 cm.

As noted above, the cells of the second layer of cells are prepared from a suitable gas-impermeable material. The thickness of the cell wall is selected according to the material of construction to provide sufficient strength to the cell wall to resist the internal gas pressure and retain the shape and form of the cell when the mattress is in use. A typical thickness of the cell wall is from 0.2 to 1.0 mm, more preferably from 0.25 to 0.6 mm, still more preferably from 0.3 to 0.5 mm. A wall thickness of about 0.35 mm has been found particularly suitable for cylindrical cells formed from polyurethane and having a diameter of about 5 cm.

The cells of the second layer of cells are preferably of a uniform shape and size. However, if desired, the second layer may be provided with cells of different shapes and sizes, so as to accommodate the needs of the patient.

The number of cells in the second layer of cells will be determined by the overall length of the mattress and the dimensions of the cells in the layer. Preferably, the individual cells and the mattress are sized to provide the second layer with from 20 to 40 cells, more preferably from 25 to 35 cells. It has been found that providing the second layer with from 28 to 32 cells is a particularly effective arrangement.

The cells of the second layer of cells are preferably in direct contact with the cells of the first layer of cells. The first and second layers preferably contain the same total number of cells, with each cell in the first layer of cells having a corresponding cell in the second layer of cells overlying it.

In one embodiment, one or more of the cells in the first layer of cells and the corresponding cells in the second layer of cells are provided by a cell assembly. The cell assembly comprises a single cell wall defining both a cell of the first layer of cells and the corresponding cell of the second layer of cells. The cell assembly further comprises a gas impermeable membrane extending internally and dividing in the interior of the cell wall into two cells, to provide a cell of the first layer of cells and a cell of the second layer of cells. The cell assembly is advantageous by being simpler and quicker to manufacture than two separate cells. In addition, employing the cell assembly for at least some of the cells of the first layer of cells and the second layer of cells provides increased stability of the mattress.

As described hereinbefore, the height of the first layer of cells is greater than the height of the second layer of cells. The ratio of the height of the first layer of cells to the height of the second layer of cells is preferably at least 1.2, more preferably at least 1.4, still more preferably at least 1.5, more preferably still at least 1.6, especially at least 1.8, more especially at least 1.9. The ratio of the height of the first layer of cells to the height of the second layer of cells is preferably up to 3, more preferably up to 2.8, still more preferably up to 2.6, more preferably still up to 2.5, especially up to 2.4, more especially up to 2.3, still more especially up to 2.2, more especially still up to 2.1. In one preferred embodiment, the ratio of the height of the first layer of cells to the height of the second layer of cells is from 1.3 to 2.9, preferably from 1.4 to 2.8, more preferably from 1.5 to 2.5, still more preferably from 1.7 to 2.3, more preferably still from 1.9 to 2.1. A ratio of about 2 is especially preferred.

As noted above and described in more detail below, in use, the cells of both the first layer of cells and the second layer of cells are inflated with a gas. Any suitable gas may be used to inflate the cells of the first layer of cells and the second layer of cells.

to Air is a most suitable and convenient gas. The mattress may be provided with means to provide gas to the cells, in order to provide the required pressure of gas and/or to change the gas pressure within the cells, as required. Suitable means, such as pumps, for providing the gas are known in the art and are commercially available.

The mattress of the present invention may comprises a base layer. The base layer, if present, underlies the first layer. The base layer is preferably formed from an expanded foam material. Suitable foam materials are well known in the art and are commercially available. Preferred foam materials are polyurethane foams, in particular open-cell polyurethane foams. The density of the foam material of the base layer is selected, together with the pressure of air within the cells of the first and second layers and the dimensions of the cells of the first and second layers, to provide the requisite level of support for the patient, when the mattress is in use.

The foam of the base layer may have any suitable density. Preferably, the density of the foam material of the base is in the range of from 20 to 50 kg/m3, more preferably from 25 to 40 kg/m3, with a foam density in the range of from 30 to 35 kg/m3 being especially preferred.

The thickness of the base is selected according to the density of the foam material, in turn selected as noted hereinbefore. The thickness of the foam base is preferably in the range of from 2 to 6 cm, more preferably from 2.5 to 5 cm, still more preferably from 2.5 to 4 cm. A base thickness of about 3 cm is particularly suitable for the mattress of the present invention.

A particularly preferred base layer comprises a polyurethane foam having a density of between 32 and 32.5 kg/m3 and a thickness of 3 cm.

To maintain the shape and form of the foam material of the base, the mattress may be provided with a covering layer extending over the surface of the base. Suitable materials for forming the covering layer are known in the art and are commercially available. A preferred material for forming the covering layer is polyvinylchloride.

In one preferred embodiment, the mattress does not comprise a base layer.

The mattress is preferably provided with a cover extending over the outer surfaces of the mattress, including the sides, ends and the exposed surfaces of the base, if present, and the second layer of cells. Suitable materials for forming the cover are known in the art and are commercially available. A preferred material for the cover is a combination of polyurethane and polyester (known commercially as multispandex).

The present invention also provides a method of operating an inflatable cell mattress. The method may be applied to any inflatable cell mattress comprising: a first layer of cells comprising a plurality of inflatable cells; and a second layer of inflatable cells overlying at least a portion of the first layer of cells, the second layer of cells comprising one or more first groups of cells and one or more second groups of cells, each of the first and second groups of cells comprising at least one inflatable cell, the first groups of cells alternating with the second groups of cells along the length of the mattress.

The method may be employed with the mattress of the first aspect of this invention with particularly advantageous results.

In the method of this invention, the cells of the first layer of cells are inflated with gas. The cells are preferably maintained at a substantially constant gas pressure during use. Accordingly, the cells in the first layer may be referred to as 'static cells'. Preferably, the gas within the cells of the first layer is kept at a constant pressure. It is preferred that all the cells of the first layer are filled with gas to substantially the same pressure. The pressure of gas within the cells of the first layer is selected to provide the required level of support to the patient, when the mattress is in use. The pressure of gas within the cells of the first layer of cells may be up to 80 mmHg, preferably up to 75 mmHg, more preferably up to 70 mmHg, still more preferably up to 65 mmHg, more preferably still up to 60 mmHg. A minimum gas pressure of 25 mmHg, more preferably 30 mmHg, still more preferably from 35 mmHg, more preferably still from 40 mmHg has been found to be suitable for providing the required level of support to a patient lying on the mattress for a prolonged period of time. Preferably, the pressure of gas within the cells of the first layer of cells is in the range of from 20 to 80 mmHg, more preferably from 25 to 70 mmHg, still more preferably from 30 to 60 mmHg, more preferably still from 35 to 55 mmHg, especially from 40 to 50 mmHg. A gas pressure of 45 mmHg in the cells of the first layer of cells is particularly preferred for many embodiments.

The pressure of gas within the cells of the first layer may be varied, according to the size and weight of the patient using the mattress. It is especially preferred that all cells in the first layer are maintained at a constant pressure at substantially the same gas pressure. However, should it be required, the first layer may be divided into two or more regions, each region comprising one or more cells, the gas pressure within the cells varying from region to region.

It is particularly preferred that the gas pressure within the cells of the first layer is kept constant during use.

To employ the method of the present invention, at least a portion of the second layer of inflatable cells has the cells divided into two groups, namely a first group of cells and a second group of cells. Each of the first and second groups of cells comprises one or more cells. The number of cells in the first and second groups is preferably the same.

The second layer of cells may comprise a single first group of cells and a single second group of cells. Preferably, the second layer comprises a plurality of first groups of cells and a plurality of second groups of cells. Preferably, the first and second groups of cells are arranged in the second layer of cells to have the first and second groups arranged in an alternating pattern along the length of the mattress, that is each of the first groups of cells is next to at least one of the second groups of cells. Preferably, each of the first groups of cells is adjacent at least one of the second groups of cells with no intervening cells between them.

In one embodiment, each of the first and second groups of cells comprises a plurality of cells, for example 2, 3, 4 or 5 cells. More preferably, each of the first and second groups of cells consists of one cell.

In the method of the present invention, the cells of the first group of cells and the second group of cells are inflated and deflated according to an inflation regime.

The inflation regime is applied alternately to the first group of cells and to the second group of cells, such that the cells of both the first and second groups of cells are inflated and deflated according to the same regime, but with the inflation and deflation of the cells of the first group of cells being out of phase with that of the cells of the second group of cells.

The inflation regime applied to the cells comprises four stages: i) an inflation period; ii) an inflated period; iii) a deflation period; and iv) a deflated period.

In stage i) of the inflation regime, the cells are inflated. The duration of stage i) may be from 0.5 minute, preferably from 0.75 minutes, more preferably from 1 minute, still more preferably from 1.25 minutes. The duration of stage i) may be up to 3 minutes, preferably up to 2.5 minutes, more preferably up to 2 minutes, still more preferably up to 1.75 minutes. The duration of stage i) may be from 0.5 to 3 minutes, preferably from 0.75 to 2.5 minutes, more preferably from 1 to 2 minutes, still more preferably from 1.25 to 1.75 minutes, more preferably still from 1.3 to 1.6 minutes. A preferred duration for stage i) of the inflation regime is about 1.5 minutes, for example 1 minute 25 seconds.

In stage ii) of the inflation regime, the cells are held in an inflated condition. The duration of stage ii) may be from 2 minutes, preferably from 2.5 minutes, more preferably from 2.75 minutes, still more preferably from 3 minutes, more preferably still from 3.5 minutes, especially from 3.75 minutes. The duration of stage ii) may be up to 6 minutes, preferably up to 5.5 minutes, more preferably up to 5 minutes, still more preferably up to 4.75 minutes, more preferably still up to 4.5 minutes. The duration of stage ii) may be from 2 to 6 minutes, preferably from 2.5 to 5.5 minutes, more preferably from 2.75 to 5.25 minutes, still more preferably from 3 to 5 minutes, more preferably still from 3.75 to 4.75 minutes. A preferred duration for stage ii) of the inflation regime is about 4.5 minutes, for example 4 minutes 25 seconds.

The cells may be inflated with gas to any suitable pressure. The pressure of the gas when the cells are fully inflated may be varied according to the weight of the person lying on the mattress. The pressure of gas within the cells when the cells are fully inflated may be from 25 mmHg, preferably from 30 mmHg, more preferably from 35 mmHg. The pressure of gas within the cells when the cells are fully inflated may be up to 70 mmHg, preferably up to 65 mmHg, more preferably up to 60 mmHg, still more preferably up to 55 mmHg. A fully inflated gas pressure of from 25 to 70 mmHg is preferred, more preferably from 30 to 65 mmHg, still more preferably from 35 to 60 mmHg, more preferably still from 35 to 55 mmHg. A fully inflated pressure of from 35 to 50mmHg is particularly preferred, especially from 38 to 50mmHg.

In stage iii) of the inflation regime, the cells are deflated. The duration of stage iii) may be from 0.5 minute, preferably from 0.75 minutes, more preferably from 1 minute, still more preferably from 1.25 minutes. The duration of stage Hi) may be up to 3 minutes, preferably up to 2.5 minutes, more preferably up to 2 minutes, still more preferably up to 1.75 minutes. The duration of stage Hi) may be from 0.5 to 3 minutes, preferably from 0.75 to 2.5 minutes, more preferably from 1 to 2 minutes, still more preferably from 1.25 to 1.75 minutes, more preferably still from 1.3 to 1.6 minutes. A preferred duration for stage Hi) of the inflation regime is about 1.5 minutes, for example 1 minute 30 seconds.

In stage iv) of the inflation regime, the cells are held in a deflated condition. The duration of stage iv) may be from 1.5 minutes, preferably from 1.75 minutes, more preferably from 2 minutes, still more preferably from 2.5 minutes, more preferably still from 2.75 minutes, especially from 3 minutes. The duration of stage iv) may be up to 5 minutes, preferably up to 4.75 minutes, more preferably up to 4.5 minutes, still more preferably up to 4.25 minutes, more preferably still up to 4 minutes. The duration of stage iv) may be from 1.5 to 5 minutes, preferably from 1.5 to 4.75 minutes, more preferably from 1.75 to 4.5 minutes, still more preferably from 2 to 4.25 minutes, more preferably still from 2.5 to 4 minutes. A preferred duration for stage iv) of the inflation regime is about 3.5 minutes, for example 3 minutes 30 seconds.

In the deflated condition, the pressure of gas within the cells is preferably less than 5mmHg, more preferably less than 4mmHg, still more preferably less than 3mmHg, more preferably still less than 2mmHg, especially less than 1mmHg.

It is to be understood that time periods for the stages of the inflation regime are +/-15 seconds.

Pressures indicated herein are gauge pressures, unless otherwise stated.

The inflation during stage i) and/or the deflation during stage iii) may be carried out continuously or stepwise, that is with step changes in the gas pressure. It is preferred that the inflation and/or deflation, preferably both inflation and deflation, are performed continuously, for example with a constant rate of change in pressure over the period of inflation and deflation.

As noted hereinbefore, the inflation regime is applied alternately to the first group of cells and the second group of cells. In this way, the inflation regime followed by the first group of cells is out of phase with the inflation regime followed by the second group of cells. It is preferred that the same inflation regime is applied to both the first and second groups of cells.

However, the inflation regime is applied to the first and second groups of cells such that such that, as the cells of one of the first and second groups of cells is inflating, the cells of the other of the first and second groups of cells are deflating. The inflation regime is applied such that at no time are all the cells of both the first and second groups of cells fully deflated. In this way, the patient lying on the mattress is always supported by cells from at least one of the first and second groups of cells.

The timing of the inflation regime applied to the first and second groups of cells is preferably such that when the cells in one of the first and second groups of cells are in phase i) of the inflation regime, the cells are inflated to from 30 to 70%, more preferably from 40 to 60%, still more preferably about 50% of the maximum inflation, while the cells in the other of the first and second group of cells are in phase iii) of the inflation regime, with the cells inflated to from 30 70%, more preferably from 40 to 60%, still more preferably about 50% of the maximum inflation.

As noted hereinbefore, the mattress comprises a gas supply system for supplying a gas, most suitably air, to the cells. The gas supply system preferably comprises at least one pump and one or more valves, which control the flow of gas to the individual cells. The operation of the gas supply system is controlled by a processor, which operates the pump and the valves to implement the inflation regime hereinbefore described. Suitable gas supply systems are known in the art.

Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying drawings, in which: Figure 1 is a diagrammatical representation of an inflatable cell mattress according to one embodiment of the present invention; Figure 2 is a diagrammatical representation of a patient lying on an inflatable cell mattress of a further embodiment of the present invention; Figure 3 is a vertical cross-sectional view of a cell according to one embodiment of the present invention; Figure 4 is a graph showing the endothelial blood flow of a patient before using a mattress according to one embodiment of the present invention; and Figure 5 is a graph showing the endothelial blood flow of the patient after using the mattress according to one embodiment of the present invention for a period of 8 weeks.

Turning first to Figure 1, there is shown an inflatable cell mattress according to one embodiment of the present invention. The mattress, generally indicated as 2, comprises a first layer 4 of cells having 30 transversely extending inflatable cells 6. Each cell 6 has a generally elliptical cross-section, as can be seen in Figure 1. The cells 6 of the first layer 4 are static cells. When the mattress 2 is in use, the cells 6 are inflated to the operating pressure and maintained in the inflated condition. The mattress 2 further comprises a second layer 10 of cells having 30 transversely extending inflatable cells 12. Each cell 12 has a generally circular cross-section, as can be seen in Figure 1. Each cell 12 of the second layer 10 overlies a corresponding cell 6 in the first layer 4. In use, the cells 12 of the second layer 10 are dynamic cells and are inflated and deflated in a cyclic manner as described in more detail hereinafter.

A cover 20 extends over the first and second layers 4, 10 of cells.

The mattress 2 further comprises a pump 30. The pump 30 is connected to the cells 6 of the first layer 4 by a line 32, through which the pump supplies air to inflate and maintain the cells 6 inflated. A pair of lines 34a and 34b extend from the pump and supply air to the cells 12 of the second layer 10. The lines 34a and 34b are connected to alternate cells 12 of the second layer 10, as shown in Figure 1.

The operation of the pump 30 is controlled by a processor 40. In particular, the processor 40 controls the pump 30 to supply air to the cells of the mattress according to the following regime: The cells 6 of the first layer 4 are inflated and maintained in an inflated condition. A typical inflation pressure for the cells 6 of the first layer 4 is 45mmHg.

The cells 12 of the second layer 10 are subjected to an inflation regime, during which each cell is inflated and deflated according to the following stages: i) an inflation period of 1 minute 25 seconds, during which the cell is inflated in a continuous manner from a pressure of below 1 mmHg to a pressure of 45mmHg; ii) an inflated period of 4 minutes 25 seconds, during which the cell is maintained in an inflated condition at a pressure of 45mmHg; iii) a deflation period of 1 minute 30 seconds, during which the cell is deflated in a continuous manner to a pressure below 1mmHg; and iv) a deflated period of 3 minutes 30 seconds, during which the cell is maintained in the deflated condition at a pressure below 1mmHg.

The cells 12 in the second layer 10 are divided into two groups, group A and group B, arranged in an ABABAB... alternating pattern along the length of the mattress 2. The inflation regime described above is applied to all the cells of group A and all the cells of group B, with the regime applied to group A being out of phase with the regime applied to group B, such that as the cells of group A are being inflated in stage i) the cells of group B are being deflated in stage iii), with all of the cells 12 being at 50% inflation at substantially the same time.

Turning to Figure 2, there is shown a mattress 102 according to a further embodiment of the present invention. The mattress 102 comprises a first layer 104 of cells having 29 transversely extending inflatable cells 106. Each cell 106 has a generally rectangular cross-section, as can be seen in Figure 2. The cells 106 of the first layer 104 are static cells. When the mattress 102 is in use, the cells 106 are inflated to the operating pressure and maintained in the inflated condition.

The mattress 102 further comprises a second layer 110 of cells having 29 transversely extending inflatable cells 112. Each cell 112 of the second layer 110 overlies a corresponding cell 106 in the first layer 104. In use, the cells 112 of the second layer 110 are dynamic cells and are inflated and deflated in a cyclic manner as described above in relation to Figure 1.

The first layer 104 of cells comprises 5 cells 106a which have a generally rectangular cross-section, as shown in Figure 2, and extend the full depth of the mattress 102 and do not have cells of the second layer overlying them.

A patient 150 is shown lying on the mattress 102, with their head support by the full depth cells 106a of the first layer 104.

Turning to Figure 3, there is shown one preferred arrangement of cells suitable for use in the mattresses of the embodiments of Figures 1 and 2. There is shown a vertical cross-section through a cell assembly 202 as it would be oriented in a mattress in normal use. The cell assembly has an outer flexible, gas impermeable membrane 204 defining an elongate inner cavity. The inner cavity 206 is divided into two cavities, an upper cavity 206a and a lower cavity 206b by an inner flexible, gas impermeable membrane 208. The cell assembly 202 may be used to provide a cell of both the first layer and the second layer in the mattresses shown in Figures 1 and 2 and described above. In particular, the lower cavity 206b may form a cell 6, 106 of the first layer 4, 104, while the upper cavity 206a may form a cell 12, 112 of the second layer 10, 110.

The cell assembly 202 is configured to provide the lower cavity 206b with a height H1 of 10cm and an upper cavity 206a with a height H2 of 5 cm, giving a ratio of H1 to H2 of 2.

Employing the mattress and method of the present invention provides significant advantages to a patient, including increased comfort, reduced discomfort and pain, and a reduction in the formation of ulcers and sores. In addition, it has been found that the mattress and method of operation provide a significant improvement in the endothelial function of the patient.

To demonstrate the advantageous effects of the present invention on the endothelial function of patients, a group of healthy people were provided with a mattress according to the present invention for use when sleeping for a trial period of 8 weeks. The endothelial function of each person was measured using post-occlusive reactive hyperaemia (PORH) testing both before and after the trial period.

Figure 4 shows the results of the PORH test of an individual before the trial, while Figure 5 shows the results of the PORH test of the same individual after the trial. As can be seen, the endothelial function, indicated by the area under the curve of the PORH-chart, significantly increased.

Claims

CLAIMSAn inflatable cell mattress, the mattress comprising: a first layer comprising a first set of transversely extending inflatable cells; and a second layer comprising a second set of transversely extending inflatable cells, the second layer of cells overlying at least a portion of the first layer of cells; wherein the ratio of the height of the cells of the second layer of cells to the height of the cells of the first layer of cells is from 1:1.9 to 1:2.1.
2. An inflatable cell mattress, the mattress comprising: a first layer comprising a first set of transversely extending inflatable cells, each cell of the first layer of cells having a height of from 9.5 to 10.5 cm; and a second layer comprising a second set of transversely extending inflatable cells, the second layer of cells overlying at least a portion of the first layer of cells, each cell of the second layer of cells having a height of from 4.5 to 5.5 cm.
3. The mattress according to either of claims 1 or 2, wherein each of the cells of the first layer of cells has an elongate cross-section.
4. The mattress according to claim 3, wherein each of the cells of the first layer of cells has an elongate cross-section having a ratio of the length of the cross-section to the width of the cross-section is from 1.1:1 to 1.5:1
5. The mattress according to any preceding claim, wherein the first layer of cells comprises one or more extended cells, each extended cell extending from the first layer of cells through the upper surface of the second layer of cells.
6. The mattress according to any preceding claim, wherein the first layer of cells comprises from 28 to 32 cells.
7. The mattress according to any preceding claim, wherein each of the cells of the second layer has a cross-section that is circular or a segment of a circle.
8. The mattress according to any preceding claim, wherein each cell in the first layer of cells has a corresponding cell in the second layer of cells, each cell of the first layer and its corresponding cell of the second layer being provided by a cell assembly.is
9. The mattress according to claim 8, wherein the cell assembly comprises a cell wall defining an interior forming both a cell of the first layer and a cell of the second layer, the cells being divided by a gas impermeable membrane extending internally of the cell wall and dividing the interior into the two cells.
10. A method for operating an inflatable cell mattress, the mattress comprising: a first layer of cells comprising a plurality of inflatable cells; and a second layer of inflatable cells overlying at least a portion of the first layer of cells, the second layer of cells comprising one or more first groups of cells and one or more second groups of cells, each of the first and second groups of cells comprising at least one inflatable cell, the first groups of cells alternating with the second groups of cells along the length of the mattress; the method comprising: inflating and deflating the cells of the first groups of cells and the cells of the second groups of cells using an inflation regime, the inflation regime comprising: an inflation period during which the cell is inflated from a deflated condition to an inflated condition during a period of from 1 to 2 minutes; an inflated period during which the cell is held in the inflated condition for a period of from 4 to 5 minutes; a deflation period during which the cell is deflated from the inflated condition to the deflated condition during a period of from 1 to 2 minutes; and a deflated period, during which the cell is held in the deflated condition for a period of from 3 to 4 minutes; wherein the inflation regime is applied to the cells of the first groups of cells and the second groups of cells such that as the cells of one of the first and second groups of cells is inflating the cells of the other of the first and second groups of cells are deflating, whereby at no time are all the cells of both the first and second groups of cells fully deflated.
11. The method according to claim 10, wherein when the cells of one of the first and second groups are 40 to 60% inflated, the cells of the other of the first and second groups are 40 to 60% deflated.
12. The method according to claim 11, wherein when the cells of one of the first and second groups are 50% inflated, the cells of the other of the first and second groups are 50% deflated.
13. The method according to any of claims 10 to 12, wherein the second layer of cells comprises a plurality of first groups of cells and a plurality of second groups of cells, wherein each of the first groups of cells and/or each of the second groups of cells consists of one cell.
14. The method according to any of claims 10 to 13, wherein the cells are inflated to a pressure of from 38 to 50mmHg.
15. The method according to any of claims 10 to 14, wherein the cells are deflated so to a pressure of less than 1mmHg.
16. The method according to any of claims 10 to 15, wherein a mattress according to any of claims 1 to 9 is employed.is
17. An inflatable cell mattress, the mattress comprising: a first layer of cells comprising a plurality of inflatable cells; and a second layer of inflatable cells overlying at least a portion of the first layer of cells, the second layer of cells comprising one or more first groups of cells and one or more second groups of cells, each of the first and second groups of cells comprising at least one inflatable cell, the first groups of cells alternating with the second groups of cells along the length of the mattress; a gas supply system for supplying a gas to the cells of the second layer of cells; and a processor for controlling the pump and configured to operate the gas supply system to inflate and deflate the cells of the first groups of cells and the cells of the second groups of cells using an inflation regime, the inflation regime comprising: an inflation period during which the cell is inflated from a deflated condition to an inflated condition during a period of from 1 to 2 minutes; an inflated period during which the cell is held in the inflated condition for a period of from 4 to 5 minutes; a deflation period during which the cell is deflated from the inflated condition to the deflated condition during a period of from 1 to 2 minutes; and a deflated period, during which the cell is held in the deflated condition for a period of from 3 to 4 minutes; wherein the processor operates the gas supply system to apply the inflation regime to the cells of the first groups of cells and the second groups of cells such that as the cells of one of the first and second groups of cells is inflating the cells of the other of the first and second groups of cells are deflating, whereby at no time are all the cells of both the first and second groups of cells fully deflated.
18. The mattress according to claim 17, wherein the second layer of cells comprises a plurality of first groups of cells and a plurality of second groups of cells, wherein each of the first groups of cells and/or each of the second groups of cells consists of one cell.
19. The mattress according to either of claims 17 or 18, wherein the mattress is as claimed in any of claims 1 to 9.