GB2108837A

GB2108837A - Air flotation mattress

Info

Publication number: GB2108837A
Application number: GB08232040A
Authority: GB
Inventors: Dr Jack Raymond Green
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-11-13
Filing date: 1982-11-10
Publication date: 1983-05-25
Also published as: GB2108837B

Abstract

An air flotation mattress serves to support a patient G on a pocket of pressurised air by means of air under pressure being fed into the mattress interior and the upper wall AB of the mattress being permeable, the region JK of the upper wall below the patient being displaced downwards by the pocket of air. In the example shown the upper and lower walls are connected by inextensible means and the mattress may be only 1 DIVIDED 2 inch (1.27 cm) thick but laid upon a deformable base. Instead the upper and lower walls may be interconnected by resilient means acting as distributed springs, and the mattress may be laid on a rigid base. <IMAGE>

Description

SPECIFICATION Air flotation mattress This invention relates to an air flotation mattress for supporting a patient on a layer or pocket of air and out of contact with the fabric of the bed.

Such support on a layer of air is extremely important for baldly burnt patients, for the prevention and alleviation of bed sores, and for other conditions where contact of the skin is uncomfortable.

In accordance with this invention, there is provided an air flotation mattress having an upper wall formed of flexible, permeable fabric, means for supplying air under pressure to the interior of the mattress, and means within the mattress interior connecting the upper wall of the mattress to its lower wall, the mattress being arranged so that in operation (and if necessary when laid upon a deformable base) a pocket of pressurised air develops in the region beneath the patient, the underlying region of the upper wall of the mattress being displaced downwardly, and said pocket of pressurised air serves to support the patient substantially out of contact with the fabric of said upper wall.

Upon the supply of air under pressure to the mattress interior, air escape occurs in generally uniformly distributed manner through the permeable upper wall. Should a patient or other object now be placed on the mattress, the air escape is relatively impeded through that area of the upper wall which is overlaid by the patient. As a consequence, a layer of increased-pressure air builds up between the patient and the underlying area of the mattress upper wall on which layer the patient becomes supported, this area of the upper wall being-displaced downwardly (relative to the remaining areas).

Embodiments of this invention will now be described, by way of examples only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic cross-section through a bed having a mattress in accordance with this invention, prior to the supply of air at working pressure; Figure 2 is a similar cross-section showing the mattress when air is supplied at working pressure to its interior, but without any patient on the bed; Figure 3 is a similar cross-section showing the mattress in use supporting a patient; and Figure 4 is a cross-section through a second embodiment of air mattress.

Referring to Figure 1, there is shown a mattress constructed of flexible fabric, its upper wall AB being permeable and connected to a lower wall CD of the mattress by resilient means disposed within the mattress interior and acting, over the area of the upper wall, as distributed tension springs. The resilient means may comprise, as diagrammatically illustrated, an array of elastic cords or springs E, or it may comprise a series of elastic membranes having opposite edges secured to the upper and lower walls of the mattress, or a body of foamed elastomer (e.g. polyurethane).

Only the upper wall AB is permeable, the remainder walls of the mattress being impermeable. The lower wall CD is supported on a base F which is shown as being rigid, but it may be flexible -for example an ordinary bed mattress.

Instead the air flotation mattress may form an integral part of the purpose-built bed.

Means are provided for supplying air under pressure to the interior of the mattress (typically a pressure rather less than one pound per square inch) and in sufficient quantity to maintain this pressure despite the escape of air through the permeable upper wall AB. Figure 1 shows the mattress with little or no applied interior air pressure, but Figure 2 shows the condition with working pressure applied, causing the upper wall to rise uniformly and extend the springs (in the example shown to twice their unstretched length).

Figure 3 shows the effect of a patient G or other object being laid on the mattress. The flow of air through the area J-K, now being overlaid by the patient, is impeded, and the air flowing through this area of the upper wall must pass sideways to escape through the gaps J and K between the patient and the mattress.As a consequence, the pressure under the patient will increase to some value PB. In the areas outside the area J-K, the amount of extension of the springs E depends upon the pressure drop (PA - P0) across the upper wall (PA being the interior air pressure and P0 being atmospheric pressure): in the area J-K, the extension of the springs E depends upon the lesser pressure drop (PAPB). For purposes of iilustration, the pressure drop (A - P) is assumed to be half of the unimpeded pressure difference (A - P0) so that the springs under the area J-K are extended, from their unstretched length, by only half as much as for the remaining springs.

Thus, as shown in Figure 3, the area of the upper wall immediately below the patient moves downwards and away from the patient as the latter is laid on the mattress, except in a peripheral region where a narrow gap forms. The pressure of air immediately below the patient increases, as the patient approaches the mattress, until the pressure difference (B - P0) is sufficient to float the patient completely out of contact with the mattress.

The pressure acting on the base F is merely the weight of the mattress, in the conditions of Figures 1 and 2. In the condition of Figure 3, the downward force due to the pressure PA on the lower wall CD will be only partly balanced, in the area LM, by the upward pull of the springs E. The effect is that the weight of the patient is exerted on the base F over the area LM. If the base F were flexible (such as an ordinary bed mattress), the base would deform as if the patient were laid directly on it: this would enable the air flotation mattress to conform more readily to the irregular shape of the supported patient.

It is the combined flexibility of the air mattress and of its underlying support which determines the flexibility of the whole. The relative flexibility of the upper mattress to which the air is supplied and of the lower supporting base is a matter of choice, the combined flexibility being the relevant factor.

In Figures 1, 2, and 3 the arrangement is shown for a base F which is rigid and the flexibility would be only that of the distributed tension springs shown at E in Figure 1. In Figure 4 an arrangement is illustrated which is at the other end of the spectrum of relative flexibilities in that the means linking the permeable upper wall of the air mattress proper to its lower wall is substantially inextensible while the base F (e.g. an ordinary bed mattress) is sufficiently flexibly deformable to accommodate the irregular shape of the patient. In this arrangement the air mattress merely serves as a flexible air duct to feed the necessary air flow to its permeable upper wall.The links between its upper and lower surfaces could be provided by a closely spaced series of strings, perhaps introduced by a weaving process or by a very porous flexible foam material cemented to the upper and lower walls. The thickness of the air supply mattress then need only be such as to ailow a reasonably free flow of air from a supply duct H at its periphery to each part of the permeable upper wall, say, of the order of half an inch (1.27 cm) or less, and is then akin to a sheet.

In order to avoid any possibility of the patient making contact with the upper wall around the peripheral region (J and K), preferably the upper surface of the air flotation mattress has a brush or fur type finish, i.e. with a multiplicity of close, outwardly projecting flexible filaments. Then the patient can make a mere brushing contact with the tips of these filaments, whilst the escape of air through the gaps J, K (between the filaments themselves) remains considerably impeded as required.

Claims

1. An air flotation mattress having an upper wall formed of flexible, permeable fabric, means for supplying air under pressure to the interior of the mattress, and means within the mattress interior connecting the upper wall of the mattress to its lower wall, the mattress being arranged so that in operation (and if necessary when laid upon a deformable base) a pocket of pressurised air develops in the region beneath the patient, the underlying region of the upper wall of the mattress being displaced downwardly, and said pocket of pressurised air serves to support the patient substantially out of contact with the fabric of said upper wall.

2. An air flotation mattress as claimed in claim 1 , in which said connecting means within the mattress interior is resilient and act, over the area of said permeable upper wall, as distributed tension springs.

3. An air flotation mattress as claimed in claim 2, in which said resilient connecting means comprises an array of elastic cords or springs.

4. An air flotation mattress as claimed in claim 2, in which said resilient connecting means comprises a series of elastic membranes having opposite edges secured to the upper and lower walls of the mattress.

5. An air flotation mattress as claimed in claim 2, in which said resilient connecting means comprises a body of foamed elastomer.

6. An air flotation mattress as claimed in any preceding claim, laid upon a rigid base.

7. An air flotation mattress as claimed in claim 1, in which said connecting means within the mattress interior is substantially inextensible as between the upper and lower walls of the mattress.

8. An air flotation mattress as claimed in claim 7, in which said inextensible connecting means comprises an array of inextensible strings or membranes.

9. An air flotation mattress as claimed in claim 7, in which said inextensible connecting means comprises a body oi foamed elastomer.

10. An air flotation mattress as claimed in any one of claims 7 to 9, laid upon a deformable base.

11. An air flotation mattress as claimed in any preceding claim, in which the upper wall of the mattress has a brush or fur type surface finish.

12. An air flotation mattress substantially as herein described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.