In recent years, inflatable supports have come into extensive use and are used widely in hospitals to prevent and treat decubitous 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 blood vessels 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 inflatable support system for the prevention of bed sores has a plurality of parallel cells alternately inflated to provide support for the user.

The inflatable support system may comprise an alternating pad or mattress for a bed or similar system for a seat.

It has been found that with such inflatable support systems the end portion or zone on which a person's heels rest when in a supine position are particularly prone to developing sores. This is exacerbated because the inflatable cells are of similar size and of such diameter that in the end zone the person's heel can either rest on an individual cell or between adjacent cells, either case being undesirable for achieving effective therapeutic bed sore relief.

One aspect of the present invention provides an inflatable support for providing pressure relief to a person resting on the support which support comprises a plurality of inflatable cells extending transversely of the support in which a group of main cells form the main body of the support and a further group of cells are disposed adjacent one end of the support to provide an end zone and wherein the end zone cells are of smaller diameter, and more numerous in number per unit area of the support, than that of the main cells.

In such an arrangement the smaller diameter end zone cells preferably are inflated to a higher pressure than the other cells of the support. Moreover, in order to achieve the desired therapeutic effect, the cells of the support are pressurized to selected predetermined pressures in predetermined sequences which is controlled by a distributor device according to the invention.

Another aspect of the invention provides a system for mitigating the development of decubitous ulcers, the system comprising an inflatable support having a plurality of inflatable cells for providing pressure relief to a person resting on the support, and comprising a distributor device for controlling ingress and egress of fluid to the cells of the support, the device having a fluid intake and fluid inlet and outlet ports and being operable selectively to cause pressurized fluid to be supplied from the fluid intake to one or more inlet ports to cause inflation of one or more cells of the inflatable body while causing fluid simultaneously to be exhausted from one or more outlet ports to cause deflation of one or more other of the cells in one mode of operation, and/or is operable to cause selected inlet ports to be supplied with pressurized fluid from the intake so that selected cells receive fluid to a predetermined pressure sequentially while causing fluid simultaneously to be exhausted from one or more exhaust ports, in another mode of operation, and further to cause all the ports, and thus cells, to be put in communication with the fluid intake and with one another, in yet another mode of operation, and to cause all the ports to be isolated from the fluid intake so that all the cells can deflate, in a still further mode of operation.

Yet another aspect of the invention provides a distributor device for controlling ingress and egress of fluid to a plurality of cells of an inflatable therapeutic support, the device having a fluid intake and fluid inlet and outlet ports and being operable selectively to cause pressurized fluid to be supplied from the fluid intake to one or more inlet ports to cause inflation of one or more cells of the inflatable support while causing fluid simultaneously to be exhausted from one or more outlet ports to cause deflation of one or more other of the cells in one mode of operation, and/or is operable to cause selected inlet ports to be supplied with pressurized fluid from the intake so that selected cells receive fluid to a predetermined pressure sequentially while causing fluid simultaneously to be exhausted from one or more exhaust ports, in another mode of operation, and further to cause all the ports to be put in communication with the fluid intake and with one another, in yet another mode of operation, and to cause all the ports to be isolated from the fluid intake so that all the cells can deflate, in a still further mode of operation.

Embodiment of the various aspects of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 is a plan view of an end portion of an inflatable mattress according to the invention;

Figure 2 is a cross-section through the end portion taken along the line

A-A in figure 1 ;

Figure 3 is a perspective sketch of an inflatable mattress according to the invention;

Figure 4 is a schematic side view of the mattress shown in figure 3, and Figure 5 is a set of sketches (Figures 5a to 5i) illustrating a pneumatic distributor control for inflating the mattress according to the invention.

Referring to the drawings, an inflatable support, in this embodiment a mattress 10 comprises a main part and an end zone 12 intended to support the heels of a person resting on the support in a supine position.

The end zone 12 comprises a plurality of inflatable elongate cells 14 which form a top layer 16 of the end zone. The main part 18 of the mattress also comprises a plurality of inflatable cells 20. All the inflatable cells of the main part of the mattress are of a generally tubular form of approximately constant cross-section arranged in a side by side series transversely of the mattress. The main cells 20 are of the order of 3"-5" in diameter and may sit in a scalloped length of a foam base 21 , as shown in figure 3 or may sit on a lower layer of inflated or inflatable cells 23, as shown in figure 4. In either case, the main cells are adapted to be inflated and deflated in a controlled sequence, which usually is alternately, to enhance the therapeutic effect provided by alternating the pressure of fluid in the cells thereby to vary the areas and degree of support experienced by a person lying or sitting on such a cellular support. The heels of a person in a supine position are particularly vulnerable to bed sores and known supports having a constant diameter array of cells are not particularly effective in providing pressure relief for the person's heels.

In the present invention the end zone cells 14 are of smaller diameter and more numerous per unit area of the support than the main cells and are of the order of 1 " diameter. The end zone cells 14 are secured to a foam material base 22.

Referring now to figure 2, the end zone cells are formed from a continuous sheet material 25 which is bunched into a multiplicity of loops in side by side relationship, and welded onto a base layer sheet 24. However, along each side of the end zone cells a manifold strip 26 is sandwiched between the upper sheet 25 forming the end zone cells and the lower base layer sheet 24. The material between each adjacent end zone cell is welded to both the base sheet 24 and to appropriate areas of the manifold strips 26 so as to allow the passage of air to be supplied through each manifold strip and thence into each of the end zone cells. In order pneumatically to connect the manifold strips to the end zone cells apertures 28 are formed in the manifold strips and the end zone cells for the ingress and egress of pressurized air. Thus, manifold strip 26a supplies air to alternate end zone cells 14a, 14c, 14e, 14g and 14| whereas manifold strip 26b supplies air to end zone cells 14b, 14d, 14f and 14h.

Pressurized air is supplied to each manifold strip through a compressor, for example, a diaphragm pump (not shown) via a pneumatic distributor 34 and hose connectors 30, 32, respectively. The pump and distributor and other control mechanisms may be accommodated in a pocket 36 formed in the foam base beneath the end zone cells and the distributor may be controlled by a hand operated controller. The distributor 34 is pneumatically connected to both the end zone cells and the main cells which are organised into discrete pressure zones (zones 1 to 3) so that the cells are sequentially pressurized and depressuhzed by alternately inflating and deflating the cells as described below. Referring now to Figure 5 of the drawings the pneumatic compression pump is driven by an H-bhdge circuit to create an AC type drive but at 12v DC. This electrical arrangement is of benefit because the diaphragm pump gives long life and is quiet in operation. A driver PCB runs the compressor pump and also drives a stepper motor to rotate the pneumatic distributor rotor 35. The distributor comprises a base plate 36 formed with air intake holes 38 through which pressurized air is supplied to the distributor rotor from the compressor pump. The base plate is also formed with ports 40 and ports 42. A pair of recessed areas 44 and 46, respectively, are formed in the rotor 35 and the rotor can be rotated by the stepper motor both clockwise and anticlockwise relative to the central axis of the main body so as to sequentially cover and uncover the two sets of ports 40, 42 which allow ingress and egress of air to and from the cells of the inflatable support. As the rotor 35 turns, ports are covered and uncovered allowing pressurized air from the compressor to be directed to the designated zone in the cells. The ports also connect previously inflated zones of the cells to atmospheric pressure to allow them to deflate.

A pressure transducer (not shown) is connected to the compressor outlet and monitors the pressure continuously. When predetermined pressures are reached the rotor is actuated or the compressor switched on/off. The hand controller can be used to show alarms, system status and allow users to set pressures/time cycles etc.

Examples of various settings referring to the cell zones shown in Figure 4 of the drawings may be as follows:

Zone A1 +B1 =40mmHg

Zone A2+B2=45mmHg

Zone A3+B3=100mmHg

Referring to Figure 5, in operation at Stage 1 (Figure 5a), the air intake holes 38 fluidically communicate with all the ports 40, 42 through recessed area 44 so that all the cellular zones are connected in an inflation process.

The compressor runs and increases the pressure. Previously pressurized zones will vent air into depressuhzed zones. This stage is referred to as the crossover period because it helps reduce wasted air. In operation at Stage 2 (Figure 5b) the rotor is rotated clockwise so that ports 42 supplying zones A1 - A3 are taken out of communication with air intake holes 38 so as to deflate Zones A1 + A2 + A3 simultaneously. Ports 40 supplying zones B1 -B3 are maintained in communication with air intake holes 38 to inflate zones B1 + B2 + B3 to a first predetermined pressure (40mmHg). When the 40mmHg predetermined pressure is reached the rotor is rotated again onto the next stage.

In operation at Stage 3 (Figure 5c), zone B1 is locked off at the preset 40mnnHg to maintain that pressure for a set period of time and then Zones B2 + B3 are further pressurized to 45mmHg. When this further predetermined pressure is reached the rotor is rotated again to Stage 4. During this period all the cells of zone A (A1 -A3)are still deflating to atmosphere through recessed area 46 and exhaust port 47..

In operation at Stage 4 (Figure 5d), zone B2 is locked off at the preset 45mmHg and Zone B3 is further pressurized to a next predetermined pressure of 100mmHg. When this higher pressure is reached the compressor is switched off. During this period all zone A cells are still deflating to atmosphere through recessed area 46 and exhaust port 47. Once the desired time period has expired then the rotor is moved to Stage 5.

In operation at stage 5 (Figure 5e), all zones are connected in an inflation process through recessed area 44. The compressor runs and increases the pressure. Previously pressurized zones will vent air into depressuhzed zones. This stage is referred to as the crossover period, as in stage 1.

Stages 6, 7 and 8 are operated in a similar process to the previous stages but with the rotor being indexed anticlockwise and inflating the zone A cells sequentially while putting the zone B cells into deflate mode.

The cycle time can be in the range from 6-20 minutes.

The benefits of this system are that it runs from a DC source allowing it to be easily used in any country. Also, the pneumatic distributor allows for an emergency deflate where rotor 34 communicates with all the ports in a function known as static where rotor 34 communicates all the system cells to the air intake holes through recessed area 44 so that all the cells are simultaneously inflated to allow for a static support for bed baths etc.