Patent Publication Number: US-2006016012-A1

Title: Device and method to prevent deep vein thrombosis

Description:
This invention relates to a device and method to prevent deep vein thrombosis in substantially sedentary person. More particularly this invention relates to a device that is combined with the baseboard of a bed and a method to use this device to prevent deep vein thrombosis (DVT).  
      For normal people this device can be made into portable devices for long distant travel (such as, airplanes, train, and all motor vehicles) to prevent DVT.  
     BACKGROUND OF THE INVENTION  
      Deep vein thrombosis can occur when a patient is confined to a bed for an extended period of time or people in long distant travel with limited use of the legs. Such a lack of activity, and particularly in the legs can lead to poor blood circulation in the legs and the potential for embolisms.  
      Deep vein thrombosis (DVT) is a common medical problem and particularly in traumatic brain injury, stroke, post operation, long term bed resting and rehabilitation patients. Current preventions can be classified to two categories: the first one is anticoagulant drugs which can reduce the risk of DVT and pulmonary embolisms, but this benefit is offset by a small and definite risk of serious hemorrhages. The second is physical methods (such as compression stockings applied to the legs) are not associated with any bleeding risk but there is insufficient evidence from randomized trials to support the routine use of physical methods for preventing DVT.  
      The multiple factors, including stasis, endothelial injury, and the status of the coagulation system, contribute to development of DVT. In the lower extremities, the stasis alone is usually the dominant factor initiating platelet aggregation and white blood cells to pass through the venous endothelial lining and damage it. Stasis is counteracted by calf and other muscular contraction. The inactivity and immobility of the muscular mass promote the pooling of blood in the calf and contribute to the development of DVT.  
      Post surgical patients and those with trauma, stroke and incapacitating malignancy, have restricted activity and often immobilized. This degree of immobilization leads to an increased incidence of thrombosis in the legs.  
      The devices described herein stimulate the ankle active range of motion and passive range of motion. As a result, calf muscular contraction is triggered, thereby preventing vein stasis, the primary factor that leads to the development of a clot. Furthermore, this device differs from current physical methods, such as pneumatic compression or compression stockings. The action of this device will improve blood circulation in the low extremities and promote the healing and recovering process. This is the result of active stimulation of the muscle mass rather than a passive stimulation. An active stimulation is more effective to prevent DVT.  
     BRIEF SUMMARY OF THE INVENTION  
      The invention is directed to a method and apparatus to assist in the prevention of DVT. The apparatus invention comprises a support with at least one resilient unit mounted on the support and a fluid in the resilient unit, and the resilient contacted by a person&#39;s foot, which compresses the resilient unit. In a further embodiment there are two resilient units with the resilient units being compressed alternatively by a person&#39;s feet, the fluid in the resilient unit flowing from one resilient unit to another upon the alternate application of pressure. A valve can be in a channel between the resilient units to regulate the pressure needed to flow the fluid from one resilient unit to another. Also associated with the channel can be a heater with sensors to maintain the fluid at a set temperature. The support for the resilient units can be the baseboard of the bed or the floor of any travel vehicles. The fluid can be a liquid or a gas. The choice of fluid and the pressure will to a degree be determined by the needs of the patient.  
      In an additional embodiment a pump can be included in the channel to assist the flow of fluid from one resilient unit to another resilient unit. This will be of use for persons early in their rehabilitation since it will move a person&#39;s feet and promote a person to put foot pressure against the resilient units. As a pressure is shared against a foot the patient will attempt to counteract this force. Such an additional embodiment can have a combined heater unit and can be connected to the baseboard of a bed or a separate portable unit.  
      In a usual treatment the person who is the patient or the passenger will in the first embodiment push a foot against one of the resilient units. Fluid will then flow from that resilient unit to the other resilient unit. Then the patient will push against the other resilient unit and fluid will flow to the first resilient unit. The person will continue the procedure for a set period of time as directed by the rehabilitation therapist.  
      In the case of a person in a sitting position such as during long distant travel, the resilient units are placed on the floor of any travel vehicle and the leg and foot movements remain the same.  
      In the use of the alternate embedment the patient will place his/her feet against the resilient units and turn on a pump that in a set cycle will flow fluid from one resilient unit to another resilient unit. This will put an alternating pressure against the person&#39;s feet and promote the application of pressure against the resilient units by the patient.  
      The result in the use of any of the embodiments is a substantial prevention of DVT in patients that have a substantial lack of mobility, and particularly a lack of mobility in the legs. This apparatus promotes leg activity and blood flow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a bed the resilient units where the support is the baseboard of a bed.  
       FIG. 2  shows a person in a bed with his/her feet alternately pressing against the resilient units.  
       FIG. 3  shows resilient units with a conduit for fluid between the resilient units.  
       FIG. 4  shows a resilient unit with an elevated reservoir.  
       FIG. 5  shows a range of motion of a person&#39;s foot against a resilient unit when compressing the resilient unit.  
       FIG. 6  shows a range of motion of a person&#39;s foot at rest against a resilient unit.  
       FIG. 7  shows a resilient unit with an integrated heater and pump.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The invention will be described in more detail in the referred embodiments with reference to the views in the figures. The invention can be modified but such modifications will be within the present concept.  
       FIG. 1  shows a bed  10  with the resilient units  30  and  32  as a part of the bed baseboard  14 . The bed has a headboard  12 , mattress  24  and side rails  16 ,  18 ,  20  and  22 . In  FIG. 2  there is shown a patient  50  covered by blanket  52  in the bed  10 . The patient&#39;s feet  54  and  56  alternately compress resilient units  30  and  32  respectively. When a resilient unit is compressed it will flow a fluid in that resilient unit to another resilient unit or to a reservoir.  
      When the device is used by a person in sitting position (figure not shown) the resilient units  30  and  32  can be place on the floor of any travel vehicles.  
      The flow of fluid from one resilient unit  30  to another resilient unit  32  is shown in  FIG. 3 . Here upon foot  56  compressing resilient unit  32 , fluid will flow from resilient unit  32  through conduit  34  to resilient unit  30 . Optionally in conduit  34  there can be a restricting valve or a pressure valve to adjust the pressure needed to flow the fluid from resilient unit  32  to resilient unit  30 . A restricting valve will narrow channel  34  to reduce the rate of flow of fluid and cause the patient to exert a greater force on the resilient units. There also can be spring loaded pressure valve where a certain amount of energy must be applied to cause the fluid to flow from one resilient unit to another. Such valves are known and available.  
       FIG. 4  shows a simple resilient unit with an elevated reservoir  38 . This reservoir is attached to resilient unit  36  by conduit  40 . This conduit can contain a valve as discussed above with regard conduit  34 . There can also be a thermostated heater to maintain the fluid in the resilient unit at a given temperature, usually body temperature.  
       FIGS. 5 and 6  show the range of motion of patient&#39;s foot  54  against resilient unit  30 . This range of motion can be effective to prevent DVT. The range of motion can be changed by the use of different shaped resilient units.  
       FIG. 7  shows a resilient unit  46  that is connected to pump/heater  44  by means of conduit  42 . In this embodiment such resilient unit will be pressurized alternatively along with another resilient unit as in  FIGS. 2 and 3 . This embodiment is useful when the patient does not as yet have sufficient strength to push on the resilient unit. By the resilient units being alternately pressurized the patient is prompted to push his/her foot against the resilient in response to the pressure. As to temperature it is preferred to maintain the temperature of the fluid at about body temperature of about 37° C.  
      The fluid can be essentially any liquid or gas. Liquid fluids are preferred. The viscosity of liquids can range from about 1 cp to about 150,000 cps. This will include water through gels.  
      The resilient units will be constructed of a rubber or other elastomer. The material should be quite resilient with the fluid and associated valving controlling the pressure that must be applied to the resilient unit. The thickness of the material should be sufficient to withstand daily use, but yet not prevent the ready deflection upon an applied force by a person&#39;s foot. Suitable elastomers include polymers and copolymers of ethylene, propylene, butane, butadiene, rubbers, foil, and polytetrafluoroethylene such as Teflon. These also can be in a laminate form. In addition, various foils can be used.