GB2197192A

GB2197192A - Alternating pressure pad

Info

Publication number: GB2197192A
Application number: GB08724815A
Authority: GB
Inventors: Rolf Schild
Original assignee: Huntleigh Technology Ltd
Current assignee: Huntleigh Technology Ltd
Priority date: 1986-10-24
Filing date: 1987-10-23
Publication date: 1988-05-18
Also published as: GB8724815D0; GB8625492D0

Abstract

An alternating pressure pad has two or more layers (5,6) each made of two sets of cells (1,2) the cells of each set being inflatable independently of the cells of the other set. The layers are so arranged that the cells of the first set, of the uppermost layer, are immediately above corresponding cells of the first set, of the next layer down. Corresponding cells of the second set, of each layer, are also arranged to overlie each other in the same fashion. A control system may inflate a given cell simultaneously with inflation of the cell immediately above or below, and may inflate the two sets of cells alternatingly. Inflation may be carried out so that the average pressure in the pad as a whole is substantially constant over time. In addition means are provided to inflate all cells simultaneously with a constant pressure well below occulsion pressure without the risk of bottoming. <IMAGE>

Description

SPECIFICATION Alternating pressure pad This invention relates to alternating pressure pads, and in particular to sanitary alternating pressure pads of the kind used in the prevention and management of decubitus ulcers in bedridden patients.

The formation of decubitus ulcers, commonly known as bedsores, results from, amongst other things, the pressure applied to certain portions of the skin of a bedridden patient. In addition, it is well known that should the lower reflex arc be broken by, for instance, lesion of the spinal cord or of nerve roots then decubitus ulcers of unusual severity and rapidity of onset are likely to develop.

It is known to meet the requirement for the prevention and management of decubitus ulcers with an alternating pressure pad comprising two sets of alternatively inflatable cells: the duration of the inflation and deflation cycles may last from under two minutes for a gentle massaging effect to over twenty minutes. Huntleigh Technology plc manufacture and supply such an alternating pressure pad system.

In such a system an inflatable cell is formed as a linear series of units roughly shaped as flattened elongate spheroids. Adjacent cells are disposed such that the necks of the units of one cell are adjacent to the portions of greatest width of the units of the adjacent cells, the entire set being formed of a large number of such cells. Generally, the diameter of such units varies from 3cm to 20cm.

Although a sheet of small units is more comfortable to the patient than a sheet of large units, it may be unable to support heavy patients or the larger bony protuberences of even relatively light patients.

Consequently, in order to provide sufficient support it has been found necessary to use units which inflate to provide a pad of substantial thickness. Hitherto, this has been achieved by the use of large diameter units since, clearly, large diameter units inflate to a greater thickness than smaller diameter units.

Patient comfort has, however, suffered: ideally, support provided by a given region of a pad should not be effected by the pressure applied by a patient to adjacent regions. Alternating pressure pads comprising large units are less able to satisfy this requirement than pads comprising smaller units but the necessity of providing sufficient supporting thickness has, in the past, entirely precluded the use of such smaller units.

In accordance with the present invention, an alternating pressure pad comprises first and second superimposed supporting layers, each layer comprising a first and a second set of alternately inflatable cells, the layers being secured together so that the cells of the first set of cells of the first layer overlie the cells of the first set of cells of the second layer, and the cells of the second set of cells of the first layer overlie those of the second set of the second layer, the pad being arranged so that the corresponding sets of cells of both layers can be inflated simultaneously and deflated simultaneously.

It will be apparent that such an alternating pressure pad reconciles the hitherto incompatible features of large thickness of large diameter units and patient comfort provided by small diameter units.

In accordance with a further embodiment of the invention, the upper skin of the cells of the upper layer may be air permeable to provide ventilation to a patient resting on the pad. Consequently, adequate air circulation is provided which results in an improved microenvironment over the skin by, for instance, reducing the humidity level.

According to another embodiment of the invention, a composite alternating pressure pad may be formed of two or more alternating pressure pads, each in accordance with embodiments of the present invention, each pad being independently controlled and forming a separate portion of the pad. This arrangement allows, for instance, a pad supporting a supine patient to be readily adapted to the patient sitting up by increasing the air pressure in the portion of the pad supporting the greater weight. Conveniently, at least one of the alternating pressure pads may be operable to be maintained at a substantially constant pressure of less than 30 mm Hg, (400 Pa), the vascular occulsion pressure. Such- a pad may provide support particulary for the head of the patient.Preferably, each cell of an alternating pressure pad comprises a series of inflatable units, each unit being shaped as an elongate spheroid of width greater than height. Alternatively, each cell may comprise a single inflatable unit shaped as an elongate cylinder of height greater than width.

According to a further embodiment of the invention an alternating pressure pad may comprise at least one further supporting layer of sets of cells similarly arranged.

It will also be apparent that although the present device will find substantial applications as a form of mattress, it may also be modified for use in a wide variety of other applications, for instance on seats and particularly wheelchair seats.

Examples of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a known alternating pressure pad, and Figures 2, 3 and 4 are schematic views of an alternating pressure pad in accordance with the present invention, each depicting the pad at different times in an inflation/deflation cycle, the ellipses being cross-sectional repre sentations of the inflatable units.

Figure 5 is a schematic view of a composite alternating pressure pad in accordance with an embodiment of the invention; Figure 6 is a schematic view of an alternating pressure pad comprising four supporting layers in accordance with a further embodiment of the invention; and Figure 7 is a schematic view of an alternating pressure pad wherein each cell comprises a single inflatable unit shaped as an elongate cylinder of height greater than width.

Referring now to Figure 1, a series of inflatable units 3 is formed into a cell 1', a set of cells being formed by alternate cells 1", 1"' etc. Similarly, a cell 2' formed part of a set of cells 2', 2" etc, the two sets of cells being alternately disposed to form into a pad. The two sets of cells, characterised by numerals 1 and 2, are alternately inflatable so that the pad forms an alternating pressure pad. Generally, the units 3 are shaped as elongate spheroids which, on inflation, have a diameter of approximately 6cm. Further, an alternating pressure pad for use as a mattress may have approximately two hundred such units and will also be formed of medical grade PVC incorporating a bacteriostat. Small holes, indicated at 4, may puncture the surface of a number of units to provide a supply of air to the skin of the patient.

Referring now to Figure 2, two similar layers 5 and 6, of sets of alternately inflatable cells are shown with corresponding cells of the two layers overlying one another. An air supply line 8 is depicted providing air to each cell of the set of cells 1 of both layers 5 and 6, whereas air supply line 7 provides air to each cell of the sets of cells 2 of both layers 5 and 6. Layers 5 and 6 are secured together by a weld 9 along the perimeter of the pad. Air supply lines 7 and 8 are fed from a compressor (not shown) indicated generally by 10.

The compressor comprises a cross over valve the function of which will be outlined below.

Figure 2 depicts the set of cells 2 on layer 5 fully inflated and overlying the set of cells 2 on layer 6 which are also fully inflated. Similarly, the sets of cells 1 on both layers are fully deflated. Referring to Figure 4, the converse obtains: the sets of cells 1 on both layers are fully inflated whereas the sets of cells 2 are fully deflated. The inflation/deflation cycles may repeat over periods varying from two minutes to over twenty minutes.

The cross-over valve operates so that, during inflation of the set of cells 1, air from the set of cells 2, in addition to air from the compressor, passes into the set of cells 1. The operation of the cross over valve is such that, as soon as, or preferably before, the pressure difference of the air in set of cells 2 over the air from the compressor becomes negligible, the air from the set of cells 2 is prevented from passing into the set of cells 1 but is, instead, vented to the atmosphere. Similarly, during inflation of the other set of cells 2, air from set of cells 1 is allowed to pass into set of cells 2 for an initial period.By properly arranging the times during which cross-over of the air from one set of cells to the other occurs, it is possible to arrange for the average pressure in the pad to remain constant over an entire inflation/deflation cycle: this obviates the problem of nausea sometimes caused by the slow vertical movements of a patient during a cycle. Figure 3 represents the pad midway between the complete inflation of a given set of cells, both sets of cells on both layers being partially inflated. Deflation of either set of overlaying cells 5 occurs solely via the cross over valve.

The upper portions of cells 1 and 2 belonging to the upper layer 5 may be air permeable, being, for instance punctured by small ventilation holes.

The description with reference to Figures 2, 3 and 4 as hereinbefore described refers particularly to the embodiment without such holes.

The operation of the embodiment having ventilation holes is, however also substantially as described above.

A composite alternating pressure pad shown in Figure 5 may also be formed, of three alternating pressure pads, each pad being independently controllable and forming a separate portion of the pad. This may be achieved by modifying an alternating pressure pad suitable for a single supine patient by dividing the pad into three separate pads so that the lower half of the patient is supported by one pad 13c and the upper half to the shoulders is supported by a second pad 13b, and the head of the patient being supported by a third pad 13a. When the patient is to sit up, for example, the second pad 13b can be supplied with air at a greater pressure than the other pads to provide adequate support of the patient. In order to provide independent control of each pad, it is necessary to provide a pair of air supply lines (not shown) to each separate pad of the composite pad. Conveniently, the three pairs of air supply lines may be each connected to a cross-over valve (not shown), the three cross-over valves being arranged to run synchronously. This may be achieved by operating both valves by a single drive means.

In another embodiment, depicted in Figure 6, four layers 18, 19, 20 and 21 of cells are arranged to overlie one another. Air lines and other elements used in the operation of this embodiment are omitted from this figure and are essentially as depicted in the embodiments illustrated by Figures 2-4.

In a further arrangement (not shown) the cross over valve of the compressor may be stopped at the cross-over point resulting in continuous inflation at a constant pressure.

Each layer of the pad is therefore maintained at a constant pressure, thereby providing con stant support. Preferably, the pressure should be below the occulsion pressure of 30 mm Hg (400 Pa) so that vascular circulation is maintained but sufficiently great to provide adequate support to prevent the patient bottoming. This is a particularly advantageous arrangement in a composite pad of the sort hiterto described whereby the pad supporting the head of the patient may be maintained at constant pressure. The further pads may be operated, preferably under the control of the patient as either alternating pressure pads or as constant pressure pads.

It will be appreciated that Figures 2, 3, 4, 5 and 6 depict inflatable units shaped as elongate spheroids of width greater than height.

The alternative arrangement wherein each cell comprises a single inflatable unit shaped as an elongate cylinder of height greater than width is depicted in Figure 7. Such a shape results in local support pressure which may be well below the occulsion pressure 30 mm Hg (400 Pa) and may be particularly suitable for embodiments wherein at least one of the alternating pressure pads is operable to be maintained at a substantially constant pressure of less than 30 mm Hg (400 Pa).

Claims

1. An alternating pressure pad comprising first and second superimposed supporting layers, each layer comprising a first and a second set of alternately inflatable cells, the layers being secured together so that the cells of the first set of cells of the first layer overlie the cells of the first set of cells of the second layer, and the cells of the second set of cells of the first layer overlie those of the second set of the second layer, the pad being arranged so that the corresponding sets of cells of both layers can be inflated simultaneously and deflated simultaneously.

2. An alternating pressure pad as claimed in Claim 1 wherein the upper skin of the cells is air permeable to provide ventilation to a patient resting on the pad.

3. An alternating pressure pad as claimed in any preceeding claim wherein the pad comprises at least one further supporting layer of sets of cells similarly arranged.

4. An alternating pressure pad according to any preceeding claim further comprising an air feed system structrued and arranged to control supply of air to the cells of said layers in such a manner that the average pressure in each of said layers remain substantially constant over time.

5. An alternating pressure pad according to Claim 4 wherein said air feed system is structured and arranged such that, to inflate the cells of the first set of each of said layers after the cells of the second set have been inflated, air is transferred from the cells of the second set to the cells of the first set for a predetermined period of time, after which, to complete inflation, air is fed into the cells of the first set from said air feed system without passing through the cells of the second set.

6. An alternating pressure pad according to Claims 1-3 comprising an air feed system structured and arranged to control supply of air to the cells of said layers in such a manner that the cells can either be inflated or deflated as in claim 4 or, by the action of a user operated switch, all the cells can be inflated simultaneously to a substantially constant pressure well below occlusion pressure, 30 mm Hg (400 Pa).

7. A composite alternating pressure pad comprising two or more alternating pressure pads, each as claimed in any preceeding claim, wherein each pad is independently controllable, and forms a separate portion of the composite pad.

8. A composite pad as claimed in Claim 7 wherein each of the sets of cells of at least one of the alternating pressure pads are operable to be maintained at a substantially constant pressure of less than occlusion pressure, 30 mm Hg (400 Pa).

9. An alternating pressure pad or a composite alternating pressure pad as claimed in any preceeding claim wherein each cell comprises a series of inflatable units, each unit being shaped as an elongate spheroid of width greater than height.

10. An alternating pressure pad or a composite alternating pressure pad as claimed in any of Claims 1-8 wherein each cell comprises a single inflatable unit shaped as an elongate cylinder of height greater than width.

11. An alternating pressure pad substantially as hereinbefore described with reference to the accompanying drawings.