Patent Application
20060236464
1. The Field of the Invention
The present invention relates generally to an inflatable mattress and, more specifically, to a mattress having multiple, fluidly-unconnected chambers that can be selectively inflated and deflated to increase and decrease the pressure exerted from positions on the mattress surface on various points of contact with the human body.
2. The Relevant Technology
There is evidence that decubitus ulcers, otherwise known as pressure sores or bedsores, may develop when a bed-ridden person is not able to move. For example, people who are unconscious, unable to sense pain, paralyzed or otherwise unable to move can remain in the same location fostering the development of the bedsores. Bedsores are ugly, generally regarded as painful and typically debilitating. To reduce the incidence of bed sores, people in attendance to the bed-ridden person need to move or rotate the bed ridden person on a regular basis and in turn vary the parts of the body that are exposed to the pressure and reduce the risk of developing bed sores. Bed sores can be found on people/patients in hospitals, nursing homes and in homes under home care. Bedsores can lead to additional medical complications, including bone and blood infections, infectious arthritis, penetrating holes below the wound that burrow into bone or deeper tissues, and scar carcinoma, a form of cancer that develops in scar tissue.
Bedsores generally form at points of pressure, where the weight of the patient's body presses the skin against the firm surface of the bed. The skin's blood supply is believed to be interrupted or reduced by the pressure in turn causing injury to skin cells which can cause them to die. Unless the pressure is periodically is relieved to allow full blood flow to the pressed areas of the skin, the skin cells in the area start to die leading to ulcerations as the body seeks to deal with the cells. The ulcerations can grow into notable bed sores some in excess of the area of a quarter or half dollar. To allow blood to flow to the areas of restriction and reduce the risk of sores, attending personnel are typically tasked to regularly turn the patients. However, turning of patients as tasked does not always happen for reasons not pertinent here.
Bedsores are commonly found on or near the tail bone area, hips, back, elbows, heels and ankles. They can become deep, extending into the muscle. Muscle is even more prone to severe injury from pressure than skin. This means that mild injury to the skin may cover a deeper, more pronounced injury to muscle. Bedsores are extremely difficult to heal, unnecessary and can be prevented. It is much easier and cheaper to prevent a bed sore than to try and heal a bedsore.
Inflatable mattresses that are seen in the literature appear to be and are believed to be difficult to operate, expensive, and unreliable. In turn, it is understood that such have enjoyed only limited acceptance. An inflatable mattress that is easily usable for a patient or hospital bed that is reliable and easy to operate is not known. An inflatable mattress that varies the pressure in separate cells under different parts of the body and that accurately and promptly operates to maintain the pressure and then vary it in accordance with individual or preprogrammed instructions is also not known.
A mattress system of the present invention includes multiple inflatable chambers, a pump, a valve assembly, a source of liquid (including gases like air), a sensor to detect the position of the inflatable chambers, a controller and interconnecting conduits. The multiple inflatable chambers are selectively inflatable and deflatable to vary the points of contact between the mattress surface and the patient's body. The inflatable mattress system of the present invention alternates, by the use of inflatable cells, the amount and location inflatable chamber pressure, thereby regulating the amount and location of mattress surface contact with a patient's body for a pre-selected period of time. Complications associated with pressure sores that result from constant contact between parts of the mattress surface and the body are thereby significantly reduced if not eliminated.
A system and method for selectively inflating and/or deflating a plurality of inflatable chambers of a mattress system is provided. The system includes a first plurality of inflatable chambers, each of which has at least one wall member forming an interior volume. The wall member is made from a flexible material selected to retain fluid. Each of the first plurality of inflatable chambers have a chamber connector for fluid communication with the interior volume. The wall member is deflectable between a first inflated position and a second inflated position that is different from the first inflated position.
The system and method also includes a number of deflectable resistors that predictably vary their respective electrical resistance upon deflection from a first configuration to a second configuration when applying an electrical signal thereto. Each of the deflectable resistors are attached to a wall member of an inflatable chamber to deflect therewith upon movement between the first inflated position and the second inflated position. The deflectable resistor generates a deflection signal reflective of said movement. A fluid source is provided for supplying a fluid under pressure into each interior volume of the first plurality of inflatable chambers.
The system and method further includes a first conduit means connected to the chamber connector for communicating fluid to and from the interior volume and a second conduit means connected to the fluid source for communicating fluid to and from the fluid source. A discharge means communicates fluid away from the inflatable mattress system from the interior volume. A valve is connected to the first conduit means, the second conduit means and the discharge means. The valve operates between a first position in which the valve places the first conduit means in communication with the second conduit means for supplying fluid from the fluid source to the interior volume and a second position in which the valve places the first conduit means in fluid communication with the discharge means. A controller is connected to each of the deflectable resistors for supplying an electrical signal and for receiving the deflection signal. The controller is connected to the valve and is configured to generate and supply operating commands for operating the valve between the first position and the second position.
In another embodiment, the inflatable mattress has a processor that is communicatively coupled to a controller. The processor has computer-executable instructions for performing a computer process for receiving a deflection signal, deriving an amount of movement from the deflection signal and directing a controller to deliver operating commands.
In another preferred embodiment, the valve is a valve assembly having a valve housing with an inlet for connecting said valve assembly to said fluid source. The valve assembly also includes a first valve plate having a first aperture and a second aperture. A second valve plate is also provided that has a plurality of outlet apertures. The second valve plate is coupled to the valve housing forming a fluid chamber. The outlet apertures are disposed at locations about the second valve plate so that the outlet apertures align with either the first aperture or the second aperture. A drive mechanism is connected to the first valve plate to rotate the first valve plate relative to the second valve plate.
In yet another preferred embodiment, the valve assembly has a three-way valve. The three-way valve is coupled to the fluid source and to the atmosphere. The three-way valve is configured for supplying the inflatable chambers with fluid from the fluid source and discharging the fluid from the inflatable chambers into the atmosphere.
In still another preferred embodiment, the valve assembly further comprises a pressure sensor for monitoring fluid pressure in each inflatable chamber. The pressure sensor takes a pressure reading within the inflatable chambers and transmits the pressure reading to a controller.
To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The various exemplary embodiments provide an inflatable mattress having multiple, fluidly isolated inflatable chambers that can be selectively inflated and deflated to increase and decrease the pressure exerted from various points of the mattress surface on a human body.
Referring to
Referring now to
Inflatable chamber dividers 35, 36, 37 are placed generally at locations within enclosure 30 corresponding to the particular shape and size of the plurality of inflatable chambers 50 in a row or grouping. For example, interior region 46 of mattress system 20 is defined between top end wall 33, a portion of side wall 31, a portion of side wall 32 and cell divider 37. As such, a grouping of plurality of mattress cells or inflatable chambers 50 would be located within the interior region 46 of mattress system 20. Interior regions 47, 48, 49 are formed in a similar manner as interior region 46.
Inflatable chamber cover 40 is generally a rectangular element having side walls 41, 42, top end wall 43, bottom end wall 44 and a removable lid 45. Removable lid 45 is secured to top end wall 43 by any conventional means appropriate for the material used to manufacture inflatable chamber cover 40. For example, if inflatable chamber cover 40 is manufactured using a fabric such as cotton, conventional sewing stitches may be used to secure removable lid 45 to top end wall 43. Removable lid 45 is then secured to side walls 41, 42 and bottom end wall 43 with suitable fasteners such a zipper, snaps, or other coupling mechanism. (not shown).
A plurality of inflatable chambers 50, designed to support the weight of a human body, are positioned within inflatable chamber enclosure 30. In the illustrated embodiment, the mattress structure of inflatable mattress system 20 is sized as a twin mattress for use in a typical hospital bed. However, any mattress size (e.g. king, queen, or full) may be manufactured using the inflatable multi-cell design described herein without departing from the intended scope and spirit of the invention.
Inflatable chamber cover 40 is adapted to fit together with inflatable chamber enclosure 30. The combination of inflatable chamber cover 40, inflatable chamber enclosure 30 and plurality of inflatable chambers 50 forms the overall structure of the inflatable mattress. Removable lid may be folded back to expose the plurality of inflatable chambers 50. Thus, any inflatable chamber within inflatable mattress system 20 may be easily replaced or repaired without having to compromise the overall structural integrity of mattress system 20. The structure and design of inflatable chambers 50 are an important aspect of the present invention, and therefore, are described in greater detail in subsequent paragraphs.
Referring now to
In a preferred construction, a group of small inflatable chambers 115, 116, 117, 134, 135, 136 are positioned where an individual's ankles and a group of small inflatable chambers 125, 126, 127, 128, 129, 130, 131, 132, 133 are positioned where an individual's ankles would typically be located on the surface of a mattress. Selective inflation and deflation of the illustrated small inflatable chambers provides a variation of the pressure at points of contact between the mattress surface and the body at the most common places for the development of bedsores on a bed-ridden individual. Since the inflatable chambers are small, alternating the amount of pressure from even 1.0 to 1.1 psi can significantly vary the pressure points so as to change the points of contact between the mattress surface and the hips and ankles of an individual. A group of medium inflatable chambers 104, 105, 106, 107, 108, 109 are located adjacent the group of small inflatable chambers. The medium inflatable chambers provide a measure of support for a grouping of small inflatable chambers.
In a preferred embodiment, the inflatable chambers are sized and placed according to the average weight and size of a typical human body. In other embodiments, inflatable chambers may be larger sized to accommodate the weight of a very large person or smaller sized to accommodate the weight of a baby or child. Preferably, elongated inflatable chambers 120, 121, 122 are sized in a range of approximately 36.0 inches by 3.7 inches to 37 inches by 4.7 inches, and are preferably 36.5 inches by 4.2 inches. Large inflatable chambers 110, 111, 112, 113 are sized in a range of approximately 13.0 inches by 11.3 inches to 14.0 inches by 12.3 inches, and are preferably 12.5 inches by 10.8 inches. Small inflatable chambers 115, 116, 117 are sized in a range of approximately 8.3 inches by 6.4 inches to 9.3 inches by 7.4 inches, and are preferably 8.8 inches by 6.9 inches. Medium inflatable chambers 104, 105, 106, 107, 108, 109 are sized in a range of approximately 13.0 inches by 6.4 inches to 14.0 inches by 7.4 inches, and are preferably 12.5 inches by 6.9 inches. Preferably, elongated inflatable chambers, large inflatable chambers, small inflatable chambers and medium inflatable chambers are approximately 3.0 inches thick.
The inflatable chambers illustrated in
Inflatable chamber 140 is constructed of any substantially non-porous, flexible material. For example, inflatable chamber 140 may be manufactured of a vinyl material, the thickness of the material falling within a range from about 0.015 inches to about 0.04 inches, and preferably, is 0.02 inches. Any similar material may be used. A suitable material should be weldable and sealable to create an interior volume in the interior of the inflatable chamber 140, such that a fluid may be introduced to inflate the cell but the fluid does not escape. In one preferred embodiment, one surface of the inflatable chamber is constructed of the non-porous, flexible material. However, one or more of the surfaces may be manufactured of the flexible material and the remaining surfaces may be manufactured of a different material.
The top surface 151 is relatively smooth and adapted to support at least a portion of the weight of an individual positioned on the surface of the inflatable mattress system 100. The bottom surface 152 has a chamber connector 155 that either introduces fluid into or releases fluid from the inflatable chamber located interior to inflatable chamber 140. Chamber connector 155 may be positioned on any surface of inflatable chamber 140 and is configured to connect to a conduit means for communicating fluid to and from the interior volume. In the illustrated embodiment, chamber connector 155 is an aperture in inflatable chamber 140 and a fitting. However, chamber connector 155 may be any element suitable for fluidly communicating between the interior volume of inflatable chamber 140 and any element that supplies, releases or measures fluid such as, for example, a valve, a connector, a PVC or metal conduit, a female or male adapter or a liquid tight flexible conduit and fitting.
A deflectable resistor 150 is secured to a surface of inflatable chamber 140 to detect the presence or absence of a pressure point, such as a patient's weight, on a particular inflatable chamber. In a preferred embodiment, deflectable resistor 150 is secured to the top surface 151. Deflectable resistor 150 consists of a coated substrate that changes in electrical conductivity as it is bent. The change from a first configuration to a second configuration results in a change in the inflatable chamber 140 from a first inflated position to a second inflated position, which varies the resistance of the deflectable resistor 150 in a predictable way. At any time, the resistance may be measured by applying an electrical signal such as a voltage or a current to the deflectable resistor 150. Connections may be made to deflectable resistor 150 to capture the deflection information so as to determine the amount of bending or movement that occurs on top surface 151 between a first inflated position and a second inflated position, referred to herein as a deflection signal that is reflective of the movement.
A suitable deflectable resistor for purposes of detecting a pressure point on the surface of inflatable chamber 140 is a Bend Sensor® potentiometer manufactured by Flex Point Sensor System, Inc., also described in U.S. Pat. Nos. 5,157,372 and 5,583,476, the disclosure of which is hereby incorporated by reference for all purposes. Deflectable resistor 150 is affixed to the surface of inflatable chamber 140 by any suitable means, and preferably is affixed by a pressure sensitive adhesive that adheres to top surface 151 without affecting the integrity of the material used to manufacture deflectable resistor 150.
Referring now to
In the particular device illustrated, controller 200 is comprised of valve controller 275, fluid controller 265 and reading device 270. In alternate embodiments, controller 200 may be a mechanical or electrical device that incorporates the functions and operations of valve controller 275, fluid controller 265 and reading device 270 in either a single device or multiple devices. Valve controller 275 controls the operation of valve assembly 215 by sending a series of signals to the valve assembly to perform various mechanical operations, such as selecting a particular inflatable chamber for inflation, deflation or measurement. Fluid controller 265 controls the strength and duration of the flow of fluid from fluid source 210 to any one of inflatable chambers 220, 225, 230 by providing a signal to fluid source 210 to initiate the introduction of fluid to inflate a selected inflatable chamber. Reading device 270 receives a deflection signal from deflectable resistors 235, 240, 245 to determine the location and amount of an individual's weight that is located on inflatable chambers 220, 225, 230.
In a preferred embodiment, controller 200 is embodied in any suitable programmable integrated circuit such as M30262 manufactured by Renesas. However, any suitable programmable integrated circuit may be used to supply operating commands that control the operation of valve 215 and fluid source 210, as well as receive deflection measurements from the surface of inflatable chambers 220, 225, 230 and pressure measurements from within the respective interior volume of inflatable chambers 220, 225, 230. For example, controller 200 may be embodied in an ASIC, or similar application specific integrated circuit.
Controller 200 is also coupled to valve 215 through a pressure sensor 255 for reading the pressure within inflatable chambers 220, 225, 230. Pressure sensor 255 is typically a pressure transducer capable of measuring the amount of pressure within an inflatable chamber when such as request is issued by either controller 200 or processor 205. However, any suitable pressure measuring device may be used. In operation, controller 200 is instructed to retrieve a pressure reading within a particular inflatable chamber, for example, inflatable chamber 220. Valve 215, via information from valve controller 275, selects inflatable chamber 220 for a reading. Once chamber 220 is chosen, the pressure reading is taken by pressure sensor 255 and relayed to processor 205 via controller 200.
Processor 205 preferably comprises any computer processor capable of executing a series of instructions to access data from controller 200 and issue commands to controller 200. For example, processor 205 may contain instructions for selecting certain inflatable chambers for inflation or deflation based on deflection information received from deflectable resistors 235, 240, 245. Processor 205 may also contain instructions for randomly selecting inflatable chambers 220, 225, 230 for inflation and deflation in a particular pattern that provides varying pressure points on the skin of an individual's body, thereby preventing the formation of bedsores.
In the illustrated embodiment, fluid source 210 is coupled to valve 215 through a three-way valve 250 and a check valve 260. However, fluid source 210 may be coupled directly to valve 215 using a conduit or fluid source may be coupled to the valve through any number of intervening devices such as a flow meter. Three-way valve 250 allows pump 210 to introduce fluid into inflatable chambers 220, 225, 230 through valve 215. In addition, three-way valve 250 is coupled to the atmosphere such that fluid may be removed from inflatable chambers 220, 225, 230 through valve 215. Check valve 260 preferably has a crack pressure of 0.15 psi, which prevents back flow through the pump. Fluid source 210 is preferably a pump that is sized to provide at least ½ pound per square inch of pressure in inflatable chambers 220, 225, 230, such as a 110 VAC model # DDL15B-101, 23 L/m linear diaphragm pump manufactured by Gast that outputs approximately 5 pounds per square inch of pressure, however, any suitable fluid source may be used that is sized in accordance with the particular requirements of the inflatable mattress system.
Valve 215 is fluidly coupled to inflatable chambers 220, 225, 230. In operation and with reference to an operating command received from controller 200, valve 215 selects a particular inflatable chamber for inflation or deflation. In inflation mode, valve 215 is operational to introduce fluid from fluid source 210 into a selected inflatable chamber. In deflation mode, valve 215 releases fluid into the atmosphere from a selected inflatable chamber using three-way valve 250. Valve 215 may be any suitable element for selectively supplying fluid from a fluid source or communicating fluid away from a mattress system. One particular embodiment of a valve 215 is described in greater detail with reference to
Referring now to
Valve housing 310 has two housing apertures. A first housing aperture is connected to a conduit 312, which is fluidly connected to three-way valve 250 illustrated in
First valve plate 300 is located within pump chamber 311. First valve plate 300 is coupled to a drive mechanism 302 that imparts rotational movement to first valve plate 300 relative to second valve plate 305. Second valve plate 305 has a plurality of outlet apertures that are fluidly connected to each inflatable chamber. Each outlet aperture is coupled to a conduit 322 using a conduit coupler 321. Preferably, conduit coupler 321 is a ¼ inch barbed fitting, however, any suitable coupling means may be used that forms an air tight seal between conduit 322 and the outlet aperture of second valve plate 305.
Referring now to
In operation, first valve plate 300 rotates relative to second valve plate 305 using a drive mechanism 302. Typically, first valve plate 300 is disk shaped and second valve plate 305 is shaped to substantially match the shape of first valve plate 300. Either first aperture 350 or second aperture 355 on first valve plate 300 aligns with an outlet aperture 365 on second valve plate 305. Outlet aperture 365 is fluidly connected to each of the inflatable chambers in the inflatable mattress system. In this way, a fluid path is selectively established to either impart fluid from a fluid source into a selected inflatable chamber or release fluid from a selected inflatable chamber into the environment.
Drive mechanism 302, typically a stepper motor, imparts rotational movement to first valve plate 300, thereby rotating first valve plate 300 relative to second valve plate 305. Unlike standard motors, a stepper motor moves in discrete increments to position first plate 300 relative to second plate 305. Such controlled movement positions either first aperture 350 or second aperture 355 over the selected outlet aperture 365 so as to allow a single inflatable chamber to be inflated or deflated without affecting the integrity of any other inflatable chamber.
In the illustrated embodiment, second drive plate 305 has 32 outlet apertures 365. Two of the apertures are not used for either an inflate operation or deflate operation, but instead are used for an alignment operation. The remaining 30 apertures are each coupled to a particular inflatable chamber and, therefore, are used in either an inflate operation or deflate operation. Controller 200 is pre-programmed to recognize which outlet aperture 365 is coupled to which inflatable chamber in the inflatable mattress system. Controller 200 may therefore receive information from processor 205 and select a particular outlet aperture 365 coupled to a particular inflatable chamber and thereafter perform an inflate operation or deflate operation or measure the pressure within the interior volume of the selected inflatable chamber.
Drive mechanism 302 is adapted to step first valve plate 300 through all 32 outlet apertures, thereby aligning either first aperture 350 or second aperture 355 with a selected outlet aperture 365 in response to a signal from controller 200. Drive mechanism 302 receives a signal from controller 200 and steps first valve plate 300 to the appropriate outlet aperture 365 on second valve plate 305 corresponding to the selected inflatable chamber.
With reference to certain reference numerals in
Valve 215 is operational to select an inflatable chamber and then either introduce fluid into the inflatable chamber of the selected inflatable chamber or release fluid from the inflatable chamber of the selected inflatable chamber. In this manner, a single inflatable chamber can be inflated and/or deflated in response to information provided from a controller coupled to a processor. In addition, once a particular inflatable chamber is selected, the pressure in the inflatable chamber may be read and recorded by a pressure sensor coupled to the controller. In addition, valve 215 provides an alignment feature that squares-up the valve assembly drive mechanism before the valve assembly is operational so that the drive mechanism does not pitch and bind.
For an inflatable chamber selection operation, controller 200 establishes that a particular inflatable chamber is to be selected. Processor 205 may instruct controller 200 to select a particular cell or controller 200 may select a particular cell on its own. Controller 200 issues an operating command or signal to valve 215 to a select a particular inflatable chamber, for example inflatable chamber 230. First valve plate 300 rotates relative to second valve plate until aperture 350 or aperture 355 aligns with the outlet aperture 365 corresponding to inflatable chamber 230. Typically, an inflate operation, deflate operation and/or measurement operation follows a selection operation.
For an inflatable chamber inflation operation, controller 200 establishes that selected inflatable chamber 230 is to be filled with fluid. Processor 205 may instruct controller 200 to inflate the selected cell or the instruction may come from controller 200. In the embodiment illustrated in
Valve assembly 302 had previously selected inflatable chamber 230, which is now selected for an inflation operation. Fluid travels from fluid source 210 into aperture 375 into fluid chamber 311. The fluid then flows through either aperture 350 or aperture 355 into outlet aperture 365 corresponding to inflatable chamber 230. Outlet aperture 365 is coupled to a conduit that is connected to the fitting in inflatable chamber 230. Outlet aperture 365, the conduit and the fitting and aperture on inflatable chamber 230 form a fluid communication path between valve assembly 302 and the inflatable chamber of inflatable chamber 230.
For an inflatable chamber deflation operation, controller 200 establishes that fluid is to be removed from selected inflatable chamber 230. As stated previously for an inflate operation, processor 205 may instruct controller 200 to deflate the selected cell or the instruction may come from controller 200. Controller 200 sends an operating command or signal to three-way valve 250 that a deflate operation is about to occur. In response to the operating command from controller 200, three-way valve 250 is placed into the deflate position, thereby creating a fluid path from valve assembly 215 to the environment to release the fluid.
Valve assembly 215 had previously selected inflatable chamber 230, which is now selected for a deflation operation. Fluid travels from the inflatable chamber 230 through the aperture and fitting in the inflatable chamber into the conduit coupled to the fitting. The fluid then flows into outlet aperture 365 that corresponds to inflatable chamber 230, through either aperture 350 or aperture 355 and into fluid chamber 311. The fluid then passes out aperture 375 disposed in valve housing 310 into three-way valve 250. The fluid is then released into the environment.
For an inflatable chamber measurement operation, controller 200 establishes that the internal pressure of selected inflatable chamber 230 is to be measured. Processor 205 may instruct controller 200 to take a pressure measurement from a particular cell or controller 200 may select a particular cell on its own. Controller 200 sends an operating command or signal to pressure sensor 255 that a measurement operation is about to occur. In response to the command from controller 200, pressure sensor 255 measures the internal pressure within the inflatable chamber of previously selected inflatable chamber 230.
Referring again to
In an alignment operation, drive mechanism 302 rotates first valve plate 300 until the beam of visible or infrared light from optical sensor 313 passes through aperture 350. Since housing aperture 380 is aligned with the reflector located on the unused aperture of the second valve plate 305, the beam of visible or infrared light passes from the emitter of optical sensor 313 through aperture 350 and reflects back to the detector of the optical senor 313, thereby producing a signal. As such, valve assembly 301 is in alignment and the alignment signal is transmitted from the optical sensor 313 to controller 200.
Controller 200 also receives measurement information regarding the deflection of deflectable resistors 235, 240, 245 located on inflatable chambers 220, 225, 230 respectively. Reading device 270 located within controller 205 is coupled to deflectable resistors 235, 240, 245. At prescribed periods of time, reading device 270 receives deflection signals from deflectable resistors 235, 240, 245. For example, if an individual's body is resting on inflatable chambers 220, 225, 230, the deflectable resistors sense a certain amount of deflection on each cell. In response, a deflection signal is transmitted from deflectable resistors 235, 240, 245 to the reading device 270 in controller 270. Reading device 270 then forwards the deflection signals to processor 205.
Processor 205 may use the deflection information from deflectable resistors 235, 240, 245 in a variety of ways. For example, the deflection information provides processor 205 with information regarding the position of a human body on inflatable chambers 220, 225, 230. Processor 205 may then instruct controller 205 to alter the pressure within the interior volumes of inflatable chambers 220, 225, 230 at prescribed intervals to vary the pressure exerted from the surface of the inflatable chambers on the skin of the individual, thereby reducing the formation of bedsores.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
