Abstract:
A system and method for maintaining an air inflation mattress configuration sufficient for patient support and comfort. Infrared illumination levels are measured within individual or groups of inflated mattress chambers. A staggered approach to illumination monitoring of chambers or sections to eliminate crosstalk between the infrared sensors is carried out. Distributed microprocessor controllers established in a network configuration utilizing controller network protocols reduces the wiring and connections necessary for the assembled system. Various mattress cushion construction techniques, such as sewing and or RF welding methods, are used for the creation of individual chambers utilizing specific types of IR translucent, transparent or reflective materials. The construction of the cushions and bladders in the system includes the use of various types of fabrics with low to high air loss qualities as required. The overall mattress assembly, including the control systems and the methodologies associated with such control systems, provide a unique approach to the maintenance of a consistently comfortable patient support surface. The use of a handheld unit for both programming the system and downloading information about the operation of the system is also anticipated. The specific cushion construction designs associated with the head, body, and foot cushion components of the mattress are tailored to operate specifically with the control capabilities (sensors and air flow regulators) of the invention.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation of currently pending U.S. application Ser. No. 11/355,679 filed Feb. 15, 2006, which claims the benefit of U.S. provisional Application No. 60/653,303, filed Feb. 16, 2005, the entire disclosures of which are each incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to therapeutic beds and mattress systems and methods for maintaining their function. The present invention relates more specifically to improved systems and methods for controlling the configuration and characteristics of an inflatable air mattress utilizing an array of networked sensors and control modules. 
   2. Description of the Related Art 
   A number of problems are associated with inflatable air mattresses used in medical settings. Some such air mattresses are designed for therapeutic use and include high and low air loss fabric enclosures as well as control systems that alter the air pressure within the mattress in order to help reduce the occurrence of bed sores and similar detrimental effects of a long term bedridden condition. While in general air mattresses must be sufficiently firm to support a patient, they must also be sufficiently soft and resilient so as to be comfortable for the patient. Likewise, when therapeutic variations in the pressure within the air mattress are implemented, it is often difficult to maintain the elevation of the patient off a mattress base over the entire surface of the mattress. If, for whatever reason, the patient makes contact through the mattress surface with the more rigid mattress base, the result is the undesirable and uncomfortable occurrence that is referred to as “bottoming”. 
   Control systems designed to maintain the inflation of therapeutic mattresses and the like must take into account significant variations in the force that a patient may exert on any single point in the mattress surface in addition to the overall force exerted by the weight of the patient across the mattress surface as an average. Point forces are generally experienced when a patient enters or exits the bed and directs their hands or feet, elbows or knees, into the mattress at a single localized point. In general, control systems that rely strictly on measurements of the pressure within an inflatable mattress fail to prevent the “bottoming” of the patient under a number of situations. 
   Some efforts to address the maintenance of mattress configuration involve the use of an increasing number of individual inflatable cells; any one of which may experience a large localized force, but with adjoining cells that would support the patient and prevent the “bottoming” from occurring. The problem with mattresses that utilize increased numbers of individual cells is that each cell must be individually connected to the inflation system and individually monitored by whatever control electronics might be put in place. Such mattresses would typically have extensive and quite complex air and electrical conduits running down and through the length of the mattress that individually address each of the inflation and control systems associated with the inflatable platform. The size, expense, complexity, and maintenance of such systems all become significant. 
   U.S. Pat. No. 6,560,804 issued to Wise et al. entitled System and Methods for Mattress Control in Relation to Patient Distance (Assignee KCI Licensing, Inc.) describes a system and method for detecting and monitoring the distance between a patient and a reference point on an inflatable air mattress and for controlling the air supply based upon changes in such distance. The devices for monitoring the patient distance include a heterodyning proximity detector, a force responsive distance sensing device, and a light responsive sensing device. The disclosure of U.S. Pat. No. 6,560,804 is incorporated herein in its entirety by reference. 
   Various other efforts have been made in the field to maintain the inflation of an air inflatable mattress at a particular height in order to maintain patient comfort. 
   SUMMARY OF THE INVENTION 
   The system of the present invention incorporates a number of unique system features and individual elements that together provide an overall system and method for maintaining an air inflation mattress configuration sufficient for patient support and comfort. While the overall system of the present invention is unique, there are additional individual components, elements, and methodologies associated with the system that are likewise unique and solve certain problems found in the prior art. In general, the disclosure that follows will focus on the following unique features and elements in the invention: 
   (1) The use of infrared illumination within individual chambers or groups of chambers. 
   (2) The staggered illumination and monitoring of alternating chambers or sections to reduce crosstalk between the infrared sensors. 
   (3) The use of distributed microprocessor controllers established on a network configuration utilizing network protocols in order to reduce the wiring and connections necessary for the assembled system. 
   (4) The use of various cushion and bladder construction techniques such as sewing and/or RF welding methods for the creation of individual chambers utilizing specific types of IR translucent, transparent, or reflective materials. 
   (5) The use of certain Gore-Tex® type fabrics with low air loss qualities in the construction of various components within the mattress system. 
   (6) The overall mattress assembly, including the control systems and the methodologies associated with such control systems and its overall ability to improve the maintenance of an appropriate inflation profile. 
   (7) The use of a handheld wireless communication unit for uploading and downloading data, programming the system, and downloading information about the operation of the system. 
   (8) Specific cushion construction designs associated with the head, body, and foot cushion components of the mattress that facilitate the operation of the sensor and controller components of the system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic block diagram of the air flow components, conduits and connectors associated with implementation of the present invention. 
       FIG. 2  is a schematic block diagram of both the primary air flow connections as well as the primary electronic signal connections for the overall system of the present invention. 
       FIG. 3  is a detailed (system level) electronic schematic diagram of the mattress block diagram and sensor signal components of the present invention. 
       FIG. 4  is a detailed (controller level) electronic schematic block diagram of the mattress controller of the present invention and its associated drivers and inputs. 
       FIG. 5  is a detailed (controller level) electronic schematic block diagram of the stepper valve controller (cushion control) components of the present invention. 
       FIG. 6  is a perspective view of the underside of the controller interlayer of the mattress system of the present invention. 
       FIG. 7  is a plan view of the underside of the controller interlayer of the mattress system of the present invention. 
       FIG. 8  is a detailed perspective view of the mattress controller enclosure of the system of the present invention. 
       FIG. 9  is a detailed perspective view of a stepper valve (cushion) controller enclosure of the system of the present invention. 
       FIGS. 10A &amp; 10B  are perspective views (top and bottom) of the body cushion mattress component of the system of the present invention. 
       FIGS. 11A &amp; 11B  are perspective views (top and bottom) of the foot cushion mattress component of the system of the present invention. 
       FIGS. 12A &amp; 12B  are perspective views (top and bottom) of the head cushion mattress component of the system of the present invention. 
       FIG. 13  is an exploded perspective view of an alternative embodiment of the body cushion mattress component of the system of the present invention showing placement of IR reflective surfaces. 
       FIG. 14  is a detailed plan view of an IR receiver/transmitter (i.e., sensor/emitter) component of the system of the present invention. 
       FIG. 15  is a schematic cross sectional view of the mattress, sensor and control components of the system of the present invention. 
       FIG. 16  is a perspective view of the installation of the system of the present invention on a typical hospital bed frame. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An overview of the system of the present invention may be discussed by reference to the schematic drawing shown in  FIG. 1 . In this overview of the system, the mattress components are shown in relation to and interconnected with the various control components of the system. In various embodiments, blower box  10  can be comprised of a blower fan  12  that incorporates a dust filter  14  on its intake and an output that incorporates a pressure transducer  16  and passes through a heater unit  18  before being passed into the conduits of the system. The output of the blower box  10  is established through hose connector  20  that incorporates a manifold of air connections as well as electrical connections (not shown) in the same connector unit (described in more detail below). In various embodiments, hose connector  20  can be single piece or multi-piece connector and can include a number of components, such as springs, latches, and the like. Hose connector  20  mates with and connects to distribution block  22 , which distributes the air flow from blower box  10  through three separate conduits. A first conduit  24  is connected to two proportional control valves  26  and  28  that are associated with the body cushion  30 . A second conduit  32  is connected to proportional control valve  34  associated with head cushion  36 , as well as proportional control valves  38  and  40  associated with foot cushion  42 . Each of the proportional control valves mentioned is connected to its respective cushion by means of quick release connector  44 . 
   Head cushion  36  is a single chamber unit (e.g., a single inflatable chamber) as is described in more detail below. The single chamber is connected by way of a quick release connector  44  to proportional control valve  34 . Body cushion  30  is a multi-chamber unit (e.g., dual inflatable chambers) having interleaved chambers for alternating the pressurized air chamber for therapeutic purposes. Each of the two separate chambers is connected by way of a quick release connector  44  to the respective proportional control valves  26  and  28 . Foot cushion  42  is a multi-chamber unit (e.g., dual inflatable chambers) structured much the same as body cushion  30 , and incorporates two interleaved chambers that are individually connected by way of quick release connectors  44  to their respective proportional control valves  38  and  40 . The specific construction of each of the cushion components of the system of the present invention is described in more detail below. 
   The control of the air pressure within head cushion  36 , body cushion  30 , and foot cushion  42  is described in greater detail herein below and forms part of the basic structure and functionality of the present invention. In general, however, these three cushion components are maintained in an inflated condition by the electronic control of proportional control valves and/or blower speed control under the operation of microprocessors or microcontrollers which include computer executable instructions, e.g., program instructions and/or algorithms that include therapeutic air inflation pressures and regimens, in addition to being connected one to another by way of a digital signal network. 
   In various embodiments, a third air conduit can be provided. In embodiments having the third air conduit, such as the embodiment shown in  FIG. 3 , the air conduit leaves from distribution block  22  to carry the flow of air to the remaining bladders associated with the mattress system of the present invention. This air conduit  46  is split between two conduits  48  and  50 . Conduit  48  passes to a stepper actuated directional control valve  52  that alternately inflates and deflates turning bladders  54  and  56 . Directional control valve  52  is operated by means of stepper motor  51 . Air is distributed from directional control valve  52  through two conduits  58  and  60 , which pass through manual CPR release block  62  which is monitored by CPR switch  61 . Each of conduits  58  and  60  incorporate pressure transducers  64  and  66  and quick release connectors  44  as they pass into their respective turning bladders  54  and  56 . The inflation of turning bladders  54  and  56  is generally accomplished in alternating fashion and is controlled by the directional control valve  52  so as to inflate one turning bladder and deflate the second turning bladder in a manner that rotates the patient to one side or the other. The orientation of the turning bladders lengthwise along the mattress system, as described in more detail below, makes this turning process possible. 
   Referring again to  FIG. 1 , in various embodiments, air conduit  50 , extending from distribution block  22  by way of air conduit  46 , can pass through an activation solenoid  68  and thereafter pass through CPR release block  62 . From release block  62  air conduit  50  continues through a pressure transducer  70  and through a quick release connector  44  before finally serving to inflate MRS (mattress replacement system) bladder  72 . MRS bladder  72  is provided with a vent to atmosphere by way of solenoid  74 . In various embodiments, a foam cushion or mattress can be implemented and can replace the MRS  72  and its associated components. In such embodiments, components such as air conduit  50  for example, can be removed. 
   The blower box  10  described above is generally incorporated into a user interface unit that mounts on the footboard of the bed on which the mattress system of the present invention is placed. In this user interface unit are contained some of the electronics associated with the programming and operation of the system, e.g., controller area network (CAN) nodes and other circuitry. Reference is now made to  FIG. 2  for an overview of the control components associated with the system of the present invention and duplicates in part the overview pneumatic diagram described above with respect to  FIG. 1 . In  FIG. 2 , blower box  10  is again seen to include blower fan  12 , which ultimately (albeit through a number of other manifold connectors not shown in this diagram) serves to provide the inflation air to left turning bladder  54 , right turning bladder  56 , foot cushion  42 , body cushion  30 , head cushion  36  and MRS bladder  72 . The electrical connections shown in blower box  10  include the electric power necessary to run heater  18 , which serves to warm the air after it passes out of the blower fan  12  as well as connections to a data I/O device  101 , e.g., a user data interface (UDI), graphical user interface (GUI), among others, which in the preferred embodiment includes an LCD display having touchscreen functionality. Otherwise, the electrical/electronic connections from user interface  100  are shown as including a power connection  102  and a communications connection  104 . As indicated above, these electrical/electronic connections are maintained through the same hose connector assembly  20  discussed above, and thereby form the electrical/electronic connection from the blower box to the mattress assembly. 
   The mattress assembly  105  itself incorporates a mattress controller  106  which receives both power and communication signals from user interface  100 . The same power and communication lines are in turn relayed to stepper valve controllers associated with each of the three cushion components of the mattress system of the present invention. These controllers are established as “network nodes” and include stepper valve controller  108  (associated with the foot cushion  42 ), stepper valve controller  110  (associated with body cushion  30 ) and stepper valve controller  112  (associated with head cushion  36 ). Each of these stepper valve controllers is directly connected to both the infrared receivers associated with the cushion to which it is attached, as well as the control valves that direct the inflation of that cushion. Stepper valve controller  108 , for example, receives signal from infrared receiver  114  and thereby controls valves  38  and  40  to maintain the appropriate inflation of foot cushion  42 . Likewise, stepper valve controller  110  is associated with infrared receivers  116 ,  118 ,  120 , and  122  as well as control valves  26  and  28 , each associated with body cushion  30 . Finally, stepper valve controller  112  is associated with infrared receiver  124  and control valve  34 , which are each associated with head cushion  36 . The networked structure of this chain of controllers makes it possible to add additional controllers at connector  113 , which can be positioned at various locations including the stepper valve controllers  108 ,  110 , and  112 , as may be required by alternative cushion structures and functionality. 
   Referring further to  FIG. 2 , left turning bladder  54  and right turning bladder  56  are each controlled from the mattress controller  106  by means of the programmed operation of directional control valve  52  shown in split configuration in  FIG. 2 . Likewise, the inflation of MRS bladder  72  is controlled by way of mattress controller  106  by means of the programmed operation of MRS clamp solenoid  68  and MRS vent solenoid  74 . In the preferred embodiment, the inflation of the MRS bladder may be varied to help establish the firmness of the overall mattress system while the turning bladders may, of course, be varied to accomplish the turning function described above. As discussed above, in some embodiments, a foam type cushion or mattress can be implemented and thus, in such embodiments, the mattress controller would not be utilized to control the foam mattress. 
   In various embodiments, the mattress controller can include a number of different configurations. For example, the mattress controller can include an MRS vent solenoid in embodiments that utilize the MRS bladder, as discussed herein. Reference is now made to  FIG. 3  which shows in greater detail the controller network of the control interlayer for the mattress system of the present invention. Mattress controller  106  is shown having direct control connections to the stepper actuated directional control valve  52  associated with the turning bladders, as well as the MRS vent solenoid  74  and the MRS clamp solenoid  68 . Likewise, mattress controller  106  serves to power (and illuminate) each of the infrared transmitters (six in the preferred embodiment)  130 ,  132 ,  134 ,  136 ,  138 , and  140 . These IR transmitters are IR light emitting diodes (LEDs) in the preferred embodiment and are operated in concert at the indicated 3 KHz signal frequency. Other frequencies are contemplated. Mattress controller  106  likewise receives input signal data from an angle sensor input  142 , a temperature sensor input  144 , and side rail position sensors input  146 . A manual CPR switch  148  is associated with CPR release block  62  described above. A pressure-in connection  150  receives pneumatic air pressure measurements from pressure gauge  16  described above. 
   In various embodiments, mattress controller  106  forms a base network node for network connection  152  that includes the network transmission and receive signal lines as well as power voltage and return lines. This network connection  152  is distributed through to each of the stepper valve controllers mentioned above as network nodes  108 ,  110  and  112 . These microcontrollers, again acting as nodes on the local network, individually receive input from the infrared receivers  114 ,  116 ,  118 ,  120 ,  122 , and  124  associated with foot cushion  42 , body cushion  30 , and head cushion  36 , respectively. In turn each of these controllers operates and controls the stepper motors connected to the proportional control valves described above. These stepper motors include stepper motor  126  associated with control valve  40  of foot cushion  42 , stepper motor  128  associated with control valve  38  of foot cushion  42 , stepper motor  130  associated with control valve  28  of body cushion  30 , stepper motor  132  associated with control valve  26  of body cushion  30 , and finally stepper motor  134  associated with control valve  34  of head cushion  36 . 
   Each of stepper valve controllers  108 ,  110  and  112  are programmed controllers that are capable of independently maintaining the appropriate inflation of their respective cushions without relying on the network connection to the mattress controller  106  or to the connection back to the user interface unit  100 . Each stepper valve controller acts as a network node in accordance with a CAN (controller area network) protocol as described in more detail below. This network structure serves to improve operation of the system as a whole and provides a highly efficient maintenance of the appropriate inflation of the mattress system components, even in response to movement by the patient that might otherwise result in “bottoming” through the mattress cushions. Each of the microcontrollers in the described preferred embodiment of the present invention may be satisfied by an H8/3687N type microcontroller IC or its equivalent. In various embodiments, the network structure can include a variety of CAN nodes, configurations, and protocols. In some embodiments, each of the stepper valve controllers and other controllers (e.g., mattress controller, and various valve controllers, among others) can be uniquely identified as nodes on the network by way of the indicated address jumpers. In other embodiments, nodes can be dynamically addressed. In some embodiments CAN nodes can be connected in a specific order and addressed in a specific order. For example, in one embodiment, CAN nodes can be connected in the following order: GUI (Network Supervisor), Blower Controller (BC), Mattress Controller (MC), Foot Valve Controller (FVC), Body Valve Controller (BVC), and Head Valve Controller (HVC). As one of ordinary skill in the art will appreciate, the various controllers can include similar controllers having the same or similar functions, and should not be limited to those described above. For example, the blower controller can include any controller that controls a rate of air flow from a blower, fan, or other source of pressurized fluid. In various embodiments, dynamic addressing can begin with a broadcast message sent on the network by the GUI node requesting all nodes to prepare for dynamic addressing. When a node receives this message, the node replies with a node identification message, which is an identification number given to each type of board. For example, in various embodiments, a BC node can have an identification number of 1, the MC node can have an identification number of 2, and a VC node can have an identification number of 3. The GUI node assigns a network address to each node that returns an identification number. In some embodiments, a sequential power-up sequence can also be implemented with the dynamic addressing process. For example, in some embodiments, when dynamic addressing begins, power is supplied to the GUI, BC, MC, and FVC nodes. After the BC, MC, and FVC nodes power up and get addressed, the FVC node relays power to the BVC node, which is the only valve controller (VC) node on the network without an address. The GUI will be able to differentiate it from the other VC nodes. Once the BVC node gets addressed it relays power to the HVC node and it is now the only VC node on the network without an address. Once the HVC node gets addressed the network is ready for normal use. 
     FIG. 4  provides further detail on mattress controller  106 , showing the microcontroller and its connection to the various inputs and outputs associated with the controller. Included as O/G inputs are the CPR switch connections  148 , the angle sensor connection  142 , the temperature sensor connection  144 , the pneumatic pressure sensor connection  150 , and the side rail sensor inputs  146 . The mattress controller circuitry shown in  FIG. 4  also incorporates a voltage regulator  160  for powering the operation of the microcontroller and each of the ancillary components. 
   The outputs of the microcontroller  106  include the 3 KHz wave form driver  162  that powers and drives the infrared transmitters in concert as discussed above. The microcontroller also includes output signals to control solenoid drivers  164  and  166  that direct the MRS vent and clamp solenoids respectively. Finally, the microcontroller  106  operates the stepper motor driver  168  that controls the stepper actuated directional control valve which inflates and deflates the turning bladders. As mentioned above, microcontroller  106  is connected to and forms a node on the CAN and the mattress controller unit maintains the CAN network protocol circuitry  170 , and the CAN transceiver circuitry  172 . 
   In various embodiments, the stepper controller can include a number of different configurations. For example, in some embodiments, the stepper controller can include one or more stepper driver circuits. In other embodiments, the stepper controller can include circuits for filtering, buffering, and gain. In some embodiments of the stepper controller, circuitry can be included or omitted which can be based on one or more desired functions to be elicited from the controller. In the embodiment illustrated in  FIG. 5  a detailed diagram of the typical stepper valve controller is provided. This diagram describes a typical example of one of the three stepper valve controllers positioned in association with each of the three cushions in the preferred embodiment of the mattress system of the present invention. Stepper valve controller  110  associated with the body cushion is used in this example as it utilizes four input data signals associated with four IR sensors. Inputs to microcontroller  110  include buffered and filtered inputs from each of the infrared sensors as shown. Buffer/filter circuits  180 ,  182 ,  184  and  186  condition the analog signals from the individual IR sensor devices for appropriate monitoring by the microcontroller. The stepper valve controller likewise incorporates a voltage regulator  202  for powering the components in the controller circuitry. 
   Outputs from the microcontroller  110  (as in each stepper valve controller) include output signals for the stepper driver circuits  188  and  190  for the two proportional control valves under the control of the particular stepper valve controller. Operation of these drivers is accomplished through a current monitoring system  192  and  194  that allows the microcontroller direct feedback on the condition or state of the two proportional control valves. As indicated above, each microcontroller has an address configuration circuit  196  set to distinguish it from the other controller nodes on the network. Each microcontroller circuit likewise includes CAN protocol circuitry  198  and CAN transceiver circuitry  200  to maintain communications over the network. 
   The CAN (Controller Area Network) is a serial bus system that was originally developed for automotive applications in the early 1980&#39;s. The CAN protocol was internationally standardized in 1993 as ISO 11898-1 and comprises the data link layer of the seven layer ISO/OSI reference model. CAN, which is now available from a large number of semiconductor manufacturers in hardware form, provides two communication services: the sending of a message (data frame transmission) and the requesting of a message (remote transmission request, RTR). All other services such as error signaling, and automatic re-transmission of erroneous frames are user-transparent, which means the CAN circuitry will automatically perform these services without the need for specific programming. 
   The CAN controller is comparable to a printer or a typewriter and CAN uses, such as in the present application, still must define the language/grammar and the words/vocabulary to communicate. CAN does, however, provide a multi-master hierarchy, which allows the building of intelligent and redundant systems which is, as mentioned above, a feature of particular importance in the operation of the inflation maintenance objectives of the present invention. If one network node is defective, the network is still able to operate. CAN also provides broadcast communication wherein a sender of information may transmit to all devices on the bus simultaneously. Thus, programming through the user interface of the present invention may be distributed to each of the controller nodes on the CAN in a manner that may effect a regimen alteration throughout the system. All receiving devices read the message and then decide if it is relevant to them. This guarantees data integrity because all devices in the system use the same information. CAN also provides sophisticated error detection mechanisms and re-transmission of faulty messages. 
   Reference is now made to  FIGS. 6 &amp; 7  for a description of the physical placements of the various control components identified and discussed above.  FIGS. 6 &amp; 7  show, in perspective and plan views respectively, the underside of the control interlayer that is incorporated into the mattress system of the present invention. These views reflect the positions of the indicated components as they would be seen if the mattress system were flipped over and the MRS bladder and turning bladders were removed (this overall structure is described in more detail below with respect to  FIG. 15 ). The controller interlayer is constructed primarily of flexible walled enclosure  210  surrounding a foam core  212  within which are positioned the various control components of the present invention. Mattress controller  106  is positioned as shown, as are stepper valve controllers  108 ,  110  and  112 . The stepper valve controllers are positioned so as to be proximate to the cushion component for which they are specifically responsible. All but one of the IR transmitters are shown in place and connected together in concert. IR transmitters  132 ,  134 ,  136 ,  138  and  140  are shown in place in  FIGS. 6 &amp; 7 . IR transmitter  130  has been removed to show the placement of IR transmitter window  131  positioned to receive placement of the transmitter on one side of controller  106 . 
   On an opposite side of the control interlayer are the IR sensors, or more specifically shown in  FIGS. 6 &amp; 7 , the IR sensor windows into the individual cushions, as described in more detail below. Sensor windows  115 ,  117 ,  119 ,  121 ,  123  and  125  are shown in  FIGS. 6 &amp; 7  positioned in association with their respective foot, body and head cushion components. Also associated with the appropriate cushion components are air flow inlet connectors  214  (associated with the head cushion), connectors  216  and  218  (associated with the body cushion) and connectors  220  and  222  (associated with the foot cushion). Manifold  22  is shown positioned to receive the single large air flow hose (not shown) to separate and distribute the air flow to three smaller conduits for subsequent distribution to the cushions and mattress components. In  FIGS. 6 &amp; 7  all air flow conduits have been removed for clarity. From manifold  22  two air flow conduits would connect with stepper valve controllers  108 ,  110  and  112  to provide the necessary air flow into the mattress cushions. A third air flow conduit connects from manifold  22  to mattress controller  106  where the necessary air flow is provided to the turning bladders and the primary MRS bladder as described above. 
   Also removed for clarity in  FIGS. 6 &amp; 7  are most of the electrical/electronic connections between the various control components. The exception to this is the 2-wire connection linking each of the IR transmitters together along one edge of the interlayer. In normal operation, a sixth IR transmitter  130  would be positioned over window  131  and would likewise be linked to the 2-wire circuit that is shown. Additional electrical/electronic connections between the components would be present as described above with respect to  FIG. 2 . In addition, the hardwired network connections between the controller enclosures, as shown and described in association with  FIGS. 3-5 , would also be present. 
   Reference is now made to  FIG. 8  for a brief description of the mattress controller  106  and its enclosure. Various electronics and electromechanical controls are included within the mattress enclosure controller. The air flow source is by way of conduit  46  which feeds conduit  48  and conduit  50 . Conduit  48  provides air flow to stepper actuated directional control valve  52  which is driven by stepper motor  51 . This provides the necessary air flow to the turning bladders by way of conduit connections  58  and  60 . 
   Conduit  50  provides air flow to solenoid valve  68  which in turn directs air flow out of the enclosure to the MRS bladder and to a vent through solenoid valve  74 . Each of the solenoid valves  68  and  74 , as well as directional control valve  52 , are electrically connected to PC board  230  on which the controller circuitry described above (for the mattress controller) is provided. The micro-controller IC is likewise positioned on PC board  230  and forms the core of the controller as a whole. The electrical/electronic connections discussed above are generally not shown in  FIG. 8  for clarity but would enter the enclosure through the ports, some of which can be water tight, shown on the sides of the enclosure. A lid (not shown) would complete the walled enclosure to generally seal it against fluids. 
   Reference is now made to  FIG. 9  for a brief description of a representative example of the stepper valve controllers that operate in conjunction with the mattress controller and provide the regulated air flow to the mattress cushions as described above. In  FIG. 9 , stepper valve controller  110 , which services the requirements of the body cushion  30  of the system, is shown as an example. It is understood that the remaining two stepper valve controllers would be either identical in structure or would comprise one-half of the operational components of the example shown. In this view, stepper motor driven proportional control valves  26  and  28  are shown. The source of air flow to the unit is shown on one side of the enclosure at “From  22 ”, indicating the source as coming from the manifold  22 . Outflow of air from the control valves is directed to body cushion  30  by way of the indicated connectors on the opposite sides of the enclosure. Each of the control valves  26  and  28  are electrically connected to PC board  240  on which the controller circuitry is provided. Here again, the electrical/electronic connections (wires) both within the enclosure and into and out of the enclosure are omitted for clarity. Control of the valve operation includes monitoring the rate of valve openings and closings in an effort to reduce overall valve noise associated with the operation of the system. In addition, control of the stepper motors involves monitoring of current as a means of error checking the control signal. The PC boards in the three stepper valve controller enclosures are essentially the same and are distinguished on the network as they are dynamically addressed during installation. Because of the distributed processing structure of the network of the system, it is possible to power-up and activate individual nodes/controllers on the system in progressive fashion. This greatly facilitates both initial implementation and subsequent maintenance of the system. A diagnostic mode of operation also facilitates these aspects of the distributed network. 
   Reference is now made to  FIGS. 10-13  for a description of the construction and configuration of the cushions associated with the mattress replacement system of the present invention.  FIGS. 10A and 10B  show the general construction of the body cushion  30  of the system of the present invention. As shown in  FIG. 1  above, body cushion is generally constructed with two interleaved chambers so as to provide alternating pulsation air flow into the cushion as a known therapy for bedridden patients. These chambers are constructed of generally box shaped channels that run parallel across the cushion. The topside view of body cushion  30  is shown in  FIG. 10A  and by way of the fabric seams shown, indicates the configuration of the interleaved channels. Air flow inlet connectors  216  and  218  are shown in  FIG. 10B  (a view of the underside of the cushion) where they would align with and connect to their corresponding connections on the control interlayer discussed above. 
   The construction of body cushion  30  is of any of a number of different high and/or low air loss fabrics that provide the airflow “outlet” for the air inflation system, as is generally known in the art. The cushion is generally constructed by sewing techniques “inside out” and is then turned “right side out” though an initially open section of the seam (shown in  FIG. 10A ). The mattress cushions of the present invention may be sewn as indicated above or may be RF (radio frequency) welded as is known in the art. The finished cushion is maintained in its position in the mattress replacement system by way of the indicated zippers (or similar attachment means) to corresponding zipper components (or similar attachment means) on the mattress replacement system enclosure material. 
     FIGS. 11A and 11B  disclose the construction of foot cushion  42  which, like body cushion  30 , is constructed of two interleaved chambers. Air flow connectors  220  and  222  are shown in  FIG. 11B  (the underside view of the cushion). The construction techniques for foot cushion  42  are the same as those described above for body cushion  30 . 
     FIGS. 12A and 12B  disclose the construction of head cushion  36  which differs from the construction of body cushion  30  and foot cushion  42 . Head cushion  36  is not designed to be subjected to an alternating chamber pressurization therapy and is therefore constructed of a single chamber with a single air flow inlet connector  214  shown in  FIG. 12B  (the underside view of the cushion). Parallel “channels” are still sewn or otherwise integrated into the cushion as shown in  FIG. 12A  for the purpose of maintaining the flat configuration of the cushion, but interior air flow between these “channels” is provided for, resulting in an integrated interior chamber. 
   Reference is now made to  FIG. 13  for a brief description of one manner of interior cushion construction that integrates IR reflective surfaces to facilitate the measurement of the IR illumination with the cushion by the IR sensors. In this example of cushion construction, cushion  250  is made up of fabric box envelop  256  and top surface  252  shown separated in this exploded view for clarity. The important distinguishing feature in this construction is the placement of IR reflective surfaces  254   a ,  254   b  and  254   c  (a variety of which are known in the art) on specific interior sides of the box shaped channels formed within the cushion. In this manner, discrete portions of the cushion become the focus of the IR illumination (thereby allowing the system to better identify the portion of the cushion that may require greater inflation) and help to prevent “cross-talk” between the IR illuminated sections of the cushion. These features, when combined with the manner of timed polling of the IR sensors discussed in more detail below, serve to provide a more accurate indication of the portion of the cushion that may require modified inflation pressures. Although the chamber construction of the cushion  250  shown in  FIG. 13  is somewhat different than the chamber construction shown in  FIGS. 10-12  the principle of IR reflective surfaces strategically placed on the interior walls of the box shaped channels is easily applicable. 
     FIG. 14  is a detailed plan view of a representative IR transmitter/sensor device of the system of the present invention. An objective in the design of the IR device is a single structure that may be configured to function either as the IR transmitter or the IR sensor. Used as an example in  FIG. 14  is IR transmitter  134  shown positioned over window  135  in control interlayer envelope material  210 . Transmitter  134  is positioned in a pocket  260  constructed of pliable polymer sheet material (such as a polyurethane material) capable of being sewn or welded to the material of the interlayer envelope. The pocket  260  is sized so as to both retain and position the IR transmitter  134 . Closure material  262  is positioned across the opening of pocket  260  to provide retention of the device within the pocket. Closure  262  is not necessarily water tight as the construction of the IR transmitter itself is, in the preferred embodiment, a generally water tight enclosure. Hook and loop type material would be one appropriate structure for closure means  262 . 
   IR transmitter/sensor  134  may include an injection molded rigid plastic enclosure having at least one side transparent to IR illumination that is directed into the associated cushion chamber. Within the rigid plastic enclosure is positioned PC board  272  on which are positioned IR LED  274  and/or IR sensor  276 . A number of IR light sources (typically solid state LED devices) and IR sensors are commercially available that are suitable for use in conjunction with the system of the present invention. The circuitry associated with the IR sensors utilized in the preferred embodiment is configured to operate the sensors in the linear region of their output (typically the saturated region) and incorporates an auto gain adjustment to place the sensor into the linear region. In this manner, a more accurate and direct correlation between illumination levels and sensor output is achieved. This approach is particularly important for smaller displacements of the mattress cushion chamber being monitored (smaller changes in the illumination level) that under previous approaches might have been missed. 
   In addition, optical filters are utilized in the preferred embodiment of the present invention to narrow the IR frequency band received and monitored. This bandwidth narrowing allows for an optimal auto gain adjustment to put the sensors into the linear region of their output as described above. 
   Although the circuitry of the system for driving the IR transmitters described above drives the devices in concert, an alternative approach would drive the transmitters and poll the corresponding sensors in banks so as to further avoid the effects of “cross talk” between chambers. Avoiding the simultaneous polling of sensor/transmitter pairs that are directed to adjacent chambers at the same time would serve to diminish or eliminate such cross talk (light from one transmitter being picked up by a sensor from a different transmitter/sensor pair). 
   Reference is now made to  FIG. 15  for a description of the manner in which the system of the present invention utilizes a measurement of IR illumination within an inflated chamber to determine when a decrease in chamber height warrants an increase in inflation pressure to that chamber to re-elevate the chamber.  FIG. 15  also provides a description of the layered arrangement of the bladder components of the system of the present invention. The mattress replacement system is intended to be placed on existing hospital bed structures and the like although the principles of operation may readily translate into original equipment manufacturing designs. In the replacement environment the system comprises MRS bladder  72  surrounded in part by system envelope  210 . Turning bladders  54  and  56  are likewise enclosed in envelope  210  and are, in the preferred embodiment, further positioned and retained within sub-envelopes integrated into envelope  210 . Various compartments and sub-envelopes may be created within envelope  210  as necessary to position and retain the various bladders, control components, cables and air flow conduits. These compartments may be sewn or welded together or they may be constructed with sections of material that removably attach one to another with zippers or hook and loop attachment surfaces. Straps sewn into the envelope and secured with buckles and ties may also be utilized to position and retain the various components of the system in place. 
   The control interlayer of the system is further shown in  FIG. 15  as a cross section generally from side to side on the bed through the center of the mattress system. In this location, body cushion  30  is shown with IR transmitter  134  positioned on one side of the cushion and IR sensor  118  positioned on an opposite side. Mattress controller  106  (which retains the circuitry to drive the IR transmitters) is shown, as is stepper valve controller  108  (which is responsible for the inflation of body cushion  30 ). Foam interlayer core material  212  is also seen in cross section in this view. Shown in dashed line form are the exterior components of the system, namely blower box  10  with display  101  and primary air flow conduit  280 , as they would be positioned on the bed in association with the replacement mattress system. 
   Operation of the IR sensor system is structured to be a measurement of illumination level within a chamber as opposed to simply the interruption of a line of sight beam of IR light. Thus the orientation of the IR transmitter and the IR sensor is not one towards the other but rather into the chamber as a whole. Light paths shown in  FIG. 15  within cushion  30  (within one or more cross-bed box shaped channel of cushion  30 ) represent the direction, dispersion and internal reflection of the IR light within the chamber and its eventual reception at the IR sensor. From this it can be seen how even slight modifications to the upper planar surface of the cushion will result in a decrease in the level of illumination received at the sensor. Significant changes in the planar surface, such as might occur if an elbow or other narrowly focused pressure were directed onto the outside surface of the cushion, would result in a more significant change in the overall level of illumination received at the sensor. In this manner, a more accurate determination of the degree of surface displacement, and of the danger of “bottoming out” can be achieved. The controllers described above and their direct connection to a bank of IR sensors as well as their direct connection to air inflation valves are therefore configured to provide a more immediate and appropriate response to the need for increased (or decreased) inflation pressures in any specific portion of the mattress system. 
   Reference is finally made to  FIG. 16  for a brief description of the manner in which the system of the present invention may be positioned on a standard hospital bed or the like. In this view, bed  290  is configured with footboard panel  284  onto which is placed and positioned the blower box enclosure  10  of the present invention. Replacement mattress system  282  is shown positioned on bed  290  much in the same manner that a standard mattress might be placed. Clamp  286  is a rigid panel connected to blower box  10  in an adjustable fashion that allows the blower box to be retained and secured to the footboard panel  284 . Blower box enclosure  10  incorporates an ergonomic handle  288  to facilitate its placement onto, and removal from, the bed. Primary air flow conduit connects the blower box  10  to manifold  22  (not seen in this view) associated with the interlayer of the mattress system  282 . As mentioned above, the requisite electrical/electronic cables and connections between the blower box and the control interlayer are incorporated into the structure of the primary air flow conduit so as to eliminate the need for additional connections. In the preferred embodiment, air flow conduit  280  incorporates a quick disconnect coupling  281  that allows the rapid separation of the blower box from the balance of the system. Electrical power cord  292  provides the necessary AC power to drive all of the electrical and electronic components of the system of the present invention. 
   Also shown in  FIG. 16  is wireless data communication device  296  that may be configured to communicate by close proximity (low power) RF signals with the various controller devices incorporated into the system. Recognizing that various calibrations, regimens, parameter settings and the like may need to be programmed into the micro-controllers of the present system, it is beneficial to utilize such close proximity data communication devices to provide a means for modifying the setting of the various controllers. The PC boards described in association with the controller enclosures shown in  FIGS. 8 and 9  may incorporate the necessary wireless communication transceiver circuitry to permit such data transmission back and forth with a close proximity handheld unit. The network protocol utilized in the preferred embodiment of the present invention (CAN protocol) may be further utilized with the wireless capability by making the hand held unit a discretely identified node on the network. The hand held unit may then act to reset the parameters programmed into the individual controllers, and/or may act to receive and download historical data associated with the performance of the controller over time in response to the various pressure and temperature changes being monitored as well as the cushion displacement measurements made by the IR sensors. 
   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 intended to be construed as a limitation of the invention. Those skilled in the art will recognize modifications of the present invention that might accommodate specific existing patient support structures or hospital bed configurations. Such modifications as to size, and even configuration, where such modifications are merely coincidental to existing structures of the bed, do not depart from the spirit and scope of the invention.