Abstract:
Method and apparatus for preventing bed sores in a bedridden patient. A low air loss bed is provided including a frame, a first set of substantially rectangular air bags for supporting a patient thereon mounted transversely on the frame, and a second set of substantially rectangular air bags for supporting a patient thereon mounted transversely on the frame, and all of the air bags are connected to a gas source. The conformation of the air bags is such that, when the first set of air bags is inflated, the patient supported thereon is moved toward the first side of the frame of the low air loss bed and, when the second set of air bags is inflated while the first set of ail bags is deflated, the patient is moved toward the second side of the low air loss bed. The conformation of the air bags also retains the patient on the top surface of the air bags when the patient is rolled in one direction or the other. 
     The first and second sets of air bags are mounted on a frame which is itself divided into sets of transversely mounted air bags so that the frame can be contoured to the patient&#39;s comfort. Also provided is means for additionally inflating the air bags under those portions of the patient which are heaviest when the frame of the bed is inclined for patient comfort. 
     The method of the present invention comprises inflating a plurality of-air bags to a selected pressure for supporting a patient thereon, inflating a first set of air bags to a pressure higher than the selected pressure to cause the patient support thereon to be rolled in a first direction on the air bags, and thereafter deflating the first set of air bags while inflating a second set of air bags to a higher pressure than the selected pressure to cause the patient to be rolled in a second direction on the air bags. A third set of air bags can be provided in which the selected pressure is maintained, thereby substantially immobilizing a portion of the patient&#39;s body.

Description:
The present application is a continuation application of application Ser. No. 08/390,233, filed Feb. 17, 1995, now U.S. Pat. No. 5,603,133, which is a application of Ser. No. 026,252, filed Mar. 3, 1993, now abandoned, which is a application of Ser. No. 671,672, filed Mar. 18, 1991, now abandoned, which is a application of Ser. No. 493,141, filed Mar. 12, 1990, now abandoned, which is a application of Ser. No. 181,922, filed Apr. 15, 1988, now abandoned, which is a continuation-in-part of application Ser. No. 057,965, filed Jun. 1, 1987, now abandoned, which is a continuation-in-part of application Ser. No. 905,553, filed Sep. 9, 1986, now abandoned, which is a continuation-in-part of application Ser. No. 784,875, filed on Oct. 4, 1985, now abandoned, which is a continuation-in-part application of application Ser. No. 683,153, filed on Dec. 17, 1984, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for alternating the air pressure of a low air loss patient support system. More particularly, it relates to a bed having a frame with two sets of air bags mounted thereto, a gas source which is mounted in the frame of the bed to supply a flow of gas to the two sets of air bags without the necessity for a separate unit having a blower and controls to supply the air bags, means on each of the air bags for moving a patient supported thereon toward one side of the frame and then back toward the other side of the frame when gas is supplied to the first set of air bags and then to the second set of air bags, and means on the air bags for retaining the patient on the air bags when the patient is moved toward the respective sides of the frames. Such a bed can be used to advantage for the prevention of bed sores and the collection of fluid in the lungs of bedridden patients. Other devices are known which are directed to the same object, but these devices suffer from several problems. In particular, U.S. Pat. No. 3,822,425 discloses an air mattress consisting of a number of cells or bags, each having a surface which supports the patient formed from a material which is gas permeable but is non-permeable to liquids and solids. It also discloses an air supply for inflating the cells to the required pressure and outlets or exhaust ports to allow the escape of air. The stated purpose of the outlets is to remove condensed vapor for the cells or bags. The outlets on that mattress may be fitted with valves to regulate the air pressure in the cells as opposed to regulating the air pressure in the cells by controlling the amount of air flowing into the cells. However, the air bed which is described in that patent and which is currently being marketed under that patent is believed to have certain disadvantages and limitations. 
     For example, that bed has a single air intake coupler, located directly and centrally underneath the air mattress, for connection of the source of air. Access to this connection is difficult since one must be on their back to reach it. The location of the connection underneath the mattress creates a limitation in the frame construction because the air hose must pass between the bed frame members. The source of air to which the air hose is connected is a blower or air pump mounted in a remote cabinet which, because it must be portable, is mounted on casters. There are many times in actual use when the cabinet must be moved in order to wheel other equipment, such as I.V. stands, around it or for access to the patient. However, relocation of this blower unit by any significant distance requires disconnection of the air hose from the frame (inconvenient because of the location up underneath the frame) or the pendent control in order to avoid wrapping the air hose around the bed frame members. Of course, disconnection of the air hose results in the loss of air pressure in the air mattress, which is even less desirable. 
     Another disadvantage with that type of bed relates to the monitoring of patient body weight. When charting fluid retention and other parameters, the patient&#39;s body weight is monitored continuously. When a patient is bedridden, the only way to monitor body weight is to weigh both bed and patient, then subtract the weight of the bed. But when a portion of the bed hangs off of the bed, as the air hose does, and when the changes in weight being monitored are measured in ounces, it is very difficult to accurately chart the changes in body weight when the patient is on such a bed. 
     Further, the bed disclosed by that patent is limited in that only a finite amount of air can be forced or pumped into the air mattress. By eliminating the outlets described in that patent entirely, the air pressure in the bags can at least be maintained at that point which represents the maximum output of the source of gas. In the case of the bed described in that patent, if it is necessary to further increase the pressure in the air bags while the outlets are being used for their stated purpose, the only way to do so is to install a larger capacity blower in the cabinet. High air pressures may be necessary, for instance, to support obese patients. A larger capacity blower generally requires more power consumption and a higher capacity circuit which may not be readily available. Also, the larger the blower, the more noise it creates which is not desirable. 
     The limitations and disadvantages which characterize other previous attempts to solve the problem of preventing bed sores in bedridden patients are well characterized in English Patent No. 1,474,018 and U.S. Pat. No. 4,425,676. 
     The prior art also discloses a number of devices which function to rock a patient back and forth by the use of air pressure. For instance, U.S. Pat. Nos. 3,477,071, 3,485,240, and 3,775,781 disclose hospital beds with an inflatable device for shifting or turning a patient lying on the bed by alternately inflating and deflating one or more inflatable cushions. U.K. Patent Application No. 2,026,315 discloses a pad, cushion, or mattress of similar construction. German Patent DE 28 16 642 discloses an air mattress for a bedridden person or hospital patient consisting of three longitudinal inflatable cells attached to a base sheet, the amount of air forced into each cell being varied so as to alternately rock the patient from one side of the mattress to the other. However, none of those mattresses or devices is designed for use in a low air loss patient support system. Further, the U.K. and German patents, and U.S. Pat. Nos. 3,477,071 and 3,775,781, disclose devices consisting of parallel air compartments which extend longitudinally along the bed and which are alternately inflated and deflated. Such a construction does not allow the use of the device on a bed having hinged sections corresponding to the parts of the patient&#39;s body lying on the bed so that the inclination and angle of the various portions of the bed can be adjusted for the patient&#39;s comfort. 
     U.S. Pat. No. 3,678,520 discloses an air cell for use in a pressure pad which is provided within a plurality of tubes which project from a header pipe such that the air cell assumes a comb-like conformation when inflated and viewed from above. Two such air cells are enclosed within the pressure pad with the projecting tubes interdigitating, and air is alternately provided and exhausted from one cell and then the other. That device is not suitable for use on a bed having hinged sections corresponding to the parts of the patient&#39;s body lying on the bed so that the angle of inclination of the various portions of the bed can be adjusted for the patients comfort, nor is it capable of functioning in the manner described if constructed in the low air loss conformation. 
     A number of patents, both U.S. and foreign, disclose air mattresses or cushions comprised of sets of cells which are alternately inflated and deflated to support a patient first on one group of air cells and then the other group. Those patents include U.S. Pat. Nos. 1,772,310, 2,245,909, 2,998,817, 3,390,674, 3,467,081, 3,587,568, 3,653,083, 4,068,334, 4,175,297, 4,193,149, 4,197,837, 4,225,989, 4,347,633, 4,391,009, and 4,472,847, and the following foreign patents: G.B. Patent No. 959,103, Australia Patent No. 401,767, and German Patent Nos. 24 46 935, 29 19 438 and 28 07 038. None of the devices disclosed in those patents rocks or alternately moves the patient supported thereon to further distribute the patient&#39;s body weight over additional air cushions or cells or to alternately relieve the pressure under portions of the patient&#39;s body. 
     There are also a number of patents which disclose an inflatable device other than an air mattress or cushion but which also involve alternately supplying air to a set of cells and then to another set of cells. Those patents include U.S. Pat. Nos. 1,147,560, 3,595,223, and 3,867,732, and G.B. Patent No. 1,405,333. Of those patents, only the British patent discloses the movement of the body with changes in air pressure in the cells of the device. None of those references disclose an apparatus which is adaptable for use in a low air loss patient support system. 
     British Patent No. 946,831 discloses an air mattress having inflatable elongated bags which are placed side-by-side and which are in fluid communication with each other. A valve is provided in the conduit connecting the insides of the two bags. Air is supplied to both bags in an amount sufficient to support the patient, thereby raising the patient off the bed or other surface on which the air mattress rests. Any imbalance of the weight distribution of the patient causes the air to be driven from one bag to the other, allowing the patient to turn toward the direction of the now deflated bag. An automatic changeover valve, the details of which are not shown, is said to then inflate the deflated bag while deflating the bag which was originally inflated, thereby rocking the patient in the other direction. That device is limited in its ability to prevent bed sores because when the patient rocks onto the deflated bag, there is insufficient air to support the patient up off the bed or other surface on which the air mattress rests, resulting in pressure being exerted against the patient&#39;s skin which is essentially the same as the pressure that would have been exerted by the board or other surface without the air mattress. Even if there were enough air left in the deflated bag to support the patient, if the air mattress were constructed in a low air loss configuration, the air remaining in the bag would be slowly lost from the bag until the patient rested directly on the bed or other surface with the same result. Finally, that device is not adaptable for use on a bed having hinged sections corresponding to the parts of the patient&#39;s body lying on the bed so that the angle of inclination of the various portions of the bed can be adjusted for the patient&#39;s comfort. 
     The present invention represents an improved apparatus over the prior art. It is characterized by a number of advantages which increase its utility over the prior art devices, including its flexibility of use, its ability to maintain air pressure, the ability to quickly and easily replace one or more of the air bags while the apparatus is in operation, and the ease of adjustment of the air pressure in the air bags. 
     It is, therefore, an object of the present invention to provide a low air loss bed comprising a frame a first set of substantially rectangular gas permeable air bags for supporting a patient thereon mounted transversely on the frame, a second set of substantially rectangular gas permeable air bags for supporting a patient thereon mounted transversely on the frame, means for connecting each of the air bags to a gas source, means integral with each of the air bags of the first set of air bags for moving the patient supported thereon toward a first side of the frame when each of the air bags in the first portion is inflated, means integral with each of the air bags of the second set of air bags for moving the patient supported thereon toward a second side of the frame when the air bags in the first set of air bags are deflated and the air bags of the second set of air bags are inflated, and integral means on each of the air bags for retaining the patient alternately supported on the first or second set of air bags when the patient is moved toward the first or second sides of the frame. 
     It is a further object of the present invention to provide an air bed, the air pressure of which can be quickly and conveniently set to support a patient of known body weight by simply setting the valves regulating the amount of air flowing from the air source. 
     Another object of the present invention is to provide a means for selectively routing an additional flow of gas from the gas source directly to the gas manifold supplying the set of air bags supporting the heavier portions of the patient without routing the flow through the gas flow controlling means. 
     Another object of the present invention is to provide a low air loss bed which is self-contained in that it requires no outboard gas source and is, therefore, more compact and convenient to use. 
     Another object of the present invention is to provide a low air loss bed upon which a patient may be maintained and which allows accurate monitoring of patient body weight. 
     Another object of the present invention is to provide a low air loss bed having an integral gas source which can be raised, lowered or tipped, and which allows the raising or lowering of a portion of the bed. 
     Another object of the present invention is to provide a low air loss gas permeable air bag which is comprised of a substantially rectangular enclosure constructed of a gas permeable material means for connecting the inside of the enclosure with a source of gas for inflating said enclosure, means for releasably securing the enclosure to a low air loss bed, integral means for moving a patient resting on the top surface of the rectangular enclosure towards the end thereof when the enclosure is inflated, and integral means at the end of the rectangular enclosure toward which the patient is moved for retaining the patient on the top surface of the enclosure. 
     Another object of the present invention is to provide an air bag with a single opening which can be quickly and easily detached from an air bed to allow the easy replacement of the air bag, even while the bed is in operation. Another object of the present invention is to provide a low air loss bed capable of rolling a patient back and forth on the bed while safely retaining the patient thereon. 
     Another object of the present invention is to provide a low air loss bed capable of alternately moving a patient in one direction and then in a second direction which is divided into at least three sections approximately corresponding to the portions of the body of the patient lying thereon which are hinged to each other and provided with means or raising and lowering the sections corresponding to the body of the patient to provide increased comfort and therapeutic value to the patient while the patient is being alternately moved in the first and second directions on the bed. 
     Another object of the present invention is to provide a low air loss bed capable of alternately rolling a portion of a patient in one direction and then in a second direction while retaining another portion of the patient in a relatively fixed position. 
     Other objects and advantages will be apparent to those of skill in the art from the following disclosure. 
     SUMMARY OF THE INVENTION 
     These objects and advantages are accomplished in the present invention by providing a frame with a source of gas mounted thereon. A plurality of sets of gas permeable air bags are mounted on the frame, each set of air bags corresponding to a portion of a patient to be supported in prone position on the bed. Each of a plurality of separate gas manifolds communicates with the gas source and one set of the sets of air bags. Also provided is a means for separately changing the amount of gas delivered by the gas source to each of the gas manifolds, thereby varying the amount of support provided for each portion of the patient. 
     Also provided is an air bag for use on a low air loss bed having a plurality of transversely mounted air bags mounted thereon comprising an enclosure for supporting a patient and distributing pressure over the body of the patient to prevent pressure points and means for connecting the inside of the enclosure with a source of gas for inflating the enclosure with gas. The enclosure is provided with means for securing the enclosure to a low air loss bed and means for moving a patient supported thereon toward one end of the enclosure when the air bag is inflated. The air bag is also provided with integral means for retaining the patient supported on the top surface of the enclosure when the patient is moved toward the end of the enclosure. 
     Also provided is a low air loss bed comprising a bed frame having a source of gas and a plurality of sets of gas permeable air bags mounted thereto. Separate gas manifolds communicate with the interior of the air bags on one set of the sets of air bags and the gas source. An air control box is mounted to the bed frame and interposed in the flow of air from the gas source to the gas manifolds, and is provided with individually adjustable valves for changing the amount of gas delivered to each of the gas manifolds. The air control box is also provided with means operable to selectively open all of the valves to the atmosphere, allowing the gas to escape from each of the sets of air bags, to collapse the air bags with the result that the patient is supported by the frame of the air bed rather than the air bags. 
     Also provided with a low air loss bed having a bed frame and a plurality of sets of air bags mounted thereto with a plurality of gas manifolds communicating separately with the gas source and the interior of the air bags. An air control box is mounted to the bed frame in fluid connection with the gas source and the gas manifolds, and is provided with valves which are individually adjustable to change the amount of the flow from the gas source through the air control box to each of the gas manifolds. The air control box is also provided with means operable to simultaneously fully open the valves to cause the air bags to fully inflate. 
     Also provided is a low air loss bed having a frame and a plurality of sets of air bags mounted thereto with a plurality of gas manifolds communicating separately with the gas source and the interior of the air bags. An air control box is also mounted on the frame, the interior of the air control box communicating with the gas manifolds and the gas source and having means therein for separately changing the amount of gas delivered by the gas source to each of the gas manifolds. The air control box is also provided with means operable to heat the gas flowing through the air control box and with means operable to switch the heating means on and off in response to the temperature in the air control box. Also provided is means having a sensor in one of the gas manifolds which is operable to selectively control the heating means, the means operable to switch the heating means on and off in response to the temperature in the air control box being operable at a predetermined temperature. 
     Also provided is a low air loss bed comprising a frame, a first set of air bags for supporting a patient thereon mounted transversely on the frame, a second set of air bags for supporting a patient thereon mounted transversely on the frame, means for connecting each of the air bags to a gas source, each of the air bags of said first set of air bags having means integral therewith for moving the patient supported thereon toward a first side of the frame when the air bags in the first set of air bags is inflated, each of the second set of air bags having means integral therewith for moving the patient supported thereon toward the second side of the frame when the air bags in the second set of air bags is inflated and the air bags in the first set of air bags is deflated, and means on the air bags for retaining the patient supported thereon when the patient is moved toward the respective first and second sides of the frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a presently preferred embodiment of the low air loss bed of the present invention. 
     FIG. 2 is a cross-sectional view of the bed of FIG. 1, showing an air bag with a second air bag therebehind taken along the lines  2 — 2  in FIG. 1, the second air bag being shown in shadow lines for purposes of clarity. 
     FIG. 3 is a schematic diagram of the air plumbing of the low air loss bed of FIG.  1 . 
     FIG. 4 is an exploded perspective view of the air control box of the low air loss bed of FIG.  1 . 
     FIG. 5A is a perspective view of one of the baseboards of the low air loss bed of FIG.  1 . 
     FIG. 5B is an enlarged, exploded perspective view of the underside of the baseboard of FIG. 5A, showing the baseboard partially cut away to show the details of attachment of a low air loss air bag thereto. 
     FIG. 6 is an end view of the low air loss bed of FIG. 1 with the head portion raised to show the construction of the frame and the components mounted thereto. 
     FIG. 7 is an end view of the low air loss bed of FIG. 1 with the foot portion raised to show the construction of the frame and the components mounted thereto. 
     FIG. 8 is a sectional view of the air box of the low air loss bed of FIG. 1 taken along the lines  8 — 8  in FIG.  9 A. 
     FIGS. 9A and 9B are cross-sectional views taken along the lines  9 A— 9 A and  9 B— 9 B, respectively, through the manifold assembly of the air box as show in FIG.  8 . 
     FIGS. 10A-10D are an end view of a patient supported upon the top surface of the air bags of the low air loss bed of the present invention as that patient ( 10 D), is rocked toward one side of the frame of the low air loss bed ( 10 A), then toward the other side ( 10 C) or supported on the air bags when all air bags are fully inflated (FIG.  10 B). 
     FIG. 11 is a composite, longitudinal sectional view of a portion of the foot baseboard of a low air loss bed constructed according to the teachings of the present invention taken along the lines  11 — 11  in FIG. 1 showing several alternate methods of attaching the air bags to the bed frame. 
     FIG. 12 is a schematic electrical diagram of the low air loss bed of FIG.  1 . 
     FIGS. 13A and 13B are top and plan views, respectively of the heater for heating the air in the air box of the low air loss bed of FIG.  1 . 
     FIG. 14 is schematic diagram of the electrical cables and controls which open and close the valves to route air to the air bags of the low air loss bed of FIG.  1 . 
     FIG. 15 is a flow chart of a presently preferred embodiment of the program for controlling the operations of the low air loss bed in FIG. 1 from the control panel shown in FIG.  12 . 
     FIG. 16 is a flow chart of the general timer subroutine for controlling the operation of the low air loss bed of FIG.  1 . 
     FIG. 17 is a flow chart of the switch processing subroutine for controlling the operation of the low air loss bed of FIG.  1 . 
     FIG. 18 is a flow chart of the rotation subroutine for controlling the operation of the low air loss bed of FIG.  1 . 
     FIG. 19 is a flow chart of the valve motor subroutine for controlling the operation of the low air loss bed of FIG.  1 . 
     FIG. 20 is a flow chart of the power fail interrupt subroutine for controlling the operation of the low air loss bed of FIG.  1 . 
     FIG. 21 is an end view of an alternative embodiment of an air bag for use on the low air loss bed of FIG.  1 . 
     FIG. 22 is an end view of one of the air bags for use on the low air loss bed of FIG.  1 . 
     FIG. 23 is an end view of another one of the air bags for use on the low air loss bed of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown a bed  10  including a frame  12 . The frame  12  is comprised of a plurality of sections  14 ′,  14 ″,  14 ′″ and  14 ″″, hinged at the points  44 ′,  44 ″ and  44 ′″, and end members  16 . Cross-members  18  (FIGS. 6 and 7) and braces  19  (FIG. 7) are provided for additional rigidity. The frame  12  is provided with headboard  20  at one end and a foot board  21  at the other end. The respective head  20  and foot  21  boards are actually constructed of two boards,  20 ′ and  20 ″, and  21 ′ and  21 ″, respectively, which are stacked one on top of the other by the vertical slats  25  on which the boards  20 ′,  20 ″,  21 ′ and  21 ″ are mounted. 
     A separate sub-frame, indicated generally at reference numeral  27  in FIGS. 6 and 7, is mounted on a base  22  comprised of longitudinal beams  24 , cross-beams  26  and cross-member  28  by means of a vertical height adjustment mechanism as will be described. The base  22  is mounted on casters  30  at the corners of the base  22 . A foot pedal  42  is provided for braking and steering the casters  30 . 
     Sub-frame  27  is comprised of cross-beams  29 , hoop brace  35 , and longitudinal beams  31  (see FIGS.  6  and  7 ). Sub-frame  27  is provided at the corners with uprights  33 , having tabs  33 ′ thereon, for mounting of IV bottles and other equipment. Means is provided for raising and lowering the sub-frame  27  relative to the base  22  in the form of a conventional vertical height adjustment mechanism, not all of the details of which are shown. Height is adjusted by rotation of axle  36  under influence of a power screw, hidden from view in FIG. 7 by drive tunnel beam  37 , which is powered by a motor which is also hidden from view. Axle  36  is journaled in the ears  38  which are mounted to the longitudinal beams  31  of sub-frame  27 . Power is transferred from the power screw to axle  36  by means of eccentric levers  39 , the axle  40  of which is journaled in drive tunnel beam  37 . Sub-frame  27  rises on levers which are pivotally mounted to the cross-beams of base  22 . The levers and the members on which they are mounted are hidden from view in FIGS. 6 and 7 by cross-beams  29 . 
     The section  14 ″ of frame  12  is mounted to the longitudinal beams  31  of sub-frame  27  by support members  41  (see FIG.  6 ). The section  14 ′ of frame  12 , with the head baseboard  52  thereon, and the section  14 ′″ of frame  12 , with foot baseboard  46  thereon, pivot upwardly from the horizontal at the hinges  44 ′ and  44 ″″, respectively. The purpose of that pivoting is to provide for the adjustment of the angle of inclination of the various parts of the body of the patient, and the details of that pivoting are known in the art and are not shown for purposes of clarity, although the motors are located within the boxes shown at  45  and are controlled from control panel  346 , and the circuitry for those functions is contained within box  43  (FIG. 7) and is explained in more detail below. Supports  17  are provided on the cross-member  18  under head baseboard  52  which rest on the longitudinal beams  31  of sub-frame  27  when head baseboard  52  is horizontal. When foot baseboard  46  is raised (FIG.  7 ), cross-bar  47  rises therewith by means of the pivoting connection created by cross-bar  47  and the notches  49  in brace  19  (cross-bar  47  is shown detached from braces  19  in FIG. 7 for purposes of clarity). The sets of notches  49  provide means for adjusting the height to which cross-bar  47  can be raised, foot baseboard  46  pivoting upwardly on brackets  51  which are pivotally mounted to the longitudinal beams  31  of sub-frame  27 . The tips  53  of cross-bar  47  rest on longitudinal beam  31  when foot baseboard  46  is lowered to the horizontal. 
     Side rails  81  are mounted to brackets  83  (see FIG. 6) which are pivotally mounted to the mounting brackets  85  mounted on the underside of head baseboard  52 . Side rails  87  are mounted to brackets  89  (see FIG.  7 ), and brackets  89  are pivotally mounted to the mounting brackets  91 . Mounting brackets  91  are affixed to the braces  19  on the underside of foot baseboard  46 . 
     The frame  12  is provided with a feet baseboard  46 , a leg baseboard  48 , a seat baseboard  50  and a head baseboard  52  (shown in shadow lines in FIG.  3 ), each being mounted to the corresponding section  14 ′,  14 ″,  14 ′″ and  44 ″″ of the frame  12  by means of rivets  54  (see FIG.  11 ). Means is provided for releasably securing the air bags  58  to the low air loss bed  10 . Referring to FIGS. 5A and 5B, there is shown a presently preferred embodiment of that releasable securing means. In FIGS. 5A and 5B, there is shown a portion of the feet baseboard  46 , which is provided with holes  64  therethrough which are alternating and opposite each other along the length of the feet baseboard  46 , as well as leg baseboard  48 , seat baseboard  50  and head baseboard  52 . Every other hole  64  is provided with a key slot  11  for receiving the post  32 , having retainer  34  mounted thereon, which projects through the bottom surface  79  of air bag  58 , the flange  71  of which is retained between patch  69 , which is stitched to the bottom surface  79  of air bag  58 , and the bottom surface  72 . Air bag  58  is shown cutaway and in shadow lines in FIG. 5B for purposes of clarity. Air bag  58  is also provided with a nipple  23  of resilient polymeric plastic material having an extension tab  15  integral therewith. To releasably secure the air bag  58  to feet baseboard  46 , or any of the other baseboards  48 ,  50 , or  52 , post  32  is inserted through hole  64  until retainer  34  has emerged from the bottom thereof. Post  32  is then slid into engagement with key slot  11  and retainer  34  engages the bottom side of feet baseboard  46  around the margin of hole  64  to retain air bag  58  in place on feet baseboard  46 . Nipple  23  is then inserted into the hole  64  opposite the hole  64  having key slot  11  therein and rotated until extension tab  15  engages the bottom of the head of flat head screw  13  to help secure nipple  23  in place. 
     In an alternative embodiment, the baseboards  46 ,  48 ,  50  and  52  are provided with means for releasably securing the air bags  58  to the low air loss bed  10  in the form of male snaps  56  (FIG. 11) along their edges. The air bags  58  are provided with flaps  60 , each of which is supplied with female snaps  62  which mate with male snaps  56 . Flaps  60  are alternatively provided with a strip of Velcro® tape  55 , and the edges of baseboards  46 ,  48 ,  50  and  52  are provided with a complementary strip of Velcro® hooks  57 , to secure each air bag  58  in place. Alternatively, flap  60  and baseboards  46 ,  48 ,  50  and  52  are provided with both Velcro® and snap fastening means. 
     The air bags  58  are substantially rectangular in shape, and are constructed of a coated fabric or similar material through which gas, including water vapor, can move, but which water and other liquids will not penetrate. The fabric sold under the trademark “GORE-TEX” is one such suitable material. The air bags  58  can include one or more outlets for the escape of the air with which they are inflated or they can be constructed in a “low air loss” conformation. The low air loss air bag shown at reference numeral  59  in FIG. 11 is a composite of a gas impermeable fabric, which makes up the bottom  72  and the walls  61  of the air bag  58 , and the gas permeable fabric described above, which makes up the top  63  of the air bag. The top  63  and walls  61  are stitched or otherwise joined at shadow lines  63 . The gas impermeable fabric is, for instance, a polymer-coated nylon. The low air loss air bag  59  allows the pressurization of the air bag  59  with a smaller flow of gas than is required to inflate air bags  58 , which results in the possibility of maintaining sufficient pressure with just one blower  108  operating while using low air loss air bags  59  or a combination of air bags  58 ,  321 ,  322 ,  325  or  328 , as will be described, with low air loss air bags  59 . 
     Referring to FIGS. 1 and 2, air bags are shown of different conformation according to their location on the frame  12  of bed  10 . For instance, the air bags mounted to the leg baseboard  48  and seat baseboard  50  are designated at reference numeral  322 . Air bags  321 ,  322 ,  325  and  328  are constructed in the form of a substantially rectangular enclosure, at least the top surface  323  of which is constructed of gas permeable material such as described above. Air bags  321 ,  322 ,  325  or  328  are provided with means for connecting the inside of that enclosure to a source of gas, such as the blower  108 , to inflate the enclosure with gas in the form of the nipple  23  (see FIG. 2) which extends through the baseboard  50  into the seat gas manifold  80  mounted thereto. Air bag  321 ,  322   325  or  328  is also provided with means for releasably securing the enclosure to the low air loss bed  10  in the form of the post  32  and retainer  34  described above. Means is provided for moving a patient  328  supported on air bags  322 ,  325  or  328  toward one side of frame  12  when air bags  322   325  or  328  are inflated and for retaining the patient  348  on the top surface  323  of air bags  322 ,  325  or  328  when patient  348  is rolled or rocked towards one side of frame  12  or the other. The means for moving patient  348  supported on air bags  322 ,  325  or  328  toward one side of frame  12  when the air bags  322 ,  325  or  328  are inflated comprises a cutout  324  in the top  323  of the substantially rectangular shape of each of the air bags  322 ,  325  or  328 . 
     Each air bag  322 ,  325  or  328  is also provided with means for retaining a patient  348  on the top surface  323  of the air bag  322 ,  325  or  328  when patient  348  is rolled toward the side of frame  12  by the inflation of air bags  322 ,  325  or  328  in the form of a pillar  326  which is integral with each air bag  322 ,  325  or  328  and which, when inflated, projects upwardly to form the end and corner of the substantially rectangular enclosure of air bag  322 ,  325  or  328 . The means for retaining patient  348  on the top  323  of air bags  322 ,  325  or  328  can also take the form of a large foam cushion (not shown) mounted to side rails  81  and  87  on both sides of bed frame  12 . That cushion can be detachably mounted to side rails  81  and  87 , or can be split so that a portion mounts to said rail  81  and a portion mounts to side rail  87 . The air pressure in air bags  322 ,  325  or  328  is then adjusted, as will be explained, until patient  348  is rocked gently against that foam cushion on one side of bed frame  12  and then back toward the other side of bed frame  12 . 
     As shown in FIG. 1, a plurality of air bags  58 ,  59 ,  321 ,  322 ,  325  and/or  328  is mounted transversely on the frame  12  of bed  10 . The air bags  322 ,  325  or  328  are divided into a first set in which the pillar  326  and cutout  324  are closer to one side of bed frame  12  than the other and a second set of air bags  322 ,  325  or  328  in which the pillar  326  and cutout  324  are closer to the second side of the bed frame  12 . The air bags  322 ,  325  or  328  of the first set and the air bags  322 ,  325  or  328  of the second set alternate with each other along the length of baseboards  46 ,  48 ,  50 , and  52 . As will be explained, the first set of air bags  322 ,  325  or  328  is inflated with air from blower − 08 , thereby causing the patient  348  supported on the air bags  322  to be rolled toward the first side of bed frame  12  and then deflated while the second set of air bags  322 ,  325  or  328  is inflated, thereby moving the patient  348  supported thereon toward the other side of bed frame  12  (see FIG.  10 ). 
     The air bags  58 ,  59  or  321  which are mounted on head baseboard  52  are provided with a flat top surface  323  so that the head of patient  348  is retained in a relatively constant position while the body of patient  348  is alternately rolled first toward one side of the bed frame  12  and then back toward the other side of bed frame  12 . Referring to FIG. 23, an air bag  321  is shown for use under the head of patient  348 . Air bag  321  is substantially rectangular in shape, but is provided with a slanted top surface  323  in the area  331  adjacent corners  448 . The height of air bag  321  is less than the height of air bags  58 ,  59 ,  322 ,  325  and  328  because when patient  348  lies upon airbags  58 ,  59 ,  322 ,  325  and/or  328 , the heavier portions, i.e., the portions of the body other than the head, sink into those air bags  58 ,  59 ,  322 ,  325  and/or  328  as shown in FIG.  10 D. When the patient  348  sinks into air bags  58 ,  59 ,  322 ,  325  and/or  328 , the head rests evenly on air bags  321  because the head does not sink into air bags  321  as far as the other portions of the body. 
     The air bags  328  mounted on the foot baseboard  46  and the air bags  328  mounted on a portion of leg baseboard  48  are also provided with a cutout  324  and pillar  326  as described for the air bags  322 . Additionally, air bags  328  are provided with a hump  330  so that the legs of patient  348  are relatively restrained from movement during the alternate back and forth movement of patient  348 , thereby helping to retain the patient  348  on the top surface  323  of air bags  58 ,  59 ,  321 ,  322 ,  325  and  328  as well as helping to distribute the pressure exerted against the skin of patient  348  over an increased area. 
     Referring to FIG. 22, there is shown an end view of an air bag  328  having hump  330  formed in the top surface  323  thereof. 
     As can be seen, when air bag  328  is inflated, hump  330  and pillar  326  project upwardly to help prevent the rolling of patient  348  too far to one side of bed frame  12  or the other. An alternative construction of air bag  322  is shown at reference numeral  325  in FIG.  21 . Air bag  325  is provided with cutout  324  of approximately the same depth as the cutout  324  of airbags  322  and  328 , but the slope of the top surface  323  in the area  327  is less than the slope of the top surface  323  in the area  329  of air bags  322  and  328 . Air bag  325 , in conjunction with the adjustment of the air pressure in the air bags  58 ,  59 ,  321 ,  322  and/or  328 , can be used under different portions of the body of patient  348  to increase or decrease the extent and speed with which patient  348  is rolled from one side of bed frame  12  to the other. For instance, air bag  325  is particularly well-suited for use under the shoulders of a patient  348 . 
     As noted above, all of the air bags  58 ,  59 ,  321 ,  322 ,  325  and  328  are substantially rectangular in shape with dimensions of approximately 18×39 inches. Each is provided with a baffle  460  attached to side walls  61  which holds the side walls  61  against bowing when the air bag  58 ,  59 ,  321 ,  322 ,  325  or  328  is inflated. Each of the corners  448  has a radius of curvature of approximately three inches, and the depth of cutout  324  is approximately ten inches. The dimension of pillar  326  of air bags  325  and  328  in the direction shown by line  450  is approximately seven inches, as is the dimension of cutout  324  in the direction shown by line  452 . The dimension of pillar  326  of air bag  322  in the direction shown by line  451  is approximately twelve inches. The dimension of the top surface  323  of air bag  325  along line  453  is approximately twenty inches, and that top surface  323  drops off into cutout  324  in a curve  455  of approximately a six inch radius. Referring to FIG. 2, the dimension of the top surface  323  along line  458  is approximately nineteen inches. The dimension of hump  330  on air bag  328  in the direction shown by line  454  is approximately five inches, and in the direction shown by line  456 , the dimension is approximately two inches. The dimension of surface  333 , as shown by line  458  is approximately fourteen inches. 
     In an alternative construction for attaching the air bags  58 ,  322  and  328  to the bed  10 , each air bag  58  (it should be understood throughout the specification that, when reference is made to an air bag  58 , the air bag could also be an air bag  59  constructed in the low air loss conformation or an air bag  321 ,  322 ,  325  or  328 ) is provided with a flanged nipple  70 , the flange  71  of which is retained between the bottom  72  of the air bag  58  between a patch  74  and the bottom  72  of the air bag. As described below, each air bag  58  is mounted separately on the baseboards  46 ,  48 ,  50 , and  52  by snapping the female snaps  62  in the flaps  60  of each of the air bags  58  over the male snaps  56  on the edges of the baseboards  46 ,  48 ,  50 , and  52  or with the VELCRO tape  55  and hooks  57 , or both. When so positioned, the flanged nipple  70  on the bottom inside  72  of the air bag  58  projects through the holes  64  and  64 ′ in the baseboards  46 ,  48 ,  50 , or  52  over which the air bags  58  are positioned. An O-ring  68  is provided in a groove (not numbered) around each of the flanged nipples  70  to insure a relatively gas-tight fit between the flanged nipple  70  and the corresponding baseboard  46 ,  48 ,  50 , or  52  through which the flanged nipples  70  protect. 
     The use of individual air bags  58 ,  59 ,  321 ,  322 ,  325  or  328  rather than a single air cushion allows the replacement of individual bags should one develop a leak, need cleaning or otherwise need attention. When it is desired to remove an individual air bag  58 ,  59 ,  321 ,  322 ,  325  or  328  from its respective baseboard  46 ,  48 ,  50 , or  52 , post  32  is slid out of key slot  11  and retainer  34  and post  32  are removed from hole  64 . Nipple  23  is then rotated until extension tab  15  rotates out of engagement with screw  13  and is pulled firmly to remove it from hole  64 . In the case of air bag  58 , female snaps  62  at each end of the air bag  58  are disengaged from the male snaps  56  (or the VELCRO strips peeled away from each other) on the edges of baseboards  46 ,  48 ,  50  or  52 , and the air bag  58  is removed by twisting flanged nipple  70  up and out of the hole  64  in the baseboard  46 ,  48 ,  50 , or  52 . Removal can even be accomplished while the patient is lying on the inflated air bags  58 ,  59 ,  321 ,  322 ,  325  or  328 . 
     For additional security in holding air bags  58  onto baseboards  46 ,  48 ,  50  and  52 , and to help insure a gas-tight fit between flanged nipple  70  and the respective baseboards  46 ,  48 ,  50  or  52  through which it projects, spring clip  73  (see FIG. 11) is inserted through nipple  70  of air bag  58 . To insert the nipple  70  into hole  64 , the hoop portion  75  of spring clip  73  is squeezed (through the fabric of air bag  58 ), causing the flanges  77  on the ends of the shank portion  101  of spring clip  73  to move toward each other so that they can enter the hole  64 . Once inserted through the hole  64 , flanges  77  spring apart, and will not permit the removal of nipple  70  from hole  64  without again squeezing the hoop portion  75  of spring clip  73 . 
     Referring to FIG. 6, there is shown an end view of a bed constructed according to the present invention. Brace  102  is secured to the cross beam  29  of sub-frame  27  by means of bolts  104 . Blowers  108  are mounted to the brace  102  by means of bolts  110  through the mounting plates  112  which are integral with the blower housing  116 . A gasket, piece of plywood or particle board (not shown), or other sound and vibration dampening material is interposed between mounting plates  112  and brace  102 . A strip of such material (not shown) can also be inserted between brace  102  and cross beam  29 . The blowers  108  include integral permanent split capacitor electric motors  114 . When motors  114  are activated, blowers  108  move air out of the blower housings  116 , through the blower funnels  118  and up the blower hoses  120  to the air box funnels  122  and on into the air box  124  (see FIGS.  3  and  6 ). 
     Blowers  108  receive air from filter box  96  through hoses  98  (see FIG.  3 ). Filter box  96  is retained within a frame  100  (see FIG. 6) for ease in removal. Frame  100  is mounted to frame  27  and is, for the most part, blocked from view by cross-beam  26  of base  22  and cross beam  29  of frame  27  in FIG.  6 . The second blower  108  is provided to increase the volume which is delivered to the air bags  58 , thereby increasing the air pressure within air bags  58 . A cover (not shown) lined with sound absorbing material can also be provided to enclose blowers  108  and thereby reduce noise. 
     The air control box  124  is an airtight box mounted on the underside of head baseboard  52  by brackets  125 , and is shown in more detail in FIG.  4 . Air box  124  is provided with a manifold assembly  126  held to the front of air box  124  by screws  119 . Manifold assembly  126  is provided with a manifold plate  145  having holes (not numbered) therein for connection to a means for changing the amount of air supplied to the air bags  58  mounted to baseboards  46 ,  48 ,  50  and  52  in the region of the feet, legs, seat, back, and head, respectively. Gasket  115  prevents the escape of air from between air box  124  and manifold plate  145 . In a presently preferred embodiment, the means for changing the amount of air supplied to the air bags  58  takes the form of a plurality of valves, indicated generally at reference numerals  128 ,  130 ,  132 ,  134  and  136 . Each of the valves  128 ,  130 ,  132 ,  134 , and  136  is provided with a motor  138  having a nylon threaded shaft  139  (see FIGS. 4,  8 ,  9 A and  9 B) mounted on the drive shaft (not numbered) of each motor  138  and held in place by set screw  149  in collar  148 . Plug  140  moves rotatably in and out along the threaded shaft  139  when limit pin  141  of plug  140  engages one or the other of the supports  142  which are immediately adjacent that particular plug  140  and which hold the motor mounting bracket  143  to the back of the full inflate plate  144 . 
     Full inflate plate  144 , having openings  202  therein forming part of valves  128 ,  130 ,  132 ,  134 , and  136 , is mounted to the back of the manifold plate  145  by hinges  146  (see also FIGS.  9 A and  9 B). A gasket  147  is provided to prevent the escape of air from between the full inflate plate  144  and manifold plate  145 . The motors  138  are not provided with limit switches, the movement of plug  140  back and forth along the threaded shaft  139  of each motor  138  being limited by engagement of plug  140  with the opening  202  as plug  140  moves forward and by the engagement of the back side of plug  140  with collar  148  as plug  140  moves back on threaded shaft  139 . An O-ring  204  is provided on plug  140  which is compressed between plug  140  and opening  202  as plug  140  moves forward into opening  202 . Compression continues until the load on motor  138  is sufficient to cause it to bind and stop. The O-ring  206  which is provided on collar  148  operates in similar fashion when engaged by the back side of plug  140 . 
     The binding of motors  138  by the loading of O-rings  204  and  206  facilitates the reversal of the motors  138  and direction of travel of plug  140  along threaded shaft  139  because threaded shaft  139  is not bound. Threaded shaft  139  is free to reverse direction and turn such that the load created by the compression of O-rings  204  or  206  is released by the turning of threaded shaft  139 , and plug  140  will rotate with threaded shaft  139  until limit pin  141  contacts support  142 , stopping the rotation of plug  140  and causing it to move along shaft  139  as it continues to turn. 
     A dump plate  150  is mounted on the outside of manifold plate  145  by means of hinges  151  (see also FIGS.  9 A and  9 B). A gasket  106  is provided to prevent the escape of air from between the manifold plate  145  and the dump plate  150 . The dump plate  150  is provided with couplers  153 , the interiors of which are continuous with the holes in manifold plate  145  when dump plate  150  is in the position shown in FIGS. 9A and 9B, for connection of the appropriate bed frame gas supply hoses  174 ,  176 ,  178 ,  180  and  18   v , as will be explained. 
     Block  154  is attached to dump plate  150  by means of screws  155 , and serves as a point at which the cable  156  can be anchored, by means of nut  157 , so that a line  158  can slide back and forth within cable  156  to allow the dump plate  150  to be selectively pivoted away from manifold plate  145  on hinge  151 . The line  158  is secured to the manifold plate  145  by the threaded cable end and locknut  159 . Line  158  is secured at its other end to the bracket  183  mounted on tube  190  (see FIG.  7 ). Bed frame  12  is provided with quick dump levers  165  on both sides thereof, .he quick dump levers  165  being connected by tube  190  so that both levers  165  provide a remote control for operation of dump plate  150  by causing the movement of line  158  through cable  156 . When either of quick dump levers  165  is moved from the position shown in FIG. 7, eccentric lever arm  181  pulls on line  158 , cable  156  being anchored on bracket  183 , so that line  158  moves through cable  156 . The details of the anchoring of cable  156  and movement of line  158  therethrough under the influence of lever arm  181  are the same as those for the anchoring of cable  160  and movement of line  162  therethrough under the influence of lever arm  185  (see below). Movement of line  158  causes dump plate  150  to pivot away from manifold plate  145 , allowing the air in air bags  58  to escape through manifolds  76 ,  78 ,  80 ,  82  and  84  and bed frame gas supply hoses  174 ,  176 ,  178 ,  180  and  182  to the atmosphere from the opening thus created between manifold plate  145  and dump plate  150  so that air bags  58  will rapidly deflate. A coil spring  201 ′ encloses line  158  within bores (not numbered) in dump plate  150  and manifold plate  145  to bias dump plate  150  and manifold plate  145  apart. 
     As is best shown on FIGS. 8 and 9B, a separate cable  160  passes through manifold plate  145  in threaded fitting  161  so that line  162  can slide back and forth therein. The line  162  is anchored in the full inflate plate  144  by means of nut  163 , which allows the full inflate plate  144  to pivot away from the manifold plate  145  on hinge  146 . Pivoting of full inflate plate  144  away from manifold plate  145  in this manner removes full inflate plate  14 −, motor mounting bracket  143 , and all other parts mounted to those parts, from the flow of air to allow the unrestricted entry of the air in air box  124  into the couplers  153  of valves  128 ,  130 ,  132 ,  134  and  136  and on into bed frame gas supply hoses  174 ,  1 , 6 ,  178 ,  180  and  182 , resulting in the rapid and full inflation of air bags  58  to raise the patient  348  to the position shown in FIG. 10B to facilitate patient transfer or other needs. A coil spring  201  encloses line  162  in a bore (not numbered) in manifold plate  145  and full inflate plate  144  to bias manifold plate  145  apart from full inflate plate  144 . 
     Line  162  is anchored at its other end on lever arm  185  (FIG. 7) which is attached to the bar  195  upon which full inflate knob  193  is mounted. Bed frame  12  is provided with full inflate knobs  193  on both sides thereof, the full inflate knobs  193  being connected by bar  195  so that both control the movement of line  162  through cable  160 . Cable  160  is affixed to bracket  187  by threaded cable end  199 , which is mounted on the DELRIN bearing  209  which is integral with support member  210  and which receives bar  195  so that rotation of full inflate knobs  193  causes line  162  to slide therein, pivoting full inflate plate  144  on hinge  146 . The weight of motors  138 , supports  142  and motor mounting bracket  143  bias full inflate plate  144  toward the position in which full inflate plate  144 , motor mounting bracket  143 , and the parts mounted thereto, are removed from the flow of gas into the couplers  153  of valves  128 ,  130 ,  132 ,  134  and  136 . This bias allows knobs  193  to act as a release such that either of knobs i 93  need only be turned enough to move the connection between line  162  and lever arm  185  out of its over center position, at which point gravity causes the plate  144  to open. Referring to FIG. 10B, patient  348  is shown lying on air bags  322  (and/or  58 ,  59 ,  321 ,  325  or  328 ) after full inflate plate  144  is opened. When knobs  193  are returned to their initial position, lever arm  185  turns to the point at which the connection between line  162  and lever arm  185  is rotated past 180° from the point at which line  162  approaches bar  195 , i.e., over center. As noted below, microprocessor  240  includes an alarm buzzer (not shown), and switches (not shown) can be provided for activating that alarm when either of knobs  193  or levers  165  are used to inflate or deflate air bags  58 ,  59 ,  321 ,  325  and/or  328  respectively. Air enters the air box  124  through air box funnels  122  in back plate  121  (FIG.  4 ). Air box funnel  122  is provided with a one-way flapper valve  117  so that air will not escape from the air box  124  when only one blower  108  is being operated. Back plate  121  is held in place on air box  124  by screws  123 , and gasket  127  is provided to prevent the loss of air from between air box  124  and back plate  121 . 
     The air box  124  is provided with a heating element indicated generally at  129  and shown in FIGS. 13A and 13B. Screws  131  secure heating element  129  in place on the bottom of air box  124 , effectively partitioning air box  124  into two compartments. Because air enters the air box  124  in one compartment (i.e., behind heating element  129 ) and leaves the air box  124  from the other compartment, a flow of air must pass through the space  135  between bulkhead  133  and the mounting bracket  137  of heating element  129 , being mixed and heated as it does. 
     Wires  167   i  and  1670  provide power to heating element  129  from power distribution board  219  as will be explained, the wire  167   i  connecting thermostats  169  and  171  and heater strip  172  in series (see FIG.  12 ). Heater strip  172  is suspended in space  135  by insulated posts  173  which are secured in the flanges  175  and  177  of bulkhead  133  and mounting bracket  137 , respectively. Thermostat  169  switches off at 140° F., thermostat  171  switches off at 180° F., and heater strip  172  must cool to 120° F. for thermostat  169  to come back on. Thermostat  171  is merely redundant and included for safety purposes. Both thermostats  169  and  171  reset automatically, the thermostat  171  coming back on at 140° F. Also provided is thermostat  194 , which includes a sensor (not shown), located in seat manifold  80 , and when the circuit containing thermostat  194  is closed due to the temperature of the air in seat manifold  80 , the pilot light  196  (see FIG. 7) comes on indicating that the circuit has been completed and that heater  172  is heating the air therein. Heater  172  cannot come on unless switch  191  has been selected and one or more of the blowers  108  is operating. Thermostats  194  also includes a control  152  for adjustment of the temperature of the gas in seat manifold  80 , and a thermometer gauge  168  for continuous monitoring of that temperature. 
     Referring to FIG. 3, the electric motors  114  of blowers  108  are switched on, forcing or pumping air (or other gases) received from filter box  96  through hoses  98  up the blower hoses  120 , through one-way valves  117 , and into air box  124 . A valve  109  is provided to provide increased control of the air pressure in air bags  58 ,  59 ,  321 ,  322 ,  325  and  328  and to seal off one of the blowers  108  so that the bed  10  can be operated on one blower or on the blower  432  (see FIG.  7 ). Valve  109  is also used to restrict the flow of air one of the blowers  109  when both blowers are operating, thereby providing additional adjustability in air pressure. The air escapes from the air box  124  through valves  128 ,  130 ,  131 ,  134  and  136  into the respective bed frame gas supply hoses,  174 ,  176 ,  178 ,  180  and  182  (see FIG.  3 ). Bed frame gas supply hoses  174 ,  176 ,  178 ,  180  and  182  route the air to the manifolds  76 ,  78 ,  80 ,  82  and  84  and  76 ′,  78 ′,  80 ′,  82 ′ and  84 ′. Bed frame gas supply hose  174  is connected to leg gas manifold  78 , which is connected by hose  332  to feet gas manifold  76 . Bed frame gas supply hose  176  routes air to back gas manifold  82 , which is connected to seat gas manifold  80  by hose  334 . Bed frame gas supply hose  178  routes air to head gas manifold  84 . Bed frame gas supply hose  180  routes air to back gas manifold  82 ′, which is connected to seat gas manifold  80 ′ by hose  336 . Bed frame gas supply hose  182  routes air from air box  124  to leg gas manifold  78 ′, which is connected to feet gas manifold  76 ′ by hose  338 . Valves  340  are provided in hoses  332  and  338  for a purpose to be explained below. Each of the gas manifolds  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ and  84  is mounted to the underside of the baseboards  46 ,  48 ,  50  and  52 , feet baseboard  46  having gas manifolds  76  and  76 ′ mounted thereto, leg baseboard  48  having gas manifolds  78  and  78 ′ mounted thereto, and seat baseboard  50  having gas manifolds  80  and  80 ′ mounted thereto. The head baseboard  52 , and its corresponding section  14 ″″ of frame  12 , is provided with two back gas manifolds  82  and  82 ′ and head gas manifold  84 . 
     Because the feet baseboard  46  extends beyond the end member  16  of the frame  12  at the foot of the bed, T-intersects  86  and  86 ′ are provided from the feet gas manifolds  76  and  76 ′, respectively, to route feet extension hoses  88  and  88 ′ to the holes  64  and  64 ′ at the extreme ends of the feet baseboard  46  (see FIGS. 3,  7  and  11 ). Clamps  65  and  65 ′ are provided to hold the feet extension hoses  88  and  88 ′ in place on the nipples  23  in holes  64  and  64 ′ and on T-intersects  86  and  86 ′. The head baseboard  52  likewise extends beyond the end member  16  of frame  12  at the head end of the bed (FIGS.  3  and  6 ), and T-intersect  92  is provided from the head gas manifold  84  to provide air to the hole  64  at the extreme end of the head baseboard  52  by means of the head extension hose  94 . A clamp  65  is provided to retain head extension hose  94  on T-intersect  92  and on the receptacle  66  in hole  64 . 
     Air enters the gas manifolds  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′, and  84  from each respective bed frame gas supply hose  174 ,  176 ,  178 ,  180  or  182  and hose  332 ,  334 ,  336 , or  338 , and then passes down the length of each gas manifold  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ or  84 . Air escapes from the gas manifolds  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ or  84  into the air bags  58  through the holes  64  and  64 ′ in the baseboards  46 ,  48 ,  50  and  52 , thereby inflating the air bags  58 . 
     The holes  64  and  64 ′ through base boards  46 ,  48 ,  50  and  52  into the respective air bags  58 ,  322  and  328  are staggered down the length of the frame  12  of bed  10 . In other words, every other hole  64 , or  64 ′ is provided with a key slot  11  (see FIG.  5 A). Air bags  322 ,  325  and  328  are provided with a single nipple  70  or  23 , respectively and a post  32  with retainer  34  thereon for engagement of key slot  11  in hole  64  or  64 ′ at the other end thereof. The air bags  322 ,  325  and  328  alternate in their orientation on baseboards  46 ,  48 ,  50  and  52 , resulting in about half the air bags  58 ,  322  and  328  being oriented with nipple  70  or  23  closer to one side of bed frame  12  than the nipple  70  or  23  of the other half of the air bags  58 ,  322  or  328  mounted thereon. 
     Because each of the bed frame gas supply hoses  174 ,  176 ,  178 ,  180  and  182  is continuous with a corresponding gas manifold  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ or  84 , the amount of air supplied to each gas manifold  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ or  84  can be varied using the valves  128 ,  130 ,  132 ,  134  or  136  on the air box  124 . Since each of the valves  128 ,  130 ,  132 ,  134  and  136  controls the amount of air supplied to one of the manifolds  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ or  84 , each valve  128 ,  130 ,  132 ,  134  or  136  controls the amount of air supplied to the set of air bags  58 ,  322  or  328  located directly above an individual gas manifold  76 ,  76 ′,  78 ,  78 ′,  80 ,  80 ′,  82 ,  82 ′ or  84 . 
     As a general rule, the legs of a patient  348  are not as heavy 2S the other portions of the body, consequently there is less air pressure needed to inflate the air bags  328  under the legs, i.e., those air bags  328  mounted to foot baseboard  46  and supplied with air through feet gas manifolds  76  and  76 ′˜ than is needed to inflate the other air bags  58 ,  59 ,  321 ,  322  or  325 . Valves  340  in hoses  332  and  338  are provided for decreasing the amount of air entering feet gas manifolds  76  and  76 ′ for that reason. Further, decreasing the amount of air delivered to manifolds  76  and  76 ′ causes the air pressure in those air bags  328  supplied with air through manifold  76  to drop more quickly than the air pressure in the air bags  58 ,  59 ,  321 ,  322  or  325  supplied with air by manifolds  78 ,  80  and  82  as valve  130  is closed during rotation of the patient  348 . Likewise, valve  340  is used to cause the pressure to drop in the air bags  328  supplied with air by manifold  76 ′ sooner than the pressure in the air bags  58 ,  59 ,  321 ,  322  or  325  supplied with air by manifolds  78 ′,  80 ′ and  82 ′ as valve  134  is closed during rotation of patient  348 . That earlier decrease in pressure in the air bags  328  under the legs of patient  348  causes the pressure changes in the air bags  58 ,  59 ,  321 ,  322  or  325  under the other portions of the body of patient  348 . 
     Also shown in FIG. 3 is the portable power unit, indicated generally at  426 . Portable power unit  426  is comprised of case  428  (see FIG.  7 ), which encloses batteries  430 , blower  432  and battery charger  434 , and hose  436 . Hose  436  is provided with a releasable coupler  438  which mates with the coupler  440  of the hose  442  which is mounted on sub-frame  27  and which connects to air box  124  through funnel  444 . Brackets  446  are mounted to subframe  27  for releasably engaging the case  428  of portable power unit  426 . Portable power unit  426  provides air pressure to support a patient when an electrical outlet is unavailable, for instance, during patient transport. 
     As shown in FIG. 4, the opening  342  in manifold plate  145 , which is aligned with the opening  202  in full inflate plate  144  (opening  202  in full inflate plate  144  (see FIG. 9B) allows the passage of air through full inflate plate  144  into the valves  128 ,  130 ,  132 ,  134  and  136 ), is continuous in the area between valves  128  and  130 . Opening  342  is a space defined by the margin of opening  342  in manifold plate  145 , the surface of dump plate  150  (shown cut away in FIG.  4 ), which abuts manifold plate  145  when dump plate  150  is closed, and the surface of full inflate plate  144 , which abuts manifold plate  145  when full inflate plate  144  is closed. Similarly, manifold plate  145  is provided with an opening  343  between valves  134  and  136 . By connecting valve  128  with valve  130  with opening  342 , the air bags  322  and  328  connected to the back, seat, leg and feet gas manifolds  76 ,  78 ,  80  and  82  are inflated simultaneously whenever the plug  140  on either of the motors  138  in valves  128  or  130  is not snugged up against full inflate plate  144  by action of motors  138 . Similarly, by connecting valve  134  with valve  136  with opening  343 , the air bags  322  and  328  connected to the back, seat, leg and feet gas manifolds  76 ′,  78 ′,  80 ′ and  82 ′ are inflated simultaneously. The air bags  58  are inflated by air passing through valve  132  to head gas manifold  84 . 
     As will be explained, means is provided for alternately inflating first the air bags  322  and  328  connected to back, seat, leg and feet gas manifolds  76 ,  78 ,  80  and  82 , respectively, and then deflating those air bags while inflating the air bags  322  and  328  connected to back, seat, leg and feet gas manifolds  76 ′,  78 ′,  80 ′ and  82 ′. The alternating inflation and deflation of the first set of air bags  322  and  328  and the second set of air bags  322  and  328  causes a patient  348  supported thereon to be alternately rocked in one direction and then the other (see FIGS. 10A-10D) because of the alternating arrangement of the cutouts  324  on air bags  322  and  328 . 
     With some patients, the air pressure in the air bags  322 ,  325  and  328  connected to the gas manifolds  76 ,  78 ,  80  and  82  is not sufficient to adequately support the patient when the air bags  322 ,  325  and  328  connected to manifolds  76 ′,  78 ′,  80 ′, and  82 ′ are deflated. That lack of support is a result of the fact that the entire weight of the patient is supported by the air bags  322 ,  325  and  328  inflated by air received from gas manifolds  76 ,  78 ,  80  and  82 , in other words, by only about half the air bags  322 ,  325  and  328 . Openings  342  and  343  allow the maintenance of a baseline air pressure in the respective sets of air bags  322 ,  325  and  328  when that set of air bags  322 ,  325  and  328  is deflated, thereby helping to support patient  348  when patient  348  is rocked in the direction of the pillar  326  of the other set of air bags  322 ,  325  and  328 . 
     For instance, to maintain a baseline pressure in the set of air bags connected to the gas manifolds  76 ,  78 ,  80 , and  82 , the plug  140  in valve  128  is set so as to allow a selected amount of air to pass through the valve  128  and on into the valve  130 , through opening  342  depending upon the weight of patient  348 . The plug  140  of valve  130  is then connected to a means for periodically causing the motor  138  to move the plug  140  into and out of engagement with full inflate plate  144 , thereby varying the amount of air allowed to pass through the valve  130  as well as on into the valve  128  and to the air bags connected to gas manifolds  76 ,  78 ,  80  and  82 . That arrangement always allows a selected amount of air to pass through the valves  128  and  130 , even when the plug  140  is against the full inflate plate  144  to completely close valve  130  as it would be when the plug  140  of valve  134  is open to the widest extent selected by the operator. After a selected period of time, the motor  138  of valve  130  reverses, and plug  140  of valve  130  begins to move away from fall inflate plate  144  to open valve  130  while the plug  140  of valve  134  begins to move toward the full inflate plate  144  to close valve  134 . In the same manner that a baseline pressure is maintained in the air bags connected to gas manifold  76 ,  78 ,  80 , and  82 , a baseline pressure is maintained in the air bags  322  and  328  connected to the back, seat, leg and feet gas manifolds  76 ′,  78 ′,  80 ′ and  82 ′, respectively, by setting the plug  140  of valve  136  to allow a selected amount of air to pass therethrough and on into valve  134  through opening  343  even when valve  134  is completely closed by plug  140 . 
     In this manner, a patient  348  (see FIGS. 10A-10D) supported on the top  323  air bags  322  and  328  can be alternately rocked from one side of the bed frame  12  to the other. To accomplish that rocking, air bags  322  and  328  are inflated to a desired pressure by activation of the switches  349 ,  350  and  351  on control panel  346  (see FIGS.  1  and  14 ). When switches  349 ,  350  and  351  are activated, the valves  128 ,  132 , and  136  are opened by movement of the plugs  140  along the shafts  139  of motors  138 . Switch  352  functions in similar fashion and opens valves  130  and  134 , the switches  349 ,  350  and  351  being used, along with switches  353 ,  354  and  355 , to adjust the air pressure in the air bags under the head, back and seat, and leg and feet portions of the body of patient  348 . Deflate switch  356 , like inflate switch  352 , closes valves  130  and  134 , reducing the air pressure in air bags  322  and  328  simultaneously. Once the desired pressure is reached, the patient  348  rests in the position shown in FIG.  10 D. The rotate switch  357  is then activated, causing patient  348  to roll toward one side of bed frame  12  as microprocessor  240  (see FIGS. 12,  13  and  15 - 20 ) directs the closing of the valve  130 . When patient  348  reaches the desired point, shown in FIG. 10A, the operator has the option of activating pause switch  358  and adjusting the air pressure in the air bags which receive air from valves  128  and  130  by operation of switches  350  and  354  to open or close valve  128 . Rotate switch  357  is then activated to cause patient  348  to roll back toward the other side of bed frame  12  as valve  130  opens and valve  134  closes under direction of microprocessor  240 . When patient  348  reaches the position shown in FIG. 10C, the operator has the option of activating pause switch  358  and adjusting the air pressure in the air bags which receive air from valves  134  and  136  by operation of switches  351  and  355  to open or close valve  136 . Rotate switch  357  is then activated and patient  348  will continue rocking until rotation is once again interrupted. Patient  348  is rocked from the position shown in FIG. 10D to the position shown in FIG. 10C (or  10 A) in approximately one minute. Pause switch  358  can be activated at any time during rotation of patient  348 , and activation of any of the switches  352 ,  356  or  357  de-activates switch  358 . 
     The hump  330  in air bags  328  provides a longitudinal barrier along the top surface of the air bags  328  such that one of the legs of patient  348  is retained on either side of the longitudinal barrier created by the humps  330  even during the alternating inflation and deflation of the bags  328 . In this maimer, the hump  330  prevents patient  348  from rolling too far to one side of the bed frame  12  or the other. Further, the legs of patient  348  do not slide and/or rub together while patient  348  is being alternately rolled from one side of the bed frame  12  to the other. It will be understood by those skilled in the art that the air bags  328  having the humps  330  therein can be replaced by air bags  322  or air bags  58  depending upon the type of therapy and the extent of motion desired for a particular patient. 
     Referring now to FIGS. 15-20, the programming of microprocessor  240  will be discussed. As shown in FIG. 15, the initialization of the program is at  242 . Variable memory is cleared at step  244 . Before internal or external interrupts are enabled, all RAM variable contents are zeroed and those requiring specific data are initialized at step  246 . Data and direction registers for the four eight bit ports of microprocessor  240  are then initialized at step  248 . 
     The control software then idles in loop  250  until it receives a 50 millisecond interrupt from the hardware interrupt timer internal to microprocessor  240 . Microprocessor  240  then sequentially executes the subroutines  252 ,  254 ,  292  and  316 , diagramed in FIGS. 16-19. General timer subroutine  252  (see FIG. 16) decrements most of the software driven timers contained in the ROM, including the bed motor “ON” run time limit timer, the electrically alterable ROM power on delay before erase timer, the cardiopulmonary switched “OFF” to the audible alarm “ON” delay timer, the audible alarm silence timer, and the front panel status pilot light blink timer. General timer subroutine  252  is entered from FIG. 15 at connector  253 , and each of the timers is assigned a number at step  255  and processed using a repeated algorithm in which, if the time value is zero at  258 , no action is taken. If the timer value is not zero, the timer is decremented at step  260  and again checked for a value of zero at  262 . If zeroed, the specific timer function is executed at  264 , otherwise the subroutine advances to the next timer for similar processing by comparing the timer number to a limit number at step  266  and incrementing the timer number at step  268  if the timer number does not correspond to the limit number. The general timer subroutine  252  is then exited when the last timer has been processed, and connects back into the control software at  270  (see FIG.  15 ). 
     The switch processing subroutine  254  is diagramed in FIG. 17, and monitors the status of the switches on control panel  348  the switches  226  and  228  in air box  124 , the contacts of thermostat  194  (see below), the status of the switches (not shown) of head control  361  (see FIG.  14 ), and pressure sensor pad switch  231 . Switch processing subroutine  254  is entered from FIG. 15 at connector  272 , assigns a number to each input at step  274 , and processes each numbered input in loop fashion. Each input is tested for status at 50 millisecond intervals at step  276  although it will be understood by those skilled in the art who have the benefit of this disclosure that other time intervals may likewise be appropriate for testing the status of the inputs. Switch status is tested by comparing the current switch status with the status of the switch from the last test at step  278 . If a change is detected, a switch bounce condition is assumed and the switch number is incremented at step  280  for processing the next switch input. If a change from the prior switch status is not detected, a switch position change test is made at step  282  and the appropriate action is taken at step  284  if a switch change is detected. If the switch status is consistent through three successive tests, no switch position change is indicated and the switch number is incremented at step  280  as described above. Switch number is compared to a limit number at step  286 , and if less then that limit number, the above processing is repeated in loop  288  for the incremented switch number. Switch processing subroutine  254  is exited when the last switch number has been processed and connects back into the control software at  290 . 
     The rotation subroutine  292 , diagrammed in FIG. 18, converts bed rotation commands from control switches  352 ,  356  and  357  (see FIGS. 1 and 14) into air valve motor function request commands. Rotation subroutine  292  is entered from FIG. 15 at connector  294 . There are five paths which can be followed by rotation subroutine  292  depending upon the status of the rotation valve sequence selected by the operator, which is tested at step  296 . If no rotation command has been selected, or if pause switch  358  was activated, subroutine  292  is exited through connector  298  back into the control software (FIG.  15 ). If switch  352  is activated, the motors  138  of valves  130  and  134  are requested to open the valves fully and the status of the timer of the valve motors  138  is tested to determine whether the requisite period of time has passed to accomplish the result at step  300 . If the requisite period of time has passed, the motors  138  of valves  130  and  134  are turned off at step  302  and subroutine  292  is exited. If the requisite period of time has not passed, the rotation timer is decremented at  304  and subroutine  292  is exited. If deflate switch  356  is activated, the motors  138  of valves  130  and  134  are requested to close the valves fully and the status of the timer of the valve motors  138  is tested to determine whether the requisite period of time has passed to accomplish that result at step  306 . If the requisite period of time has passed, the motors  138  of valves  130  and  134  are turned off at step  308  and subroutine  292  is exited. If the requisite period of time has not passed, the rotation timer is decremented at  304 ˜ and subroutine  292  is exited. If rotate switch  357  is activated, valves  130  and  134  are requested to alternately open and close under timer control and the rotation mode timer status is tested at step  310  to determine whether the time has expired, in which case the timer is incremented to the next timer mode at step  312  and the mode timer is initialized at  314  before exiting subroutine  292 . If the requisite period of time has not expired, the rotation timer is decremented at  304  and subroutine  292  is exited. 
     The valve motor subroutine  316 , diagrammed in FIG. 19, converts valve motor movement commands generated by the switch processing and rotation subroutines  254  and  292 , respectively, in the valve motor operations, i.e., starting, braking, coasting, and reversing each of the motors  138  used to open and/or close valves  128 ,  130 ,  132 ,  134 , and  136 . Valve motor subroutine  316  is entered at connector  318 . Each motor  138  is assigned a number at step  320  and is tested for its requested status, i.e., run or stop, and direction as compared to its current status at step  370 . Whenever a running motor is requested to stop, the status of that motor is tested at step  372 , and if stopped or stopping, the brake timer is tested at step  374  to determine whether the brake timer is zeroed. If the brake timer is not zeroed, the brake timer is decremented at step  376  and tested again at step  378  to determine whether the brake timer is zeroed. If so, the brake is released at step  380  and the number assigned to that motor  138  is compared to the limit number at step  382  to determine whether that motor  138  is the last motor. If the status of the motor  138  is running at step  372 , the motor  138  is turned off and the brake set at step  388 , and timer is then initialized at step  390 . If the motor  138  is not the last motor, the motor counter is incremented at step  386  and the above processing repeated. 
     Referring again to step  370 , if the requested status of the motor  138  tested is that the motor  138  is to run, the current motor status is tested at  392 . If the status of the motor  138  being tested is that the motor  138  is stopped or stopping, the requested status and the current status of the motor are compared to determine whether they are the same at step  394 . If the requested status and the current status are not the same, the brake timer is tested to determine whether the brake timer is at zero at step  396 . If the brake timer is not zeroed, the brake timer is decremented at step  398  and the number assigned that motor  138  is tested at step  382  to determine whether that motor  138  is the last motor. If motor  138  is not the last motor, the motor timer is decremented at step  386  and the above processing repeated. If the brake timer—is zeroed at step  396 , the direction of rotation of motor  138  is reversed at step  400 , motor  138  is turned on at step  402 , the motor run timer is initialized at step  404 , and the number assigned to that motor  138  is tested at step  382  to determine whether that motor  138  is the last motor. If motor  138  is not the last motor, the motor timer is decremented at step  386  and the above processing repeated. If the requested status and the current status are the same at step  394 , motor  138  is turned on at step  402 , the motor run timer is initialized at step  404 , and the number assigned to that motor  138  is tested to determine whether that motor  138  is the last motor. If motor  138  is not the last motor, the motor timer is decremented at step  386  and the above processing repeated. 
     Returning to step  392 , if the current status of motor  138  is that the motor  138  is running, the requested status and the current status are compared at step  406  to determine whether they are the same. If requested and current status are not the same, motor  138  is switched off and the brake is set at  388 , the brake timer is initialized at step  390 , and processing continues as described above. If the requested and current status of motor  138  are the same, the motor run timer is tested at step  408  to determine whether the run timer is zeroed. If the run timer is not zeroed, the motor run timer is decremented at step  410  and tested again at step  412  to determine whether the run timer is zeroed. If so, motor  138  is turned off at step  414  the number assigned to motor  138  is compared to the limit number at step  382  to determine whether motor  138  is compared to the limit number at step  382  to determine whether motor  138  is the last motor, and processing continues as described above. If the run timer is zeroed at step  408  or  412 , the number assigned to motor  138  is compared to the limit number at step  382  to determine whether motor  138  is the last motor and processing continues as described above. 
     A power fail interrupt subroutine  416 , diagrammed in FIG. 20, writes certain controller configuration parameters such as blower and rotation mode status in the electrically alterable ROM in the event of a power failure or when low air loss bed  10  is unplugged. Power-fail interrupt subroutine  416  is entered upon receipt of an interrupt from an external hardware interrupt (not shown). If the electrically alterable ROM power on delay before erase timer (EEROM timer) tested at step  418  is zeroed, low air loss bed  10  has been powered on for more than a few seconds such that the electrically alterable ROM is available for writing, and the aforementioned parameters are stored to memory at step  420  and the EEROM timer is initiated at step  422  before returning to the codes before the interrupt at step  424 . If the EEROM timer is not zeroed at step  418 , low air loss bed  10  has probably just been powered on and the memory is not available for writing. Should the control software (see FIG. 15) receive a power interruption that generates the power fail interrupt and performs the memory write but does not actually interrupt power to the control software, power fail interrupt subroutine  416  initializes the EEROM timer and will be available to rewrite the memory after the EEROM timer has once again timed out. 
     As noted above, the frame  12  is hinged at  44 ′,  44 ″ and  44 ′″, allowing the baseboards  46  and  52  to be raised from the horizontal, changing the angle of inclination for the comfort of  348  patent or for therapeutic purposes. However, especially when head baseboard  52  is raised, the deviation from the horizontal places a disproportionate amount of the weight of patient  348  on the air bags  322  over the legs  48  and seat  50  baseboards. In a presently preferred embodiment of the present invention, there are only three air bags  322  mounted on each of the baseboards  48  and  50 , such that a great proportion of the patient&#39;s weight, which is spread out over more than 20 of the air bags  58 ,  322  and  328  when the sections  14 ′,  14 ″,  14 ′″ and  14 ″″ are all in the same horizontal plane, is concentrated onto as few as six of the air bags  322 . A pressure sensor pad switches  231  are placed flat on legs baseboard  08  and seat baseboard  50  so that, in the event a portion of the patient&#39;s body contacts either one of those switches  231 , action can be taken to boost the air pressure in the air bags  322  mounted to seat baseboard  50 . For instance, in a presently preferred embodiment, the above-described buzzer is activated by contact with either of the pressure sensor pad switches  231 , the alarm buzzer is silenced by activating switch  347 , and the air pressure in air bags  322  mounted to seat baseboard  50  is raised by activation of switches  350  and  351 . Those operations can also be programmed directly into microprocessor  240  such that the alarm buzzer is unnecessary because correction of the air pressure in those air bags  322  is automatic when, for instance, a patient&#39;s yhead and upper body is raised by activating switch  233  (see below). 
     Referring to FIGS. 1,  4 ,  6 , and  9 B, air chucks  212  are provided in the dump plate  150  which communicate, in airtight sealing relationship, to the opening in each of the couplers  153  of valves  128 - 136 . Using these air chucks  212  as a take off point for air pressure lines  213  and corresponding air pressure gauges  241  (see FIG.  1 ), the pressure in each sealed bed frame supply hose  174 - 182 , and hence, in each set of air bags  58 ,  59 ,  321 ,  322 ,  325  and/or  328  can be checked and the appropriate valves  128 - 136  adjusted to give a desired air pressure in an individual set of air bags  58 ,  59 ,  321 ,  322 ,  325  and/or  328 . Gauges  241  are enclosed within case  243  which can be releasably mounted to head or foot boards  20  or  21 , respectively by J-brackets  245 . 
     Referring to FIG. 12, there is shown a schematic electrical diagram of a low air loss bed constructed according to the teachings of the present invention. Alternating current enters the circuitry in electric cord  218 , which is connected to power distribution board  219 . Power distribution board  219  includes a power supply module  220  to supply power to microprocessor  240  through cable  222  and solid state relays to control each of the blowers  108  and heater strip  172 . Power distribution board  219  provides power to the motors within boxes  45  for raising, lowering and positioning the frame  12  of low air loss bed  10  by means of lead  223  which connects to junction box  224 . Power distribution board  219  also powers the electric motors  114  of blowers  108 . Each of the blowers  108  is provided with a capacitor  236 , and a pilot light  221  is provided on control panel  348  (see FIG.  13 ). Switches  192  are provided on control panel  346  for activation of each blower  108 . 
     Referring to FIG. 13, the sensor (not shown) of thermostat  194  is located in seat manifold  80 , and when the circuit containing thermostat  194  is closed due to the temperature of the air in seat manifold  80 , heating strip  172  is switched on by microprocessor  240 . Thermostat  194  also includes a control  189  for adjustment of the temperature of the gas in seat gas manifold  80 , and switch  191  on control panel  346  can be used to activate or deactivate the heating function. 
     Limit switches  226  and  228  are provided in manifold plate  145  and on full inflate plate  144 , respectively (see FIGS. 4,  8 ,  9 A and  13 ). Limit switch  226  is closed when push button  230  is engaged by dump plate. When push button  230  is disengaged by the movement of dump plate  150  away from manifold plate  145  under the influence of levers  165 , the circuit is opened and blowers  108  are shut off. Limit switch  228  is affixed to full inflate plate  144  by screws  232 , and the circuit is open when lever arm  234  engages manifold plate  145 . When full inflate plate  144  is opened under the influence of full inflate knobs  193 , limit switch  228  is closed, activating the buzzer which is incorporated into microprocessor  240 . A switch  347  is provided on control panel  346  to silence that buzzer. 
     Control panel  346  is connected to controller  198  by ribbon connectors  200 . Controller  198  includes microprocessor  240  and the other necessary circuitry. Controller  198  is provided with plug-type receptors  205  for receiving the plugs  207  of cables  108 ,  211 ,  225 ,  227  and  229 . 
     Cable  208  connects controller  198  to thermostat  194  and the pressure sensor pad switches  231 . Cable  211  connects directly to power distribution board  219  and feeds power to controller  198  while conducting control signals to power distribution board  219  to control the functions of blowers  108  and heating element  72 . Cable  170  is provided with separate wires  189   i  and  186   o  for each motor  138  and plug  225  at other end from plug  207  which engages the connector  166  in the wall of air box  124 , thereby conducting low voltage D.C. current to each of the motors  138  by wires  189   i  and  189   o . Cable  170  is also provided with separate wires  226   i  and  226   o  and  228   i  and  228   o  connecting separately to limit switches  226  and  228  respectively. 
     Cable  227  is provided with plugs  359  and the other end from plug  207  for engaging a complementary plug  360  on a separate hand control  361  which duplicates the function of switches  349 - 358  on control panel  346 . Hand controls  361  are shown schematically in FIG. 14 because they are similar in construction and circuitry to that portion of controller  198  and keyboard  346  which functions are duplicated. Plugs  359  are provided on both sides of bed frame  12  (not shown in FIG. 14) to facilitate easy access to the board for adjustment by hospital personnel. 
     Cable  229  is provided with plugs  362  and  363  at the other end from plug  207  for engaging complementary plugs  364  and  366 , respectively. Plug  364  is located in the circuitry of the board frame  12  in circuit box  43  (see FIG.  7 ), shown schematically at box  367 . Plug  366  is located on a hand control, shown schematically at  368 , which duplicates the function of switches  233  and  235 - 239  on control panel  346 . When hand control  368  is used to adjust the angle of inclination of head and foot baseboards  54  and  46 , respectively, signals generated by activation of the switches (not shown) on hand control  368  are transmitted directly to the circuitry  367  of bed frame  12 . 
     Although the present invention has been described in terms of the foregoing preferred 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.