Abstract:
A therapeutic treatment bed with features to enhance the care and comfort of burn patients and others subject to extensive recuperative periods. Among the features are patient engaging fluidized bead surfaces integral with the upper surfaces of air cushions provided by an air bed. Detachable conformation of the fluidized bead surfaces is also provided.

Description:
This application is a cont. of Ser. No. 08/714,528 filed Sep. 16, 1996, now abandoned. This a cont. application Ser. No. 08/428,689 filed Apr. 25, 1995, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to therapeutic beds and, more particularly, to therapeutic beds of the type having an air cushion support together with an integral fluidized bead surface. 
     2. Background 
     The care of patients requiring extensive recuperative periods presents many extraordinary challenges which have not been adequately addressed in the past. Not the least of these challenges is providing a patient support surface that is both sturdy and easy to use, while simultaneously providing preventive therapy and intervention for the numerous complications associated with extended confinement to bed. Burn victims, for instance, typically require extremely low patient interface pressures, high air flow, as well as low shear forces. It is well-known in the art that two of the most ideal patient support surfaces for the immobile patient are low-air-loss beds and fluidized bead beds. Low-air-loss bed and mattress examples are described in U.S. Pat. Nos. 5,005,240 (KINAIR) and 5,022,110 (FIRSTSTEP). Examples of bead beds are described in U.S. Pat. Nos. 4,564,965 (CLINITRON), 5,008,965 (FLUIDAIR), and 5,036,559 (ELEXIS). 
     Conventional bead beds typically include a bathtub-like tank filled with medical-grade silicone microspheres (or “beads”). Each individual bead typically has a soda-lime core encased within a silicone sphere approximately 100 microns in diameter. A diffuser board is positioned horizontally at the base of the tank, separating two compartments within the tank—an upper compartment which contains the beads and a smaller, lower compartment which serves as a plenum chamber filled with air for fluidizing the beads. With appropriate blowers and temperature control systems, air is blown into the plenum chamber, from which the pressurized air is forced upwardly through the diffuser board and further (often in bubble-like manner) through the beads, giving the beads a liquid-like quality. A filter sheet is draped over the top of the tank to contain the beads while allowing the upward passage of air. The patient can lie either directly on the filter sheet or on a second cover sheet. Despite the liquefied state of the beads, the patient remains buoyant because of the relative density of the beads. 
     Although such bead beds may actually provide the most therapeutic surface from the standpoint of pressure and microclimate at the patient interface (i.e., interface between patient and mattress), conventional bead beds have many drawbacks. Traditionally, bead bed manufacturers have thought that a significant depth of beads was required in order to provide an adequate patient support with good fluidization. Fluidizing the resulting volume of beads inherently required heavy-duty blowers and related equipment, not to mention the extra structural requirements for the frames of such beds. Conventional bead beds are extremely heavy (approximately 2,000 pounds), which not only makes them difficult to maneuver, but also requires that they be used only in buildings having extremely sturdy support. Second-story placement in wood-frame houses is typically avoided without assessment by a structural engineer. The poor maneuverability and excessive weight may also present risks to caregivers who are not properly trained in safely maneuvering such heavy objects. 
     Handling a patient in a conventional bead bed is also plagued with difficulty, largely because caregivers must reach down into the tank and lift the patient up or out for handling. The teaching of U.S. Pat. No. 5,008,965 attempted to address this situation by providing separate air bladders within the bead compartment for displacing the beads upwardly, hence, lifting the patient relative to the tank. Still others, such as illustrated in U.S. Pat. No. 5,036,559 (ELEXIS), have attempted to address the problem by providing deflatable or otherwise collapsible tank walls instead of the traditionally rigid walls. Related difficulty is faced by the patient who is attempting to sit up in such beds. Although foam wedges and the like are often used to help prop up the patient, props present the obvious downfall of interfering with the therapeutic benefits of the bead surface. Using props also renders such products more difficult to manipulate than conventional hospital beds which have automatic bed functions such as head-up, Trendelenberg and the like. 
     Air beds, on the other hand, eliminate many of these problems. Not only are the mattresses of the air beds lighter due to the lighter supporting medium (i.e., air versus beads), but lighter-duty supportive equipment and structural members are needed as well. Moreover, air beds permit many of the user-friendly features of standard hospital beds, such as sit-up, Trendelenberg, and the like, not to mention retractable side rails and radioluminescence. The extra space beneath the patient surface also allows not only for extra storage, but also for adding accessory therapeutic units such as percussion and hyper-hypothermia treatment. 
     Many other advantages and disadvantages of low-air-loss beds and air fluidized bead beds will be understood by those of ordinary skill in the art, especially after reviewing this specification. 
     SUMMARY OF THE INVENTION 
     It is a fundamental object of the present invention to improve over the prior art, including to provide a therapeutic patient treatment bed and related methods which facilitate the care and comfort of bed-ridden patients, while simultaneously addressing the complications associated with immobility. 
     This and other objects are addressed by providing a therapeutic patient treatment bed wherein the patient support surface comprises an air cushion with integral fluidized bead surfaces. The beads may be fluidized by the same air flow as is utilized for inflating the patient support air cushion. Unlike many prior bead beds, the invention described herein allows the patient support surface to be positioned as desired, providing a lightweight, full-featured fluidized bead bed. Moreover, because air flow can be compartmentalized into a plurality of air bags or cushions, each with independent bead surfaces, the present invention also enables a wide variety of additional surface therapies not previously available with bead beds, including pulsation, percussion, and kinetic therapies. The fluidized bead surfaces may also be detachable for facilitating infection control procedures. 
    
    
     Many other objects, features, variations and advantages of the invention will be evident from a review of the further descriptions herein, particularly when reviewed by one of ordinary skill in the art with the benefit of the accompany drawings, appended claims and the prior art. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a patient treatment bed  20  (absent its cover sheet) configured and operatively inflated for typical use, which comprises a presently preferred embodiment of the present invention. 
     FIG. 2A is a perspective view of an air bag  21  of the bed  20  shown in FIG.  1 . 
     FIG. 2B is a partial cross-sectional view of the airbag  21  shown in FIG.  2 A. 
     FIG. 3A is a partially-exploded perspective view of an air bag  171 , which is an alternate embodiment of the air bag  21  shown in FIGS. 2A-B. 
     FIG. 3B is a partial cross-sectional view of the air bag  171  shown in FIG. 3A, including its fluidized bead pouch  172 , taken along lines  3 B— 3 B in FIG.  3 A. 
     FIG. 4A is a partially-exploded perspective view of an air bag  121 , which is a second alternative of the air bag  21  shown in FIGS. 2A-2B. 
     FIG. 4B is a cross-sectional view of the airbag cap  130  as shown in FIG.  4 A. 
     FIG. 4C is a partial cross-sectional view of the main part  129  of the air bag  121  shown in FIG.  4 A. 
     FIG. 4D is a partial cross-sectional view of an alternative embodiment  129 ′ of the main part  129  shown in FIG. 4C, from the same perspective as shown in FIG.  4 C. 
     FIG. 5 is a perspective view of an alternate embodiment  320  of the invention. 
     FIG. 6 is a more detailed perspective view of the mattress  320  of the alternate embodiment shown in FIG. 5, absent its frame  319  and cover sheet  380 . 
     FIGS. 7A and 7B are views of the unassembled upper wall  27  and filter sheets  41  and  42  of bead pouch  22 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Although most aspects of the invention described and claimed herein could be embodied in many different types of beds, mattresses and/or cushions, the bed  20  shown in FIG. 1 is considered to be a presently preferred embodiment of that invention. Referring to FIG. 1, there is shown a patient treatment bed  20  that is uniquely suited for treatment of burn patients and other patients subject to extensive recuperative periods. Bed  20  includes a frame  19  supporting a plurality of patient support air bags  21 , which are uniquely adapted with bead pouches  22 . One fairly basic aspect of the invention can be embodied in one or more cushions such as patient support air bags  21 , operatively associated with one or more fluidized bead containment pouches  22  and means for fluidizing the same, all of which may or may not be mounted on a frame such as frame  19 . 
     One advantage of the invention is that it can be implemented as a relatively simple upgrade to a pre-existing air support. Typically, the only change needed will be to replace one or more of the air cushions of the pre-existing support with new cushions that are specially-adapted to implement the present invention. In some cases, however, it may be that additional blower capacity is needed due to the relatively large amount of air required to fluidize the bead pouches  22  as compared to the amount of air that may be needed to sustain inflation of the pre-existing support. Those of skill in the art will understand how to increase blower capacity, such as by adding an additional blower or redirecting existing blowers. The term “host platform” is used in this description to refer to the preexisting support. Modifications to the host platform may be described in detail, whereas unmodified details will be described only to the extent desired for reference. 
     The host platform  20  may be any of a number of commercially available patient air supports, preferably low-air-loss patient treatment beds. Host platform  20  of the preferred embodiment comprises a low-air-loss bed presently commercialized under the trademark “KINAIR III,” commercially available from Kinetic Concepts, Inc. of San,Antonio, Tex. (“KCI”). The KINAIR III bed is described in substantial detail in U.S. Pat. No. 5,005,240, dated Apr. 9, 1991, incorporated herein by this reference. Other suitable host platforms include, but are not limited to, those marketed by KCI under the trademarks “HOMEKAIR,” “THERAPULSE” and “BIODYNE II.” All of these platforms are commercially available from Kinetic Concepts, Inc. The THERAPULSE bed is described in substantial detail in U.S. Pat. No. 5,044,029, dated Sept. 3, 1991, incorporated herein by this reference. The BIODYNE II bed is described in substantial detail in U.S. Pat. No. 5,142,719, dated Sep. 1, 1992, also incorporated herein by this reference. Other host platforms might include wheelchairs with therapeutic air cushions or stand-alone therapeutic air mattresses mounted on any desired support. 
     As suggested above, the principal difference between bed  20  and a commercially available KINAIR III bed is the adaptation of its air bags  21  to include fluidizable bead pouches  22 . A simple form of such an adapted air bag  21  can be made by cutting a rectangular hole in the upper surface of an existing KINAIR III air bag and sewing a similarly-shaped, air-permeable bead pouch  22  over the hole. An air bag  21  made in such manner is shown in FIGS. 2A&amp;B, as part of a presently preferred embodiment of the invention. Conventional stitching techniques can be used to provide a smooth outer surface for the adapted bag  21 . For instance, although it is stated to sew the bead pouch “over” the hole, it will be understood by those of skill in the art that an acceptable technique for minimizing exposed edges would be to sew (or otherwise attach) the pouch from the inside of air bag  21 , around the perimeter of the rectangular hole  39  in the air bag&#39;s upper surface  27 . Conventional seam-sealing techniques can also be used to minimize loss of air through the seams  40   a - 40   d , as well as any other seams in bag  21 , to minimize any unnecessary air leaks in the air bag  21 . Such a construction enables the air bag  21  enclosure to serve as an effective plenum chamber for fluidizing the beads within the bead pouch  22 ; the space  48  enclosed by air bag  21  is, hence, referred to as the “plenum space”  48 . 
     Referring to FIGS. 2A&amp;B, each adapted air bag  21  includes bead pouch  22  formed integrally therein. Such integral construction ensures simplicity of manufacture and use, while minimizing any excessive loss of air, as might be more likely with a two-part construction. The air bag  21  can be disinfected through laundering with a dilute bleach solution in the same manner as conventional air bags. Due to the inclusion of the bead pouch  22 , adequate drying of the air bag  21  may require operative connection of the air bag  21  to a host platform. Such operative connection helps dry the beads by virtue of the air blowing through beads  200 . Although the exact length of time needed to dry the beads  200  may vary, twenty-four hours will generally be more than adequate. The drying time should be however long it takes to dry the beads so they can be adequately fluidized, while also respecting any infection control concerns. 
     One alternative embodiment of air bag  21  is described further herein as air bag  171 , with reference to FIGS. 3A&amp;B. Such alternative air bag  171  utilizes a bead pouch  172  that is adapted to be removed from a pocket  198 ′ in the end wall  175  of the air bag  171 . The pouch  172 , therefore, can be removed and disinfected or disposed of separate from any low-air-loss components. Another alternative embodiment of air bag  21  is described further herein as air bag  121 , with reference to FIGS. 4A-D. Such alternative air bag  121  also utilizes a two-part construction for its bead pouch  122 . Air bag  121  is different, though, in that its bead pouch  122  is embodied in a removable cap  130  for air bag  121 . In such alternative, the bead containment pouch  122  is removed from the air bag  121  by removing the cap  130  as a whole, so that the pouch  122  can then be disinfected or disposed of separate from any low-air-loss components. Other embodiments are also disclosed. 
     Each of the air bag embodiments  21 ,  171 ,  121  and  121 ′ are made from the same basic fabrics—a low-air-loss material and a filter sheet material. The low-air-loss material in the preferred embodiment is a polymer-coated nylon material commercially available under the trademark “GORE-TEX” from W. L. Gore &amp; Associates, Inc. of Elkton, Md. Such low-air-loss material has very little air permeability yet has a moisture vapor transmission rate in excess of 4700 g/m 2 /24 hours. In the preferred embodiment, the filter sheet fabric is constructed of 63-micron monofilament polyester fiber thread with 40-micron nominal mesh opening and 15% open area. The filter fabric is commercially available from Tetko, Inc. of Briarcliff Manor, N.Y. One possible alternative that might be considered is to use a similar multifilament fabric rather than the monofilament. Other suitable alternatives will be evident to those of skill in the art. 
     Regarding the construction of the air bag embodiments  21 ,  171 ,  121  and  121 ′, there are several common elements. Although most of such common elements are also common with the commercially-available KINAIR III air bags, brief reference is made to each of such common elements (referring to reference numerals used in FIG.  2 A). Air bag  21 , to begin with, is formed to have the general shape (when inflated) of a rectangular prism, as shown in FIG.  2 A. Air sac  21  has six generally rectangular walls  23 - 28 , which may be considered as three pairs of opposed similar walls: opposite side walls  23  and  24 , opposite end walls  25  and  26 , and opposite top and bottom walls  27  and  28 . Each of such walls  23 - 28  is formed primarily of the low-air-loss material referenced above, cut in pieces that are stitched (or otherwise joined) to adjacent pieces along their adjoining edges. As will be understood by those of ordinary skill in the art, particularly with reference to a commercially-available KINAIR III air bag, certain walls may actually be formed from the same piece of material as another wall, while other walls may be formed of a combination of one or more pieces of material. The edges between two adjoining walls, hence, may not in actuality constitute seams between fabric pieces. The sheet of material which forms the top wall  27 , for instance, actually extends beyond each of its edges  27   a - 27   d  shown in FIG.  2 A. Fabric-gathering seams and conventional stitching techniques are used to generally form each of the four corners  27   e - 27   h  of upper wall  27 . That same piece of fabric which forms upper wall  27 , further, extends partially down each of the opposite side walls  23  and  24  and each of the opposite end walls  25  and  26  to a seam (not shown) with an adjoining piece of fabric slightly above the level of baffle  127 . Again, such sewing techniques and the general construction for the various walls  23 - 28  of air sac  21  will be evident to those of ordinary skill in the art, particularly with reference to commercially-available air sacs. It is also noted that in certain alternative embodiments it may be desired to form the air cushions in different shapes, such as the cut-out shape of the BIODYNE air sacs, or the relatively flat (or “low profile”) shape of the air sacs used in products such as the DYNAPULSE product, also available through Kinetic Concepts, Inc. 
     Still referring to common elements of the air bag embodiments  21 ,  171 ,  121  and  121 ′, as well as the KINAIR III air bags, each air bag  21 ,  171 ,  121  and  121 ′ also has a post  43  and an air inlet  44  operatively secured to the bottom wall  28  thereof, as is standard for KINAIR III air bags, for attachment to the host platform  20 . Such hardware  43  and  44  are standardly employed in a manner which allows entry of air into a space  48  enclosed by the main part  29  of air bag  21 , such air being blown by blowers such as standardly included in the host platform  20 . Each air bag  21  further comprises a baffle  34  also constructed of low-air-loss fabric, although less costly alternative fabrics may be desired as air permeability and low skin shear benefits are not necessary for baffle  127 . Baffle  127  functions to ensure the desired prismatic shape of the inflated bag  21  (i.e., that of a rectangular prism). The baffle  127  is sewn, or attached by other equivalent means, at its edge  35  to the inside surface of the front side wall  23  of the air bag  21 . The baffle  127  is similarly sewn, or attached by other equivalent means, at its edge  36  to the inside surface of the rear side wall  24  of the air bag  21 . The end-to-end length of baffle  127  as measured from edge  37  to edge  38  is sufficiently less than the end-to-end length of air bag  21 , as measured from end  25  to end  26 . That shorter length allows substantial air flow around the baffle. Said air flow is as depicted by arrows (including arrows  33   a-c  in FIGS.  2 A&amp;B). The preferred embodiment provides a minimum 4-inch opening between end wall  25  and edge  37  as well as end wall  26  and edge  38 . 
     Further understanding of the hardware  43 - 44  and sewing techniques utilized in the preferred embodiment may be gathered to some extent with reference to U.S. Pat. No. 5,062,171, dated Nov. 5, 1991, incorporated herein in its entirety by this reference. 
     Referring to FIG. 2B, there is shown a sectional view of a fluidized bead containment pouch  22  (viewed on the vertical plane  2 B— 2 B indicated in FIG.  2 A). The bead containment pouch  22  is substantially rectangular from above (rectangular shape generally visible in FIG. 2A) and comprises rectangular top and bottom filter sheets  41 - 42 . Unless sheets  41  and  42  can be readily made together as a seamless pouch, sheets  41  and  42  are sewn or otherwise joined to each other around their perimeters (i.e., along edges  40   a - 40   d ) in a substantially sealed manner so as to form a substantially closed pouch for containing beads  200 . In the preferred embodiment, filter sheets  41  and  42  are constructed of the same filter sheet fabric as described previously herein. By making pouch  22  seamless or by providing sealed seams  40   a-d , leakage of beads  200  from pouch  22  can be minimized. Once filled with beads  200  to the desired extent and sealed closed, the pouch  22  is then sewn (or otherwise attached) to the upper wall  27  of air bag  21 , around the perimeter of hole  39 . 
     The preferred size of upper and lower filter sheets  41  and  42  (and, hence, pouch  22 ) will be best understood from the description of the preferred method for making pouch  22 . With reference to FIGS. 7A &amp; 7B, there is shown a plan view of the cut-outs for the upper wall  27  and bead pouch  22 , respectively. As mentioned, the rectangular hole  39 , which is cut out of upper wall  27 , is a substantially rectangular hole. The preferred dimensions of such hole are 5 inches (along edges  39   c &amp; d  of hole  39 ) by 23 inches (along edges  39   a &amp; b  of hole  39 ). The pouch  22  begins at a single piece  86  of filter sheet fabric cut in the shape as shown in FIG.  7 B. The overall dimensions of piece  86  are nominally 49 inches (in length) by 6½ inches (in width), although lower sheet  42  is tapered in its primary dimension to 4 inches. The dimensions  401 - 406  of piece  86  are 15½, 4½, 4½, 4, 6½ and 24½ inches, respectively. Once piece  86  is cut as shown in FIG. 7B, the piece is folded al center line  87  and edges  41   a &amp; b  are sewn (inside out) and sealed to edges  42   a &amp; b  to give pouch  22  its basic shape. Then, the assembly is pulled right side out and filled with beads  200  (not shown in FIG. 7B) through an opening formed between edges  41   c  and  42   c , after which the same edges  41 c and  42   c  are sewn and sealed. The seams formed by the unions of edges  41   a-c  and  42   a-c , and a final edge formed by the fold  87 , are then sewn and sealed to upper wall  27  along the perimeters of hole  39 . The result produces a bead pouch  22  that is slightly tapered along its midsections. Given the amount of material used by seams (approximately ¼ inch for each seam), the final width of lower filter sheet  42  which is exposed to the beads  200  is approximately 3 inches at its narrowest point and 5 inches at its longitudinal ends adjacent to seams  40   c &amp; d . The remaining dimensions of FIGS. 7A&amp;B are as shown therein. 
     The resulting size is generally such that in every air bag  21  on bed  20  included a pouch  22 , then the entire patient could be supported on the bead pouches  22 . Certain ones of air bags  21  may have differently sized pouches  22 , or may not have pouches at all. In the bed  20  illustrated in FIG. 1, for instance, head air bags  98  have shorter pouches (only about 10 inches long), and the last air bag  99  does not have a pouch  22  at all. Further, air bags with and without pouches  22  can be mixed and matched along the length of the bed  20  to achieve a desired surface. For patients with local bums, for instance, the fluidized bead surface may be limited to that region of the patient where the bum is located, while the rest of the patient is supported on conventional KinAir III air bags. In other cases, the bead surface may be limited to the seat section as that is where weight concentration is greatest. In any case where pouches  22  are included in a given air bag  21 , however, the upper sheet  41  is preferably about 2 inches wider than the lower sheet  42 , for reasons mentioned elsewhere herein. 
     The beads  200  contained in each bead pouch  22  are preferably medical grade microspheres of the type commonly employed in air fluidized bead beds. Such beads range in size from 50 to 150 microns in diameter and are commercially available from a number of sources, including Potters Industries, Inc. of Carlstadt, N.J. A single bead pouch  22  preferably contains about a two pounds of beads, although quantities of bead material from ¼ to 30 pounds or more per air bag may be suitable. The bead pouch  22  is also not completely filled, so that the beads are free to fluidize therein. Consequently, when air flows through bead pouch  22  without a patient supported thereon, the upper filter sheet  42  tends to billow upwardly, forming an air space  201  above the beads  200 . 
     The pouch  22 , hence, is integrated with air bag  21  in a manner that encourages air flow from space  48 , through pouch  22 , tending to fluidize any quantity of beads  200  within pouch  22 . Because the low-air-loss GORE-TEX fabric has very low air permeability, the air that inflates the air bag  21  tends to flow, more particularly, from plenum  48 , through the lower filter sheet  42 , through the beads  200  and excess space  201 , and on through the top filter sheet  41 , as suggested by arrow  33   c . By using the same air for bead fluidization as is used to inflate the air bag  21 , greater fluidization is achieved in those pressure zones in which air bags are inflated to higher pressures, which usually occurs with those air bag zones supporting heavier body portions (such as a patient&#39;s seat section). Hence greater fluidization is provided where it tends to be needed most—beneath the locations where the interface pressures are also greatest. 
     It is also noted, however, that lower filter sheet  42  may require some degree of air flow restriction in order to prevent excessive loss of air from within air bag  21 . The balance of the amount of air flow that will be desired through lower filter sheet  42  will depend on a variety of circumstances, including the blower capacity of the host platform  20 , the volume of beads  200  in each air bag  21 , and the number of air bags  21  which are adapted with bead pouches  22 . In one preferred embodiment, it has been found that air-impermeable strips  89   a &amp; b  may be adhered to the outer surface of lower filter sheet  42  to reduce and concentrate air flow through lower filter sheet  42 . Such strips  89   a &amp; b  are preferably composed of commercially available sealing tape such as is used for waterproofing grommets in the clothing industry. Suitable sealing tape is a ¾-inch Teflon sealing tape commercially available through the W. L. Gore Company. Strips  89   a &amp; b  (and similar strips sealing seams  40   a &amp; b ) preferably around the entire length of bead containment pouch  22  on the lower surface of lower filter sheet  42 . Such configuration of sealing strips  89   a-d  leaves three sections  88   a-c  of lower filter sheet  42  unobstructed for free flow of fluidizing air therethrough. Due to the 3-inch width of lower filter sheet  42 , sections  88   a-c  end up being three strips of unobstructed filter sheet running the length of bead containment pouch  22 . Each of strips corresponding to sections  88   a-c  are approximately ¼-inch wide, although that width dimension will flare toward the ends  40   c  and  40   d  of bead containment pouch  22  as the bead containment pouch itself flares as well. 
     It is noted that once the air has passed through pouch  22 , its direction of flow is determined based on other factors. For instance, if a conventional, high-air-loss cover sheet is used, some of the fluidizing air will pass through the cover sheet while the remainder will be diverted to the sides of the bed  20  by that cover sheet. If a cover sheet is not used, then more of the fluidizing air would tend to rise upwardly around the patient&#39;s body. 
     It is also noted that the profile shape of the pouch  22  (i.e., the cross-sectional shape such as shown in FIG. 2B) depends on a variety of factors. Such factors include but are not limited to the size of the bead pouch  22 , the relative porosity of the filter sheets  41  and  42 , the air pressure within plenum space  48 , the quantity of beads  200  within pouch  22 , and the patient weight. In many cases, the bead pouch  22  tends to arch upwardly due to the pressure within air bag  21 , in contrast to the cigar-like shape shown in FIG.  2 B. Two practical concerns with this occurrence are (i) that the beads  200  might migrate downward at the sides of the pouch  22  due to gravity, and (ii) that the arching might restrict free fluidization by compressing the beads between the upper and lower filter sheets  41  &amp;  42 . One contemplated way of reducing such concerns is the inclusion of a vertical baffle (not shown) spanning between the lower filter sheet  41  and the horizontal baffle  34 , in the same general manner as illustrated in FIG.  4 D. Another technique that is preferred is to make the upper filter sheet  41  wider and longer than the lower sheet  42  (approximately 2 inches in each dimension) so that the lower sheet  42  tends to be more taut (and, hence, less arched) than the upper sheet  41 . Yet another technique is to increase the volume of the beads  200  in a given air bag  21 , such as by starting the bead pouch  22  at the level of baffle  34 , with beads filling up roughly the entire upper third of the air bag  21 . 
     Although simple, the construction of air bag  21  might be found to be less than ideal for disinfecting on a routine basis, Referring to FIGS. 3A-4D, alternate embodiments of air bag  21  are shown which allow detachment of bead pouch  22  (or its equivalent) so that the bead containment pouch may be disinfected separately. 
     The first of such alternatives is shown in FIGS. 3A&amp;B as air bag  171 . Air bag  171  is adapted with a removable bead pouch  172 . The removable pouch  172  consists only of its upper and lower filter sheets  191  and  192  and the beads  200  contained therebetween. Rather than being permanently sewn to air bag  171 , pouch  172  is inserted within (and removable from) a pocket  198 ′ near the upper wall  177  of air bag  171 . Access to the pocket  198 ′ is provided through an opening  199  in the end wall  175  of the air bag  171 . For minimizing loss of air pressure through opening  199 , the opening  199  may be covered and/or sealable by a Velcro flap (not shown) or the like. The pocket  198 ′ is formed of two layers of filter sheet material  197  and  198  just beneath the upper wall  177  of the air bag  171 . Layers  197  and  198  are joined by conventional techniques along the opposite edges  177   a  and  177   b  of upper wall  177  to form pocket  198 ′. The upper wall  177  is also provided with a rectangular filter sheet panel  189  for allowing free flow of air through bead pouch  172 . An alternative of air bag  171  excludes the upper filter sheet layer  197  of pocket  198 ′. 
     With such construction, the pouch  172  can be removed and disinfected or disposed of separate from the low-air-loss components of air bag  171 . Such low-air-loss components can then be disinfected using standard laundering techniques for air bags. The bead containment pouch  172  may be disinfected by infection control techniques which are standard and well-known in the art for fluidized bead systems. Such infection control procedure may involve destroying the filter sheet layers  191  and  192  of the pouch  172  and pouring the beads  200  through a sieve screen into a conventional decontamination tank. Decontamination can then be achieved by a thermal process of heating the beads to 122° F. for at least 24 hours. Further benefits of such removable conformation of bead pouch  172  will be apparent to those of skill in the art. 
     A second basic type of alternative to air bag  21  is shown in FIGS. 4A-C as air bag  121 . Like air bag  171 , air bag  121  also has a two-part construction adapted with a removable bead pouch  122  to facilitate infection control. The removable pouch  122 , however, is embodied in a removable cap  130  that fits over the top of a main part  129  of air bag  121 . The main part  129  can be disinfected through laundering in the same manner as with conventional air bags, and the cap  130  can be disinfected separately. Although the particular technique used for disinfecting the cap should be chosen based on the effectiveness of each technique, it is presently thought that adequate disinfection may be achieved by placing the entire cap  130  into a conventional microsphere decontamination unit, together with a separate bead lot. Such a decontamination is intended to raise the temperature of the cap above 120° F. for more than a 24-hour period. Other disinfection techniques, such as chlorination, gamma radiation and/or autoclaving, may be considered as additional alternatives. 
     The main part  129  of air bag  121  is much like the construction of a standard KinAir III air bag, except that the main part  129  includes a filter sheet panel  147  and Velcro tabs  131   a-d . Cap  130  includes the bead containment pouch  122  and Velcro tabs  132   a-d . The shape and construction of cap  130  is such that it fits snugly over the main part  129  when the main part  129  is inflated, with tabs  132   a-d  positioned to mate with tabs  131   a-d  for releasably securing the cap  130  in place. Once so positioned, cap  130  positions bead pouch  122  over the filter sheet panel  147 , so that air escaping through panel  147  is directed through pouch  122 , tending to fluidize the beads  200  therein. To optimize fluidization, Velcro tabs  132   a-d  and  131   a-d  may be enlarged or replaced with other connections providing a better seal. Improving such seal ensures that the only significant escape for air from the air bag  121  is through bead pouch  122 . The size of the panels  147  and pouch  122  is much the same as that of the pouch  22  in the first embodiment, although panel  145  is preferably narrower than pouch  122 . 
     With reference to FIG. 4D, an alternative construction of main part  129  is shown, designated as  129 ′. Particularly, main part  129 ′ includes a vertical baffle  149  coextensive with the conventional horizontal baffle  227 ′. Vertical baffle  149  spans is joined by stitching between the centerline  150  of panel  147 ′ to form a trough-like crease along the top of main part  129 ′. Such trough-like crease not only tends to bias beads  200  toward the centerline  150 , but its stitched joinder increases fluidization (by introducing stitch holes in panel  147 ′) along the centerline  150  where the beads  200  are drawn. 
     Referring to FIGS. 5 &amp; 6, there is shown an alternate embodiment  320  of the bed  20  shown in FIGS. 1-2B. Bed  320  generally consists of an air mattress  318  (and related components) mounted on a standard bed frame  319 . The mattress  318  is sectioned into three basic support cushions  318   a ,  318   b , and  318   c , as is standard for a variety of mattress and mattress overlay products. Each basic support cushion  318   a, b  or  c  is supplied with air flow from a standard air supply unit  315  through corresponding supply hoses  316   a-c . Each cushion includes a series of six vertical baffles (not numbered) to ensure retention of a relatively flat shape. Examples of such patient support mattress systems are found in the commercially available FIRSTSTEP SELECT, HOMEKAIR DMS and DYNAPULSE products, each commercially available through Kinetic Concepts, Inc. The particular system illustrated in FIGS. 5&amp;6 is a modified FIRSTSTEP SELECT unit. As with the previously-described embodiments, the mattress  318  is substantially the same as the commercial version of that product. The only significant difference being the addition of fluidizable bead containment pouches  322   a-c  and any additional blowers that might be needed (if any) to fluidize the same. As will be evident to those of skill in the art, the size of the bead containment pouches  322   a-c  can be varied as desired. For instance, in FIG. 6, it is shown that the size of the pouch  322   b  positioned for supporting the seat section of a patient is larger than the other two pouches  322   a &amp; c . Thus, greater therapy can be provided in the seat section (or in any other areas) where the therapeutic need is greater. The particular method of adapting the cushions  321   a-c  with an appropriate number of bead containment pouches  22  is not critical but will be understood from an understanding of the preferred embodiment of air bag  21 . Another variation (not shown) of bed  320  can be made by replacing substantially all of the top surface of the mattress  318  with a single fluidizable bead pouch. 
     The invention described herein allows combination of a fluidized bead patient support surface, well-known in the art to be an ideal patient support surface, with the advantages of low-air-loss beds. Such advantages will be evident to those skilled in the art and include, but are not limited to, vertical and/or articulated displacement of the patient support surface, side to side rotation of the patient, automatic percussion of the patient&#39;s chest area, and built-in scales, all of which are well-known in the art and may be described in the literature available for the commercial products KFNAIR III, HOMEKAIR, THERAPULSE and BIODYNE II. 
     Unique advantages afforded by each of the many possible host platforms  20  for implementation of the invention described herein will also be apparent to those skilled in the art. Said advantages will generally vary with the basic capabilities of the chosen host platform  20 . One of the more interesting has been found by using air bags like air bag  21  to replace the air bags of a THERAPULSE bed, commercially available through Kinetic Concepts, Inc. Utilization of the THERAPULSE bed as host platform  20  allows the caregiver to establish various pressures within air bags  21  corresponding to differing regions of the patient&#39;s body, and also allows automatic pulsation of bead fluidization. A caregiver can, thus, vary the level of fluidization for different parts of the body, and also pulse that fluidization as well. Although the air bags  21  as a whole generally become softer at lower pressures, the beads  200  generally become more stiff with lower degrees of fluidization. Hence, pulsing the fluidization with the THERAPULSE as host platform  20  will cause the beads  200  in the air bags  21  to vary from soft, to stiff, to soft, and so on. Not only will adjacent air bags  21  vary in opposite phase (as is normal for THERAPULSE pulsation), but stiffness of the bead pouch  22  surface will vary in opposition to the air pressure in the air bag  21  as a whole. 
     Another alternative embodiment, which is not shown in the drawings, is adapted to provide a dedicated air flow for purposes of fluidizing the beads  200  in each air bag  21 . The concept for this alternative is to allow separate control of the air supply directed to the plenum used for fluidizing the bead pouch  22  and to reduce the size of that plenum chamber. With a smaller, separately controlled plenum, the pressure of the air fluidizing the beads can be increased to achieve greater fluidization without increasing the pressure of the air bag  21  as a whole. To do this, a separate inflatable chamber is defined within air bag  21  directly adjacent the bead pouch  22 . The inflatable chamber serves as the plenum for fluidizing the bead pouch  22 , and a separate air supply is directed to that plenum. The construction of the separate plenum within the air bag  21  would be designed in any manner desired, although the simplest approach uses the same low-air-loss material as the remainder of air bag  21 . The separate dedicated air flow might be directed through a separate air inlet for the air bag  21 . A collapsible air conduit within air bag  21  would also serve to direct the flow of air from the second air inlet to the dedicated plenum. Although conventional air conduit may be suitable, a fabric conduit (also formed of sealed low-air-loss material) may be adequate to serve this purpose. By providing a separate air flow dedicated to fluidization, the inflation of the air bag  21  as a whole could, thus, be varied independently from the fluidization of the bead pouch  22 . Similar adaptations of the other alternative embodiments could also be made. 
     Many other alternatives, variations and modifications of the present invention will be evident to those of skill in the art and are contemplated to fall within the scope of the present invention. Although the present invention has been described in terms of the foregoing preferred and alternate embodiments, this description has been provided by way of explanation only and is not to be construed as a limitation of the invention, the scope of which is limited only by the following claims and any amendments thereto.