A pressure controlled inflatable pad apparatus

Abstract: The present invention relates to a pressure controlled inflatable pad apparatus for supporting a body. The apparatus comprises an inflatable pad (1), a source of inflating fluid (4) to provide a flow of said fluid to the pad (1) for inflating the pad (1). There is also a sensor (11) and a connection (20,21,8) for fluid to flow, during said inflating flow of fluid, from the interior of the pad (1) through the sensor (11) to exhaust. The sensor (11) is arranged when located beneath the pad (1) to reduce fluid flow to exhaust if the pad (1) is insufficiently inflated to support the body.

Description: The present invention relates to a pressure controlled inflatable pad apparatus, in particular, a pressure controlled alternating inflatable pressure pad apparatus. Alternating pressure pads are well known for 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. Alternating pressure pads generally comprise two sets of alternately 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. A high air pressure in the pads may be needed to support the bony protuberances of a patient and to ensure that the patient is lifted sufficiently away from deflated cells of the pad so that adequate pressure relief is provided. .A low air pressure, however, is desirable since it provides a pad which is softer and more comfortable. Optimal pressure support therefore not only varies from patient to patient but also during a given inflation cycle of the pad since the pressure supporting points will change during a cycle. The required optimal support pressure will vary even more as a patient changes from a supine to a sitting position. It is known to provide a manually adjustable pressure controller to set an optimal pad support pressure. This may be a regulator for the compressor supplying air to the alternating pressure pad. It is also known to provide an automatic pressure controller comprising a convoluted compressible tube placed under the pad. In such a system, a small amount of air is diverted through the tube, the passage of air being detected by a pilot valve. When the support pressure in the pad is so inadequate that the pressure exerted by a patient causes the tube to be compressed shut, the pilot valve actuates a throttle which diverts a fixed proportion of air, such as one third, from the compressor to the pad thereby to increase the support pressure. When the tube is not closed, the fixed proportion of air is vented to the air via a relief valve. Such a system, however, is complex, costly and inefficient. WO89/08438 (PCTGB 89/00232) in the name of Huntleigh Technology plc describes a pressure controller which has a means which is sensitive to fluid pressure which is adapted to open a valve when the predetermined pressure in an alternating pressure pad is reached. This pressure controller also comprises a sensor pad which is compressible in dependence upon a patient's weight distribution on the alternating pressure pad. If the patient is not suitably supported, the sensor pad will reduce the escape of fluid from the valve thereby ensuring that more fluid is supplied to the alternating pressure pad until the patient is supported as required. This arrangement necessitated the use of four connecting tubes between the pump and the mattress and the use of a suitable means for sensing fluid pressure. The applicants, therefore sought to develop a pressure controller which achieved the same result with a similar arrangement. WO 92/07540 (PCT/GB91/01842) published on 14-5-92, also in the name of Huntleigh Technology Plc describes a further modified pressure controller. In this arrangement, the number of connecting tubes is reduced and the fluid flows from the fluid supply line through the pressure pad and subsequently directly from the fluid supply line through the sensor to exhaust. However, this arrangement still required the use of a fluid connection running through the pad. Reference should also be made to US Patent Serial No. 4,797,962 which describes a system for controlling the air supply to a convalescent bed having different air segments for supporting different areas of the body. However, this arrangement has large numbers of connecting tubes thus making it a very complex system. According to the present invention, there is provided a pressure controlled inflatable pad apparatus for supporting a body comprising an inflatable pad, a source of inflating fluid to provide a flow of said fluid to the pad for inflating the pad and a sensor, the sensor being arranged when located beneath the pad to reduce fluid flow to exhaust if the pad is insufficiently inflated to support the body, characterised in that there is a connection at the pad for fluid to flow during said inflating flow of fluid from the interior of the pad directly through the sensor to exhaust. Preferably, the inflatable pad is a pressure pad of alternately inflatable sets of cells. In one embodiment, there are separate connections from each set of cells, each connection having a non-return valve and the connections being jointed to form a single outlet to the sensor which has a single fluid flow reducing passage. In another embodiment, there are separate connections from each set of cells and the sensor is provided with respective separate fluid flow reducing passages. Preferably, a rotary valve is connected to the source of inflation fluid having an inlet and two outlets, each outlet being connected to one set of cells. Preferably, the rotary valve can be stopped in a position such that each set of cells is inflated simultaneously as a static pressure pad. Alternatively, the inflatable pad is a static pressure pad. In a further aspect, the present invention provides an apparatus for supporting a body comprising an inflatable pad having a plurality of separately inflatable segments, a source of inflation fluid to provide a flow of said fluid to the segments to inflate the segments, a respective fluid supply line to each segment and a respective sensor for each segment of the pad, a respective connection at each segment taking fluid, flowing through each supply line to the respective segments, to flow subsequently directly through the respective sensor to exhaust, each sensor being arranged when located beneath its respective segment of the pad to reduce fluid flow to exhaust if said segment is insufficiently inflated to support the body. Preferably, each fluid supply line is provided with a flow restrictor to allow the separate segment to be inflated to different support pressures. In one embodiment, each sensor is connected directly to the interior of its respective segment. In another embodiment, each sensor is connected to the fluid supply line to its respective segment. Preferably, each segment of the inflatable pad is a pressure pad of alternately inflatable sets of cells. Alternatively, each segment of the inflatable pad is a static pressure pad. Preferred embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a schematic representation of a first preferred embodiment of the present invention; Figure 2 is a schematic representation of a second preferred embodiment of the present invention; Figure 3 is a schematic representation of a third preferred embodiment of the present invention. Figure 1 depicts an inflatable pad 1 which is alternating and comprises two sets of cells 2 and 3. Both sets of cells 2 and 3 are supplied with air from a pump or compressor 4 via a rotary valve 5. A pair of supply lines 6 and 7 lead from the rotary valve 5 to the pad 1 - supply line 6 being connected to the set of cells 2 and supply line 7 being connected to the set of cells 3. A sensor pad 11 is connected directly to the interior of the pad 1 by connecting lines 20 and 21. Each of the connecting lines 20 and 21 has a non-return valve 9 and 10 respectively. The sensor pad 11 will be located beneath a patient or the body to be supported. In Figure 1 the connecting lines 20 and 21 join to form a single output line 8 to the sensor pad 11. The sensor pad 11 comprises a single compressible tube 12 arranged in a convoluted path. Air passing through the sensor pad 11 is "blocked" by a relief valve 13 pre-set to a predetermined pressure which sets the minimum pressure to which cells 2 and 3 inflate. However, the relief valve 13 can be dispensed with if no minimum pressure value is necessary. In use, the pump 4 will deliver air (or another inflation fluid) to the pad 1 via rotary valve 5 so that each set of cells 2 and 3 is alternately inflated. The inflation/deflation cycle may repeat over periods varying from two minutes to over twenty minutes. The rotary valve 5 operates so that during inflation of the set of cells 2, air from the set of cells 3, in addition to air from the pump 4 passes into set of cells 2. This is the "cross-over" point. Further, when, or preferably before, the pressure difference of the air in set of cells 3 over the air from the pump 4 becomes negligible, the air from set of cells 3 is prevented from passing in to set of cells 2. Similarly, during inflation of the other set of cells 3, the air from set of cells 2 is allowed to pass into set of cells 3 for an initial period. The rotary valve 5 includes a stator 14 having an inlet 15 and outlets 16a and 16b and a rotor 17 which is motor driven. The inlet 15 of the stator is connected to pump 4 and the outlets 16a and 16b are connected to sets of cells 3 and 2 respectively. The rotor 17 is provided with a vent 18 and an inlet port 19. During one revolution of the rotor 17 within the stator 14, first one set of cells and then the other is connected to the pump 4. However, there is a point in the cycle when both sets of cells 2 and 3 are connected to each other via the rotor 17. This is the "cross-over point" and occurs when the rotor 17 is positioned with its inlet port 19 extending between outlets 16a and 16b. Deflation of the cells 2 and 3 is effected by a vent 18 in the rotor 17 which communicated alternately with outlets 16a and 16b. The air leaving the interior of the pad 1 is only able to pass through the non-return valves 9 and 10 in connection lines 20 and 21 in one direction in order to prevent air leaking back through any deflated cells when the inflated cells are fully inflated. The air in lines 20 and 21 is combined to form a single outlet line 8 before passing into the compressible tube 12 in the sensor pad 11. If the weight of the patient is such that the compressible tube 12 is compressed even though the cells are inflated, the air exhausting to the atmosphere via relief valve 13 will be reduced and the air supplied from the pump 4 will continue to inflate the cells until the weight of the patient is no longer able to compress tube 12. Thus, air exhausted to the atmosphere now depends upon the compression of the sensor pad 11 and is a function of the weight distribution of the patient. Normal operation occurs when the pressure within the cells rises to the predetermined value and air can pass freely through the sensor pad because the alternating pressure pad is giving the required support to the patient. It will be appreciated that the sensor could comprise separate compressible tubes 12 for air from each of the supply lines rather than using an outlet line 8 and a single compressible tube 12. Clearly, this is a simple and efficient arrangement which requires only a small number of connecting tubes between the compressor and mattress. The pressure controlled inflatable pad depicted in Figure 1 could easily be adapted for use with a static pressure pad system in either of the following ways: (a) The rotary valve 5 is omitted and the pump 4 is connected directly via supply lines 6 and 7 to the pad 1; or (b) The rotary valve 5 is retained but the rotor is stopped at the cross-over point so that the two sets of cells 2 and 3 in the pad 1 are connected in parallel making the arrangement operate as a static system. Although the sensor pad 11 is shown connected via connection lines 20 and 21 to the opposite end of pad 1 to supply lines 6 and 7, it will be appreciated that the sensor pad 11 could be connected at any point on the pad 1 provided that it takes the air directly from the interior of the pad 1. Figure 2 depicts a second preferred embodiment of the present invention where the pump 4 feeds a segmented pressure pad comprising three separate pressure pads 1a, 1b and 1c. In this figure like reference numerals represent like features to those in Figure 1. As in Figure 1, the pressure pads 1a, 1b and 1c are alternating pressure pads having sets of alternately inflatable cells. Each pressure pad 1a, 1b and 1c, has its own sensor pad 11a, 11b and 11c, respectively. In this arrangement, the sensor pads 11a, 11b and 11c are each connected directly to the interior of the pressure pads 1a, 1b and 1c via non-return valves in a similar manner to Figure 1. Each of the supply lines 6a, 7a, 6b, 7b and 6c, 7c, is provided with a flow restrictor 22 which can be a region of reduced diameter of the tube or could be achieved alternatively by choosing appropriate lengths of a standard tube. In this way, there will be a pressure drop across the restrictor 22 depending on the flow rate through it which will allow the separate pads 1a, 1b and 1c, to be held at different pressures. Thus, the segmented pressure pad can provide areas of different support to a patient or other body placed upon it. For example, a mattress having such a segmented pressure pad could be adjusted so that the legs of the patient are not over-supported when the trunk of the patient is at an optimum support pressure. It should be noted that only a single pump 4 of adequate capacity is required to feed each separate segment which greatly simplifies the arrangement. Furthermore, there need only be two pipes connecting the pump to the mattress assembly. Figure 3 also depicts a segmented pressure pad but in this third embodiment the sensor pads 11a, 11b and 11c are connected to the supply lines 6a, 7a, 6b, 7b and 6c, 7c, which lead out from the pressure pads 1a, 1b and 1c. As in Figures 1 and 2, the pressure pads 1a, 1b and 1c, comprise two sets of alternating cells. It will be appreciated that both the embodiments in Figures 2 and 3 could easily be adapted for use with a static pressure pad arrangement as described earlier in connection with Figure 1. It is envisaged that the present invention could be utilised not only in the medical field in the form of a mattress but also in other fields where support of a body or object is to be finely adjusted.

Claims: A pressure controlled inflatable pad apparatus for supporting a body comprising an inflatable pad (1), a source of inflating fluid (4) to provide a flow of said fluid to the pad (1) for inflating the pad (1), and a sensor (11), the sensor (11) being arranged when located beneath the pad (1) to reduce fluid flow to exhaust if the pad (1) is insufficiently inflated to support the body, characterised in that there is a connection (20,21,8) at the pad (1) for fluid to flow during said inflating flow of fluid from the interior of the pad (1) directly through the sensor (11) to exhaust. An apparatus as claimed in Claim 1, wherein the inflatable pad (1) is a pressure pad of alternatively inflatable sets of cells (2,3). An apparatus as claimed in Claim 2, wherein there are separate connections (20,21) from each set of cells (2,3), each connection having a non-return valve (9,10) and the connections (20,21) being joined to form a single outlet (8) to the sensor (11) which has a single fluid flow reducing passage (12). An apparatus as claimed in Claim 2, wherein there are separate connections (20,21) from each set of cells (2,3) and the sensor (11) is provided with respective separate fluid flow reducing passages. An apparatus as claimed in any of Claims 2 to 4, further comprising a rotary valve (5) connected to the source of inflation fluid (4) having an inlet (15) and two outlets (16a,16b), each outlet being connected to one set of cells. An apparatus as claimed in Claim 5, wherein the rotary valve (5) can be stopped in a position such that each set of cells (2,3) is inflated simultaneously as a static pressure pad. An apparatus as claimed in Claim 1, wherein the inflatable pad (1) is a static pressure pad. A pressure controlled inflatable pad apparatus for supporting a body comprising an inflatable pad having a plurality of separately inflatable segments (1a,1b,1c), a source of inflation fluid (4) to provide a flow of said fluid to the segments ((1a,1b,1c) to inflate the segments, a respective fluid supply line (6a,7a,6b,7b,6c,7c) to each segment and a respective sensor (11a,11b,11c) for each segment of the pad, a respective connection at each segment taking fluid, flowing through each supply line to the respective segments, to flow subsequently directly through the respective sensor to exhaust, each sensor being arranged when located beneath its respective segment of the pad to reduce fluid flow to exhaust if said segment is insufficiently inflated to support the body. An apparatus as claimed in Claim 8, wherein each fluid supply line (6a,7a,6b,7b,6c,7c) is provided with a flow restrictor (10a,9a,10b,9b,10c,9c) to allow the separate segments to be inflated to different support pressures. An apparatus as claimed in Claim 8 or Claim 9, wherein each sensor is connected directly to the interior of its respective segment. An apparatus as claimed in Claim 8 or Claim 9, wherein each sensor is connected to the fluid supply line to its respective segment. An apparatus as claimed in any of Claims 8 to 11, wherein each segment of the inflatable pad is a pressure pad or alternately inflatable sets of cells. An apparatus as claimed in any of Claims 8 to 11, wherein each segment of the inflatable pad is a static pressure pad.

Inventors: SCHILD ROLF, SCHILD, ROLF
Applicants: HUNTLEIGH TECHNOLOGY PLC
Application year: 1993
Main classification: A47C27
IPC codes: A47C27, A61G7