Inflatable support

Abstract: The present invention relates to a low air loss mattress 10 for continuously supporting a person lying thereon, comprising an upper layer 12 of inflatable cells, and a separate lower layer of inflatable cells 13. The lower layer of inflatable cells 13 is always maintained at a constant higher pressure than the upper layer of cells 12 to prevent a person lying on the mattress 10 from contacting the underlying support surface, in particular, when sitting or during transport. Cells 11 forming the upper layer 12 may be inflated at different pressures to provide optimum support to different parts of the body.

Description: The invention relates generally to low air loss support systems and more particularly to a low air loss mattress or similar which can be used on hospital beds. In recent years, low air loss beds have come into extensive use and are used widely in hospitals to prevent and treat decubitus ulcers which are commonly referred to as bed sores. A primary cause of bed sores is the inability of the patient to move so as to relieve pressure points. These pressure points typically occur in the area of a bony protuberance which results in a cut-off of the blood flow in the skin and soft tissue adjacent to the protuberance when distortion of capillary beds curtails blood flow. When the blood flow in the capillaries is blocked due to excessive external (interface) pressure, the cells in that area begin to die and may result in a wound which is called a bed sore. Mobile persons do not have this problem because they continually move even when asleep which eliminates the cut-off of blood flow for too long a period. A typical low air loss support system has a plurality of parallel gas or vapour-permeable cells inflated to provide support for the patient. The low air loss support systems provide gradual leakage of air from the cells, either by having holes at selected locations or by providing a cell material which is permeable to air. Usually, air is pumped from a manifold on one side of the bed through the cells extending transversely of the bed. The air is wholly or partially exhausted through the holes or pores in the cells. The air losses necessitate the use of a rather large air pump, and the systems constructed of this type tend to be bulky and expensive. Ideally, each inflatable cell should have a sufficient height to allow a substantial amount of depression of each cell for supporting the patient over a larger surface area and the pressure within the inflated cell should be as low as possible to maximise the pressure reducing effect. However it is important that no part of the mattress is depressed to such an extent by the patient lying thereon that the patient makes contact with any underlying support surface. Such a problem is frequently encountered when a patient is in the sitting position on the bed or in the event of a power failure when the cells continue deflating through air loss through the holes but the pump is no longer inflating the cells. A similar problem may occur during transport of a patient when the cells may have to be disconnected from the pump for a period of time. It is known from US 5 243 723 A to have an air mattress comprising multiple layers of inflatable cells where the upper layers although normally alternately inflated/deflated can provide a low air loss upper surface with the lower layers inflated at a higher pressure to provide a stable base. However, the problems of providing optimum support for a patient still exist. The present invention is designed to alleviate these .problems of the existing low air loss support systems. According to the invention, a low air loss support comprises an upper layer of inflatable cells, overlying a lower layer of inflatable cell(s), means for inflating the layers of cells so that when inflated the upper layer continuously and directly supports a patient lying thereon, the upper surface of the cells having holes for the passage of air to provide ventilation for a patient lying thereon, the lower layer inflated to a pressure always pre-set at a higher level than the pressure in the upper layer and maintained at the higher pressure characterised in that, the inflation pressure in the cells in the upper layer is adjustable to provide different cells at different pressures to provide optimum support to the different parts of the body to be supported thereon. The lower layer of cell(s) inflated and maintained at a higher pressure provides a "safety net" for a patient supported on the mattress and prevents the patient contacting the underlying support surface in the event of the patient sitting on the mattress or during transport of the patient or power failure. Advantageously, the lower layer maintained at the higher pressure further gives optimum contact area for the patient when in the sitting or near sitting positions on the mattress. Moreover, the inflation pressure in the cells in the upper layer being adjustable to provide different cells at different pressures provides optimum support to the different parts of the body to be supported thereon, for example, the buttocks of the patient are heavier than say the head or the heels and would require greater pressure for optimum support than the head and heels. The air pressure in the lower layer may be maintained by conventional means, for example, a non-return valve or by solenoids. Preferably, the lower layer is maintained at the higher pressure by means of a control system which periodically boosts the pressure in the lower layer, to compensate for leakage in the system. Since the pressure in the lower layer is sealed and only boosted periodically, the pump only has to maintain the low air loss system in the upper layer thereby allowing a smaller less expensive compressor to be used. According to another aspect, the invention covers a method of providing an inflatable support for a patient comprising the steps of providing an inflatable support having an upper layer of cells and a lower layer of cells, inflating both layers to a maximum pressure, isolating the lower layer at that pressure and maintaining the lower layer at that pressure and automatically adjusting the upper layer to a pressure to provide optimum support for a patient according to the patient's weight. Preferably, the method further includes the step of automatically adjusting the pressure in the cells of the upper layer to different pressures respectively to provide optimum support to the different parts of a body lying thereon. An example of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of the low air loss mattress according to the invention; Figure 2 is a schematic diagram of cells comprising integral upper and lower layers; Figure 3 is a schematic diagram of one embodiment of a low air loss system according to the invention; Figure 4 is a schematic diagram of a second embodiment of a low air loss system according to the invention; Figure 5 is a third embodiment of a low air loss system according to the invention; and Figure 6 is a schematic diagram of a pressure controller comprising bellows. Referring to Fig. 1, a mattress 10 comprises a plurality of inflatable tubes 11 which form two layers 12, 13 each layer consisting of tubes arranged in parallel extending transversely of the mattress 10. The tubes 11 in the upper layer 12 are held substantially vertically above the tubes 11 in the lower layer 13 by means of straps 14 or retainers on a cover (not shown) covering the tubes to present a smooth surface for a patient to lie on. Alternately, as shown in Figure 2, the upper and lower layers are formed by double chamber cells 11 having one-way valves 33 in the wall 34 separating the chambers. The lower layer 13 may be a single cell extending continuously under the multi-celled upper layer, or either/both layers may comprise longitudinal tubular cells or either/both layers may comprise non-tubular cells. The upper surface of the tubes 11 have holes 15, and as shown in Figures 3 to 5 each tube 11 on the upper layer 12 is connected to a manifold 21 for supply of compressed air from a compressor 25. The tubes 11 comprising the lower layer 13 are similarly connected to a second manifold 22 leading from the compressor 25. The tubes 11 in the upper layer 12 are arranged in sections A, B, C, D, and each section is arranged to be inflated to different pressures depending upon the area of the patient supported thereon. Section A may support the heels, Section B, the thighs, Section C, the buttocks and Section D the head. The tubes 11 within a section may be connected to the manifolds by restrictors or variable orifices 31 so that each section is inflated at a different pre-set pressure. The outlet 35 from the pump 25 may be supplied directly to both the manifolds feeding the upper and lower layers respectively or via a non-return valve 27 or plenum chamber 40. The pressure in the tubes 11 is set by means of a pressure controller 26 which may have input from a pressure sensor 28 or the pressure controller 26 may comprise bellows 33 as shown in Figure 6. The pressure in the lower layer 13 is always pre-set at a level higher than the pressure in the upper layer 12. The pressure in the upper layer 12 may be set to correspond to the weight or other similar characteristic of the patient to be supported thereon. Both the layers may be inflated to a pre-set maximum pressure with the lower layer 13 then sealed and retained at that pressure by means of a non-return valve 27 or similar in the outlet from the pump. The pressure in the upper layer 12 then automatically adjusts to a pressure which is calculated to provide the optimum support according to the weight of the patient to be supported thereon. When the pressures in either of the layers 12,13 is less than the pre-set or adjusted pressures respectively, either due to excessive air loss through the air holes in the upper layer 12 or leakage in the lower layer 13, the pressure controller 26 will activate the compressor to boost the pressure in the respective layers 12,13 to the set values. Since the lower layer 13 is inflated and sealed at the same pressure, the compressor in the pump only has to maintain the low air loss system within the lesser volume of the upper layer thereby allowing a smaller less expensive compressor to be used. Figures 3 shows a low air loss system comprising a single air supply with the pressures in the layers controlled by pneumatic restrictors 31. Figure 4 shows a low air loss support system comprising a dual air supply with the pressures in the layers controlled by pressure sensor input. Figure 5 shows a similar configuration to Figure 4 with a multiple air supply to the mattress via a plenum chamber 40. The low air loss mattress may comprise an upper layer adjusted to the same pressure throughout and not at different pressures. In use, the low air loss mattress is used in lieu of the standard bed mattress or alternately may be laid on top of the bed mattress, if desired. The low air loss system may be incorporated in a similar application of a cushion, pad or similar inflatable support for a patient for lying or sitting thereon.

Claims: A low air loss mattress (10) comprising an upper layer (12) of inflatable cells (11), overlying a lower layer (13) of inflatable cell(s) (11), means (25) for inflating the upper and lower layers (12,13) of cells (11), so that when inflated the upper layer (12) continuously and directly supports a patient lying thereon, the upper surface in the cells (11) having. holes for the passage of air to provide ventilation for a patient lying thereon, the lower layer (13) of cell(s) (11) inflated to a pressure always pre-set at a higher level than the pressure in the upper layer (12) and maintained at the higher pressure characterised in that , the inflation pressure in the cells (11) in the upper layer (12) is adjustable to provide different cells (A,B,C,D) at different pressures to provide optimum support to the.different parts of a body to be supported thereon. A low air loss mattress (10) as claimed in claim 1, characterised in that the lower layer (13) is maintained at the higher pressure by means of a control system (26) which periodically boosts the pressure, to compensate for leakage from the system. A method of providing an inflatable support (10) for a patient comprising the steps of providing an inflatable support (10) having an upper layer (12) of cells (11) and a lower layer (13) of cells (11), inflating both layers (12,13) to a maximum pressure, isolating the lower layer (13) at that maximum pressure and maintaining the lower layer (13) at that pressure and automatically adjusting the upper layer (12) to a pressure to provide optimum support for a patient according to the patient's weight. A method as claimed in claim 3, characterised in that the cells (A,B,C,D) in the upper layer (12) can be automatically adjusted to different pressures respectively to provide optimum support to the different parts of a body supported thereon.

Inventors: COOK STEPHEN JOHN, MCLEOD ALASTAIR GEORGE, SCHILD ROLF, COOK, STEPHEN JOHN, MCLEOD, ALASTAIR GEORGE, SCHILD, ROLF
Applicants: HUNTLEIGH TECHNOLOGY PLC
Application year: 1998
Main classification: A47C27
IPC codes: A61G7