Abstract:
Apparatus for promoting blood flow in an extremity are disclosed including a gas source and a bladder assembly including a first bladder and a second bladder independently coupled to the gas source. The bladder assembly may be sized to fit within a shoe of a patient and may include a first bladder encircling a second bladder. A controller is operably coupled to the gas source and is configured to control the flow of gas from the gas source to the first and second bladders in order to periodically commence inflation the first and second bladders in sequence.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. The Field of the Invention 
         [0002]    This application relates to apparatus and method for the treatment of deep vein thrombosis, and, more particularly, to devices for applying an external compressive force to the lower extremities to promote blood flow. 
         [0003]    2. The Relevant Technology 
         [0004]    Contraction and relaxation of the muscles of the calf is responsible for the majority of movement of blood out of the lower extremities through the veins, hence venous circulation becomes stagnant when the calf muscles are at rest, increasing risk for deep venous thrombosis (DVT). 
         [0005]    Gravity likewise plays a role in venous circulation. Long periods of sitting or standing create pressure on the valves within the veins of the legs. Over time, these valves can break allowing blood to pool in the veins of the calf. This process known as deep venous insufficiency (DVI) is a lifelong disease process with no surgical solution. 
         [0006]    To decrease the risk of venous thrombosis while hospitalized, segmental pressure devices have been created, such as apparatus marketed under the trade name PLEXIPULSE. These devices are proven to lower incidence of clotting while immobile. However, these devices are bulky, non portable, and expensive, making them impractical for home use or daily wear. These devices are therefore ineffective for aiding in the prevention of DVI through daily use. 
         [0007]    Patients with DVI may be treated using medical compression stockings, which are an elastic stocking with graded compression, such as compression stocking offered for sale under the trade name MEDIVEN. These stockings often cause patients discomfort due to the tight compression and thick material. The tight compression also causes the compression stockings to be difficult to put on, requiring in some instances aid from a mechanical device to put the stocking over the heel of the foot. 
         [0008]    It is known that both DVI and DVT may be controlled by applying cyclical pressure to a person&#39;s lower extremities to aid in venous blood flow. Currently available devices use bulky, non-portable motors and include complex cuffs and bladders that wrap entirely around a person&#39;s leg. Devices of this type are not readily portable and are not meant to be worn during a person&#39;s normal daily activities. Examples of such devices are described in U.S. Pat. Nos. 5,263,473; 5,014,681 and 5,674,262. 
         [0009]    Another example of such a device is described in U.S. Pat. No. 6,290,662, which describes a boot formed of an inelastic material which completely surrounds the foot and a single-chambered bladder is positioned within the boot. This device is cumbersome and does not permit a person to wear normal shoes. This oversight makes the device impractical for daily wear and will tend to lead to poor patient compliance. Furthermore, surrounding any extremity with a rigid inelastic material inhibits movement and gives no room for swelling thus inhibiting circulation and increasing the risk for DVT, as well as being painful to those with severe DVI and foot swelling. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    These and other limitations may be overcome by embodiments of the present invention, which relates generally to medical devices and methods for promoting circulation in an extremity, such as a foot. 
         [0011]    In one aspect of the invention an apparatus for promoting circulation in an extremity in accordance with an embodiment of the present invention includes a gas source and a bladder assembly including a first bladder and a second bladder independently coupled to the gas source. The bladder assembly may be sized to fit within a shoe of a patient and may further be sized to occupy all or less than an instep portion of the patient&#39;s shoe. The first bladder may encircle the second bladder, such as a plane generally parallel to the sole of a shoe in which the bladder assembly is mounted. 
         [0012]    In another aspect of the invention, a controller is operably coupled to the gas source and is configured to control the flow of gas from the gas source to the first and second bladders in order to periodically inflate the first and second bladders. 
         [0013]    In another aspect of the invention, the controller is configured to first commence inflation of the first bladder followed by commencing inflation of the second bladder. The controller may further be configured to maintain the first and second bladders in an inflated state prior to permitting deflation of the first and second bladders. 
         [0014]    These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    To further clarify at least some of the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only illustrated embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0016]      FIG. 1  illustrates a schematic block diagram of an apparatus for promoting circulation in an extremity in accordance with an embodiment of the present invention; 
           [0017]      FIG. 2  illustrates a user interface for a controlling an apparatus for promoting circulation in an extremity in accordance with an embodiment of the present invention; 
           [0018]      FIG. 3  illustrates a housing for mounting a control unit of an apparatus for promoting circulation in an extremity in accordance with an embodiment of the present invention; 
           [0019]    Figure illustrates the housing of  FIG. 3  mounted to a shoe in accordance with an embodiment of the present invention; 
           [0020]      FIG. 5  illustrates ports of a bladder assembly for promoting circulation in an extremity in accordance with an embodiment of the present invention; 
           [0021]      FIGS. 6A through 6C  illustrate gas sources suitable for inflation of a bladder assembly to promote circulation in an extremity in accordance with an embodiment of the present invention; and 
           [0022]      FIGS. 7A through 7C  illustrate a method for inflating a bladder assembly to promote circulation in an extremity in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0023]    Referring to  FIG. 1 , a control unit  10  and bladder assembly  12  according to embodiments of the invention provide for deep vein insufficiency (DVI) and deep vein thrombosis (DVT) prophylaxis. The bladder assembly  12  is positionable adjacent a patient&#39;s foot  14 , such as under the arch of the patient&#39;s foot  14  such that the bladder assembly  12  may apply pressure to the deep veins within the sole of the foot upon inflation. For example, the bladder assembly  12  may be positioned under the deep plantar venous arch of the foot. In some embodiments, the bladder assembly is sized to occupy an area equal or less than the instep  16  of the patient&#39;s foot, such as all or less than the area between the metatarsal-phalangeal joint and the talo-navicular and calcaneocuboid joints. 
         [0024]    The bladder assembly  12  may include a first bladder  12   a  and a second bladder  12   b  each in fluid communication with a supply tube  18   a ,  18   b , respectively. In the illustrated embodiment the first bladder portion  12   a  encircles the second bladder  12   b , however, other relative sizes and shapes are possible. In the illustrated embodiment the first bladder portion  12   a  encircles the second bladder  12   b  in a plane generally parallel to the sole of a shoe in which the bladder assembly is removably mounted. 
         [0025]    The supply tubes  18   a ,  18   b  provide parts of fluid paths in fluid communication with a gas source  20  for selectively filling the first and second bladders  12   a ,  12   b  with pressurized air, or other fluid. The gas source  20  is controlled by a controller  22  that may be embodied as an electronic circuit, general purpose central processing unit (CPU), mechanical regulator, or other device suitable for the timed control of fluid flow. 
         [0026]    The controller  22  controls the flow of gas from the gas source  20  to the bladders  12   a ,  12   b  in order to periodically apply pressure to the plantar veins of the patient&#39;s foot  14 . The cyclic application of pressure encourage blood flow out of the lower extremities and relieve pressure on the valves within the veins of the legs, thereby reducing the conditions conducive to the development of DVI and DVT as discussed hereinabove. 
         [0027]    The controller  22  and gas source  20  may be coupled to a battery  24  providing electrical power. The battery  24  may be charged by means of a kinetic generator  26  operable to generate electrical energy based on movement of the generator  26 . For example, any of the class of devices including a spring mounted magnet positioned within a conductive coil may serve as the kinetic generator  26 . Alternatively, the battery  24  may be a replaceable alkaline battery or a rechargeable battery chargeable by an external source such that the kinetic generator  26  may be eliminated. 
         [0028]    The controller  22  may receive inputs from a patient using the control unit  10  and bladder assembly  12  or a medical professional treating the patient. Inputs may be received by means of one or both of a user interface  28  or a wireless receiver  30  operable to receive infrared signals or signals according to a wireless communication protocol such WiFi, WiMax, Bluetooth, and the like. 
         [0029]    Referring to  FIG. 2 , in one embodiment, the user interface  28  may include such inputs as an on/off button  32 , a frequency input  34  enabling an operator to input the frequency with which the bladders  12   a ,  12   b  are inflated, and a pressure input  36  enabling an operator to input the pressure to which the bladders  12   a ,  12   b  will be inflated. Alternatively, the inputs to turn on the device or alter the inflation frequency and pressure may be received by the wireless receiver  30  from a remote control device capable of receiving the same inputs as the user interface  28  and translating the inputs to wireless signals. Use of a remote control device may advantageously allow a user to adjust the device without bending down, which may be advantageous for patient&#39;s having limited mobility. Use of a remote control also advantageously allows a patient to turn off the device while walking when the artificial pumping of the device may not be needed. Further, the frequency and/or pressure of the bladders  12   a ,  12   b  can be controlled or set separately, together, or independently. For instance, the pressure of the bladder  12   a  can be set higher or lower than the pressure of the bladder  12   b  and/or at a different frequency. 
         [0030]    In some embodiments, the controller  22  may be programmed to prevent a user from adjusting the pressure and/or frequency of inflation of the bladders  12   a ,  12   b  to levels that are non-therapeutic. For example, the controller  22  may be programmed to enable a user to alter the inflation frequency to once every two to five minutes but no less than once every five minutes. The controller  22  may also be programmed to enable adjustment of the inflation pressure from 65 mmhg to 100 mmhg but not less than 65 mmhg. Such adjustments enable the operation of the device to be tuned to conserve battery life or to suit a patient&#39;s condition but prevent adjustment to the point that therapeutic benefits are no longer being achieved. In still other embodiments, pressure and frequency adjustments are not permitted by the controller  22  in order to prevent adjustment to non-therapeutic levels. 
         [0031]    Referring to  FIGS. 3 and 4 , the control unit  10  may include a housing  38  containing some or all of the components of the control unit  10  discussed hereinabove. A fastener  40  may secure to the housing to selectively secure the housing  38  to a patient or to an item of the patient&#39;s clothing. For example, the fastener  40  may be embodied as a resilient clip  42  such that a portion of the patient&#39;s footwear  44 , or other clothing, may be captured between the clip  42  and the housing  38  to secure the housing  38  to the patient&#39;s footwear  44  having the bladder assembly  12  positioned on the insole  46  of the footwear  44  such that the bladder assembly  12  will engage the instep  16  of a patient&#39;s foot  14  inserted within the footwear  44 . In some embodiments, the bladder assembly may be fastened to or integrally formed with the insole  46 . In other embodiments, the bladder assembly  12  is removably placed over the insole  46  either with or without the use of fasteners, such as a hook and loop fastening system such as VELCRO. The supply tubes  18   a ,  18   b  have sufficient length to extend between the bladder assembly  12  positioned on the insole  46  and the housing  38  clipped to the footwear, such as the laces or upper of the footwear  38 . In some embodiments, a magnet  48  may be mounted to the clip  40  adjacent a corresponding magnet  50  mounted to the housing  38  such that magnetic attraction between the magnets  48 ,  50  augments the biasing force of the clip  40 . 
         [0032]    The supply tubes  18   a ,  18   b  may couple to ports  52   a ,  52   b  either protruding from or accessible within housing  38  and in fluid communication with the gas source  20 . For example, the ports  52   a ,  52   b  may include any toolless pneumatic coupler known in the art such that the supply tubes  18   a ,  18   b  can be readily connected to and disconnected from the ports  52   a ,  52   b . A patient may use differently sized supply tubes  18   a ,  18   b  depending on the type of footwear with which the control unit  10  and bladder assembly  12  are used. A patient may use longer supply tubes  18   a ,  18   b  when wearing tall boots, for example. 
         [0033]    Referring to  FIG. 5 , the bladder assembly may likewise include ports  54   a ,  54   b  in fluid communication with the bladders  12   a ,  12   b  respectively. The ports  54   a ,  54   b  may likewise include any toolless pneumatic coupler known in the art such that the supply tubes  18   a ,  18   b  can be readily connected to and disconnect from the ports  54   a ,  54   b.    
         [0034]    Referring to  FIG. 6A , in some embodiments, the controller  22  is operable to control power supplied to a gas source  20  embodied as a compressor  60 . The compressor  60  may be a miniature energy efficient compressor, such as that used in the wrist mounted blood pressure device marketed under the trade name RELION. In some embodiments, the compressor  60  is capable of generating pressures of about 65 mm/HG or more. The compressor  60  may be coupled to a reservoir  62  storing pressurized gas. A pressure sensor  64  may be positioned within the reservoir  62  and output to the controller the pressure within the reservoir  62 . The controller  22  may be programmed to control power supplied to the compressor  60  in order to maintain the gas within the reservoir  62  at a specified pressure based on the output of the pressure sensor  64 . 
         [0035]    Electrically actuated valves  66   a ,  66   b  may have inputs in fluid communication with the reservoir  62 . Alternatively, the valves  66   a ,  66   b  have inputs in direct fluid communication with the compressor  60  and the reservoir  62  may be eliminated. Outputs of the valves  66   a ,  66   b  are selectively placed in fluid communication with the supply tubes  18   a ,  18   b , such as by means of coupling the supply tubes  18   a ,  18   b  to the ports  52   a ,  52   b . The controller  22  may open the electrically actuated valves  66   a ,  66   b  in order to supply pressurized gas to the bladders  12   a ,  12   b  in a cyclical manner. Deflation of the bladders  12   a ,  12   b  may be accomplished by turning off power to the compressor  60  while the valves  66   a ,  66   b  are maintained open such that gas is allowed to leak through the compressor  60  from the bladders  12   a ,  12   b . Alternatively, the valves  66   a ,  66   b  may have two states—one in which the compressor  60  or reservoir  62  is in fluid communication with the bladders  12   a ,  12   b  and another in which the bladders  12   a ,  12   b  are placed in fluid communication with the atmosphere and fluid flow from the compressor  60  or reservoir  62  is substantially cut off. 
         [0036]    In yet another alternative embodiment, electrically actuated relief valves  68   a ,  68   b  may be placed in fluid communication with the ports  52   a ,  52   b  downstream from the valves  66   a ,  66   b . The controller  22  may be programmed to close the valves  66   a ,  66   b  and then open the relief valves  68   a ,  68   b  to vent air from the bladders  12   a ,  12   b . The controller  22  may be further programmed to close the relief valves  68   a ,  68   b  valves prior to opening of the valves  66   a ,  66   b.    
         [0037]    Referring to  FIG. 6B , in an alternative embodiment, the compressor  60  may be eliminated and a reservoir  70  may be placed in fluid communication with the valves  66   a ,  66   b . The reservoir  70  may be readily replaceable, such as a CO 2  cartridge. In such embodiments, the valves  66   a ,  66   b  may be actuated by the controller  22  to place the reservoir  68  in fluid communication with the supply tubes  18   a ,  18   b  in order to inflate the bladders  12   a ,  12   b . In such embodiments, the bladders  12   a ,  12   b  may be deflated by means of relief valves  68   a ,  68   b  that are opened after the valves  66   a ,  66   b  are closed in order to vent air from the bladders  12   a ,  12   b . The relief valves  68   a ,  68   b  may be closed before opening the valves  66   a ,  66   b . Alternatively, relief valves  68   a ,  68   b  may be eliminated and the valves  66   a ,  66   b  may have two states—one in which the reservoir  70  is in fluid communication with the bladders  12   a ,  12   b  and another in which the bladders  12   a ,  12   b  are placed in fluid communication with the atmosphere and fluid flow from the reservoir  70  is substantially cut off. 
         [0038]    Referring to  FIG. 6C , in yet another alternative embodiment, the valves  66   a ,  66   b  are eliminated and two compressors  60   a ,  60   b  are used, each controlled by the controller  22  to provide independent inflation of the bladders  12   a ,  12   b . In such embodiments, deflation of the bladders  12   a ,  12   b  may be accomplished by turning off the compressors  60   a ,  60   b  and allowing gas to leak from the bladders  12   a ,  12   b  through the compressors  60   a ,  60   b.    
         [0039]    Referring to  FIGS. 7A-7C , the bladders  12   a ,  12   b  may be periodically inflated according to the illustrated method in order to more effectively increase blood flow through the lower extremities. In some embodiments, the bladders  12   a ,  12   b  are independently inflated sequentially. Referring to specifically to  FIG. 7A , in use the bladder assembly  12  is positioned on the insole  46  of the patient&#39;s footwear  44  such that the lower surface  70  of the patients foot  14  rests on the bladder assembly  12 , with or without an intervening covering such as stockings, nylons, or the like. As noted above, the bladder assembly  12  may be positioned to apply pressure to the plantar veins, such as the deep plantar venous arch. As shown in  FIG. 7A , the bladder assembly  12  is initially deflated. The bladder assembly  12  may be removably positioned within the footwear  44  such that the bladder assembly  12  may be used with different pairs of shoes. The bladder assembly  12  may also be available in multiple sizes to accommodate different sizes of feet and different types of shoes. 
         [0040]    Referring to  FIG. 7B , the controller  22  may then cause the gas source  20  to inflate the bladder  12   a , such as by performing one or both of opening the valve  66   a  or powering a compressor  60  or  60   a . As noted above, the bladder  12   b  may encircle the bladder  12   a . Inflation of the bladder  12   a  may therefore result in pooling of blood within the area of the patients foot  14  encircled by the bladder  12   a.    
         [0041]    Referring  7 C, following inflation of the bladder  12   a , the bladder  12   b  may be inflated, such as by performing one or both of opening the valve  66   b  or powering a compressor  60  or  60   b . Inflation of the bladder  12   b  may commence following commencement of inflation of the bladder  12   a  either before or after the bladder  12   a  is completely inflated. For example, the controller  22  may commence inflation of the bladder  12   b  following a wait period of between about 0.5 and 3 seconds following commencement of inflation of the bladder  12   a . In the illustrated embodiment, the bladder  12   a  remains inflated while the bladder  12   b  is inflated, such as by keeping the valve  66   a  open or continuing to power a compressor  60   a . Inflation of the bladder  12   b  following inflation of the bladder  12   a  may increase effectiveness of the device as blood that is pooled within the opening defined by the bladder  12   a  during inflation of the bladder  12   a  is forced out during inflation of the bladder  12   b.    
         [0042]    Referring again to  FIG. 7A , following inflation of the bladder  12   b , the bladders  12   a ,  12   b  may then be permitted to deflate. In some embodiments, the bladders  12   a ,  12   b  are permitted to deflate following a wait period, such as a period of between about 1 and 5 seconds, or between about 2 and 3 seconds. Typically the elasticity of the bladders  12   a ,  12   b  and the weight of the patient&#39;s foot  14  are used to force air from the bladders  12   a ,  12   b . As noted above, air may be allowed to escape from the bladders  12   a ,  12   b  according to various methods, such as by turning off power to compressors  60   a ,  60   b , leaving the valves  66   a ,  66   b  open while the compressor  60  is unpowered, closing the valves  66   a ,  66   b  and opening relief valves  68   a ,  68   b , or by changing the valves  66   a ,  66   b  to a state that vents the bladders  12   a ,  12   b  to the atmosphere. Following deflation of the bladders  12   a ,  12   b , the bladders  12   a ,  12   b  may be again inflated as shown in  FIGS. 7B and 7C  according to a frequency specified by the controller  22 . For example, in one therapeutic regime the bladders are inflated about every one to five minutes, or about every two to three minutes. 
         [0043]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.