Patent Application
20140201909
1. Field of the Invention
The field of the present invention relates to body support systems that include elements for pressure redistribution and which include one or more internal air flow guides. The system also establishes pathways for drawing heat and moisture away from surface(s) contacting and supporting a reclining body on the body support system.
2. Background
Those that care for persons confined to beds and wheelchairs understand the role body support systems play with respect to the prevention and treatment of pressure ulcers. Pressure ulcers, which are also known as bedsores, pressure sores, and decubitus ulcers, rapidly develop when prolonged pressure, heat, and moisture are applied to the skin. Persons at risk of developing pressure ulcers commonly are those who have one or more medical conditions that render them fully or partially immobile. Their inability to move, or to change positions more frequently when reclining or seated, causes an uncomfortable distribution of pressure applied against the skin that can directly lead to the development of pressure ulcers.
As uncomfortable distribution of pressure is applied against the skin, blood vessels become pinched, which in turn decreases blood supply at sites where pressure is applied. Heat, resulting from friction, rising body temperature, etc., also decreases blood supply at sites where the pressure is applied. And moisture from incontinence, perspiration, and exudate at these sites further exacerbates the skin, first causing bonds between epithelial layers to weaken, and thereafter causing skin maceration. Failure to address prolonged instances of pressure, heat, and moisture also can cause pressure ulcers to become sites that breed infection. These infection sites often lead to illness, and in severe cases—death.
Considering the severe consequences if pressure ulcers are not effectively treated, the ability of body support systems to relieve pressure from building up against the body and to affect heat and moisture levels at support surfaces is critical. Sufficient measures to prevent and treat pressure ulcers should, therefore, include the selection of body support systems that can redistribute pressure, withdraw heat, and draw away or evaporate moisture from support surfaces. Systems that redistribute pressure frequently are classified as either dynamic or static. Dynamic systems are driven, using an external source of energy (typically direct or alternating electrical current) to alter the level of pressure by controlling inflation and deflation of air cells within the system or the movement of air throughout the system. In contrast, static systems maintain a constant level of air pressure and redistribute pressure through use of materials that conform to body contours of the individual sitting or reclining thereon. Quantitative measurement of two parameters—Heat Withdrawal Capacity and Evaporative Capacity—also may be used to indicate a support surface's ability to withdraw heat and evaporate moisture.
Although foam is frequently used in both static and dynamic body support systems, few, if any, systems incorporate foam to redistribute pressure, withdraw heat, and draw away or evaporate moisture buildup at foam support surfaces. While foam has been incorporated into some body support systems to affect moisture and heat, most of these systems merely incorporate openings or profiles in foam support layers to provide air flow paths. In addition, few, if any, systems specify use of internal air flow guides with specific parameters related to heat withdrawal and moisture evaporation (i.e. Heat Withdrawal Capacity and Evaporative Capacity) at foam support surfaces. Hence, improvements continue to be sought.
Various configurations of body support system are described herein. Each type of support system includes at least one uppermost comfort layer with a support surface, a central core, and a bottommost foundation layer. In preferred embodiments, the uppermost comfort layer is manufactured from a temperature and pressure sensitive cellular polymer material such as viscoelastic open cell polyurethane foam. Positioned below the uppermost comfort layer is a central core that includes multiple elements for pressure redistribution and control of air flow and/or moisture vapor throughout the system. Disposed within the central core are one or more air flow guides that form an air flow path within the core of the body support system for air and/or moisture vapor transport. These air flow guides are preferably manufactured from a low air loss material such as reticulated open cell polyurethane foam.
A more complete understanding of various configurations of the body support systems disclosed herein will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by consideration of the following detailed description. Reference will be made to the appended sheets which will first be described briefly.
The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure. In the drawings, wherein like reference numerals refer to similar components:
Indentation Force Deflection (hereinafter “IFD”) is a measure of foam stiffness and is frequently reported in pounds of force (lbf). This parameter represents the force exerted when foam is compressed by 25% with a compression platen. One procedure for measuring IFD is set forth in ASTM D3574. According to this procedure, for IFD25 at 25%, foam is compressed by 25% of its original height and the force is reported after one minute. Foam samples are cut to a size of 15″×15″×4″ prior to testing.
Air permeability for foam samples typically is measured and reported in cubic feet per square foot per minute (ft3/ft2/min). One method of measuring air permeability is set forth in ASTM 737. According to this method, air permeability is measured using a Frazier Differential Pressure Air Permeability Pressure machine. Higher values measured, using this type of machine, translate to less resistance to air flow through the foam.
“Heat Withdrawal Capacity” refers to the ability to draw away heat from a support surface upon direct or indirect contact with skin. “Evaporative Capacity” refers to the ability to draw away moisture from a support surface or evaporate moisture at the support surface. Both of these parameters, therefore, concern capability to prevent excessive buildup of heat and/or moisture at one or more support surfaces. The interface where a body and support surface meet may also be referred to as a microclimate management site, where the term “microclimate” is defined as both the temperature and humidity where a body part and the support surface are in contact (i.e. the body-support surface interface). Preferably, the measurement and calculation of Heat Withdrawal Capacity and Evaporative Capacity are conducted according to standards issued by the Rehabilitation Engineering and Assistive Technology Society of North America (“RESNA”).
Turning in detail to the drawings,
The body support system 10 includes a plurality of uppermost comfort layers 12, with each layer having a foam support surface 14. The foam support surface 14 forms an upper or top surface of the body support system. Each foam support surface 14 comes into direct or indirect contact with a body of an individual person or patient (not shown) when the body is in a partial or full seated or lying position. In this system configuration, the plurality of uppermost comfort layers 12 are coupled to internal air flow guides 16 (
The uppermost comfort layers 12 may be formed of a cellular polymer, such as an open cell polyurethane foam. The uppermost comfort layers 12 preferably are manufactured from materials having a temperature and pressure sensitive cellular polymer structure. Such structures include viscoelastic open cell polyurethane foams that optionally are reticulated. Viscoelastic open cell polyurethane foams have the ability conform to body contours when subjected to compression from an applied load and then slowly return to their original uncompressed state, or close to their uncompressed state, after removal of the applied load. One definition of viscoelastic foam is derived by a dynamic mechanical analysis that measures the glass transition temperature (Tg) of the foam. Nonviscoelastic resilient polyurethane foams, based on a 3000 molecular weight polyether triol, generally have glass transition temperatures below −30° C., and possibly even below −50° C. By contrast, viscoelastic polyurethane foams have glass transition temperatures above −20° C. If the foam has a glass transition temperature above 0° C., or closer to room temperature (e.g., room temperature (20° C.)), the foam will manifest more viscoelastic character (i.e., slower recovery from compression) if other parameters are held constant.
In addition, in some configurations, at least a portion of an uppermost comfort layer is reticulated. Reticulated polyurethane foam materials include those materials manufactured using methods that remove or break cell windows. Various mechanical, chemical and thermal methods for reticulating foams are known. For example, in a thermal method, foam may be reticulated by melting or rupturing the windows with a high temperature flame front or explosion, which still leaves the strand network intact. Alternatively, in a chemical method the cell windows may be etched away using the hydrolyzing action of water in the presence of an alkali metal hydroxide. If a polyester polyurethane foam has been made, such foam may be chemically reticulated to remove cell windows by immersing a foam slab in a heated caustic bath for from three to fifteen minutes. One possible caustic bath is a sodium hydroxide solution (from 5.0 to 10.0 percent, preferably 7.5% NaOH) that is heated to from 70° F. to 160° F. (21° C. to 71° C.), preferably from 120° F. to 160° F. (49° C. to 71° C.). The caustic solution etches away at least a portion of the cell windows within the foam cellular structure, leaving behind hydrophilic ester polyurethane foam.
Materials used for the uppermost comfort layers may be classified as low air loss materials. Materials of this type are capable of providing air flow to a support surface for management of heat and humidity at one or more microclimate sites.
In the body support system 10 shown in
In addition to the properties referred to above, the central torso supporting comfort layer 28 also may have a substantially porous and air permeable structure. In preferred embodiments, the central comfort layer has a porosity ranging from about 65 pores per inch (ppi) to about 75 ppi and air permeability values ranging from about 150 cubic feet per square foot per minute (ft3/ft2/min) to 350 ft3/ft2/min. Because the central comfort layer 28 includes a central uppermost foam surface 31 that contacts heavier body parts, e.g., buttocks, hips, thighs, which are very susceptible pressure ulcer formation, increased porosity and air permeability in these areas can be beneficial. The increased porosity and air permeability further allows for added control of Heat Withdrawal Capacity and Evaporative Capacity, as further described below.
Adjacent to the plurality of uppermost comfort layers 12 is a plurality of foam surrounds or rails 32. The foam surrounds or rails 12 generally are firmer than other portions of the construction to support an individual when sitting at the side or end of the mattress. The plurality of foam surrounds or rails 32 includes a foot rail 34, a head rail 36, a left side rail 38a and a right side rails 38b. As shown in
One or more air flow units 48 are disposed within the body support system 10 to facilitate air flow along one or more air flow paths 18, depending upon the positioning of air inlets and air outlets within the system 10. Both air inlets and air outlets may be defined in one or more cavities 46 positioned within the system. Air flow units 48 may be configured to generate air flow using either positive or negative pressure. One type of suitable air flow unit is a 12V DC Blower sold by Delta Electronics. The use of air flow units 48 facilitates withdrawal from and removal of moisture and heat at foam support surfaces 14 for control of both Heat Withdrawal Capacity and Evaporative Capacity of one or more foam support surfaces of the body support system 10.
As shown in
An air flow unit 48 may include a screen 50 coupled to a filter (not shown), which in combination are used to filter particles, spores, bacteria, etc., which would otherwise exit the body support system 10 into the room air through air flow unit 48. During operation, the air flow unit 48 may operate to reduce and/or increase pressure within the system to facilitate air flow along air flow paths 18 from an air inlet 20 to an air outlet 22. Regardless of the placement of an air flow unit 48 within the system, it should be configured to exhaust air 52 to the surrounding environment, as particularly shown in
Optionally, a pillow or plug (not shown) may fill any cavity 46 of the body support system 10 when the air flow unit 48 is removed and the body supporting system is used in a static condition (i.e., without air flow through the core of the body support system).
The body support system 10 may be encased in a protective, waterproof, moisture vapor permeable cover (not shown), such as fabric laminate constructions incorporating polyurethane coatings or expanded polytetrafluoroethylene (ePTFE) When in use, the body support system 10 may be covered by a textile bedding sheet (not shown).
A wireless controller 54 also may be used to control various aspects of the system 10. For example, a wireless controller may control the level and frequency, rate, duration, and amplitude of air flow and pressure that travels through the system. A wireless controller also may include one or more alarms to alert a patient or caregiver of excessive use of pressurized air, synchronization issues and power failure at surface power unit. In addition, a wireless controller also may be used to vary positioning of the body support system if the system is so configured to fold or bend
Referring particularly to
As an example of a multiple portion internal air flow guide, the internal air flow guide 16 may include an upper body portion 16a, a central body portion 16b, and a lower body portion 16c, as shown particularly in
Materials used to manufacture an internal air flow guide, therefore, have physical properties that relieve pressure and facilitate air flow. Preferably, the internal air flow guide(s) comprise open cell polyurethane foams that have been reticulated. Singular or multiple internal air flow guides formed from cellular polymer material(s) preferably have a foam density of ranging from about 1.3 lb/ft3 to about 2.5 lb/ft3, and preferably from about 1.6 lb/ft3 to about 2.2 lb/ft3. In addition, each respective air flow guide formed from cellular polymer material(s) has an IFD ranging from about 10 lbf to about 80 lbf, and preferably from about 25 lbf to about 40 lbf. Porosity of singular or multiple internal air flow guides formed from cellular polymer material(s) preferably ranges from about 10 ppi to about 30 ppi.
The body support system 10 also includes a plurality of additional support layers 60 positioned under the internal air flow guide 16 for further support of a body in a supine position. The plurality of support layers 60 includes an upper support layer 62, a central support layer 64, a lower support layer 66, and a foundation support layer 68. Support layers 62, 66, 68 may be formed from open cell polyurethane foam having a density ranging from about 1.0 lb/ft3 to about 3.0 lb/ft3, and preferably from about 2.4 lb/ft3 to about 2.8 lb/ft3. In addition, each support layer 62, 66, 68 of cellular polymer material has an IFD25 ranging from about 5 lbf to about 250 lbf and preferably from about 50 lbf to about 70 lbf. The lower support layer 66 is preferably “soft” or “softer”, such that placement of a foot is particularly comfortable when the body is in a fully supine position. As such, preferably, the density of cellular polymer material forming the lower support layer 66 ranges from about 1.0 lb/ft3 to about 1.3 lb/ft3 and the IFD25 of the cellular polymer material forming the lower support layer 66 ranges from about 10 lbf to about 20 lbf. Support layer 64 may be formed from open cell polyurethane foam having a density ranging from about 1.0 lb/ft3 to about 3.0 lb/ft3, and preferably from about 1.4 lb/ft3 to about 2.0 lb/ft3. In addition, the central support layer 64 of cellular polymer material preferably has an IFD25 ranging from about 5 lbf to about 250 lbf and preferably from about 30 lbf to about 40 lbf.
As shown particularly in
The uppermost comfort layer 112 and the internal comfort layers 180a, 180b are preferably manufactured from the same material, such as a cellular polymer. For example, each respective comfort layer may be manufactured from materials having a temperature and pressure sensitive cellular polymer structure, including viscoelastic open cell polyurethane foams, reticulated polyurethane foams, and low air loss materials. Such cellular polymer materials preferably have a density ranging from about 1.5 lb/ft3 to about 8.0 lb/ft3, and preferably from about 3.0 lb/ft3 to about 5.0 lb/ft3. In addition, the comfort layer has an IFD25 ranging from about 5 lbf to about 20 lbf and preferably from about 8 lbf to about 15 lbf. In addition, each comfort layer also may be reticulated, such that it has a substantially porous and air permeable structure with a porosity ranging from about 65 pores per inch to about 30 pores per inch and air permeability values ranging from about 5 cubic feet per square foot per minute (ft3/ft2/min) to 1000 ft3/ft2/min.
The internal air flow guides 116a, 116b and the air flow blocks 182a, 182b, 184a, 184b are preferably manufactured from cellular polymer materials that facilitate air flow. One example is reticulated open cell polyurethane foam. These air flow guides and blocks when formed of cellular polymer materials preferably have a density of ranging from about 1.3 lb/ft3 to about 2.5 lb/ft3, and more preferably from about 1.6 lb/ft3 to about 2.2 lb/ft3. In addition, each respective air flow guide and block formed from cellular polymer materials has an IFD25 ranging from about 10 lbf to about 80 lbf and preferably from about 25 lbf to about 40 lbf. Porosity of internal air flow guides and blocks formed from cellular polymer materials preferably ranges from about 10 ppi to about 30 ppi.
Referring to
Two air flow units 148a, 148b also are positioned within cavities 199a, 119b to facilitate air flow along one or more air flow paths 118a, 118b and exhaust air 152 to the surrounding environment. Air flow units 148a, 148b are configured to generate air flow, using either positive or negative pressure. When using negative pressure, the air flow units in combination with the air flow guides draw moisture and heat away from the foam support surface 114. In other system configurations (not shown), air flow unit 148a, 148b may be external to the system 100 and include one or more connecting members (not shown), such as tubing or piping. Alternatively, air flow units 148a, 148b may be mounted onto or in an accessible location near or adjacent the system. Each air flow unit 148 also preferably includes a screen 150a, 150b coupled to a filter (not shown) to capture particles exiting the system. A wireless controller 154 also may be used for control of various aspects of the system 100, as described with reference to the first system configuration 10.
The body support system 200 includes a singular uppermost comfort layer 212, having a foam support surface 214 that comes into direct or indirect contact with a body (not shown) when the body is in a partially or fully seated or lying position on the body support system 200. In this system configuration, the uppermost comfort layer 212 is coupled to and positioned over internal air flow guides 216 (
As shown particularly in
The surround 232 may be a unitary piece or separate pieces that include a foot rail, a head rail, and side rails. As shown particularly in
In the system configuration shown in
As particularly shown in
The upper support layer 262, central support layer 264, and foundation support layer 268 are positioned within the system 200 for further support of a body in a supine position. Defined within the upper support layer 262 are channels 213 used to align the longitudinal air flow guides 202 such that the guides 202 are coupled to the uppermost comfort layer 212 (
One or more of the elements included within each respective system 10, 100, 200 disclosed herein may also incorporate antimicrobial devices, agents, etc. Because air and vapors can carry bacteria, viruses, and other potentially harmful pathogens, the systems may be provided with devices and agents that prevent, destroy, mitigate, repel, trap, and/or contain potentially harmful pathogenic organisms. In addition to bacteria and viruses, such organisms include, but are not limited to, mold, mildew, dust mites, fungi, microbial spores, bioslimes, protozoa, protozoan cysts, and the like. Preferred antimicrobial devices and agents include ULTRA-FRESH manufactured by Thompson Research Associates, Toronto, Canada.
The following examples were performed to measure Evaporative Capacity and Heat Loss (i.e., heat withdrawal) of foam support surfaces. The following testing conditions, therefore, were meant to simulate body loading conditions of foam testing support surface(s), having a flat profile, as particularly shown in body support systems 10, 100, 200, described above.
Testing equipment included: (1) a conditioned foam testing support surface; (2) a measuring unit configured to control temperature and water supply on the foam testing support surface; (3) a thermal guard; (4) bedding and (5) weights.
For this test, the conditioned foam testing support surface was the uppermost surface of a foam mattress having a structure comparable to that shown in
The measuring unit included a metallic test plate, a heating element block with an internal heating element, and a temperature controller with a temperature sensor.
The thermal guard included a high thermal conductivity material with heating elements, a thermal guard temperature sensor, and a controller used to maintain the thermal guard temperature and the measuring unit at the same level. The thermal guard was used to prevent heat leakage from the measuring unit.
Bedding included a standard cotton bed sheet that covered the testing support surface, and a medium-weight cotton blanket over the cotton bed sheet.
Weights were used to maintain an average interface pressure over at the body-support surface interface between 0.5 psi and 0.7 psi.
Testing was performed over approximately a two-hour period and variables determined, according to the following:
Thermal resistance (Rdry) was calculated according to the following formula:
where Tm=temperature of the measuring unit in ° C. and Ta=temperature of the atmosphere in ° C.
Full saturation (Psat) (i.e., at 100% relative humidity) was determined from a saturated steam table. Partial Pressure (Pa) (except for full saturation) was determined by multiplying Saturated Pressure (Psat) at specific temperatures by relative humidity (RH %).
Apparent Evaporative Resistance (Rwet) was calculated according to the following formula:
Calculate the apparent evaporative resistance for the surface under the selected test condition as the arithmetic mean of the six trials.
Evaporative Heat Flux (Qevap) was calculated according to the following formula:
Evaporative Capacity was calculated according to the following formula:
Thus, various configurations of body support systems are disclosed. While embodiments of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. Moreover, the examples described herein are not to be construed as limiting. The invention, therefore, is not to be restricted except in the spirit of the following claims.
