Patent Publication Number: US-7716761-B1

Title: Adaptive positioning system

Description:
This patent application is a continuation-in-part application (CIP) claiming the benefit of copending U.S. patent application Ser. No. 11/198,578 (filed Aug. 5, 2005) entitled MEDICAL PROCEDURES POSITIONING SYSTEM, which is a continuation-in-part (CIP) of U.S. patent application Ser. No. 11/175,811 (filed Jul. 6, 2005) entitled ARTICULATED BED (abandoned). The present application is also related to copending U.S. patent application Ser. No. 11/677,058 (filed Feb. 21, 2007) entitled ADAPTIVE ARTICULATED BED. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to adjustable beds and patient positioning systems. 
     BACKGROUND 
     Recurrent and chronic pain, especially that originating in the lower back and/or neck, are common medical complaints for which the recommended treatments range from conservative (e.g., bed rest) to highly invasive (e.g., spinal surgery followed by bed rest). Treatment recommendations vary because no single mode of therapy has been generally recognized as superior. Each treatment choice is associated with its own costs and side effects, but recovery is typically prolonged, painful and expensive regardless of the choice. See, e.g., U.S. Pat. No. 5,653,665, which is incorporated herein by reference. And the pain may be aggravated by poor sleeping habits (e.g., a tendency to sleep face-down). See, e.g., U.S. Pat. No. 6,073,288, which is incorporated herein by reference. The resulting state of chronic pain predisposes patients to insomnia and excessive use of medication, thus increasing the cost of medical care and risking the development of dependency. 
     Chronic pain that is actually precipitated or aggravated by bed rest is also often reported by patients confined to bed for reasons such as accidental injuries or cancer. A common condition in all such periods of bed rest is that the patients are often not really at rest. Rather, they are propped in a variety of positions that are moderately comfortable for only a limited time. Movement out of these positions typically induces more pain. See, e.g., U.S. Pat. No. 6,807,698 B2, which is incorporated herein by reference (hereinafter the &#39;698 patent). 
     For some bed-ridden patients, movement is so restricted by the attendant pain that blood circulation and respiration are sufficiently compromised to lead to development of decubitus ulcers and/or pulmonary complications. Attentive nursing care can alleviate such problems, but at relatively high cost. Several therapeutic beds have been proposed to provide a minimal level of patient movement in the form of controlled oscillatory support. See, e.g., the &#39;698 patent as well as U.S. Pat. Nos. 5,299,334, and 6,691,348 B2, and 6,708,358 B2 and 6,862,761 B2, which are incorporated herein by reference (hereinafter the &#39;334 patent, the &#39;348 patent, the &#39;358 patent and the &#39;761 patent respectively). 
     To support an immobilized patient, the &#39;334 patent discloses a generally rectangular patient support table that can be pivoted about transverse and longitudinal axes. The &#39;348 patent describes features alleviating the drawbacks and difficulties of prior art beds for a bed-ridden patient who is physically unable to move himself. Both the &#39;334 and the &#39;348 patents describe structures to restrain or limit movement of a patient&#39;s body during tilting or tipping of a bed (i.e., preventing a patient from falling off the bed). But neither &#39;334 patent nor the &#39;348 patent describe features designed to allow a patient to move by himself or herself so as to assume and/or adjust postures commonly observed in natural sleep (e.g., a lateral recumbent position with knees and hips flexed, a position known to relieve lower back pain). See, e.g., U.S. Pat. No. 4,910,818, which is incorporated herein by reference, and U.S. Pat. No. 6,374,440 B1, which is incorporated herein by reference (hereinafter the &#39;440 patent). 
     A person lying in a right lateral recumbent position (i.e., with the person&#39;s weight being supported primarily by the person&#39;s right side), with knees and hips flexed to relieve lower back pain, is shown schematically in FIG. 1 of the &#39;440 patent. While this position is temporarily beneficial and may even induce sleep, the weight of the patient&#39;s uppermost arm, combined with muscle relaxation that accompanies sleep, tends to twist the patient&#39;s upper torso into a face-down position while the flexed knees and hips prevent the patient&#39;s lower body from turning with the upper torso. The result is a twisting of the patient&#39;s spine which can aggravate lower back pain. 
     SUMMARY OF THE INVENTION 
     The invention includes methods and apparatus related to various embodiments of an adaptive positioning system that facilitates research, diagnosis, and treatment related to persons supported on the positioning system. Rotation of a supported person about longitudinal and/or transverse axes, with simultaneous and/or delayed processing of data related to spontaneous and/or induced movement of the person, aids clinical assessment of neuromuscular and related problems while placing and/or maintaining a person in a relatively favorable position (e.g., to facilitate diagnosis or treatment, to relieve pain and/or to promote rest). Real-time recording of raw and processed data allow further processing, including comparisons of individual responses within clinical classifications and group studies to assess efficacy. 
     One embodiment of an adaptive positioning system comprises a plurality of longitudinal elements and at least one frame member having an adjustably fixed spatial relationship with a plurality of the longitudinal elements, thus forming a conforming assembly capable of supporting a person. The conforming assembly is rotatably supported (as on one or more longitudinal bearings) by support means and is shaped to conform at least partially to a person supported on the assembly. Hence, rotation (by rotation means) of the conforming assembly (via at least one frame member) about a longitudinal axis tends to also rotate a supported person thereon about a longitudinal axis. Note that where edge-to-edge pivotal connection is described herein, physical connection may be achieved either at or closely adjacent to the respective edges as, for example, by a hinged joint. 
     Rotary motion about a longitudinal axis of at least one frame member having an adjustably fixed spatial relationship with a plurality of the longitudinal elements of a conforming assembly tends to cause rotation about a longitudinal axis of a person supported on the assembly, and tends to change the weight distribution of a supported person on the assembly. A function of any such change of weight distribution may comprise one or more variables such as, e.g., changing pressure on one or more of the individual longitudinal elements, changing torque values on one or more longitudinal elements, and/or changing torque about support means bearings. Further, a supported person may move spontaneously or move in conjunction with conforming assembly rotation about a longitudinal axis, and moves of either or both kinds may in general be reflected by changes in a function of one or more variables related to weight distribution on the conforming assembly. Such variables are detected by one or more sensors on the adaptive positioning system. 
     Control means generate at least one control signal combining one or more such functions of weight distribution with one or more set points representing predetermined angular orientations (e.g., those related to mechanical limitations and/or safety) of a supported person about longitudinal and/or transverse axes. Angular positions of a conforming assembly about longitudinal and/or transverse axes can be adapted for individual persons for diagnosis and/or treatment, to achieve, maintain or increase personal comfort, and/or to reduce personal discomfort. Angular position changes to accomplish such adaptations are achieved via at least one control signal generated by at least one processor component (comprising, e.g., a computer) of the control means, the control signal encoding the combination of at least one set point and a function of weight distribution on the conforming assembly. 
     The control signal(s) control one or more motive components of the rotation means to achieve desired rotation of a supported person about a longitudinal and/or transverse axis. Since rotation means comprises at least one motive component (e.g., electric motors and/or fluid-actuated cylinders), a control signal may comprise a plurality of signal components such as one or more electrical voltages (transmitted to motive components, e.g., wirelessly or via one or more electrical conductors) and/or one or more pressurized fluids (transmitted to motive components, e.g., via one or more pipes or tubes). Signal components and control signals themselves may be encoded (i.e., multiplexed) so as to address a subset of motive components. 
     An embodiment of an adaptive positioning system schematically illustrated herein comprises a plurality of substantially planar longitudinal elements, each longitudinal element having first and second longitudinal edges and first and second ends (see, e.g.,  FIG. 1  and U.S. Pat. No. 5,224,228, incorporated herein by reference, herein the &#39;228 patent). At least one frame member has an adjustably fixed spatial relationship with each longitudinal element. Such an adjustably fixed spatial relationship may be achieved, for example, through one or more reversibly lockable hinges (see, e.g.,  FIG. 1  and U.S. Pat. No. 4,531,417, incorporated herein by reference, herein the &#39;417 patent). Such hinges may pivotally connect longitudinal edges of the longitudinal elements to each other and/or to at least one frame member to form a conforming assembly configurable in a predetermined shape capable of rotating a supported person about a longitudinal axis. The conforming assembly has first and second side edges. 
     Alternatively, first and second ends of a plurality of longitudinal elements may be adjustably fixed to head and foot frame members respectively to form a conforming assembly configurable in a predetermined shape capable of rotating a supported person about a longitudinal axis. In such an alternative embodiment, adjustable fixation of longitudinal element ends to one or more frame members (e.g., to head and foot frame members) may obviate the need for pivotal edge-to-edge connection of longitudinal element as described above. 
     In the schematically illustrated embodiment of  FIG. 1 , support means support the conforming assembly above a floor and comprise a longitudinal bearing, one or more bearing supports, and base members. Bearing supports such as those of  FIG. 1  may incorporate one or more adjustable length elements to facilitate height adjustment of the conforming assembly and/or rotation of the conforming assembly about a transverse axis. When such adjustable length elements are present, the longitudinal bearing is pivotally mounted to bearing supports. Components of support means may take a variety of forms analogous in part to, for example, the undercarriage 11 of the &#39;228 patent, or the base 22 of the &#39;761 patent, structure 10 of the &#39;334 patent, or structure 212 of the &#39;358 patent. Support means in general comprise at least one longitudinal bearing (see, e.g.,  FIG. 1 ). Each longitudinal bearing, in turn, facilitates rotation about at least one longitudinal axis of the conforming assembly. 
     Rotation means of the schematically illustrated embodiment of  FIG. 1  facilitate angular rotation of the conforming assembly to a predetermined angular position about a longitudinal axis. Components of rotation means may take a variety of forms analogous in part to, for example, the mover 19 of the &#39;761 patent, the motors 56 and 56A with extensible and retractable cylindrical screws 60 and 60A respectively of the &#39;228 patent, the hydraulic pump 12 with hydraulic cylinders of the &#39;334 patent, or the carriage 230 carrying the drive systems 250 and 252 of the &#39;358 patent. 
     Control means generate at least one control signal for control of rotation means, the control signal encoding at least one set point and at least one function of weight distribution on a conforming assembly. The function may be linear or nonlinear, and control means to generate the function (see  FIG. 1 ) comprise at least one processor, at least one set point input device connected to the processor(s), at least one sensor for weight distribution information, and at least one transmission line for carrying a control signal and/or weight distribution information obtained from one or more sensors on a conforming assembly. Additional control means components such as computers, data storage devices and transmission lines may be added, for example, to collect, analyze, apply and store weight distribution data and/or physiologic measurements specified in research protocols. Such additional control means components can provide feedback on a supported person&#39;s response to conforming assembly rotation(s), and treatment protocols may thus be adapted to increase the likelihood of one or more desired responses. 
     Note that with appropriate matching of modality for control signals and weight distribution information (e.g., electrical, pneumatic or hydraulic), and any needed switching, a single transmission line may alternately carry, for example, a control signal and weight distribution information. Each variable included in the function of weight distribution on a conforming assembly, as well as physiologic measurements is obtainable from sensors on the positioning system and/or from an appropriately instrumented person supported on the positioning system. 
     In alternative embodiments, the conforming assembly may additionally comprise one or two multiuse lateral reverse-foldable longitudinal assemblies pivotally, and reversibly-lockably, connected longitudinally edge-to-edge (e.g., as by a longitudinal reversibly-lockable hinge) to the first and/or second conforming assembly side edges. Such lateral reverse-foldable longitudinal assemblies may be folded away to facilitate access or may function, for example, as bed rails, to assist personal movement to or from a conforming assembly, or when configured as described below, to support weight over the conforming assembly. 
     Each lateral reverse-foldable longitudinal assembly comprises a plurality of foldable and reversibly-lockable longitudinal elements. Schematically illustrated examples herein include an inner foldable element pivotally, and reversibly-lockably connected longitudinally (e.g., as by a longitudinal reversibly-lockable hinge) to an outer foldable element so that the outer foldable element can rotate about one or more longitudinal axes between a reversibly-locked first position (e.g., a closed position) and a reversibly-locked second position (e.g., an extended position). Through rotation of the adjacent inner foldable element, an outer foldable element in an extended position may thus be positionable to support weight (e.g., a hand grip for a supported person) over a portion of the conforming assembly. When two lateral reverse-foldable longitudinal assemblies are present with their respective outer foldable elements in extended position, the respective outer foldable elements may be temporarily joined and locked longitudinally, edge-to-edge, for supporting weight (e.g., a small winch for lifting a patient) over a portion of the conforming assembly. 
     Alternative embodiments of the adaptive positioning system may also comprise one or more longitudinal elements which, in turn, comprise at least one multiuse port for allowing access to a patient supported on the conforming assembly. Such a port may comprise, for example, an individually hinged or removable portion of the longitudinal element. Alternatively, such a port may comprise a longitudinal slot in a longitudinal element, with one or more longitudinally movable supports having a cumulative length less than that of the slot and being slidingly secured within the slot. Each hinged or removable portion comprising a port may be opened without materially affecting support of a patient on the conforming assembly, while providing sufficient clearance to allow procedures such as physical examination of the patient or spinal puncture. Alternatively, one or more longitudinally movable supports may be moved longitudinally in a slot to distribute support for a patient along the slot while simultaneously allowing flexible access to a patient via a movable port optionally locatable at any of a variety of positions along the slot. 
     The shape of a conforming assembly is a function of the relative spatial relationships among its longitudinal elements. Since at least one frame member has an adjustably fixed spatial relationship with each longitudinal element, the shape can be adapted to comfortably accommodate the body habitus and weight distribution of an individual patient. In use, the conforming assembly&#39;s shape, as well as its angular position (relative, e.g., to support means) about one or more longitudinal axes (and optionally about one or more transverse axes), is adapted to comfortably support a patient. The coupling between the support means and the conforming assembly provides, in various embodiments, for rotation of the conforming assembly (and thus rotation of a patient supported by the conforming assembly) about one or more longitudinal axes (and optionally one or more transverse axes) to generally maximize patient comfort by, for example, reducing any tendency for the patient&#39;s upper torso to twist into a face-down position. 
     For example, in an embodiment of an adaptive positioning system that is schematically illustrated herein, a first functional portion of the conforming assembly comprises a first longitudinal element that provides support primarily for a patient&#39;s back, thereby supporting a first portion of the patient&#39;s weight. Simultaneously, a second functional portion of the conforming assembly comprises a second longitudinal element that provides support primarily for the patient&#39;s lower side, thereby supporting a second portion of the patient&#39;s weight. The magnitude of the first portion of the patient&#39;s weight supported by the conforming assembly can be smoothly adjusted to reduce any tendency for the upper torso of a particular patient to twist into a face-down position. 
     Smoothly adjusting the magnitude of the first portion of a patient&#39;s weight supported by the conforming assembly may require continuous adjustment of the angular position of the conforming assembly (relative, e.g., to support means) about a longitudinal axis, and/or adjustment of the relative spatial relationship of the first functional portion of the conforming assembly with respect to the second functional portion of the conforming assembly. In general, these variables, plus (optionally) the angular position of the conforming assembly about a transverse axis (relative, e.g., to support means), may be adjusted for a particular patient to maximize the patient&#39;s comfort and reduce any tendency for the patient&#39;s upper torso to twist into a face-down position. Note that since the conforming assembly can be adapted to generally conform to a laterally recumbent patient in providing both back and lower side support, rotation of the conforming assembly about a longitudinal axis (or optionally a transverse axis) tends to rotate the supported patient in a similar manner. 
     In the above illustrative example, the minimum magnitude of conforming assembly support for the first portion of a particular patient&#39;s weight is an empirically determined magnitude required to achieve a desired reduction of the tendency for the patient&#39;s upper torso to twist into a face-down position. This minimum magnitude of conforming assembly support is achieved by compensatory rotation about a longitudinal axis that is just sufficient to counteract (i.e., to compensate for) the tendency for that particular patient&#39;s upper torso to twist into a face-down position. A desired degree of such compensatory longitudinal rotation of the conforming assembly (and the patient) may be estimated by using one or more pressure sensors to measure pressure exerted on the first functional portion of the conforming assembly (which primarily supports the patient&#39;s back). Should this measured pressure(s) fall below a predetermined value, compensatory longitudinal rotation may be used to increase the magnitude of conforming assembly support for the first portion of the patient&#39;s weight, as indicated by increasing the measured pressure on the first portion of the conforming assembly, to the above-described minimum. 
     As an alternative or supplement to the above pressure measurement, a sensor may be used to measure the torque exerted by the first portion of a conforming assembly on the second portion of the conforming assembly. If the first and second functional portions of a conforming assembly are joined by a reversibly lockable longitudinal hinge, and if only the second functional portion of the conforming assembly is directly (adjustably) fixed to and supported by at least one frame member, then the measured torque across the locked longitudinal hinge will generally be a function of the first portion of the patient&#39;s weight supported by the conforming assembly. Should the patient&#39;s upper torso begin to twist into a face-down position (due, for example, to muscle relaxation when the patient falls asleep), the measured value of torque across the hinge would decrease below a predetermined value, signaling a need for compensatory longitudinal rotation of the conforming assembly (and the patient). Such compensatory longitudinal rotation adaptively increases the first portion of weight supported by the conforming assembly sufficiently to counteract any upper torso twist thus detected. 
     In various embodiments of the positioning system, the process of pressure and/or torque measurement described above, followed by compensatory rotation of an conforming assembly (and a patient), may be accomplished manually (e.g., by an observer who monitors the patient&#39;s position or by the patient) or automatically (e.g., by a control means designed to maintain measured torque and/or pressure at predetermined values). A subset of such predetermined valves may be designated as set points which may be empirically determined for each patient to reduce to a desired extent any tendency for that patient&#39;s upper torso to twist into a face-down position due, for example, to slight patient movement. Since conscious or unconscious movement is to be expected from time to time in a resting patient, these set points will typically vary over time in different patients. 
     Referring to the above illustrative example, manual or automatic control of compensatory conforming assembly rotation may be supplemented or replaced by continuous adaptive adjustment of the relative angular relationships between longitudinal elements of the first and second portions of a conforming assembly. Such adjustment may increase patient comfort and is facilitated by reversibly lockable hinges joining adjacent longitudinal elements and/or by fixing adjacent longitudinal elements within a rigid frame. Such relative angular relationship adjustments may involve alteration of the manner in which longitudinal elements are adjustably fixed within a rigid frame, and they are also facilitated in certain embodiments by reversibly lockable longitudinal hinges joining longitudinal elements edge-to-edge. 
     In general, each longitudinal hinge of a conforming assembly joins adjacent edges of a pair of longitudinal elements, thereby allowing rotation of these adjacent longitudinal elements with respect to each other about a longitudinal axis. If such a hinge is reversibly lockable, a smoothly adjustable relative angular relationship (i.e., a relative angular relationship that may be smoothly changed to a desired state and then temporarily fixed in that state) may be established between those two adjacent longitudinal elements. In a conforming assembly in which all longitudinal elements are joined edge-to-edge with reversibly lockable hinges, relative angular relationships among all longitudinal elements of the conforming assembly can be smoothly adjusted and temporarily fixed, whether the longitudinal elements are adjacent or non-adjacent. Further, at least one frame member may be coupled to only a single longitudinal element (or a set or subset of all longitudinal elements in the conforming assembly) to provide the required support for the conforming assembly and the patient and to allow continuous adjustment of the rotation angle of the conforming assembly about one or more longitudinal axes (and optionally about one or more transverse axes). Thus, a relatively rigid conforming assembly is created that may be smoothly rotated (with a patient) about a longitudinal axis and/or a transverse axis independent of the (temporarily) fixed relative angular relationship(s) between functional portions of the conforming assembly. 
     Smoothly adjustable rotation of the conforming assembly about a longitudinal axis can smoothly transfer an adjustable portion of the weight of a laterally recumbent patient from the patient&#39;s side to the patient&#39;s back or vice versa. Sufficient weight support may thus be provided through the patient&#39;s back to substantially reduce the tendency for the patient&#39;s upper body twist the patient&#39;s spine by rotating toward a face-down position during sleep. In other words, a first portion of the patient&#39;s own weight acts to maintain the patient&#39;s back in comfortable contact primarily with the first functional portion of the conforming assembly. And while such comfortable contact is maintained, the patient&#39;s upper torso will tend not to rotate into a face-down position. Simultaneously, a second portion of the patient&#39;s weight is primarily supported by the second functional portion of the conforming assembly through the patient&#39;s side, thereby allowing the patient to establish and maintain a resting posture with knees and hips flexed to relieve lower back pain. 
     Note that adjacent edges of a conforming assembly&#39;s longitudinal elements may or may not be joined. When not joined, such edges may be maintained adjacent (but still adjustable) by being temporarily fixed in a rigid frame. The manner in which the longitudinal elements are temporarily fixed in such a frame may be, for example, by adjustably fixing the ends and/or by allowing limited rotational movement of the ends in their attachment to the relatively rigid frame to form a framed conforming assembly. Alternatively one or more longitudinal elements may be hinged, but not locked, to longitudinal elements that are themselves fixed in a frame to form a free-form conforming assembly. 
     If a smoothly adjustable relative angular relationship is temporarily fixed between at least the outermost two longitudinal elements of the conforming assembly, then the resulting patient support surface will have a degree of flexibility related to the number of hinged-but-unlocked and/or adjacent-but-not-hinged longitudinal joints between the outermost two longitudinal elements. Such a conforming assembly may conform even more closely to a patient and may adapt to patient movement by alteration of the relative angular relationship of one or more pairs of longitudinal elements between the outermost two longitudinal elements while simultaneously supporting the patient&#39;s weight distributed as desired between first and second functional portions of a conforming assembly. 
     An adaptive positioning system may then comprise a choice of conforming assembly configurations for supporting the patient. Further, one or more longitudinal elements of a conforming assembly, or the rigid frame of a framed conforming assembly, may be coupled to and supported by support means in a manner analogous to that schematically illustrated herein, or in any other manner known to those skilled in the art, provided that first and second portions of the patient&#39;s weight are safely and comfortably supported in a desired (smoothly adjustable) distribution by first and second functional portions of a conforming assembly respectively. Further, smoothly adjustable compensatory longitudinal rotation (and optionally transverse rotation) must be allowed. Thus, support means may be coupled to and provide support along two longitudinal support axes, the support axes being spaced apart laterally. In other embodiments, a single longitudinal support axis may be used. By smoothly adjusting the coupling between the support means and the longitudinal support axis or support axes, the conforming assembly can be rotated about a transverse axis and/or a longitudinal axis parallel to or coincident with one of the longitudinal support axes. 
     Note that rotation of a laterally recumbent patient supported by any configuration of a conforming assembly approximately ninety degrees about a longitudinal axis can substantially interchange the support functions of the first and second functional portions of the conforming assembly as described in the above illustrative example. That is, the first functional portion of the conforming assembly may become the portion that primarily supports the patient&#39;s lower side), and the second functional portion of the conforming assembly may become the portion that primarily supports the patient&#39;s lower side. By providing an appropriately strengthened conforming assembly, this interchange of patient support functions can be accommodated by an adaptive positioning system so as to allow a patient to transition easily from a left lateral recumbent position to a right lateral recumbent position and vice versa. In such embodiments, a third functional portion of the conforming assembly may be desirable to support the patient during transitions between left and right lateral recumbent positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an adaptive positioning system comprising longitudinal elements, a frame member, a stand-off link, support means, rotation means and control means. 
         FIGS. 2A-2E  schematically illustrate a series of partial cross-sections of a patient&#39;s upper thorax as supported by a first functional conforming assembly portion and a second functional conforming assembly portion during a typical transition from a right lateral recumbent position ( FIG. 2A ) to a left lateral recumbent position ( FIG. 2E ). 
         FIG. 3  schematically illustrates a partial end-on view of an embodiment of a conforming assembly comprising two longitudinal elements that are adjustably fixed parallel to a frame member. 
         FIG. 4  schematically illustrates a partial end-on view of the conforming assembly embodiment of  FIG. 3 , but additionally comprising first and second lateral reverse-foldable longitudinal assemblies. 
         FIG. 5  schematically illustrates a partial end-on view of the general form of the conforming assembly embodiment of  FIG. 4  wherein one of the lateral reverse-foldable longitudinal assemblies has been raised in preparation for further extension. 
         FIG. 6  schematically illustrates a partial end-on view of the general form of the conforming assembly embodiment of  FIG. 5  wherein one of the lateral reverse-foldable longitudinal assemblies has been further extended for supporting weight over a longitudinal element. 
         FIG. 7  schematically illustrates a partial end-on view of the general form of a conforming assembly embodiment comprising one lateral reverse-foldable longitudinal assembly which has been extended for supporting weight over a longitudinal element, and another lateral reverse-foldable longitudinal assembly which has been folded away between a longitudinal element and a frame member, the longitudinal element and the frame member being spaced apart by a stand-off link. 
         FIG. 8  schematically illustrates a partial end-on view of the general form of a conforming assembly embodiment comprising one lateral reverse-foldable longitudinal assembly which has been extended for supporting weight over a longitudinal element, and another lateral reverse-foldable longitudinal assembly which has been reversibly-locked in position to assist personal movement to or from a conforming assembly. 
     
    
    
     DETAILED DESCRIPTION 
     A schematically illustrated adaptive positioning system embodiment  109  is shown in  FIG. 1  and comprises a conforming assembly  99  which acts as an articulated surface capable of supporting, and generally conforming to, a person. Conforming assembly  99  comprises two substantially planar longitudinal elements  10  and  20  having an adjustably fixed spatial relationship to frame member  30 . Frame member  30 , in turn, is supported on longitudinal bearing  32 . 
     A reversibly lockable hinge  15  is segmented to facilitate reversibly lockable connection of frame member  30 , (optionally via stand-off link  16 ), to first longitudinal edge  14  of longitudinal element  10  and to second longitudinal edge  24  of longitudinal element  20 . When present, stand-off link  16  allows planar longitudinal elements  10  and  20  to be oriented substantially parallel to and spaced apart from frame member  30  (see, e.g.,  FIGS. 1 and 7 ). 
     Conforming assembly  99  has first and second side edges  22  and  12  respectively. Longitudinal element  10  comprises a port  71  for allowing access to a person supported on conforming assembly  99 , and longitudinal element  20  comprises distributed pressure sensor  70 . Angular rotation sensor  72  senses the angular positions about reversibly lockable hinge  15  of planar longitudinal elements  10  and  20 . Torque sensor  73  senses torque about reversibly lockable hinge  15  exerted by planar longitudinal elements  10  and  20 . When stand-off link  16  is absent or relatively short, the algebraic sum of torques exerted about reversibly lockable hinge  15  by planar longitudinal elements  10  and  20  approximates torque exerted about longitudinal bearing  32  by conforming assembly  99 . An estimate of torque exerted about longitudinal bearing  32  by conforming assembly  99  (and any person supported thereby) may be obtained as a function of force exerted by fluid-actuated cylinder  62 , such force being a function of fluid pressure in cylinder  62  and transmission line  77 . 
     Support means  89  comprises a longitudinal bearing  32  supported by first and second bearing supports  88  and  87 , which are rigidly held substantially parallel and vertical by a base  86 . The illustrated embodiment of base  86  comprises two longitudinal base members  40  and  40 ′ connected by two transverse base members  50  and  50 ′. Note that the lengths of first and/or second bearing supports  88  and  87  can optionally be adjusted manually or automatically via one or more adjustable length elements  64  which may optionally be incorporated to tilt conforming assembly  99  about a transverse axis. Such tilt, when desired, is facilitated by pivotal connection of bearing supports  88  and  87  to longitudinal bearing  32 . 
     Rotation means  60  rotates frame member  30 , and thus longitudinal elements  10  and  20 , of conforming assembly  99  about a longitudinal axis (i.e., that of longitudinal bearing  32 ). A supported person (not shown) on conforming assembly  99  would thus be analogously rotated about a longitudinal axis. Rotation means  60  comprises a fluid-actuated cylinder  62  pivotally mounted between a longitudinal base member  40  of base  86  and frame member  30  of conforming assembly  99 . 
     Control means  75  generates a control signal for controlling fluid-actuated cylinder  62  of rotation means  60 . To facilitate control of rotation means  60 , control means  75  comprises a set point input device  74  (in this embodiment, a keyboard) connected to processor  69 , and transmission lines  76 ,  77 ,  78  and  79 . The transmission lines are for carrying the control signal to rotation means  60  (transmission line  77 ) and for carrying weight distribution information (e.g., variables related to weight distribution) from conforming assembly  99  (transmission lines  76 ,  78  and  79 ). The control signal for the illustrated embodiment comprises pressurized fluid (not shown) which is transmitted to fluid-actuated cylinder  62  of rotation means  60  via transmission line (e.g., a pipe)  77 . The control signal encodes at least one set point (entered via set point input device  74 ) and a function of (variables related to) weight distribution on conforming assembly  99 . Variables related to such weight distribution for the illustrated embodiment are generated by distributed pressure sensor  70  on longitudinal element  20 , torque sensor  73  for sensing torques on reversibly lockable hinge  15 , and angular rotation sensor  72  on reversibly lockable hinge  15 . 
     Referring to reversibly lockable hinge  15  connecting first longitudinal edge  14  of longitudinal element  10  to second longitudinal edge  24  of longitudinal element  20 , a variety of reversibly lockable hinges known to those skilled in the art may be used. One example is the hinge-type angle setting device described in the &#39;417 patent. Note that the angle setting devices of the &#39;417 patent is smoothly and substantially continuously adjustable to establish or change a desired relative angular relationship between the structures so hinged. Further, the hinge of the &#39;417 patent is reversibly temporarily lockable at a desired relative angular relationship simply by leaving the actuator in a temporarily fixed position. This may be accomplished, for example, by manually clamping the actuator or by controlling the actuator via a high-mechanical-advantage linkage (such as a worm-drive gear motor) that remains in a stable state in the absence of power input. The latter configuration is not shown but could be used in an automatic control system. Note also that the angle setting devices of the &#39;417 patent could be used to impart continuously adjustable compensatory longitudinal rotation to conforming assembly  99 , either manually or automatically. 
     After longitudinal element  10  (the first functional portion of illustrated conforming assembly  99 ) is rotated with respect to longitudinal element  20  (the second functional portion of illustrated conforming assembly  99 ), establishing a relative angular relationship between the first and second functional portions that adapts positioning system  109  for the patient, reversibly lockable hinge  15  is reversibly locked. Conforming assembly  99  is then typically smoothly rotated about a longitudinal axis (that is, rotated about longitudinal bearing  32  in the illustrated embodiment), smoothly adjusting this longitudinal rotation until the first portion of the laterally recumbent patient&#39;s weight just exceeds a minimum magnitude. 
     Note that this continuously adjustable longitudinal rotation of conforming assembly  99  may be independent of the adjustable relative angular relationship established between the first and second functional portions of conforming assembly  99 . That is, the angular relationship may be held constant while longitudinal rotation is continuously varied. Conversely, longitudinal rotation may be held constant while the relative angular relationship is continuously varied. But since the desired minimum magnitude of the first portion of the patient&#39;s weight may be influenced by both the longitudinal rotation variable and the relative angular relationship variable, these variables may be optimized by serial or simultaneous adjustment, either manual or automatic, to maximize patient comfort and/or to minimize pain. 
     The desired minimum magnitude of the first portion of supported weight required for an individual patient may be empirically determined as the magnitude just sufficient to compensate for the tendency of the patient&#39;s upper torso to twist into a face-down position. This minimum magnitude is ordinarily revised from time-to-time so as to adapt to the patient&#39;s movements as they change the need for compensatory longitudinal rotation. 
     Longitudinal rotation is facilitated in the illustrated embodiment by longitudinal bearing  32 , which is part of support means  89  and rotatably supports second longitudinal element  20  near its longitudinal edge  22 . Thus, second longitudinal element  20  may longitudinally rotate about, and simultaneously be partially supported by, longitudinal bearing  32 . Such longitudinal rotation of second longitudinal element  20  is controlled in this embodiment by rotation means  60  (comprising fluid-actuated cylinder  62 , which is pivotally mounted between support means  89  and a point near longitudinal edge  24  of longitudinal element  20 ). 
     The schematically illustrated positioning system  109  comprises a distributed pressure sensor  70  on longitudinal element  20  for sensing a portion of a patient&#39;s weight being supported by longitudinal element  20 . Several embodiments of distributed pressure sensor  70  are known to those skilled in the art. An example is described in U.S. Pat. No. 5,799,533, incorporated herein by reference. 
     The schematically illustrated positioning system  109  further comprises a torque sensor  73  and an angular rotation sensor  72  connected to reversibly lockable hinge  15  for indicating variables which may comprise a function of weight distribution on conforming assembly  99 . In the configuration of conforming assembly  99  that is schematically illustrated in  FIG. 1 , torque sensor  73  is used in estimating the portion of a supported person&#39;s weight being supported by longitudinal element  10  through torque exerted on reversibly lockable hinge  15  by longitudinal element  10 . Angular rotation sensor  72 , which provides information on the relative angular relationship between longitudinal element  10  and longitudinal element  20 , is also used in estimating the portion of a supported person&#39;s weight being supported by longitudinal element  10 . Several embodiments of torque sensor  73  and angular rotation sensor  72  are known to those skilled in the art. For example, an embodiment which senses torque as a function of measured strain (specifically capacitively-measured torsional strain), is described in U.S. Pat. No. 6,601,462 B1, incorporated herein by reference. Relative angular rotation, on the other hand, is often sensed using devices incorporating rotary potentiometers, rotary switches, rotary counters and/or rotary transformers. 
       FIGS. 2A-2E  illustrate an example series of schematic partial cross-sections of a patient&#39;s upper thorax T supported by a first functional conforming assembly portion  100  (on the left in the illustrations) and a second functional conforming assembly portion  200  (on the right in the illustrations) during a typical patient&#39;s transition from a right lateral recumbent position ( FIG. 2A ) to a left lateral recumbent position ( FIG. 2E ). The illustrations are intended only to be broadly representative of a typical transition. Actual angular positions of functional portions  100  and  200 , as well as the actual patient position at each stage and the actual weight distribution between functional portions  100  and  200 , will be specific for each actual patient. The short straight dark arrows perpendicular to functional portions  100  and  200  schematically indicate the changing relative amounts of support typically provided to a patient by each functional portion during the transition. Note that a variably inflatable and/or gel-filled longitudinal cushion between the patient and functional portions  100  and  200  may provide additional patient support and comfort, while facilitating lateral patient movement during the transition. 
       FIG. 2A  shows schematically that the portion of patient weight supported by functional portion  200  (indicated by the hollow-headed arrow) is relatively larger than the portion of patient weight supported by functional portion  100  (indicated by the solid-headed arrow). In  FIG. 2B  the patient&#39;s weight is roughly evenly distributed between functional portions  100  and  200 , and the patient will have a tendency to slide laterally right from the position shown in  FIG. 2B  to the position shown in  FIG. 2C  where all of the patient&#39;s weight is supported by functional portion  200 . Since a patient will generally be capable of at least limited movement, appropriate adjustment of the relative angular relationship between functional portions  100  and  200  makes use of gravity to assist the patient&#39;s lateral slide while allowing the patient to control the slide so as to come to rest in the position shown in  FIG. 2C . To continue with the transition, functional portion  100  is rotated clockwise with respect to functional portion  200  in  FIG. 2D . While this rotation of functional portion  100  does not change the support of all of the patient&#39;s weight by functional portion  200 , it does prepare for the subsequent counter-clockwise rotation of functional portion  200  which will transfer a relatively larger portion of the patient&#39;s weight support to functional portion  100 , leaving a relatively smaller portion to be supported by functional portion  200 . The clockwise rotation of functional portion  100  shown in  FIG. 2D  tends to resist any lateral slide of the patient to the left during subsequent counter-clockwise rotation of functional portion  200  to the position shown in  FIG. 2E . Note that the relative angular positions of functional portions  100  and  200  in  FIG. 2E  is virtually a mirror image of their respective positions in  FIG. 2A , signifying completion of the transition from right lateral recumbent to left lateral recumbent. Note also that an actual patient smoothly transitions among positions analogous to (but not necessarily identical to) the positions illustrated in  FIGS. 2A-2E . To maximize comfort and/or minimize pain during a transition, the patient (or an observer or an automatic control system) may pause for an indefinite or predetermined period in any position analogous to an illustrated position or in any position intermediate between the illustrated positions. 
       FIG. 3  schematically illustrates a partial end-on view of an embodiment of a conforming assembly  199  comprising two longitudinal elements  110  and  120  adjustably fixed parallel to a frame member  130  via reversibly lockable hinge  115 . Conforming assembly  199  is supported by support means  189 , which comprises longitudinal bearing  132  and bearing support  188  (shown partially), together with base members (not shown) which relatively rigidly hold bearing support  188  vertical. Rotation means  160  comprises fluid-actuated cylinder  162  which is pivotally-mounted to frame member  130  and to one or more base members (not shown). 
       FIG. 4  schematically illustrates a partial end-on view of the conforming assembly embodiment of  FIG. 3 , but additionally comprising first and second lateral reverse-foldable longitudinal assemblies  209  and  209 ′ pivotally, and reversibly-lockably, connected longitudinally edge-to-edge to longitudinal elements  120  and  110  respectively. As illustrated, reversibly-lockable pivotal connection of first and second lateral reverse-foldable longitudinal assemblies  209  and  209 ′ to longitudinal elements  120  and  110  respectively is achieved by reversibly-lockable longitudinal hinges  115  and  115 ′ respectively. 
     Lateral reverse-foldable longitudinal assemblies  209  and  209 ′ comprise, in turn, inner foldable elements ( 81  and  81 ′ respectively) pivotally, and reversibly-lockably, connected longitudinally (e.g., by reversibly-lockable longitudinal hinges  215  and  215 ′ respectively, as illustrated) to outer foldable elements ( 82  and  82 ′ respectively, as illustrated). Lateral reverse-foldable longitudinal assemblies  209  and  209 ′ can rotate about longitudinal axes from reversibly-lockable first positions (analogous, for example, to the respective positions in  FIG. 4 ) to “bed rail” and “raised” positions such as the general forms of the left and right assemblies of  FIG. 5  respectively. Note that the outer foldable element of the left assembly of  FIG. 5  is reverse-folded compared to the analogous element shown in  FIG. 4 . 
     From the above “raised” position, an outer foldable element may be extended to a reversibly-lockable position capable of supporting weight over a portion of a conforming assembly (analogous, for example, to the general form of the extended position of the right assembly of  FIG. 6 ). In certain embodiments (not shown), first and second lateral reverse-foldable longitudinal assemblies may be extended from the first and second edges of a conforming assembly respectively so as to allow them to be temporarily joined longitudinally, edge-to-edge, (as, for example, by one or more clamps (not shown)) to support greater weight than that supportable by a single such assembly over a portion of a conforming assembly. 
     Note also that a lateral reverse-foldable longitudinal assembly having an inner foldable element somewhat narrower than the longitudinal element to which it is hinged may be reverse-folded in a manner analogous to the reverse-folding of the outer foldable element of the left assembly shown in  FIG. 5  as noted above. Thus, the left assembly shown in  FIG. 7  is then folded away in a space created by a stand-off link between a frame member and a longitudinal element generally in the form schematically illustrated. Alternatively, a lateral reverse-foldable longitudinal assembly may be reversibly-locked in a substantially horizontal position to assist personal movement to or from a conforming assembly, as schematically illustrated by the general form on the left portion  FIG. 8 .