CA2237580A1

CA2237580A1 - Dynamic seating support system

Info

Publication number: CA2237580A1
Application number: CA002237580A
Authority: CA
Inventors: Peter W. Linley; Hugh O'neill
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-11-14
Filing date: 1996-11-14
Publication date: 1997-05-22
Also published as: WO1997017869A1; EP0874572A4; AU7679696A; US5678891A; JP2000500365A; EP0874572A1; US5713631A; AU714208B2; US5662384A

Abstract

A seating support cushion system (10) has a seat cushion (14) with an H-shaped inflatable cell (45) that is inflated alternatingly with a pair of inner cells (54, 56) fill in the voids of the "H" shape, with one cell (56) in the rear of the cushion (14). This rear cell (56) also preferably has a recess (60) and a secondary crossbar portion (56a) adjacent to the crossbar cell (44). A back cushion (12) has two sets (18, 25) of alternatingly inflated, laterally extending cells (19-23, 26-29) forming a spinal recess (27a) and a pair of inflatable, opposing, and longitudinally extending side support cells (32, 34) positioned adjacent to the outer edges of the laterallly extending back cells (19-23, 26-29).

Description

CA 02237~80 1998-0~-13 DYNAMIC SEATING SUPPORT S~STEM
~3ACICGROUND OF THE INVENTION
Technical Field The present invention relates to the field of dynamically inflated seating systems, and in particular, to such systems designed to provide periodic relief of 5 pressure on selected bodv regions during seating.

Background Art The principle of distributing the bodv mass of a person over a ~ider surface area and reducing pressures selectively through the use of cyclically applied air 10 pressure is well Icnown. The seated position, for patients w ho can tolerate it, is often preferred by clinicians for at least part of each day. It helps to drain secretions and provides maximal lung expansion and aeration, thus helping to reduce pneumonia risk. Seated positioning also improves mental orientation in elderly patients and allo~vs a greater participation in the activities of daily living.
15 Unfortunately, ~hen patients at high lisk for pressure sore development are placed in seated positions for longer than about ten minutes, the chance of tissue breakdo~vn, particularly over the ischial tuberosities~ coccyx and sacrum, increases substantially.
It is Icno~n to provide son~e relief to the region of the ischial tuberosities 20 with a selectively inflatable cell positioned in a pelvic recess formed in a fixed-support resilient cushion, as is disclosed in U.S. Pat. No. 4,796,948 issued to Paul et al. A similar design with left and right inflatable cells is disclosed in U.S. Pat.
No. 5,022,385 issued to Harza. Both of these devices provide increased support under the ischial tuberosities ~ithout removing the support from the resilient seat 25 cushion laterallv supporting the inflatable cell(s). These designs therefore provide significant pressure variation under the ischial tuberosities, b-lt do not significantly valy the pressures occurring Oll the resilient cushion, ~hich provides for a constant amount of support.

CA 02237~80 1998-0~-13 DISCLOSURE OF INVENTION
The present invention provides a seat support wllicll provides alternating support regions bv dvnamic inflation of sets of cells to ~videlv varv the pressure throughout the seat cushion surface area. In one aspect of the invention, a 5 dynamically inflatable seat cushion provides interlllittent support on the ischial tuberosities while restraining moven-ent of the seated person toward the front of the seat.
A cushion support system according to the present invention includes a seat cushion having first and second mating sets of inflatable cells. The first set 10 includes a pair of spaced-apart elong:ate longitudinal cells extellding along a cushion a~xis corresponding to the longitudinal axis of a person supported on the support system7 and a first transverse cell extending laterally between the longitudinal cells. The second set includes a pair of axially spaced inner cellspositioned between the pair of longitudinal cells and separated by the transverse 15 cell. Pressure means is provided for alternatinglv inflating and deflating the first and second sets of cells so that a person seated on the seat cushion is supported primarily by alternate sets of cells.
In another aspect of the invention, the support system includes a back cushion adapted for extending upwardlv along the back of a chair when the 20 support system is positioned on a ch,air with the seat cushion on the chair seat.
The back cushion includes two sets of interdigitated elongate lateral back cells, with the cells in the two sets alternating in position along the cushion axis. The lateral back cells form a spinal depression extending longitudinally along at least a portion of the back cushion along tlle cushion aYis for receiving the spine of a25 person supported 011 the support svsteln.
In yet another aspect of the invention, the baclc cushion includes a pair of opposing, longitudinally extending side support cells positioned adjacent to theouter edges of the laterallv e,Ytending baclc cells. These cells are preferabl~,~
inflatable to a fixed pressure that is preferablv adj~lstable.

CA 02237~80 1998-0~-13 In the prefelred embodiment, a seating support cushion system is provided that has a seat cushion and a back cushioll. The seat cushion has an H-shaped inflatable cell, ~ith the sides of the "H'~ e~tending yarallel to a cushion axis that corresponds to the longitudinal aYis of a person sitting 011 the cushion, and therefore parallel to the thighs. The crossbar cell is midwav in the cushion. A pair of inner eells fill in the "H" shape, with one cell in the rear of the cushion positioned for supporting the ischial tuberosities. This rear cell also preferably has a reeess for receiving the coccvx witho-lt significant pressure and has a crossbar cell portion adjacent to the crossbar cell.
The inflation of the baclc and seat cells is coordinated so that the top of the pelvis is pressed forward at the same time that the inner cells are inflated. The pelvis is thus rolled fon-~ard while it is held in a stable position on the seatcushion. The preischial crossbar eells provide SUppOIt and resists the tendency of the seated person to slide fonvard on the cushion.
Use of such a SUppOlt system provides dynamic pressure reduction for a seated person, allowing persons ~vith sacral ~llcers to be maintained in a seated position when necessaly for medical intelvention or socialization. Like~rise, persons at high risk for slcin breakdowll can be maintained in the seated position for a number of hours with protection against sustained high interfaee pressures.
These and other features and advantages of the present invention will be apparent from the preferred embodiment described in the followillg detailed description and illustrated in the accompan~ying dra~vings.

BRIEF DESCRIPI'ION OF DRAWINGS
FIG. 1 is a top view illustrating the cushion support svstem of the invention with the back and seat cushions lying flat and uninflated.
FIGs. 2A and 2B are cross sections talcen along line 2-2 in FIG. 1 illustrating t~vo alternating states of inflation of the cusllion cells.
FIGs. 3A and 3B are cross sections talcen along line 3-3 in FIG. 1 CA 02237~80 l998-0~-l3 illustrating two alternating states of inflation of the cushion cells.
FIGs. 4A and 4B are cross sections taken along line 4-4 in FIG. 1 illustrating two alternating states of inflation of the cushion cells.
FIGs. SA and 5B are cross sections taken along line ~-5 in FIG. I
5 illustrating two alternating states of inf}ation of the cLIshion cells.
~ IG. 6 is a cross section talcen along line 6-6 in FIG. I illustrating thegeneral shape of an inflated back cell.
FIG. 7 is a simplified schematic of the electrical and airflovv circuits of the air pump shown in FIG. 1.
FIGs. 8A, 8B and 8C are illustrations of the pressure distribution between a person seated on the cushion support svstem of FIG. I and the seat and back c~lshions for three inflation states of the cushions.

BEST MODE FOR CA'RRYING 0~1T THE INVENTION
1 5 Stn~cture Referring initially to FIG. 1, a seating cushion support svstem 10 is shown.
System 10 includes back cushion 1 ,! and seat cushion 14 whicll extend along a cushion axis 16 corresponding to the longitudinal aYis of a person supported on the c~lshions. These cushions are made of a suitable flexible and sealable material, 20 such as polv!~ rethane, nvlon or PVC:, and are preferablv covered by a ~aterproof, moisture-vapor permeable fabric, not showll. These cushions mav be fonned as a single unitary assembly, or as separate cushions that mav or may not be connected7 such as bv snap connecti.ons or bv releasable fabric, SUCIl as that known by the proprietary name VELCROT~'. The cusllions and even the cells ~i~thin each25 cushion could also be held in a unitalv assembly bv a cover having pockets conforming to the associated cells. Svstem 10 is poltable, requiring a chair with a fixed back and seat, such as a conventional wheel chair or geri-chair. It will also fit on many types of conventional chairs.
Back cushion 12 has a first set 18 of laterallv extendillg compartments or CA 02237~80 1998-0~-13 cells 19, 20, 21, 22 and 23, and a second set 25 of laterallv e~tending cells 267 27, 28 and 29. These cells are interdigitated and vary in cross-sectional size from small at the top and bottom and large in the middle, as sho~ rn.
Two lateral support air cells 32 and 34 are inflatable for providing sideways 5 support to the person's trunk. Various embodimellts mav be provided for inflating cells 32 and 34. One embodiment, as sho~n in solid lines in FIGs. I and 6 is to have the cells manually inflatable through manually operable valves, such as valve 30. The cells may then be inflated to a pressure selected to accommodate the desired comfort level or size of the person supported bv the cushion.
Cells 32 and 34 may also be filled with a resilient foam, such as foam 31 sho~vn in cell 32 in FIG. 6. With valves 30 for manuallv inflating the lateral support cells, as in the first embodiment, the cells become self-inflating when the valve is opened. Further, the cell pressure can be increased by manually furtherinflating the cell, or reduced by pressing out some of the air in the cell.
In a third embodiment, shou~ in dashed lines in FIG. 1, one of the pressurized air tubes, SUCll as tube 80, can have a feed tube 33 connected to the lateral cells. Pressurized air is applied through a manuallv controlled check valve 35 until cells 32 and 34 are inflated. After inflation, the check valve is turned off and an exhaust valve 37 is then manuallv controlled to vent excess air if a reduced 20 cell pressure is desired.
Alternatively to the third embodiment, the pressure provided by check valve 35 could be set manually, such as bv controlling the pressure applied by a spring on a ball valve. Valve 37 is then not needed, since vah~e 35 maintains the lateral support cells at a desired firmness. If a continuous air supplv is needed, tube 33 2~ could be connected to tubing 76 through a second checlc valve as ~vell.
Each laterally e~ctending back cell has a generallv uniform size along its length, except for a restlicted region in the center, such as region 27a of cell 27, v~hich is produced by a narrowing in the edges. As sho~n in the cross section tal<en along line 6-6, as sho~vll in FIG. 6, ~hen the back cells are inflated, the CA 02237=.80 1998-0=.-13 W O 97/17869 PCT~US96118215 restricted region is smaller in diameter tl1an the portions of the cell on each side of the restricted region. As a result, a recess 36 is p.~oduced that e~ctends axially along the length of the back cushion. When a person is supported on the support system, the person's spine aligns witl- and is received in recess 36, avoiding 5 excessive pressure on the bony prot1~berances caused bv the vertebrae.
Seat cushion l 4 also has t~-ro sets of cells, sets 38 and 40. Set 38 includes opposing inner longitudinal cells 42 and 43 e,Ytending along and spaced from thesupport axis or center of the cusl ion. These cells are preferablv about nineteen centimeters (seven and one-half inclles) apart so tl1at they generall~ align ~ith the lO person's thighs and support the trochanters. Interconnecting cells 42 and 43 just fo~vard of the center of the seat is ~hat is referred to as a preischial crossbar cell 44. Cell 44 is positioned about t~rentv centimeters (eight inches) from the rear of the seat so that it is fol~rard of the ischial tuberosities of a s~lpported person. Cells 42, 43 and 44 form, in combinatiorl a composite H-shaped cell 45. Ribs 47 and 48 extend longitudinally through the centers of inner longitudinal cells 42 and 43, respectively, for about three-fourths the length of the cells. The ribs, in the fonn of I-beams, fom1 slight recesses or grooves 50 and 5 l, respectively, in the surface of the cells, as showl1 in FIGs. 4B and 5B. The result is that the cells are flatter overall, for providing stabler support for the thighs, with enlarged rear portions for 20 providing greater support under the buttocks.
Set 40 of the cells in seat cushion l 4 includes centrally located and longitudinally spaced inner or center cells 54 and 56. These cells fill the space between inner longitudinal cells 42 and 43 and are separated aYiall~ by crossbarcell 44. Fon~ard center cell 54 has a rib 58 extending along its length and rear25 center cell 56 has a rib 60 extending along the rear three-fourths of the cell. Rib 60 is about half as high as ribs ~7, 48 and 58, thereby producing a pronounced groove or recess 61, as sl1o~n in FIG. 3A. Recess 6 l is centrally located at the rear of the seat c~1shion for receiving ancl applving n1il1imal pressure to the coccvx of a seated person. The rear cell is preferablv al)out t~\~entv centilneters (eight incl~es) CA 02237~80 1998-0~-13 long and nineteen centimeters (seven and one-half inches) ~-~ide. This results in the ischial tuberosities of an adult being located at appro~Yimately the sites 62 and 63 identified by the "+" s~nbols. These sites are preferably located about thirteen centimeters (five inches) from the rear of the seat cusllion and about 5 fifteen centimeters (six inches) apart.
The fon~ard section 56a of rear center cell 56 adjacent to crossbar cell 44 is not restricted by a rib. Section 56a, as sho~l in FIG. 4A, forms a secondary crossbar cell 66. Cell 66, which could also be made as a separate cell from cell 56, is enlarged relative to the rear portion of cell 56 having rib 60, as shown in FIG.
3A. Cell 66 functions similarlv to crossbar cell 44 in inhibiting the folv~ard sliding of a person seated on cushion 14.
Lastly, set 40 of the seat cusllion also contains outer longit~ldinal cells 68 and 70 extending along cells 42 and 43, respectivelv. These cells provide lateral support to the thighs when cells 42 and 43 are deflated~ as showll in FIGs. 3A, 4A
15 and 5A.
As shown in FIG. l? the cells in each set of cells, generally spealdng, are interconnected by connecting sections, such as section 72 connecting back cells 26 and 27, or section 74 connecting cells 56 and 70. The cells in back cushion set 18 and seat cushion set 40 are inflated and deflated together through tubing 76 20 which conducts air from an air pump assernblv 78. Similarlv, tubillg 80 connects sets 25 and 38 together and to the pump as sho~v~l, using conventional tubing connectors and a T-junction.
As will be described, the pump cvclicallv inflates alternate sets of cells in each cushion. Pump assemblv 78 is preferablv constructed as illustrated in FIG. 7 25 using conventional components. A rocker SwitC}l ~2 is used to turn the pump on and off. A pump motor 83 drives a reciprocating or other appropriate air pUlllp mechanism 84. Ambient air passes into pump 84 and then passes through a controllable safety or relief valve 86. A dial 87 on a face of the pump assemblyhousing is coupled to valve 86 for controlling the magllit-lde of air pressure to be CA 02237~80 1998-0~-13 applied to the cushions. This pressure is preferably in the range of 60 mm Hg to100 mm Hg.
The pressurized air is conducted to the cells through a two-way valve 88 driven by a valve motor 89. The cuITent to the valve motor, which determines the5 speed of the motor, is controlled bv a rheostat 90 in turn controlled manually by a dial 91. The speed of the valve motor determines the cycle time in s~itching theinflation between the respective sets of cells in the back and seat cushions.
Pressurization of the cells is showll by LEDs 94 and 96 via a micro switch 98. The micro switch is controlled by an in-line pressure sensor, not shown, with . 10 one of the LEDs indicating low pressure and the other indicating full pressure.
As has been mentioned, the cells in seat cushion 14 are preferabl~,~ made of polyurethane, nvlon, or PVC. These materials are air-impermeable in order to provide full inflation of the cells wit}~ a low volume of air flow. The moisture-vapor permeable fabric covering provides for a substantial amount of ventilation of 15 the person/cushion interface. It is important to remove condensed body vaporsand to cool the interface slcin surface in order to minimize slcin breakdown.
The ventilation and cooling of the personlcushion interface is significantly enhanced by the placement of numerous near-microscopic laser-produced holes in the central upper surface of the seat cushion. These holes allow for the escape of 20 air from the cells generallv uniformlv across the upper surfaces of H-shaped cell 45 and the two inner cells 54 and 56, as illustrated in FIGs. 2A, 2B, 3A, 3B, 4A, 4B, 5A and 5B. This limits the ventilation fiom the cushion cells to the support areas, thereby allowing for use of a lower volume air pump than would be required if all of the cushion surfaces were air permeable. Such holes mav also be provided in 25 selected cells of the back cusllioll. The use of a vapor-permeable covering on the cushion further allows for dissipation of the ventilated air, as well as ventilation and coolillg of the cushion surface supporting a person.

CA 02237C,80 1998-0C,-13 Operation During operation after initial inflation of all of the cells, one set of cells in each of the seat and back cushions is deflated at a time. Deflation of the sets of cells is provided by releasing air through valve 88 to the atmosphere, as is 5 conventionall~ lcno~vn. The inflation cycle is preferably bet~veen five and fifteen minutes in total duration. For therapeutic purposes, a cvcle time of about ten minutes is desirable. During a single cycle, the cells in all of the sets are initially inflated. Then one set of cells in each cushion is deflated, after which all sets of cells are inflated again, and then the other set of cells in each cushion is deflated.
10 The deflated sets of cells are then inflated to complete tlle c~cle. In that features of the invention do not require both the seat and back cushions, operation may be for only the seat cushion or only the bacl~ c~lshion. Svstelll 10 may also be configured accordingl ~r, which is to say, the features of the seat cushion may be provided in a systenl without a back cushion.
FIGs. 2-5 illustrate by respective figure identifiers "A" and "B" the different conditions of the sets of cells during alternate deflation periods, as vie~ved along cross section lines 2-2 through 5-5 in FIG. 1. The figures with the "A" identifier illustrate the state of the associated cells with the cells in onlv sets 18 and 40 inflated. The figures with the "B" identifier illustrate the state of the associated 20 cells with the cells in only sets 25 and 38 inflated.
FIGs. 2A and 2B illustrate the cells along line 2-2 in FIG. 1, which sho-vs the orientation and relationship of the back and seat cushions during use. FIG. 2A
shovvs that when center rear cell 56 in the seat cushion is inflated for supporting directly the isch}al tuberosities, baclc-cushion cell 20, whicll has an enlarged25 diameter compared to cell 26 just belo~v it, is also inflated. Cell 20 is positioned at approximately the top of the pelvis.
FIG. 2B sho~s the cell inflation on the altemate portion of the cycle. It is seen that cell 20 provides a significant forward pressure at the top of the pelvis relative to the position of the pelvis ~hen cells 26 and 27 are inflated. The pelvis CA 02237~80 1998-0~-13 is thus rolled fon~ard at a time ~vherl the ischial tuberosities are well supported on inner cell 56. The fo~ ard, enlarged portion of cell 56, described above as a secondary crossbar cell 66, tends to resist fonvard n otion of the person due to the forward motion of the pelvis due to cell 20. Support system 10 thus provides a 5 roclcing motion in the pelvis during the alternating pressure cycles, while maintaining the person in the desired position on the seat cushion.
As shown in FIG. 2B, ~vhen support in the seat cushion is transferred to H-shaped cell 45, that crossbar cell 44 serves not only to support weight of the person, but also to resist move~nent of the person's seat fon~ard on the seat 10 cushion. A comparison of FIGs. 3B and 4B shows that the inner longitudinal cells 42 and 43 have enlarged regions (sho~n in FIG. 3B) at the rear of the cells, andthat forward of these enlarged regiorls these cells are flatter and thinner. Theenlarged regions provide increased support of the buttocks. This increased support, however, tends to urge the person for~vard in the seat. The crossbar cell 15 compensates for this to hold the per.son substantially in a fixed position.
FIGs. 8A-8C illustrate the pressure distribution on a representative person seated on the cushions of support system 10 durillg the three phases of a support cyde. These images were produced by a commercially available pressure distribution measuring svsten~. FIG. 8B shows the pressure distribution when all20 cells are fully inflated. The vvllite areas represent no press-lre, the outer dark areas represent lo w pressurel and the lighter internal areas represent moderate pressure.
The lower portion of the image represents the seat cushion and the upper area represents the back cushion.
Addressing initially the pressures experienced on the seat cushion, with full 25 inflation as showll in FIG. 8B, the area of greatest pressure is in the region of the ischial tuberosities. The area to the rear of the ischial tuberosities, corresponding to the position of the coccvx, has ver~ light or no pressure in any of the images.
FIG. 8A re~r~sents the pressure distribution wllell only cell sets 18 and 40 are inflated. It is seen that there is relativelv light pressure in the region of H-CA 02237~80 1998-0~-13 shaped cell 45, Wit}l high pressure on the t~o inllel cells 54 and 56. The darlcest regions of the image ~ithill the lighter interl1lediate rings indicates the location of the highest pressure. It is apparent that the greatest amount of pressure is under the pelvic region and on the ischial tuberosities.
FIG. 8C sho~vs that when the inner seat cells 54 and 56 are deflated and the H-shaped cell 45 is inflated, there is only low pressure belo~ the pelvic region.
The heaviest pressure is along the thighs witll moderate to high pressure on thepreischial crossbar cell 44. The alternating inflation c~cle, referencing the figures, is thus from f~lll inflation (FIG. 8B) to yartial inflation, in this case inflation of 10 sets 18 and 40 (FIG. 8A), then back to full inflation (FIG. 8B), followed by partial inflation, now inflation of sets 25 and 38 (FIG. 8C) and back to full inflation (FIG. 8B).
Referring now to the press~lre distributioll associated ~th the baclc cushion, it is very apparent that there is essentiall~ no pressure applied to the spinal column 15 in any of the inflation states, as is indicted bv the minimal pressure up the center of the back cushion. The highest pressure on the back exists ~vhen the shoulder blades are supported on inflated cell 28, as sho~l in FIG. 8C. This pressure is reduced to a moderate level w hen all the cells are inflated, as shown in FIG. 8B, and reduced to a lo~v level u~hen cell 2~ is deflated and adjacent cells 21 and 22 20 are inflated, as sho~l in FIG. $A.
In the demonstration that produced the images in FIGs. 8A-8C, the seated person apparently was not seated as far back as possible, and therefore did not experience the forward pressure of cell 20 on the lo~!~rer baclc, as described. This effect could be increased by increasing the size of this cell if experience indicates 25 that people do not sit with the pelvis as close to the lo~er back c~lshion as intended, in order to obtain the full benefits of s~stem l O.
Although the present invention has been described in detail ~vith reference to a particular preferred embodiment, persons possessing ordinar~ slcill in the art to which this invention pertains ~ill appreciate that various modifications and enhancements mav be made without departing from the spirit and scope of the claims. For instance, enlarged cell regions in the preferred embodiment could beprovided as separate cells, and cells having ribs could be fonned as separate cells.
The baclc-cushion cells could be provided as spaced-apart pairs of cells~ vvith one 5 cell of each pair on each side of the center. This construction would also form spinal recess 36. There are many variations ill the structure of the cushions that could produce the same or similar support surfaces. The above disclosure is thusintended for purposes of illustration and is not limitation.

Claims

What is claimed is:

1. A dynamically inflatable support system (10) comprising:
a seat cushion (14) having first and second mating sets of inflatable cells (38,40), the first set (38) including a pair of spaced-apart elongate longitudinal cells (42,43) extending along a cushion axis (16) corresponding to the longitudinal axis of a person supported on the support system, the second set (40) including inner cell means (54,56) positioned between the pair of longitudinal cells (42,43), at least one of the first and second sets of cells (38,40) further including transverse cell means (44,66) extending laterally between the longitudinal cells (42,43) intermediate the ends of the longitudinal cells; and pressure means (78) for alternatingly inflating and deflating the first and second sets of cells (38,40) so that a person seated on the seat cushion(14) is supported primarily by alternate sets of cells (38,40).

2. A support system (10) according to claim 1 wherein the transverse cell means (44,66) comprises a first transverse cell (44) in the first set of cells (38).

3. A support system (10) according to claim 2 wherein the transverse cell means (44,66) further comprises a transverse cell portion (56a) in the inner cell means (54,56) and positioned adjacent to the first transverse cell (44), the first transverse cell (44) and the transverse cell portion (56a) being alternately inflated and deflated.

4. A support system (10) according to claim 1 wherein the inner cell means (54,56) comprises a pair of inner cells (54,56) separated by the transverse cellmeans (44,66) and one of the inner cells (56) is positioned adjacent to the center rear of the cushion (14) for supporting, when inflated, the ischial tuberosities of a person seated on the seat cushion.

5. A support system (10) according to claim 4 wherein the one inner cell (56) is at least thirteen centimeters or five inches long and at least fifteen centimeters or six inches wide.

6. A support system (10) according to claim 5 wherein the one inner cell (56) is about twenty centimeters or eight inches long and nineteen centimeters or seven and one-half inches wide.

7. A support system (10) according to claim 4 wherein the transverse cell means (44,66) is positioned at least thirteen centimeters or five inches from the rear of the cushion.

8. A support system (10) according to claim 7 wherein the transverse cell means (44,66) is positioned about twenty centimeters or eight inches from the rear of the cushion.

9. A support system (10) according to claim 1 wherein the inner cell means (56) is adjacent to the rear of the seat cushion, the support system (10) further comprising means (60) defining a depression positioned centrally in the rear of the inner cell means (56).

10. A support system (10) according to claim 1 wherein the longitudinal cells (42,43) are positioned at least fifteen centimeters or six inches apart for supporting, when inflated, the trochanters of a person seated on the seat cushion (14) and relieving the ischial tuberosities.

11. A support system (10) according to claim 10 wherein the longitudinal cells (42,43) are positioned about nineteen centimeters or seven and one-half inches apart.

12. A support system (10) according to claim 1 further comprising a back cushion (12) adapted for extending upwardly along the back of a chair when the support system is positioned on a chair with the seat cushion (14) on the chair seat, the back cushion (12) including two sets (18,25) of interdigitated elongate laterally extending back cells (19-23,26-29), with the cells in the two sets (18,25) alternating in position along the cushion axis (16), and wherein the pressure means (78) alternately inflates and deflates the first and second sets (18,25) of back cells.

13. A support system (10) according to claim 12 wherein one cell (20) of one of the sets (18) of cells in the back cushion (12) is aligned with the top of the pelvis of a person supported in the support system, the pressure means (78) inflating the one cell (20) concurrently with the inner cell means (54,56) in the seat cushion for rolling the pelvis forward when the inner cell means (54,56) is inflated.

14. A support system (10) according to claim 12 wherein the sizes of the cells within each set (18,25) of back cells vary progressively with larger intermediate cells (20, 21, 27) to provide a contour conforming to the contour of the back of a person supported on the support system (10).

15. A support system (10) according to claim 12 wherein the back cushion (12) further comprises a pair of opposing, longitudinally extending side supportcells (32,34) positioned adjacent to the outer edges of the laterally extending back cells (19-23,26-29).

16. A support system (10) according to claim 15 wherein the side support cells (32,34) are inflatable.

17. A support system (10) according to claim 16 wherein the side support cells (32,34) are self-inflating.

18. A support system (10) according to claim 16 further comprising means (33,35,37) coupling the pressure means (78) to the side support cells (32,34) for inflating the side support cells.

19. A support system (10) according to claim 18 wherein the coupling means (33,35,37) includes control means (35) for controlling the pressure in theside support cells (32,34).

20. A support system (10) according to claim 18 wherein the coupling means (33,35,37) maintains the inflation pressure of the side support cells (32,34).

21. A support system (10) according to claim 20 wherein the coupling means (33,35,37) provides continuous inflation of the side support cells (32,34).

22. A support system (10) according to claim 12 wherein at least a portion of the interdigitated elongate laterally extending back cells (19-23,26-29) have an intermediate portion of reduced size (27a) which form a spinal depression (36) extending longitudinally along at least a portion of the back cushion (12) alongthe cushion axis (16) for receiving the spine of a person supported on the support system (10).

23. A support system (10) according to claim I wherein at least a portion of the surfaces of the inflatable cells of the seat cushion are air permeable.

24. A support system (10) according to claim 23 wherein only the upper surfaces of cells (45,54,56) of the seat cushion (14) are air permeable.

25. A dynamically inflatable support system (10) comprising:
a back cushion (12) adapted for extending upwardly along the back of a chair, the back cushion (12) including first and second sets (18,25) of interdigitated elongate laterally extending back cells (19-23,26-29), with the cells in the two sets (18,25) alternating in position along the cushion axis (16), at least a portion of the back cells having intermediate portions (27a) of reduced size which form a spinal depression (36) extending longitudinally along at least a portion of the back cushion (12) along the cushion axis (16) for receiving the spine of a person supported on the support system; and pressure means (78) for alternatingly inflating and deflating the first and second sets (18,25) of cells.

26. A support system (10) according to claim 25 wherein the back cushion (12) further comprises a pair of opposing, longitudinally extending side supportcells (32,34) positioned adjacent to the outer edges of the laterally extending back cells (19-23,26-29), the side support cells (32, 34) being inflatable separately from the first and second sets (18, 25) of cells.

27. A support system (10) according to claim 26 wherein the side support cells (32,34) are self-inflating.

28. A support system (10) according to claim 27 further comprising means (33,35,37) coupling the pressure means (78) to the side support cells (32,34) for inflating the side support cells.

29. A support system (10) according to claim 28 wherein the coupling means (33,35,37) includes control means (35) for controlling the pressure in theside support cells (32,34).

30. A support system (10) according to claim 28 wherein the coupling means (33,35,37) maintains the inflation pressure of the side support cells (32,34).

31. A support system (10) according to claim 30 wherein the coupling means (33,35,37) provides continuous inflation of the side support cells (32,34).

32. A dynamically inflatable support system (10) comprising:
a back cushion (10) adapted for extending upwardly along the back of a chair, the back cushion (12) including first and second sets (18,25) of interdigitated elongate laterally extending back cells (19-23,26-29), with the cells in the two sets (18,25) alternating in position along the cushion axis (16), and a pair of opposing, longitudinally extending side support cells (32,34) positioned adjacent to the outer edges of the laterally extending back cells (19-23,26-29), the side support cells (32, 34) being inflatable separately from the first and second sets of cells (18, 25); and pressure means (78) for alternatingly inflating and deflating the first and second sets (18,25) of cells.

33. A support system (10) according to claim 32 wherein the side support cells (32,34) are self-inflating.

34. A support system (10) according to claim 32 further comprising means (33,35,37) coupling the pressure means (78) to the side support cells (32,34) for inflating the side support cells.

35. A support system (10) according to claim 34 wherein the coupling means (33,35,37) includes control means (37) for controlling the pressure in theside support cells (32,34).

36. A support system (10) according to claim 34 wherein the coupling means (33,35,37) maintains the inflation pressure of the side support cells (32,34).

37. A support system (10) according to claim 36 wherein the coupling means (33,35,37) provides continuous inflation of the side support cells (32,34).