Abstract:
A vibrating patient support apparatus has a resonant referencing percussion device preferably located internally to a cover of a mattress of the apparatus. The percussion device delivers a percussion or vibration at a controlled operating frequency that is preferably slightly less than a resonant frequency located internal to the mattress of the apparatus. With the various weight distributions of a patient, the device is capable of determining the ever shifting resonant frequency via control signals received by a controller from a pressure sensor or accelerometer of the device. Because the operating frequency is slightly less than the natural resonating frequency, energy of the system is conserved. Because the operating frequency is not the controller calculated resonant frequency, wear on the device and potential damage is minimized.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional patent application Ser. No. 60/677,728, filed May 4, 2005, the advantages and disclosure of this application is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to a patient support apparatus and more particularly to a resonant frequency referencing percussion device of a vibrating patient support apparatus.  
       BACKGROUND OF THE INVENTION  
       [0003]     Patient support systems are well known in the art for providing therapy to a patient. A typical patient support apparatus comprises a mattress having a plurality of air bladders for supporting the patient against the bias of gravitational forces, a percussion device that alternates inflation and deflation of air bladders to provide percussion and vibration therapy to the patient, and a rotation device, usually positioned beneath the mattress, to rotate the patient from side to side. Percussion, vibration, and rotation therapy assist in reducing pulmonary problems and bed sores, respectively.  
         [0004]     One example of a rotation device in a mattress is shown in U.S. Pat. No. 5,611,096 to Bartlett et al. and incorporated herein by reference in its entirety. The rotation device of Bartlett et al. has two selectively inflatable and deflatable air bladders lying longitudinally beneath the mattress to provide rotation therapy to the patient for reducing bed sores. A controller including an operator input panel and display is used to control the rotation device. The input panel includes a plurality of raised buttons for advancing through and adjusting parameters associated with rotation functions.  
         [0005]     An example of a percussion or vibrating device in a mattress is shown in U.S. Patent Application Publication No. 2004/0193078 A1, to Flick et al. and incorporated herein by reference in its entirety. The percussion device of Flick et al. discloses a vibrating pad having a plurality of bladders that fill and deflate with the flow of air or fluid at a prescribed frequency controlled by a controller causing the above mattress or mattress cushion to vibrate. This vibration therapy is capable of reducing pulmonary problems such as the accumulation of secretions in the lungs.  
         [0006]     Unfortunately, controllers of known percussion devices do not sense or process displacement amplitude with displacement frequency of the vibrating media of the bladders. Hence, known percussion devices are not capable of detecting and/or utilizing natural resonant frequencies of the vibrating media. If the operating vibration frequency of known percussion devices is too distant from the natural resonant frequency, energy is wasted. If the operating vibration frequency is unintentionally at the natural resonant frequency, then damage or accelerated wear of the patient support apparatus may occur.  
       SUMMARY OF THE INVENTION  
       [0007]     A vibrating patient support apparatus has a resonant referencing percussion device preferably located internally to a cover of a mattress of the apparatus. The percussion device delivers a percussion or vibration at a controlled operating frequency that is preferably slightly less than a resonant frequency located internal to the mattress of the apparatus. With the various weight distributions of a patient, the device is capable of determining the ever shifting resonant frequency via signals received by the controller from a pressure sensor or accelerometer of the device. Because the operating frequency is slightly less than the natural resonating frequency, energy of the system is conserved. Because the operating frequency is not the controller calculated resonant frequency, wear on the device and potential damage is minimized.  
         [0008]     Preferably, the patient support apparatus includes a number of other devices for patient comfort and therapeutic treatment substantially located in a manageable and light weight mattress. All the devices are generally light weight with moving parts generally being bladders, thus relatively quiet when operating. For ease of manufacturing and cost, a substantial portion or all of the devices operate off of a common pump for preferably flowing pressurized air to an assortment of bladders. For instance, the percussion device preferably has bladders. Moreover, the apparatus preferably has a bladder operated rotation device for rotating a patient to minimize bed sores, a bladder operated firmness setting device for providing patient comfort, and an air loss control system for flowing air through the mattress to control temperature.  
         [0009]     Objects, features and advantages of the present invention include a patient support apparatus that has a relatively lightweight and manageable mattress having numerous devices for therapeutic treatment. Other advantages of the apparatus include a relatively simple and robust design that is inexpensive to manufacture, reduces wear and warranty costs and reduces energy consumption. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0010]     Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0011]      FIG. 1  is a perspective view of a patient support apparatus of the present invention positioned on a hospital bed frame;  
         [0012]      FIG. 2  is a cross-sectional view of the patient support apparatus taken along the line  2 - 2  in  FIG. 1 ;  
         [0013]      FIG. 3  is a cross-sectional view of the patient support apparatus taken along the line  3 - 3  in  FIG. 1 ;  
         [0014]      FIG. 4  is a schematic view of a control system of the patient support apparatus;  
         [0015]      FIG. 5  is a schematic view of an air flow system of the present invention;  
         [0016]      FIG. 6  is a schematic view of a resonant percussion device of the present invention;  
         [0017]      FIG. 7  is a partial enlarged cross section taken from the circle  7  of  FIG. 3 ;  
         [0018]      FIG. 8  is a cross section similar in perspective to  FIG. 7  and of a second embodiment of the patient support apparatus;  
         [0019]      FIG. 9  is a cross section similar in perspective to  FIG. 7  and of a third embodiment of the patient support apparatus;  
         [0020]      FIG. 10  is a cross section similar in perspective to  FIG. 7  and of a fourth embodiment of the patient support apparatus;  
         [0021]      FIG. 11  is a cross section similar in perspective to  FIG. 7  and of a fifth embodiment of the patient support apparatus; and  
         [0022]      FIG. 12  is an amplitude versus frequency graph. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a vibrating patient support apparatus of the present invention is generally shown at  10 .  
         [0024]     Referring to  FIG. 1 , the patient support apparatus  10  of the present invention is shown in combination with a mobile hospital bed frame  12 . As illustrated, the hospital bed frame  12  typically includes a plurality of side rails  14  that can be lowered for patient transfer and raised to confine a patient. The hospital bed frame  12  can also include a plurality of adjustable sections including an adjustable head section  16  that is pivotally adjustable relative to a main body section  18  of the bed frame  12  to allow the patient to sit up while eating or visiting with family.  
         [0025]     Still referring to  FIG. 1 , the patient support apparatus  10  preferably comprises a generally self-contained mattress or pad assembly  20  having a patient support surface  22 . The mattress  20  is referred to as being self-contained since a substantial portion of the working components of the mattress  20  that are used to carry out multiple functions, including a plurality of therapeutic functions, are enclosed by a cover  24  of the mattress  20 . The cover  24  can be any conventional material including, but not limited to natural fibers, polymeric materials, or combinations thereof. The cover  24  is preferably a vapor permeable material to be used in conjunction with a low air loss mechanism  26  of the mattress  20  described below.  
         [0026]     Referring to  FIG. 4 , a controller  72  of the patient support apparatus  10  controls operation of a main pump  50  preferably located externally of the mattress  20 . The main pump  50  supplies a controlled amount of pressurized air to multiple systems or devices of the mattress  20  that are generally located internally to the cover  24  of the mattress  20 . These systems include; a low air loss device  82  having a low air loss control system  56  and the low air loss mechanism or perforated tubing  26 , a firmness setting device  84  having a main valve system  58  and a main air bladder  36  (see  FIG. 3 ), a percussion device  86  having a percussion control system  60  and a percussion mechanism  38 , and a rotation device  88  having a rotation control system  62  and a rotation mechanism  40 . The rotation mechanism  40  is preferably two air bladders  42  located beneath the percussion mechanism  38 . The percussion mechanism  38  is preferably a plurality of air bladders  39  located beneath the main air bladder  36  of the mattress  20 . The main air bladder  36 , percussion mechanism  38 , and rotation mechanism  40  are supported within the cover  24  of the mattress  20  by a base cushion  44  positioned within a perimeter of the frame  34 . The base cushion  44  can be rigid or flexible and comprise an air bladder, or simply be constructed of conventional bedding materials such as foam, and the like.  
         [0027]     Preferably, a pendant  28  of the controller  72  is supported by a tower  30  coupled electrically to the mattress  20  and preferably supported structurally by the bed frame  12 . The pendant  28  includes user interface  32  of the patient support apparatus  10  used to operate at least a portion of the functions of the mattress  20 . The user interface  32  is preferably of a touch-screen display type that is well known to those skilled in the art for operator input, as well as output, based upon the particular software used to configure the user interface or touch-screen display  32 . Here, the touch-screen display  32  has input and output capabilities. These features are shown in application Ser. No. 11/260,452, filed Oct. 27, 2005, hereby incorporated by reference.  
         [0028]     Referring to  FIGS. 2-4 , the mattress  20  has a generally peripheral frame  34  of a conventional bedding frame material. Such material can include, but is not limited to foam, polymeric materials, metal, gels, or combinations thereof. Generally disposed internally to the cover  24  of the mattress  20  is the main air bladder  36  of the firmness setting device  84 , which is positioned within the perimeter of the frame  34  and immediately below an upper portion of the cover  24 . The main air bladder  36  acts as the primary support for the patient and with a controlled flow of air into and out of the bladder  36  can be useful in controlling the temperature of the bedding material exposed to the patient.  
         [0029]     The percussion-vibration mechanism  38  of the percussion device  86  is positioned below the main air bladder  36 , hereinafter referred to as the percussion mechanism  38 . The percussion mechanism  38  provides both percussion and vibration therapy to the patient. The particular therapy being employed is dependent on the frequency or the number of beats per second generated by the percussion mechanism  38 . For example, and not to be limited to these examples, the percussion therapy usually employs 1-7 beats per second (i.e. 1-7 hertz) and the vibration therapy employs 7 to 25 beats per second (i.e. 7-25 hertz). The percussion mechanism  38  may employ mechanical fingers or rollers to impart the percussion motion, but preferably comprises a pair of inflatable percussion bladders  39 , best shown in  FIG. 3 , having fingerlike cells that oscillate between inflated and deflated states to provide the percussive movement required. Such a mechanism is illustrated in U.S. Patent Application Publication No. 2004/0193078 to Flick et al., previously referenced.  
         [0030]     Preferably, a rotation mechanism  40  of the rotation device  88  for rotation therapy is positioned below the percussion mechanism  38 . The rotation mechanism  40  provides rotation therapy to the patient by rotating the patient from side to side. Along with percussion and percussion-vibration therapy, rotation therapy assists in reducing bed sores and pulmonary problems of the patient. The rotation mechanism  40  is preferably a pair of longitudinally positioned rotation bladders  42 , shown in  FIG. 3  and described in the &#39;078 publication to Flick et al. The rotation bladders  42  are independently inflated and deflated to raise one side of the patient, lower the patient, and then raise the other side of the patient such that the patient experiences a side-to-side rotation that shifts pressures between the patient and the bladder  36  of the firmness setting device  84  of the mattress  20 .  
         [0031]     Referring to  FIGS. 3 and 4 , the low air loss mechanism  26  of the mattress  20  used in conjunction with the encapsulating yet permeable cover  24  is preferably positioned inward of the cover  24 . In operation, air is pumped from the low air loss mechanism  26  through the permeable cover  24  to reduce the temperature below the patient support surface  22  and decrease the chance of skin maceration that lowers the risk of bed sores. Preferably, the main pump  50  delivers pressurized air to the perforated tubing of the mechanism  26  disposed within the frame  34  and under the cover  24 . The tubing is external to the main air bladder  36 , the percussion mechanism  38 , and the rotation mechanism  40 .  
         [0032]     Referring specifically to  FIG. 2 , a first control unit  46  of a main control system  70  in the form of a rigid box and preferably not of the mattress  20  is shown adjacent to a foot end  48  of the mattress  20 . The first control unit  46  encloses the main pump  50  and a power circuit board  52  of a main control system  70  for operating the main pump  50  and transferring power to the rest of the mattress components generally located in a second control unit  54 . As shown, the first control unit  46  fits neatly below the foot end  48  of the mattress  20 , but is not incorporated within the cover  24  of the mattress  20 . Of course, other configurations with the first control unit  46  inside the cover  24  are also possible. Such configurations are illustrated in the &#39;078 publication to Flick et al. In a preferred embodiment, the main pump  50  is used to inflate the main air bladder  36 , the percussion bladders  39 , and the rotation bladders  42 , and to convey air to the perforated tube  26 .  
         [0033]     The second control unit  54  of the main control system  70  in the form of a rigid box is shown beneath the cover  24  of the mattress  20  within the perimeter of the frame  34  (see  FIG. 2 ). The second control unit  54  encloses the low air loss control system  56  for controlling the low air loss mechanism  26 , the main valve system  58  for inflating and deflating the main air bladder  36 , the percussion control system  60  for controlling the percussion mechanism  38 , the rotation control system  62  for controlling the rotation mechanism  40 , and a main circuit board  64  in operative communication with these systems and the power circuit board  52  of the first control unit  46 . The second control unit  54  also preferably encloses a processor  74  and memory  78  of the controller  72  for controlling operation of these systems  56 ,  58 ,  60 ,  62  and the main pump  50 . These systems  56 ,  58 ,  60 ,  62  may comprise motors, solenoid valves, and/or motor-controlled valves, as disclosed in the &#39;078 publication. It should be appreciated that each of these separate control systems  56 ,  58 ,  60 ,  62  may also represent portions of a larger system. Those skilled in the art will now recognize that the systems employed for controlling operation of the loss air loss mechanism  26 , main air bladder  36 , percussion mechanism  38 , and rotation mechanism  40  may assume a variety of configurations.  
         [0034]     Referring to  FIG. 4 , the main control system  70  of the patient support apparatus  10  is schematically illustrated. The main control system  70  includes the controller  72  which comprises the processor  74 , the touch-screen display  32 , a display driver  76  for driving the touch-screen display  32 , the memory  78 , and a communication interface  80 . The controller  72 , via communication interfaces  80 , is also in operative communication with the low air loss control system  56 , main valve system  58 , percussion control system  60 , rotation control system  62 , and the main pump  50 .  
         [0035]     Referring to  FIG. 5 , an air flow schematic of the patient support apparatus  10  is shown. The air flow schematic generally shows the movement of air through conduits from an air source  94  (preferably outside air at atmospheric pressure) via the main pump  50  to the second control unit  54  and more specifically, to the low air loss control system  56 , the main valve system  58 , the percussion control system  60 , and the rotation control system  62 . Each of these systems  56 ,  58 ,  60 ,  62  preferably comprises valve controls for operating their respective mechanisms, i.e., the perforated tube  26 , the main air bladder  36 , the percussion bladders  39 , and the rotation bladders  42 . Such valve controls are described in more detail in the previously referenced &#39;078 publication to Flick et al. herein incorporated by reference. It should be appreciated that each of the separate control systems  56 ,  58 ,  60 ,  62  may be portions of a larger valve system, or the control systems  56 ,  58 ,  60 ,  62  may represent direct connections between the main pump  50  and the respective perforated tube  26  or bladders  36 ,  39 ,  42 .  
         [0036]     With further regards to the percussion device  86  and more specific to the present invention,  FIG. 6  illustrates the percussion device  86  having the previously described percussion control system  60  and the percussion mechanism  38 . Referring to  FIG. 7 , the percussion mechanism  38  also has a resonating pad  100  located between the main bladder  36  and the percussion bladders  39 , and a sensor  102  preferably being a pressure transducer located in preferably each percussion bladder  39  for sensing air pressure. Referring to  FIG. 12 , the resonating pad  100  is made of a resiliently flexible material having at least one known natural resonant frequency  104  that theoretically has a corresponding amplitude (displacement) that extends to infinity. The natural resonant frequency  104  is of the pad  100  when in an unloaded state (i.e. no patient weight) and as best illustrated by the solid amplitude vs. frequency curve  106  of  FIG. 12 .  
         [0037]     In operation, and assuming no patient load is placed upon the resonating pad  100  of mechanism  38 , (see  FIG. 12 ), the percussion device  68  inflates and deflates the plurality of bladders  39  at a baseline operating frequency  108  for optimal energy efficiency. In order to substantially reduce wear and potential damage of the device  86  via excessive vibration amplitude or displacement, the baseline operating frequency  108  is close to but is not at the resonant frequency  104  of the pad  100 . Generally, the baseline operating frequency  108  of the percussion device  86  is slightly less than any chosen one of the at least one resonant frequencies  104 . To optimize percussion therapy, the material and size of the resonating pad  100  is chosen with consideration made to the range of weight distributions of the patient that will tend to shift the amplitude vs. frequency curve  106 . This shift or addition of compressive weight on the resonating pad  100  generally alters the resonating frequencies of the pad  100  and is best illustrated as the shifted curve  110  having shifted resonating frequencies  112  in  FIG. 12 .  
         [0038]     For ease of explanation, each bladder  39  has a pressure transducer  102 , thus each bladder  39  can react to weight changes of the respective overhead portion of the patient. However, one skilled in the art would now know that a plurality of bladders  39  could be controlled by one pressure transducer  102 . If, for instance possibly due to manufacturing cost, only one pressure transducer  102  is utilized, its optimal location would be toward the center of the mattress  22  or under the lungs of the patient since percussion therapy is primarily used for treatment of the lungs.  
         [0039]     In operation of the percussion device  86  with the weight of a patient on the mattress  22 , the variable speed air pump  50  operates through the percussion control system  60  that preferably includes a double diaphragm valve system  99  for controlled inflation and deflation of the percussion bladders  39 . The inflation of the percussion bladders  39  by the pump  50  is oscillated such that the pressure in the percussion bladders  39  is increased and decreased, thereby lifting and dropping the patient. The weight of the patient not only shifts the resonating frequency to curve  110  but also adds a biasing force against the percussion bladders  39  preferably distributed through the pad  100 . This force correlates with a pressure increase in the percussion bladders  39 . The pressure inside the percussion bladders  39  is continuously monitored by the pressure transducers  102  and communicated to the controller  72 . As the speed of the pump  50  is changed, the pressure inside the percussion bladders  39  created by patient&#39;s potentially changing weight is monitored by the controller  72  to continually adjust for an optimal operating frequency  114  that correlates to a maximum pressure (pressure correlates to force divided by area, and area correlates to amplitude). The controller  72  then operates the pump  50  to achieve the optimal frequency  114  for percussion therapy for that particular patient.  
         [0040]     Referring to  FIG. 8 , a second embodiment of a mattress  22 ′ is illustrated. In the second embodiment, the resonating pad  100  of the first embodiment is generally omitted. The percussion device  84 ′ of the second embodiment operates similarly to the first embodiment except that the main air bladder  36 ′ also functions as the resonating pad of the first embodiment, hence, it is the resonating frequency of the bladder  36 ′ that is generally monitored indirectly by the pressure sensors  102 ′. As best illustrated in  FIG. 9 , a third embodiment of a mattress  22 ″ is illustrated that is similar to the second embodiment except that a main cushioning member  36 ″ of the mattress  22 ″ is not a bladder but a generally homogeneous and passive cushion preferably having a known natural resonating frequency.  
         [0041]     Referring to  FIG. 10 , a fourth embodiment of a mattress  22 ″′ is illustrated wherein the sensors  102  of the first embodiment are generally replaced with accelerometers  102 ″′ of the fourth embodiment. The accelerometers  102 ″′ are positioned to measure displacement of a resonating pad  100 ″′ that directly corresponds to amplitude of vibration and/or percussion. Referring to  FIG. 11 , a fifth embodiment of a mattress  22 ″″ is illustrated that is similar to the fourth embodiment except that a main cushioning member  36 ″″ of the mattress  22 ″″ is not a bladder but is a generally homogeneous and passive cushioning member  36 ″″ preferably having a known natural resonating frequency. In the fifth embodiment, the accelerometer  102 ″″ is preferably located in the cushioning member  36 ″″.  
         [0042]     While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention. For instance, the term mattress as applied to mattress  20  is not meant to be limited to a patient&#39;s bed, but may apply to any pad assembly that supports all or any portion of a patient against the bias of gravitational forces and whether or not the patient is intended to actual sleep upon the mattress or pad assembly.  
         [0043]     In light of the present invention, one skilled in the art would now realize that the bladder  36  may be a passive cushioning member thus generally eliminating the firmness setting device  84  altogether. Such a the cushioning member  36  could be a soft pad and/or made of a homogeneous material similar to the foam or gel of the frame  34 . Moreover, the air pump  50  and associated conduits could be replaced with a temperature controlled fluid pump system or a central pump system capable of handling a plurality of beds.