Abstract:
An equalizing pressure control system for connection to at least two pressure zones of a body support. The equalizing pressure control system ensures that an object will be slowly and safely lowered to a static position in the event of a sudden failure of an external pump or a supply pressure to the at least two pressure zones.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an equalizing pressure control system for slowly and safely lowering a patient to a stable position in the event that a powered supply pressure fails or is turned off. 
   BACKGROUND OF THE INVENTION 
   Heretofore, inflatable cushioning devices for use with body supports, such as a mattress, sofa, seat, or the like, typically included a plurality of air cells or bladders that are inflated to support a person. The air cells provide support to the person, and can be inflated to a desired pressure level to provide the person with a predetermined level of comfort and support. 
   In the medical field, cushioning devices including a plurality of air cells are often used to provide different levels of support under various portions of a patient&#39;s body. For example, a mattress may include separate air cells located in the upper, middle, and lower portions of the mattress. These air cells can be inflated to different pressures to support the upper, middle, and lower portions of the patient&#39;s body with different pressures. 
   An external pump may cyclically inflate a plurality of air cells for providing alternating pressure therapy for a patient. The external pump may also provide supply pressure to inflate for providing tilting of the patient. In the event of a pump failure, the sudden termination of the supply pressure can result in an abrupt lowering of the patient. 
   Accordingly, there exists a need to arrive at an adequate pressure equalization device, and a body support utilizing such a device in the event of a pressure supply failure. 
   SUMMARY OF THE INVENTION 
   The present invention provides an equalizing pressure control system for connection to at least two pressure zones of a body support. The equalizing pressure control system ensures that a patient will be slowly and safely lowered to a static position in the event of a sudden failure of an external pump or a supply pressure to the pressure zones. The pressure zones may provide alternating lifting under a patient or may provide lifting for tilting a patient. 
   The first general aspect of the present invention provides an apparatus comprising: a first flow restrictor operatively positioned between at least two pressure zones for restricting a flow of fluid between the at least two pressure zones; a second flow restrictor connecting the first flow restrictor with a pressure relief valve, and wherein the second flow restrictor provides a greater flow resistance to the fluid than the first flow restrictor, and wherein the pressure relief valve selects a level of fluid pressure in the at least two pressure zones. 
   The second general aspect of the present invention provides a body support comprising: a plurality of fluid cells; a plurality of manifold systems, each with an interconnected group of fluid cells; an alternating fluid pressure system applying alternating fluid pressure to the manifold systems; an equalizing pressure control system controlling the fluid pressure in the manifold systems when the alternating fluid pressure is removed, wherein the equalizing pressure control system equalizes the fluid pressure in each manifold system to a selected pressure level and includes at least one flow restrictor that allows fluid to flow in both directions. 
   The third general aspect of the present invention provides a body support comprising: a plurality of bladders; a supply apparatus for supplying a pressurized fluid to each bladder; an equalizing pressure control system for controlling the pressurized fluid in the plurality of bladders when the supply apparatus is removed or shut off, wherein the equalizing pressure control system equalizes the fluid pressure in each bladder to a selected pressure level. 
   The fourth general aspect of the present invention provides a method comprising the steps of: providing a first fluid cell filled with a fluid at a first fluid pressure level; providing a second fluid cell filled with the fluid at a second fluid pressure level; equalizing the fluid pressure between the first fluid cell and the second fluid cell to a third pressure level; and adjusting the third pressure level to a fourth pressure level. 
   The fifth general aspect of the present invention provides an apparatus comprising: at least two manifold systems, each with an interconnected set of fluid cells; a supply apparatus for supplying pressurized fluid to each interconnected set of fluid cells; and an equalizing pressure control system operatively interconnected with the at least two manifold systems for equalizing the fluid pressure in each fluid cell. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention will best be understood from a detailed description of the invention and an embodiment thereof selected for the purposes of illustration and shown in the accompanying drawings in which: 
       FIG. 1  illustrates a partial cross sectional view of an equalizing pressure control system; 
       FIG. 2  illustrates a plan view of another embodiment of the support system apparatus including the equalizing pressure control system; 
       FIG. 3  illustrates a plan view of another embodiment of the support system apparatus including the equalizing pressure control system; 
       FIG. 4  illustrates a plan view of another embodiment of the support system apparatus including lifting pods and the equalizing pressure control system; and 
       FIG. 5  illustrates a plan view of another embodiment of the support system apparatus including the equalizing pressure control system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Although certain embodiments of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of the preferred embodiment. The features and advantages of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. Although the drawings are intended to illustrate the present invention, the drawings are not necessarily drawn to scale. 
   An equalizing pressure control system  100  is illustrated in  FIG. 1 . The equalizing pressure control system  100  includes a first conduit  102 , a second conduit  104 , a third conduit  106 , a pressure relief valve  108 , a first flow restrictor  110 , and a second flow restrictor  112 . The first conduit  102  connects a first pressure zone  114  with the second conduit  104  and the third conduit  106 . The second conduit  104  connects a second pressure zone  116  with the first conduit  102  and the third conduit  106 . The first flow restrictor  110  is placed in the first conduit  102 . The second flow restrictor  112  is placed in the third conduit  106 . The pressure relief valve  108  includes an outlet conduit  118  connected to the fluid exhaust reservoir  54 . Generally, the fluid  36  included in the fluid exhaust reservoir  54  is atmospheric air, however, any suitable fluid  36  (e.g., water, nitrogen, etc.) can be used. 
   Typically, the first pressure zone  114  and the second pressure zone  116  may include fluid  36  pressures that are different from each other. A pressurized fluid supply source  120  may supply pressurized fluid  36  through a conduit  122  to the first pressure zone  114 . Additionally, the pressurized fluid supply source  120  may supply pressurized fluid  36  through a conduit  124  to the second pressure zone  116 . A control system  126  controls the pressurized fluid  36  delivered to the first pressure zone  114  and the second pressure zone  116 . The pressurized fluid supply source  120  may supply alternating high and low pressure fluid  36  to the first pressure zone  114  and to the second pressure zone  116 . For example, a high pressure fluid  36  may be supplied through the conduit  122  to the first pressure zone  114 , and a low pressure fluid  36  may be supplied through the conduit  124  to the second pressure zone  116 . Next, a low pressure fluid  36  may be supplied through the conduit  122  to the first pressure zone  114 , and a high pressure fluid  36  may be supplied through the conduit  124  to the second pressure zone  116 . 
   The alternating fluid  36  flow provided by the pressurized fluid supply  120  to the first pressurized zone  114  and to the second pressurized zone  116  is higher than the flow passing between the first pressurized zone  114  and the second pressurized zone  116  through the first flow restrictor  110 . The first flow restrictor  110  may restrict flow by any suitable means that allows fluid to flow in both directions (e.g., orifice, porous material, etc.). Preferably, the first flow restrictor  110  has a flow diameter  128  of about 0.016 inches. The alternating fluid  36  flow provided by the pressurized fluid supply  120  to the first pressurized zone  114  and to the second pressurized zone  116  is higher than the flow passing out through the second flow restrictor  112 . The second flow restrictor  112  may restrict flow by any suitable means that allows fluid to flow in both directions (e.g., orifice, porous material, etc.). Preferably, the second flow restrictor  112  has a flow diameter  130  of about 0.004 inches. The second flow restrictor  112  has a flow diameter  130  smaller than the flow diameter  128  of the first flow restrictor  110 . Therefore, while pressurized alternating fluid  36  flow is being supplied to the first pressure zone  114  and the second pressure zone  116 , the flow between the first pressure zone  114  and the second pressure zone  116 , through the first flow restrictor  110  and the second flow restrictor  112 , is so small that there is a negligible effect on the differential pressure between the first pressure zone  114  and the second pressure zone  116 . 
   If the pressurized fluid supply  120  should be turned off or should fail, the fluid  36  will slowly flow between the first pressure zone  114  and the second pressure zone  116  through the first flow restrictor  110 . The second flow restrictor  112  has a much smaller flow diameter  130  than the first flow diameter  110  so that the pressure in the first pressure zone  114  and the second pressure zone  116  will essentially equalize. Then, the fluid  36  slowly passes through the second flow restrictor  112 , through the pressure relief valve  108 , and through the outlet conduit  118  to the fluid exhaust reservoir  54 . The pressure relief valve  108  determines the final pressure level of the fluid  36 . The pressure setting of the pressure relief valve  108  may be previously determined or may be manually selected. Thus, if the pressurized fluid supply  120  is turned off, the equalizing pressure control system  100  will equalize the pressure between the first pressure zone  114  and the second pressure zone  116  and will control the final pressure to a selected level. Therefore, a patient resting upon the first pressure zone  114  and the second pressure zone  116  will be slowly and safely lowered to a stable level position at a selected support pressure. 
   The pressurized fluid supply source  120  may supply a steady pressure fluid  36  to the first pressure zone  114  and to the second pressure zone  116 . For example, the first pressure zone  114  may be supplied a steady high pressure fluid  36 , while the second pressure zone  116  may be supplied a steady low pressure fluid  36 . The steady high pressure fluid  36  may be used to tilt a patient resting upon the first pressure zone  114  and the second pressure zone  116 . The patient will tilt from the first pressure zone  114  toward the second pressure zone  116 . In the event of turning off or the failure of the pressurized fluid supply  120 , the patient will be slowly and safely lowered to a stable level position in a manner similar to that described above. The equalizing pressure control system  100  will equalize the pressure between the first pressure zone  114  and the second pressure zone  116  and will control the final pressure to a selected level. 
   Another embodiment of the equalizing pressure control system  100  includes the addition of a third flow restrictor  111  (shown in phantom) in  FIG. 1 . The third flow restrictor  111  is in the second conduit  104 . The third flow restrictor may restrict flow by any suitable means (e.g., orifice, porous material, etc.). Preferably, the third flow restrictor  111  includes a flow diameter  129  of about 0.016 inches. If the pressurized fluid supply  120  should be turned off or should fail, the fluid  36  will slowly flow between the first pressure zone  114  and the second pressure zone  116  through the first flow restrictor  110  and the third flow restrictor  111 . The second flow restrictor  112  has a much smaller flow diameter  130  than the first flow diameter  110  and the third flow diameter  129 , so that the pressure in the first pressure zone  114  and the second pressure zone  116  will essentially equalize. Then, the fluid  36  slowly passes through the second flow restrictor  112 , through the pressure relief valve  108 , through the outlet conduit  118 , and into the exhaust reservoir  54 . The pressure relief valve  108  determines the final pressure level of the fluid  36 . The pressure setting of the pressure relief valve  108  may be previously selected or may be manually selected. Thus, if the pressurized fluid supply  120  is turned off, the equalizing pressure control system  100  will equalize the pressure between the first pressure zone  114  and the second pressure zone  116  and will control the final pressure to a selected level. Therefore, a patient resting upon the first pressure zone  114  and the second pressure zone  116  will be slowly and safely lowered to a level position with a selected support pressure. 
     FIG. 2  illustrates a plan view of another embodiment of the support system apparatus  206 A. The support system apparatus  206 A includes an equalizing pressure control system  100 A which will equalize the pressurized fluid  36  between the support zones “E” and “F”, in the event that the alternating pressure system  230 , which supplies alternating high and low pressure fluid  36  to conduits  208  and  210 , is turned off or fails. When conduit  232  is connected to shut off valve  220 , and conduit  234  is connected to shut off valve  228 , the alternating pressure is supplied to conduits  208  and  210 . The conduits  208  and  210  supply the alternating fluid  36  to pressure zones “E” and “F.” The alternating pressure system  230  can include any means for supplying the fluid  36  under pressure including a pump, compressor, etc. Also, included in the alternating pressure system  230  is any means such as a valve (not shown) for periodically switching the pressurized fluid  36  between conduit  232  and  234 . Each support zone “E” and “F,” comprises at least one support cell  14 , optionally comprising a deformable or elastic material. Each support cell  14  includes at least one intake valve  40  and at least one port  43 . Each intake valve  40  includes a check valve (not shown) allowing fluid  36  to flow into the support cell  14 , while preventing fluid  36  from flowing out of the support cell  14 . Each port  43  allows unimpeded fluid  36  flow into or out of the support cell  14 . Each intake valve  40 J- 4 Q is connected to the intake control system  44 , which is connected to the fluid supply reservoir  52 . Generally, the fluid  36  included in the fluid supply reservoir  52  is atmospheric air, however, any other suitable fluids can be used. 
   The ports  43 Q,  43 O,  43 M, and  43 K in zone “E” are connected to conduit  208 . The ports  43 J,  43 L,  43 N, and  43 P in zone “F” are connected to conduit  210 . The equalizing pressure control system  100 A includes a first flow restrictor  110 A, a second flow restrictor  112 A, and a pressure relief valve  108 A, and an outlet conduit  118 A. The first end  212  of conduit  208  is connected to the first flow restrictor  110 A. The first end  222  of conduit  210  is connected to the second flow restrictor  112 A. A conduit  132  connects the second flow restrictor  112 A with the first end  222  of the conduit  210 . A conduit  134  connects the second flow restrictor  112 A with the pressure relief valve  108 A. The outlet conduit  118 A connects the pressure relief valve  108 A with the exhaust reservoir  54 . The pressure control level of the pressure relief valve  108 A may be manually adjusted or may be preselected. 
   The shut off valve  220  can be a “quick disconnect” type that allows fluid  36  to flow through the shut off valve  220  when the conduit  232  is connected, and prevents any flow of the fluid  36  when the conduit  232  is disconnected. The shut off valve  228  can also be a “quick disconnect” type that allows fluid  36  to flow through the shut off valve  228  when the conduit  234  is connected, and prevents any flow of the fluid  36  when the conduit  234  is disconnected. 
   The alternating fluid  36  flow provided by the alternating pressure system  230  to pressure zones “E” and “F” is much higher than the flow passing between the pressure zones “E” and “F” through the first flow restrictor  110 A. The alternating fluid  36  flow provided by the alternating pressure system  230  is much higher than the flow passing out through the second flow restrictor  112 A. Preferably, the first flow restrictor  110 A has a flow diameter of about 0.016 inches. The second flow restrictor  112 A preferably has a flow diameter of about 0.004 inches. The second flow restrictor  112 A has a flow diameter smaller than the flow diameter of the first restrictor  110 A. Therefore, while pressurized alternating fluid  36  flow is being supplied between pressure zone “E” and pressure zone “F,” the flow through the first flow restrictor  110 A and the second flow restrictor  112 A is so small that there is a negligible effect on the differential pressure between the pressure zone “E” and the pressure zone “F.” 
   If the alternating pressure system  230  should be turned off or should fail, the fluid  36  will slowly flow through the first flow restrictor  110 A between the pressure zone “E” and the pressure zone “F.” The second flow restrictor  112 A has a much smaller flow diameter than the flow diameter of restrictor  110 A, so that the pressure in the pressure zone “E” and the pressure in the pressure zone “F” will essentially equalize. Then, the fluid  36  flow slowly passes through the second flow restrictor  112 A, through the pressure relief valve  108 A, through the outlet exhaust  108 A and into the exhaust reservoir  54 . Generally, the fluid  36  included in the fluid exhaust reservoir  54  is air, however, any suitable fluid  36  (e.g., water or nitrogen) can be used. The pressure relief valve  108 A determines the final pressure level of the fluid  36  in the pressure zones “E” and “F.” Therefore, a patient resting upon the pressure zones “E” and “F” will be slowly and safely lowered to a level position with a selected support pressure. 
     FIG. 3  illustrates another embodiment of the support system apparatus  206 B. The support system apparatus  206 B is similar to the support system apparatus  206 A ( FIG. 2 ), except the support system apparatus  206 B has eliminated the intake valves  40 F- 40 Q. The support system apparatus  206 B includes an equalizing pressure control system  100 B. The alternating pressure system  230  supplies alternating high and low pressure fluid  36  to conduit  208  and  210 . When conduit  232  is connected to the shut off valve  220 , and conduit  234  is connected to shut off valve  228 , the alternating pressure is supplied to conduits  208  and  210 . The conduits  208  and  210  supply the alternating fluid  36  to pressure zones “E” and “F.” The alternating pressure system  230  can include any means for supplying the fluid  36  under pressure including a pump, compressor, etc. Also, included in the alternating pressure system  230  is any means such as a valve (not shown) for periodically switching the pressurized fluid  36  between conduit  232  and  234 . 
   The ports  43 Q,  43 O,  43 M, and  43 K in zone “E” are connected to conduit  208 . The ports  42 J,  43 L,  43 N, and  43 P in zone “F” are connected to conduit  210 . The equalizing pressure control system  100 B includes a first flow restrictor  110 B, a second flow restrictor  112 B, a pressure relief valve  108 B, and an outlet conduit  118 B. The first end  212  of conduit  208  is connected to the first flow restrictor  110 B. The first end  222  of conduit  210  is connected to the second flow restrictor  112 B. A conduit  132  connects the second flow restrictor  112 B with the first end  222  of the conduit  210 . A conduit  134  connects the second flow restrictor  112 B with the pressure relief valve  108 B. The outlet conduit  118 B is connected with the exhaust reservoir  54 . The pressure control level of the pressure relief valve  108 B may be manually adjusted or may be preselected. 
   The alternating fluid  36  flow provided by the alternating pressure system  230  to pressure zones “E” and “F” is much higher than the flow passing between the pressure zones “E” and “F” through the first flow restrictor  110 B. The alternating fluid  36  flow provided by the alternating pressure system  230  is much higher than the flow passing out through the second flow restrictor  112 B. Preferably, the first flow restrictor  110 B has a flow diameter of about 0.016 inches. The second flow restrictor  112 B preferably has a flow diameter of about 0.004 inches. The second flow restrictor  112 B has a flow diameter smaller than the flow diameter of the first flow restrictor  110 B. Therefore, while pressurized alternating fluid  36  flow is being supplied between pressure zone “E” and pressure zone “F,” the flow through the first flow restrictor  110 B and the second flow restrictor  112 B is so small that there is a negligible effect on the differential pressure between the pressure zone “E” and the pressure zone “F.” 
   If the alternating pressure system  230  should be turned off or should fail, the fluid  36  will slowly flow through the first flow restrictor  110 A between the pressure zone “E” and the pressure zone “F.” The second flow restrictor  112 B has a much smaller flow diameter than the flow diameter of restrictor  110 B, so that the pressure in the pressure zone “E” and the pressure in the pressure zone “F” will essentially equalize. Then, the fluid  36  flow slowly passes through the second flow restrictor  112 B, through the pressure relief valve  108 B, through the outlet exhaust  118 B and into the fluid exhaust reservoir  54 . Generally, the fluid  36  included in the fluid exhaust reservoir  54  is air, however, any suitable fluid  36  (e.g., water or nitrogen) can be used. The pressure relief valve  108 B determines the final pressure level of the fluid  36  in the pressure zones “E” and “F.” Therefore, a patient resting upon the pressure zones “E” and “F” will be slowly and safely lowered to a level position with a selected support pressure. 
     FIG. 4  illustrates a plan view of another embodiment of support system apparatus  300 A including lifting pods  302 A and  302 B. The support apparatus  300 A includes an equalizing control system  100 C. The lifting pods  302 A and  302 B include bladders  303 A and  303 B, respectively, for containing a fluid  312 . The support cells  14 AAA- 14 HHH lie above the lifting pods  302 A and  302 B. The conduit  531  connects the port  307  in the bladder  303 A of the lifting pod  302 A with the connector  451 . The conduit  306  connects the connector  451  with the pressure apparatus  304 . The connector  451  may be a “quick disconnect” type that allows fluid  312  to flow through the connector  451  when the conduit  306  is connected, and prevents any flow of fluid  312  when the conduit  306  is disconnected. 
   The conduit  530  connects the port  309  in the bladder  303 B of the lifting pod  302 B with a connector  453 . The connector  453  may also be a “quick disconnect” type that allows fluid  312  to flow through the connector  453  when the conduit  308  is connected, and prevents any flow of the fluid  312  when the conduit  308  is disconnected. 
   The pressure apparatus  304  may include, for example, a hand pump, a powered pump, or a compressor to provide pressurized fluid  312  to each of the conduits  306  and  308 . The pressure apparatus  304  is supplied with fluid  312  from the fluid supply reservoir  52 . The controller  310  selectively controls the application of the pressurized fluid  312  to the conduits  306  and  308 . For example, pressurized fluid  312  may be selectively applied to the conduit  308 . The fluid  312  flows from the pressure apparatus  304  through the conduit  308 , the connector  453 , the conduit  530 , and through the port  309  into the bladder  303 B of the lifting pod  302 B. The lifting pod  302 B inflates and lifts the portion of the support cells  14 AAA- 14 HHH lying in a zone “KKK”. 
   Similarly, pressurized fluid  312  may be selectively applied to conduit  306 . In this case the fluid  312  flows from the pressure apparatus  304  through the conduit  306 , the connector  451 , the conduit  531 , and through the port  307  into the bladder  303 A of the lifting pod  302 A. The lifting pod  302 A inflates and lifts the portion of the support cells  14 AAA- 14 HHH lying in the zone “JJJ.” 
   The equalizing pressure control system  100 C includes a first flow restrictor  110 C, a second flow restrictor  112 C, a pressure relief valve  108 C, and an outlet conduit  118 C. A conduit  140  connects the conduit  531  with the first flow restrictor  110 C. A conduit  142  connects the conduit  312  with the first flow restrictor  110 C and the second flow restrictor  112 C. A conduit  144  connects the second flow restrictor  112 C with the pressure relief valve  108 C. The outlet conduit  118 C connects the pressure relief valve  108 C with the fluid exhaust reservoir  54 . 
   Generally, the fluid  36  included in the fluid supply reservoir  52  and the fluid exhaust reservoir  54  is air, however, any suitable fluid  36  (e.g., water or nitrogen) can be used. The fluid supply reservoir  52  and the fluid exhaust reservoir  54  may comprise the same reservoir, and may comprise an ambient source of fluid  36  such as atmospheric air. 
   The first restrictor valve  110 C prevents fluid  312  from quickly and easily passing between bladder  303 A and  303 B, so that fluid supplied by the pressure apparatus quickly flows into either bladder  303 A or  303 B. The first flow restrictor  110 C has a flow diameter of about 0.016 inches. The second flow restrictor  112 C has a diameter of about 0.004 inches. If the pressure apparatus  304  should be turned off or should fail, the fluid pressure in the bladders  303 A and  303 B is controlled by the equalizing pressure control system  100 C. The fluid  312  will slowly flow through the first flow restrictor  110 C between the bladder  303 A and the bladder  303 B. The second flow restrictor  112 C has a much smaller flow diameter than the flow diameter of the first restrictor  110 C, so that the pressure in the bladder  303 A and the bladder  303 B will equalize. Then, the fluid  312  flow slowly passes through the second flow restrictor  112 C, through the pressure relief valve  108 C, through the outlet exhaust  118 C, and into the exhaust reservoir  54 . The pressure relief valve  108 C determines the final pressure level of the fluid  312  in the bladder  303 A and the bladder  303 B. Therefore, a patient tilted between the bladder  303 A and the bladder  303 B, will be slowly and safely lowered to a stable level position, and will be supported by a selected support pressure. 
   Another embodiment of a support system apparatus  206 D is illustrated in  FIG. 5 . The support system apparatus  206 D includes an equalizing pressure control system  100 D. The support system apparatus  206 D includes fluids cells  414 A,  414 B,  414 C, and  414 D. Fluid cells  414 A and  414 C include ports  430 A and  430 C, respectively. A first set of fluid cells  434  includes the fluid cells  414 A and  414 C. The ports  430 A and  430 C of the fluid cells  414 A and  414 C, respectively, are connected to a first manifold  432 . The first set of fluid cells  434  may include one or any additional number of interconnected fluid cells  414  (not shown). Fluid cells  414 B and  414 D include ports  430 B and  430 D, respectively. A second set of fluid cells  436  includes the fluid cells  414 B and  414 D. The ports  430 B and  430 D of the fluid cells  414 B and  414 D, respectively, are connected to a second manifold  438 . The second set of fluid cells  436  may include one or any additional number of interconnected fluid cells  414 . 
   The first manifold  432  is connected to a valve  440 . The second manifold  438  is connected to a valve  442 . The valves  440  and  420  may be opened or closed for controlling the pressurized fluid  36  flow. A supply apparatus  420  supplies pressurized fluid  36 . The supply apparatus  442  may include any suitable pressure generating apparatus (e.g., a hand pump, a powered pump, a compressor, a pressurized tank, etc.). Generally, the pressurized fluid  36  is air, however, any suitable pressurized fluid  36  (e.g., water, nitrogen, etc.) can be used. 
   The supply apparatus  420  is connected to a conduit  444  and a conduit  446 . The conduit  444  is connected to the valve  440 , and the conduit  446  is connected to the valve  442 . When the valve  440  is opened, the supply apparatus  420  supplies pressurized fluid  36  through the conduit  444 , through the first manifold  432 , through the ports  430 A and  430 C, and into the first set of fluid cells  434  (fluid cells  414 A and  414 C). The valve  440  is closed when a desired pressure level is obtained in the first set of fluid cells  434 . 
   When the valve  442  is opened, the supply apparatus  420  supplies pressurized fluid  36  through the conduit  446 , through the second manifold  438 , through the ports  430 B and  430 D, and into the second set of fluid cells  436  (fluid cells  414 B and  414 D). The valve  442  is closed when a desired pressure level is obtained in the second set of fluid cells  436 . The pressure level in the first set of fluid cells  434  may be different from the pressure level in the second set of fluid cells  436 . Additionally, alternating pressurized fluid  36  may be applied to the first set of fluid cells  434  and to the second set of fluid cells  436 . 
     FIG. 5  illustrates a partial cross-sectional view of the equalizing pressure control system  100 D. The equalizing pressure control system  100 D includes a conduit  448 , and a flow restrictor  110 D. The flow restrictor  110 D is located within the conduit  448 . A first end  450  of the conduit  448  is connected to the first manifold  432 , and a second end  452  of the conduit  448  is connected to the second manifold  438 . Pressurized fluid  36  passes between the first manifold  432  and the second manifold  438  through the flow restrictor  110 D. The flow restrictor  110 D may restrict flow by any suitable means (e.g., orifice, porous material, etc.). The flow restrictor  110 D may have a flow diameter  128 D of about 0.016 inches. The flow restrictor  110 D is sized so that when pressurized fluid  36  is being supplied to the first set of fluid cells  434  and to the second set of fluid cells  436 , the flow between the first set of fluid cells  434  and the second set of fluid cells  436 , is so small that there is a negligible effect on the differential pressure between the first set of fluid cells  434  and the second set of fluid cells  436 . 
   When the valves  440  and  442  are shut off, the pressurized fluid  36  is trapped in the first set of fluid cells  434  and in the second set of fluid cells  436 . If the pressure level is different between the first set of fluid cells  434  and the second set of fluid cells  436 , then the equalizing pressure control system  110 D slowly equalizes the fluid pressure between the first set of fluid cells  434  and the second set of fluid cells  436 . The pressurized fluid  36  slowly flows between the first set of fluid cells  434  and the second set of fluid cells  436  through the flow restrictor  110 D until all the fluid cells  414 A- 414 D contain equal pressure. Therefore, a patient resting upon the first set of fluid cells  434  and the second set of fluid cells  436  will be slowly and safely lowered to a stable level position. 
   While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.