IMPROVED SUPPORT SYSTEM FOR WHEELCHAIRS AND METHOD OF SUPPORTING A SEATED PATIENT

Abstract: A seated person is supported e.g. in a wheelchair (10) such that varied pressures are exerted on affected body areas adequate to improve blood perfusion thereat. A first, primary resilient support or cushion (30) has an inset opening (32) therein in which a second, inflatable fluid support element (40) is received, the inflatable support element (40) being located beneath the ischial tuberosities and normally being deflated whereby minimal pressures are generated on the body areas above it. Fluid may be supplied to inflate the second support element (40) thereby supporting a greater proportion of the body weight and lowering the pressures on the portions contacting the first support element (30). The inflatable support element (40) is controllably inflated and deflated by a bleed valve, a timer and an air compressor (50), so that cyclic pressure changes are exerted on the affected body areas by the two support elements (30, 40) thereby enhancing blood perfusion, comfort and lessening the likelihood of development of ulcers.

Description: The present invention relates to a support device for a patient according to the first part of claim 1, and a wheel-chair, according to claim 10. It also relates to a method of supporting a seated patient according to claim 11. Heretofore, a great deal of development effort has been expended toward improving wheelchairs and other types of seats which receive and hold non-ambulatory persons for extended periods of time. While great strides forward have been made in developing support systems for patients in a supine position so as to avoid the incidence of decubitus ulcers and the like, successes have not heretofore been achieved for patients in a sitting attitude. In fact, virtually no systems are known for use in wheelchairs and other similar type seats for improved prolonged sitting conditions with the exception of foam cushions of various densities and configurations, conventional air inflated cushions of various shapes and designs, gel filled cushions, water filled cushions and attenuating pressure pads or devices. In such prior art arrangements, the devices have generally been of singular construction, that is the entire surface of the support cushion is basically the same. While support structures of the type described above do, in fact, add to the general comfort of the patient, constant pressures persist against the affected body portions of the patient such that ultimately discomfort results as well as a reduction of blood flow which could lead to the development of decubitus ulcers or pressure sores. In fact, since the whole upper body weight of a person is supported by the relatively small body area in the chair seat, extremely high pressures may be experiences, up to about 266 kPa (200 mm Hg), on the ischial tuberosities. No system presently available as exemplified above is capable of achieving pressures low enough to prevent the development of pressure sores or ulcers in the most acute cases. No such system has thus been successfully employed in the wheelchair type environment as is contemplated by the present invention. Presently recommended techniques for wheelchair-ridden patients require the patient periodically to physically lift and hold himself off the cushion with his arms for as great a period of time as possible, thus removing pressure from the buttocks during the lift periods. While such techniques are certainly better than nothing, only limited success may be achieved thereby, and at the same time they lead to extreme fatigue of the patient if the procedure is practiced over any extended period of time. In general, body tissue without bony prominences thereunder will withstand higher pressures before tissue damage occurs. Conversely, body tissue having bony prominence therebeneath, such as the ischial tuberosities, is subject to the development of ulcers at lower surface pressures due to higher pressures generated at the tissue-bone interface. In order, therefore, to provide optimal support, it is necessary to provide a support system in which pressures generated on bony prominences, such as the ischial tuberosities, are normally lower than the pressures on the surrounding areas of the buttocks. The present invention achieves the aforementioned optimal situation, and provides a novel device for supporting a patient in a sitting position while at the same time improving patient comfort and reducing the incidence of the likelihood of development of decubitus ulcers. There is no known prior art that is believed to anticipate or suggest the present invention. GB-A-1,313,988 discloses a seat assembly for a wheelchair having complementary first and second support areas, the second support means being inset within the first support means. The said support means provide respective support surfaces, and they are mechanically reciprocated relative to one another by a cam mechanism. US-A-2,819,712 discloses an inflatable cushion especially for airplane pilots. To avoid discomfort, the cushion is designed so that at all times it exerts no pressure at all on the ischial tuberosities; this is achieved by placing openings coincident with the tuberosities in the cushion. An object of the present invention has been to provide an improved support device or cushion arrangement for wheelchairs and other chairs. Thus, we have been seeking to develop an improved seating arrangement for persons confined in a sitting attitude for prolonged periods of time. Another object of the present invention has been to provide an improved method for adding to the comfort of persons confined in a sitting attitude for prolonged periods of time which may reduce the incidence of the development of decubitus ulcers. Commencing from GB-A- 1 313 988 the present invention provides a support device for supporting a patient in a sitting position, which includes complementary first and second resilient support means with respective, relatively-displaceable support surfaces each for supportive contact with different areas of the patient's posterior, the second support means being inset within the first support means for supportive contact with the ischial tuberosities area of the posterior, characterised in that the second support means is a normally-deflated, fluid-inflatable member and in that the device includes a fluid supply means, means associated with the supply means to control the supply of fluid to and from the second support means for inflating and deflating the same, and timing means associated with the control means for intermittently actuating the control means according to a predetermined timing sequence to supply fluid to the second support means so that, in use, pressures exerted on the different areas of the patient's posterior contacted by the first and second support means are periodically varied. More specifically, in a preferred embodiment of the present invention, a foam annulus is provided as a first or primary resilient support means having a predetermined shape to serve as a peripheral cushioning material for receipt of a person thereon. An inflatable element serves as the second support means, is received within the first support means and is operatively connected to a supply of fluid, preferably air. A compressor powered by alternating or direct current provides for inflation of the second support means adequately to a support a person properly in a sitting attitude thereon, and preferably to raise the person slightly off the first support means. A bleed valve is associated with the fluid supply means in this embodiment and may be adjustable according to the weight of a patient residing on the cushion or to operate on a predetermined timing sequence. The bleed valve thus determines the maximum fluid pressure within the second support means and also permits a controlled deflation of same. Additionally, control means, preferably timer control means, may be operatively associated with the fluid supply means periodically to inflate the second support means. The first and second support means are intended to exert different pressures on respective affected body portions. When the second support means is deflated, as is normal, surface pressures under the ischial tuberosities which are most vulnerable to damage are very low. By periodically inflating the second support means pressures under the ischial tuberosities are increased while pressures generated on the other areas are reduced. This provides improved blood perfusion and lessens the likelihood of ulcers. Thus, by periodic inflation of the normally deflated second support means adequate to relieve pressures exerted on body portions contacting the first, resilient support means, improved blood circulation in the portions residing on said first support means can be achieved. Thereafter, deflation of the second support means beyond a predetermined level shifts pressures to the previously unaffected body portions contacting the first support means whereby full blood circulation can return to the body portions below the ischial tuberosities. Such periodic pressure shifting thus achieves enhanced comfort overall and an improved blood circulation across the body portion contacting the seat, lessening the likelihood of development of ulcers. Preferably, in a support device according to this invention, the fluid supply means comprises an air compressor e.g. powered by a DC source in controlled communication with the said inflatable second support means, and the device includes valve means operatively associated with the said inflatable support means for regulating predetermined inflation and deflation thereof dependent upon the weight of a person sitting thereon; the timing means being operatively associated with the compressor for intermittently causing fluid to be admitted to the said support means according to the predetermined timing sequence. Further, a chair such as a wheelchair incorporates the support device according to this invention, wherein the first resilient support means is located at a sitting area of the chair and defines an open area in a generally central portion of the sitting area, and the second, inflatable support means is received in the open area whereby the first and second support means cooperate to define the surface on which a person is intended to sit, the inflatable support means being located to receive the person's ischial tuberosities thereover, the fluid supply means operatively associated with the inflatable second support means includes means to controllably deflate the second support means when a person resides thereon, the deflating means for example being a bleed valve, and the supply of fluid to the second support means at predetermined intervals being such that pressures developed on portions of the posterior in contact with the first and second support means may be cyclically increased and decreased, with pressure decreases in use being adequate to permit improved blood circulation in areas directly thereover compared to other body areas receiving higher pressures. According to another aspect of the invention, there is provided a method for supporting a person in a sitting disposition, comprising: a) providing a primary resilient support means and an inflatable support means beneath the person's buttocks, the inflatable support means being located beneath the person's ischial tuberosities, b) maintaining the inflatable support means in a state of deflation whereby low pressures are exerted on body areas below the ischial tuberosities while normal pressures are generated on other body areas in contact with the primary support means, and c) periodically inflating and deflating the inflatable support means (40) according to a predetermined time sequence determined by a timing means to apply an upward force on the buttocks area above the inflatable support means sufficient to reduce pressures on the body areas in contact with the primary support means, the predetermined periods of inflation being shorter than the periods of deflation. The invention will be more readily understood from a reading of the following non-limitative description and by reference to the accompanying drawings which show a preferred embodiment of the invention. In the drawings: Figure 1 is an isometric view of a wheelchair equipped with a patient support device according to the present invention, Figure 2 is a top plan view of the patient support device, Figure 3 is a vertical cross-sectional view through the support device as illustrated in Figure 2 taken along the line III-III, and Figure 4 is a schematic illustration of an embodiment of operative control circuitry associated with a patient support device according to the present invention. Making reference to the figures, preferred embodiments of the present invention will now be described in detail. Figure 1, for example, illustrates a typical installation of a patient support device according to the present invention. The support device of the present invention may be utilized in any chair or seat, for instance a wheelchair 10 as illustrated. As can be seen in Figure 1, chair 10 includes a support frame 12 to which conventional wheels 14 and 16 are secured for mobility of chair 10. Support frame 12 has a seat support surface 18 and a back support surface 20 secured thereto, both of which can be of conventional construction though either or both could be modified for permanent installation of a support device according to the present invention thereon. As also illustrated in Figure 1, located atop the seat surface 18 and thus forming a surface on which a person would reside in a sitting attitude is a first and principal support means 30 that is configured for receipt within the normal wheelchair seat area. First support means 30 is an annular structure having a generally rectangular outer periphery. An annulus or opening 32 is defined in an interior portion of the first support means 30 located to receive the ischial tuberosities thereover. First support means 30 may be any resilient material that will afford comfort to a person sitting thereon, but preferably is a polymeric foam cushion material, the resilience of which affords comfort while at the same time having adequate density or firmness that a person sitting thereon will not totally compress same. While the first support means 30 is illustrated as an annulus, such is not essential, and it may take any other shape so long as there is an opening located to receive the ischial tuberosities thereover. In the most preferred embodiment, as can be seen from Figures 1, 2 and 3, first support means 30 is also provided with an upper contour that is conducive to comfort. Note, for example, in Figure 3, that upper surfaces 34 taper inwardly from an outer periphery 35 towards opening 32, thus defining somewhat of a central depression on an upper surface of the support means 30. Also, as may be seen in Figure 1, upper surface 34 of first support means 30 is also preferably contoured for receipt of a person's legs. A second, inflatable support means 40 is located within opening 32 and is intended to be positioned with respect to the patient such that the ischial tuberosities of the patient are located thereover. While inflatable support means 40 may assume any desired shape and construction, a polymeric envelope 42 is preferred having a connector element 44 located in a wall of same. Most preferably, as shown in Figures 1 and 3, support means 40 includes a depressed area 41 in an internal portion of same, whereby, when inflated, the increased pressures are developed only on the ischial tuberosity areas. A tubular conduit 46 is secured to connector 44 in communication with an interior chamber 43 defined by envelope 42. An opposite end of tubular conduit 46 is operatively associated with a fluid supply means generally indicated as 50 (see Figure 4) for supplying air under pressure to the interior of fluid support means 40 for proper inflation of same. Fluid control means 50 includes an air compressor 52 which is operatively connected with tubular conduit 46 and thus is in communication with interior chamber 43 of inflatable support means 40. Air compressor 52 is also electrically connected to a source of power 54 illustrated as a battery, though an alternating current power source could equally be utilized in conjunction with the present invention. In a most preferred embodiment, fluid supply means 50 is secured to a wheelchair 10 with the power source being rechargeable batteries which are also secured to the chair frame 12 for movement there with. A master switch 56 for determining the state of operativeness of the overall system is provided between the source of power 54 and compressor 52, and in a wheelchair environment could be located on an arm of the chair (Figure 1) or some other location conveniently accessible to a patient. Likewise, electrically connected between power source 54 and air compressor 52 for operation when master switch 56 is in the on position is a timer control means 58 which may be present according to the dictates of the system to actuate and deactuate compressor 52 according to a predetermined time sequence. A bleed valve 60 is also provided between air compressor 52 and inflatable support means 40 for a purpose described hereinafter. With the control means 50 as described above, when air compressor 52 is actuated, air is supplied via tubular conduit 46 to interior chamber 43 of inflatable support means 40 to properly inflate same to a degree similar to that illustrated in solid line in Figure 3, to a maximum pressure as dictated by bleed valve 60. Inflatable support means 40 is intended to remain fully inflated for a predetermined period of time only. For example, bleed valve 60 may be adjusted to the weight of a person sitting on the support system of the present invention. The person's weight then overcomes the resistance of the bleed valve 60 whereby air escapes therethrough in a controlled manner to achieve deflation of support means 40. Such adjustment also controls the maximum fluid pressure within means 40 as noted above. With timer means 58 present according to the rate of deflation of inflatable support means 40 based in part on the patient's weight, after a predetermined period of time, timer switch 59 will close to return power to compressor 52 whereby support means 40 will be reinflated. Alternatively, timer means 58 may control off-on operation of both bleed valve 60 and air compressor 52 in a set time controlled sequence. In operation, inflatable support means 40 should remain deflated for about 80 to 90 percent of the time during which the other portions of the buttocks and the thighs bear virtually all of the body weight with pressures developed on the vulnerable ischials being minimal. During the remaining about 10 to 20 percent of the time, support means 40 may be inflated to cause the ischial tuberosities to support most of the body weight, thus relieving pressure from the other affected body areas. Hence timer means 58 could be preset to cause compressor 52 to maintain support means 40 inflated for only one to two minutes every 10 minutes while opening bleed valve 60 and deactuating compressor 52 during the remaining eight to nine minutes of the ten minute cycle. Such one to two minute period is generally not adequate time at the higher pressure to create tissue damage, and thus is acceptable. In the normal mode of operation with support means 40 deflated, first support means 30 develops pressures on the buttocks and thigh areas ranging from about 53 to 80 kPa (40 to 60 mm Hg), while the buttocks area under the ischial tuberosities receives minimal pressures, generally below about 26.7 kPa (20 mm Hg). At such minimal pressure levels on the ischial tuberosities, tissue damage is unlikely. When support means 40 is inflated, pressures are generated on areas of the buttocks under the ischial tuberosities in a range of from about 133 to 200 kPa (100 to 150 mm Hg). Inflation of support means 40 further lifts the patient slightly off the primary support means 40, permitting a reduction of pressures generated on the buttocks and thighs of about 26.7 kPa (20 mm Hg). Such reduction permits good blood perfusion in the areas where the reduced pressures exist, while the increased pressures generated by inflated support means 40 are not maintained for a long enough period to create tissue damage thereat. Systematic inflation and deflation of inflatable support means 40 can thus effectively shift pressure emphasis from one body area to another so long as the duration of inflation i s not long enough to create tissue damage. Such procedure permits good blood perfusion in all of the affected body areas, significantly reducing the incidence of decubitus ulcers, and also greatly enhances comfort of the individual sitting on the support. A further important characteristic of the support of the present invention is found in the fact that should the inflatable support means 40 fail, the ischial tuberosities will receive the generally minimal pressures noted above and should not experience tissue damage. A preferred embodiment of the present invention has been described above. A number of changes, however, could be made thereto. For example, both the first and second support means could be inflatable with inflation and deflation cycles as described above so as to vary pressures on the affected body areas of a person residing thereon. Separate inflating means could be provided for the inflatable first and second support means, or a single inflating means appropriately coupled through control means adapted to control the degrees and periods of inflation of the respective support means. Moreover, if desirable, the shapes of the various support means may vary from that as illustrated in Figures 1 through 3 so long as the intended result is accomplished.

Claims: A support device for supporting a patient in a sitting position, which includes complementary first and second resilient support means with respective, relatively-displaceable support surfaces each for supportive contact with different areas of the patient's posterior, the second support means being inset within the first support means for supportive contact with the ischial tuberosities area of the posterior, characterised in that the second support means (40) is a normally-deflated, fluid-inflatable member and in that the device includes a fluid supply means (52), means (50) associated with the supply means (52) to control the supply of fluid to and from the second support means (40) for inflating and deflating the same, and timing means (58) associated with the control means (52) for intermittently actuating the control means according to a predetermined timing sequence to supply fluid to the second support means so that, in use, pressures exerted on the different areas of the patient's posterior contacted by the first and second support means (30, 40) are periodically varied. A support device according to claim 1, wherein the first support means (30) surrounds the inset second support means (40) and has adequate density that the first support means is not fully compressed by a patient sitting thereon, the said support means for instance being a polymeric foam. A support device according to claim 1 or claim 2, wherein the fluid supply means comprises an air compressor (52), for example a battery-powered compressor. A support device according to claim 3, wherein the fluid control means comprises valve means (60) for relieving air pressure in the said second support means (40) for deflating the said second support means (40) and the timing means (58, 59) for actuating and deactuating the compressor (52) according to the predetermined timing sequence. A support device according to claim 1, wherein the fluid supply means comprises an air compressor (52) e.g. powered by a DC source in controlled communication with the said inflatable second support means (40), and the device includes valve means (60) operatively associated with the said inflatable support means (40) for regulating predetermined inflation and deflation thereof dependent upon the weight of a person sitting thereon; the timing means (58) being operatively associated with the compressor for intermittently causing fluid to be admitted to the said support means (40) according to the predetermined timing sequence. A support device according to any of claims 1 to 5, further comprising a chair, such as a wheelchair (10), which defines a sitting area wherein the said support device is located. A support device according to any of claims 1 to 6, wherein upper, support surfaces of the first and second support means are contoured for improved comfort. A support system according to any of claims 1 to 7, wherein the second support means (40) defines a depressed area (41) in its upper surface. A support device according to any of claims 1 to 8, wherein the timing means is operative to effect a timing sequence wherein the second support means is intermittently inflated and deflated, the periods of inflation to the periods of deflation being in the ratio range of 2:8 to 1:9. A chair, such as a wheelchair, incorporating the support device according to claim 1, wherein the first resilient support means (30) is located at a sitting area of the chair and defines an open area (32) in a generally central portion of the sitting area, and the second, inflatable support means (40) is received in the open area (32) whereby the first and second support means (30, 40) cooperate to define the surface on which a person is intended to sit, the inflatable support means (40) being located to receive the person's ischial tuberosities thereover, the fluid supply means operatively associated with the inflatable second support means (40) includes means (60) to controllably deflate the second support means when a person resides thereon, the deflating means for example being a bleed valve, and the supply of fluid to the second support means (40) at predetermined intervals being such that pressures developed on portions of the posterior in contact with the first and second support means (30, 40) are cyclically increased and decreased, with pressure decreases in use being adequate to permit improved blood circulation in areas directly thereover compared to other body areas receiving higher pressures. A method for supporting a person in a sitting disposition, comprising: a) providing a primary resilient support means (30) and an inflatable support means (40) beneath the person's buttocks, the inflatable support means being located beneath the person's ischial tuberosities, b) maintaining the inflatable support means (40) in a state of deflation whereby low pressures are exerted on body areas below the ischial tuberosities while normal pressures are generated on other body areas in contact with the primary support means (30), and c) periodically inflating and deflating the inflatable support means (40) according to a predetermined time sequence determined by a timing means to apply an upward force on the buttocks area above the inflatable support means sufficient to reduce pressures on the body areas in contact with the primary support means, the predetermined periods of inflation being shorter than the periods of deflation. A method according to claim 11, wherein the inflatable support means (40) is kept deflated for from 80 to 90 percent of the time, and is inflated for from 10 to 20 percent of the time, that the person is seated thereon. A method according to claim 11 or claim 12, wherein the inflatable support means (40) has an adjustable check valve (60) operatively associated therewith, which check valve is adjusted according to the person's weight.

Inventors: OLSHANSKY, KENNETH, PAUL, PATRICK R.D., PRICE, JAMES H.
Applicants: SSI MEDICAL SERVICES, INC.
Application year: 1986
Main classification: A61G5
IPC codes: A61G7, A61G5