Abstract:
A method and apparatus for the prevention of deep vein thrombosis (DVT), pulmonary embolism (PE), lower extremity edema, and other associated medical conditions by adjusting the temperature of the muscles of a foot or a leg, and/or applying vacuum or negative pressure to increase blood flow. A human extremity such as a leg is exposed to a negative pressure environment and/or a thermally controlled environment within a medical device. In one aspect, the device is portable. A thermal exchange unit and, optionally, a vacuum or negative pressure unit, are provided to increase blood flow and vasodilation. The device can be programmed by a controller in a manner to stimulate the muscles of the extremity to reduce pooling of blood therein.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a continuation-in-part of U.S. patent application Ser. No. 11/566,575, filed Dec. 4, 2006 now U.S. Pat. No. 8,066,752, which is a continuation of U.S. patent application Ser. No. 10/948,121, filed Sep. 23, 2004, now issued U.S. Pat. No. 7,160,316, issued Jan. 9, 2007, which claims benefit of U.S. provisional patent application Ser. No. 60/505,798, filed Sep. 24, 2003. This application also claims benefit of U.S. provisional patent application Ser. No. 60/821,201, filed Aug. 2, 2006. Each of the aforementioned related patent applications are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention generally relate to methods and apparatus for increasing circulation and/or adjusting the temperature of a human. Embodiments of the invention may be used, for example, to prevent deep vein thrombosis (DVT). 
     2. Description of the Related Art 
     Venous thromboembolic disease continues to cause significant morbidity and mortality. Hospitalization in ranges of 300,000 to 600,000 persons a year is due to venous thrombosis and pulmonary embolism (PE), originating from blood clots in the veins and some clots traveling to the lung. PE is estimated to be the third most common cause of death in the United States, resulting in as many as 50,000 to 200,000 deaths a year. 
     Following various types of surgical procedures, as well as trauma and neurological disorders, patients are prone to developing DVT and PE. Regardless of the original reasons for hospitalization, one in a hundred patients upon admission to hospitals nationwide dies of PE. Patients suffering from hip, tibial and knee fractures undergoing orthopedic surgery, spinal cord injury, or stroke are especially at high risk. Therefore, prevention of DVT and PE is clinically important. 
     Studies indicated that factors contributing to the development of DVT include reduction of blood flow, vascular stasis, increase vessel wall contact time, coagulation changes, blood vessel damage, and pooling of blood in the lower extremities. It is believed that slowing of the blood flow or blood return system from the legs may be a primary factor related to DVT with greatest effect during the intraoperative phase. Also of concern is the postoperative period. Even individuals immobilized during prolong travel on an airplane or automobile may be at risk. Generally, without mobility, return of the blood back to heart is slowed and the veins of an individual rely only on vasomotor tone and/or limited contraction of soft muscles to pump blood back to the heart. One study shows that travel trips as short as three to four hours can induce DVT and PE. 
     Current approaches to prophylaxis include anticoagulation therapy and mechanical compression to apply pressure on the muscles through pneumatic compression devices. Anticoagulation therapy requires blood thinning drugs to clear clots in the veins which must be taken several days in advance to be effective. In addition, these drugs carry the risk of bleeding complications. Pneumatic compression devices, which mechanically compress and directly apply positive message-type pressures to muscles in the calf and foot sequentially, are not comfortable, are difficult to use even in a hospital, and are too cumbersome for mobile patients or for use during prolonged travel. In addition, most of them are heavy weighted and there are no portable or user friendly devices. 
     Therefore, there remains a need for an apparatus and method to increase blood flow and/or regulate body temperature in a human which can be used in reducing clots in a human extremity and preventing deep vein thrombosis. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention provide methods and apparatus for increasing blood flow and/or controlling body temperature which can be used in preventing deep vein thrombosis. In one embodiment, a lower extremity device is provided for regulating temperature and/or providing a vacuum or a negative pressure on a human extremity, such as a leg, foot, or calf of a leg, in order to increase blood flow on the human extremity and prevent deep vein thrombosis. The lower extremity device includes a hard or soft chamber body defining a hard or soft chamber therein, a vacu-seal attached to an opening of the hard or soft chamber body for contacting a human extremity therein and providing a space between the seal and the hard or soft chamber body, and one or more apertures on the hard or soft chamber body. One or more thermal exchangers, which are placed inside the lower extremity device, permanently or detachably, are connected to one or more thermal exchange lines. The one or more thermal exchangers are also connected via one or more supply lines and return line through the one or more apertures of the hard or soft chamber body to a thermal source, a heating source, a cooling source, and/or, a thermal fluid source in order to regulate the temperature to the human extremity. In addition, one or more vacuum lines can be connected through the one or more apertures of the hard or soft chamber body to one or more vacuum pumps in order to apply vacuum to the hard or soft chamber. In another embodiment, the lower extremity device can be used in combination with a mechanical compression device or the lower extremity device can itself be modified to include one or more pressure-applying pads in order to apply mechanical compression to a lower extremity of a mammal, in addition to regulating the temperature and/or applying vacuum to the lower extremity. 
     In still another embodiment, a method of preventing DVT includes providing a lower extremity device to a mammal, the lower extremity device comprising a hard or soft chamber body, a seal attached to an opening of the hard or soft chamber body for contacting the lower extremity therein and providing a space between the seal and the hard or soft chamber body, and one or more thermal exchangers, regulating the temperature of the lower extremity using the lower extremity device, vasodilating an arteriovenous anastomoses (AVAs) blood vessel of the lower extremity of the mammal, and reducing the constriction of the AVA blood vessel using the lower extremity device, thereby increasing blood flow of the lower extremity and decreasing clotting within the veins. The method can further include applying mechanical compression to the lower extremity of the mammal. The method may optionally include reducing the pressure of the hard or soft chamber of the lower extremity device, such as to vacuum levels. 
     In a further embodiment, a method of preventing DVT includes regulating the temperature of one or more extremities of a mammal and exposing the one or more extremities to a vacuum or a reduced pressure environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a cross-sectional view of one embodiment of an exemplary lower extremity device. 
         FIG. 2  is a section view of an exemplary seal having a foot disposed therein according to one embodiment of the invention. 
         FIG. 3  is a perspective view of an exemplary thermal exchange unit according to one embodiment of the invention. 
         FIG. 4  is a top view of another thermal exchange unit according to another embodiment of the invention. 
         FIG. 5  is a perspective view of another thermal exchange unit according to another embodiment of the invention. 
         FIG. 6  is a perspective view of an exemplary foot device according to one embodiment of the invention. 
         FIG. 7  is a perspective view of two exemplary foot devices according to one embodiment of the invention. 
         FIG. 8  is a perspective view of an exemplary leg device according to one embodiment of the invention. 
         FIG. 9  is a top view of another exemplary leg device of the invention. 
         FIG. 10  illustrates one embodiment of a control unit connected to a device according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention include a method and an apparatus for preventing deep vein thrombosis (DVT). In one embodiment, an apparatus for preventing deep vein thrombosis (DVT) is provided to increase blood flow in a mammal&#39;s extremity by regulating the temperature of the mammal&#39;s extremity, vasodilating an arteriovenous anastomoses (AVAs) blood vessel of the mammal&#39;s extremity, reducing constriction of the AVA blood vessel, and/or increasing vasomotor tone. In particular, the invention provides a non-invasive, convenient apparatus for efficiently adjusting the temperature, applying vacuum, and/or applying compression pressure or forces, to the mammal&#39;s extremity to increase blood flow, promote venous blood return, and reduce blood clots. 
     Arteriovenous anastomoses (AVAs) are specialized blood vessels located in the palms of the hands and the soles the feet which are connected to arteries and veins. Not wishing to be bound by theory, it is believed that, by heating or preventing the temperature from cooling off, to open up the AVA vessels, reduce constriction of the AVA vessels, and increase vasomotor tone, adjusting the temperature of an extremity may increase blood flow in the AVA vessels and increase venous return pressure, thereby preventing clots in the veins and preventing DVT. 
     In addition, embodiments of the invention provide subjecting portions of an extremity of a mammal to a reduced pressure environment, preferably under vacuum to cause dilation of vascular structures within the portions under the reduced pressure and increase blood flow, thereby reducing venous clots and preventing DVT. Apparatus according to aspects of the invention includes a hard or soft chamber body and a vacu-seal defining a hard or soft chamber space therebetween. The pressure of the hard or soft chamber space can be regulated to a level lower than atmospheric pressure, such as a pressure level of zero mm-Hg to about −120 mm-Hg. 
     Generally, the apparatus to increase blood flow and prevent deep vein thrombosis (DVT) includes a hard or soft chamber body defining a hard or soft chamber therein, a vacu-seal, one or more apertures in the hard or soft chamber body, and one or more thermal exchange units attached to the hard or soft chamber body through the one or more apertures. The seal may include a sealing portion attached to an opening of the hard or soft chamber body and adapted to provide a vacuum seal for the hard or soft chamber body. The seal may further include a vacu-seal body portion adapted to contact a portion of a human extremity, resulting in a hard or soft chamber space between the seal and the hard or soft chamber body such that vacuum or reduced pressure can be applied inside the hard or soft chamber space. 
     In one embodiment, the hard or soft chamber body is adapted to be connected between one or more thermal sources and the thermal exchange units via one or more thermal exchange supply lines and one or more thermal exchange return lines passing through at least one aperture in the hard or soft chamber body in order to regulate or maintain the temperature of the mammal&#39;s extremity. In another embodiment, the hard or soft chamber body is connected to a vacuum port and a pump via one or more additional lines through the one or more apertures in the hard or soft chamber body in order to reduce the pressure inside the hard or soft chamber space and provide a negative pressure environment that vasodilates the vasculature of the mammal&#39;s extremity. The vasodilation of the vasculature may also help to increase the thermal exchange between the one or more thermal exchange units and the mammal&#39;s extremity. 
     The extremity of a mammal includes legs, feet, toes, calfs, limbs, ankles, hands, etc. While embodiments of the invention will be described further below with respect to a foot device, it is recognized that the foot device described below may be adapted for use with other extremities that have vasculature structures suitable for the vasodilation methods described herein. Regulating the temperature of the mammal&#39;s extremity may include elevating and/or maintaining the temperature. The mammal may be a human or other mammal. People at high risk of DVT, PE and other conditions, such as edema, wound swelling, venous stasis ulcers, diabetic wounds, decubitous ulcer, orthopedic surgery patients, spinal cord injured individuals, among others, can benefit from the invention. 
       FIG. 1  is a cross-sectional view of one embodiment of a foot device  100  and a thermal exchange unit  104 . The foot device  100  includes a vacu-seal  108  and a hard or soft chamber body  102  defining a hard or soft chamber  150  to provide an enclosure in which a mammal&#39;s extremity may be positioned therein and exposed to temperature regulation and/or a vacuum environment. The thermal exchange unit  104  can be permanently or detachably placed inside the hard or soft chamber  150  to provide thermal exchange for a foot received therein. 
     The hard or soft chamber body  102  can be made of any durable material, such as elastomers, polycarbonates, polypropylenes, composite materials, an acrylic material, polystyrenes, high density polyethylenes (HDPE), low density polyethylenes (LDPE), poly(vinyl chloride), urethanes, polyurethanes, graphites, fiberglass, glass, rubbers, stainless steels, titanium, aluminum, light weight metal alloys (e.g., aluminum alloys, titanium alloys, etc.), polymeric materials, or any biocompatible, disposable material. The hard or soft chamber body  102  can be made of disposable low cost materials. For example, the hard or soft chamber body  102  is made of a disposable acrylic material that allows viewing of a foot positioned inside the hard or soft chamber  150 . As another example, the hard or soft chamber body  102  may be made of materials that may be sterilized via autoclaving or ethylene oxide sterilization. This is especially important if the apparatus is used during surgery where sterile conditions are very important. 
     The vacu-seal  108  may be made of a material that is biocompatible (and therefore safe for contact with the skin of a mammal) and capable of producing an airtight seal. In one embodiment, the vacu-seal  108  is detachably disposed inside the hard or soft chamber  150 . In another embodiment, the vacu-seal  108  is made of a disposable material, such as disposable liners or insert materials, to be used with a non-disposable hard or soft chamber body  102 . For example, the material of the vacu-seal  108  may be polyurethane, urethane, among others. One example of the seal material is PS series thermoplastic polyurethane from Deerfield Urethane, Inc. Disposable seal materials may be manufactured and packaged such that they are sterile before use. In another embodiment, the hard or soft chamber body  102  is made of non-disposable material while the vacu-seal  108  is made of disposable material to meet health and safety requirements. 
     The vacu-seal  108  may include a vacu-sealing portion  120  disposed around a top opening  128  of the foot device  100  to provide a hard or soft chamber space  110  between the vacu-seal  108  and the thermal exchange unit  104 . The top opening  128  is configured to receive a foot, a leg, or other extremity of a mammal. A foot disposed in the hard or soft chamber  150  is secured to the foot device  100  by the vacu-seal  108  attached to the foot device  100  through the sealing portion  120  of the vacu-seal  108  of the foot device  100 . 
     The hard or soft chamber space  110  inside the hard or soft chamber  150  is vacu-sealed by the vacu-sealing portion  120  and adapted to be connected to a vacuum port  112  through an aperture  114  of the hard or soft chamber body  102 . The vacuum port  112  is also adapted to be connected to a vacuum pump (not shown) for reducing the pressure of the hard or soft chamber space  110  inside the hard or soft chamber  150 . The vacuum port  112  may be covered by a protective sheath. The position of the aperture  114  can be located near any convenient portion of the hard or soft chamber body  102 . In addition, the pressure level inside the hard or soft chamber  150  can be monitored by a vacuum sensor (not shown) placed inside the hard or soft chamber space  110  with a vacuum sensor port attached to the hard or soft chamber body  102  via an aperture in the hard or soft chamber body  102 . 
     Accordingly, the pressure inside the hard or soft chamber  150  may be regulated in a range from atmospheric pressure to sub-atmospheric levels. For example, the hard or soft chamber space  110  inside the hard or soft chamber  150  can be adjusted to a negative pressure level, such as between about zero to about −120 mmHg, or between about −20 mmHg and about −80 mmHg, when the vacu-sealing portion  120  is vacu-sealed. 
     One or more thermal exchange units  104  may be provided to one or more portions of the hard or soft chamber body  102  to adjust (increase, reduce, or maintain) the temperature of the foot received therein. The thermal exchange unit  104  may include a thermal-exchange fluid medium, a heated fluid, heated air, a cooled fluid, or cooled air flown therein and provided from a fluid source (not shown) via one or more fluid supply lines. Alternatively, the thermal exchange unit may include an electric pad, as described in detail in  FIGS. 3-5 . For example, the thermal exchange unit  104  may be a water heating pad having heated water flown therethrough. The one or more fluid supply lines and/or one or more fluid return lines having the thermal-exchange fluid medium flown therein between the thermal exchange unit  104  and the fluid source may pass through one or more apertures (not shown) or holes in the hard or soft chamber body  102 . The position of the apertures for the one or more fluid supply lines and the one or more fluid return lines in the hard or soft chamber body  102  can be located near any convenient portions of the hard or soft chamber body  102  and can be close to the aperture  114  or grouped together with the vacuum port  112  for passing through the hard or soft chamber body  102  via a single aperture. 
     The foot device  100  may further include a controller unit  160  connected to various parts of the foot device  100  for regulating the functions of the foot device  100 , including adjusting the fluid flow in and out of the thermal exchange unit  104 , regulating the temperature of the thermal exchange unit  104 , monitoring the pressure level inside the hard or soft chamber  150  via one or more vacuum sensors, adjusting the vacuum pump and the vacuum level inside the hard or soft chamber  150 , and monitoring the temperature of the foot received in the hard or soft chamber  150 , among others. 
     Good contact with the thermal exchange unit is important in maximizing thermal transfer to a mammal&#39;s extremity. However, the pressure differential from ambient pressure to the interior of the hard or soft chamber may cause, for example, a foot to be arched or pulled up near the sole of the foot and lose optimal contact for efficient thermal exchange. The force caused by the pressure differential is approximately equal to the area of the sole of the foot times the pressure differential. For example, the pressure differential may be approximately three pounds. In addition, the foot may be forced off the thermal exchange unit through normal jostling or positioning of the patient. 
     Accordingly, a flexible membrane  106  is provided between the thermal exchange unit  104  and the hard or soft chamber body  102  to enhance the surface contact between the thermal exchange unit  104  and the foot  130 . The flexible membrane  106  may collapse against the thermal exchange unit  104  under a sub-atmospheric pressure or a vacuum pressure level within the hard or soft chamber  150 . The flexible membrane  106  may comprise any suitable flexible material, for example, gas permeable thermoplastics, elastomeric materials, such as C-FLEX.RTM. (Consolidated Polymer Technologies, Inc., Largo, Fla.), DynaFlex (GLS Corporation, McHenry, Ill.), and other elastomeric materials with similar properties. In one embodiment, the flexible membrane  106  comprises a material that is temperature resistant. 
       FIG. 2  is a sectional view of the vacu-seal  108  having a foot  130  disposed therein. The vacu-seal  108  includes the vacu-sealing portion  120  and a body portion  122  which can be shaped to an extremity of a mammal, such as the foot  130  of a human. The vacu-sealing portion  120  is applied to the top opening  128  of the vacuum hard or soft chamber  150  by overlapping the vacu-seal  108  form the inside to the outside of vacuum hard or soft chamber  150 . The body portion  122  may be formed to conform to the shape of the foot  130  like a sock The angle α may be less than 90°, such as between about 70° to about 90°, e.g., about 75°. 
     In addition, there is a hole  124  provided between the vacu-sealing portion  120  and the vacu-seal body portion  122 . In one embodiment, the hole  124  is covered the ankle area of the foot  130  providing a vacuum seal between the ankle and the Vacuum hard or soft chamber. The  124  is sized to stretch (because of the material selected) to shape and size of the ankle to form a vacuum seal. There may be different shapes and sizes of the hole  124  depending on the mammal&#39;s foot. 
     The vacu-seal body portion  122  may include a temperature sensor  140 , which is positioned in contact with the foot  130 , for measuring the temperature of the foot  130 . A foot disposed in the foot device  100  may rest on the vacu-seal body portion  122  above the thermal exchange unit  104 . The temperature sensor  140  may be, for example, a  400  series thermistor temperature probe, available from YSI Temperature, located in Dayton, Ohio. The temperature sensor  140  is connected to the controller unit  160  of the foot device  100 . In an alternative embodiment, the vacu-seal  108  may include the thermal exchange unit. In another embodiment, the vacu-seal  108  may include an in-use sensor indicating the use of the product. In addition, the in-use sensor of the vacu-seal  108  may indicate how many times the vacu-seal  108  have been used. 
     The vacu-seal body portion  122  may further include an air permeable portion  126 , made of a permeable membrane material or a breathable material to permit the flow of air, etc. Examples of breathable materials are available from Securon Manufacturing Ltd. or 3M company. The permeable portion  126  may be positioned near any portion of the body portion to provide permeable outlets, allowing the vacuum to have the proper effect on the extremity and providing a barrier keeping the hard or soft chamber  150  from contamination for the comfort of the patient. As exemplarily shown in  FIG. 2 , the permeable portion  126  is positioned near the toe portions of the foot  130 . 
     The vacu-sealing portion  120  can be wrapped around the top opening  128  of the hard or soft chamber  150  near the hole  124  of the vacu-seal  108 . A pressurized seal is ultimately formed by vacu-sealing the vacu-sealing portion  120  to the hard or soft chamber  150  and pumping air out of the vacu-sealing portion  120  of the vacu-seal  108  via an air port. In addition, the air inside the hard or soft chamber  150  can be pumped out via the vacuum port  112  connected to a vacuum pump. With the vacu-sealing portion  120  properly sealed to the foot  130  under vacuum, the negative vacuum pressure applied to the hard or soft chamber  150  via the vacuum port  112  also pulls the vacu-seal  108  away from the foot  130  because F vacu-seal  and F vac  act in opposition to one another, thereby reducing the total force, F total , and thus reducing the tourniquet effect. For example, a F vacu-seal  of 80 mm Hg and a high F vac  can reduce the F total  to 40 mm Hg. 
     The vacu-seal  108  that seals the foot  130  under vacuum to the hard or soft chamber  150  plays an important role in the performance of the foot device because it prevents leakage of air into the vacuum or sub-atmospheric environment of the hard or soft chamber  150 . It is recognized that the vacu-seal  108  is one example of a seal that may be used with the hard or soft chamber  150 . A seal having the sealing portion with minimal leakage is preferable since it reduces the amount of air that must be continuously removed from the apparatus with an enclosed foot as vacuum is applied. However, a vacu-seal that exerts too much force on the foot may reduce or eliminate the return blood flow to the body, thus reducing the effectiveness of the foot device, and potentially creating adverse health effects. The vacu-seal  108  may also be attached to the hard or soft chamber  150  with mechanical fasteners or other fastening units. One example includes one or more mating rings which can snap into the vacuum hard or soft chamber  150 . Another example includes the use of a tape with a removable liner, such as 3M removable tapes, etc., which can be removed when ready to use. 
     In one embodiment, the vacu-seal  108  is a single use seal. In another embodiment, the single use seal remains attached to the hard or soft chamber after use, and the hard or soft chamber and the attached seal are disposed of after a single use. In still another embodiment, the vacu-seal  108  may be removed from the hard or soft chamber and the hard or soft chamber may be used repeatedly with another vacu-seal. 
     In one embodiment, the vacu-sealing portion  120  may comprise a strip of releasable adhesive tape ranging from 0.5 inches to 6 inches in width, e.g., a width large enough to cover the bottom of the foot  130 . The vacu-sealing portion  120  may have different widths along the interface between the vacu-sealing portion  120  and the vacu-seal body portion  122 . The vacu-sealing portion  120  may comprise an adhesive face and a backing portion. The vacu-sealing portion  120  is generally long enough that when wrapped end over end around the edge of the top opening, an overlap of about 0.5 inches or larger, such as about 2 inches, is present. The overlap is preferably not to encourage the user to wrap the vacu-seal around the foot too tightly and thus create a modest vacu-sealing force, e.g., less than 20 mm Hg. 
     The material of the vacu-sealing portion  120  may comprise a releasable adhesive material for attachment to a mammal extremity in some portion and a more permanent adhesive in other portions thereof for attaching the vacu-seal  108  to the hard or soft chamber body  102 . The releasable adhesive material may be any of a wide variety of commercially available materials with high initial adhesion and a low adhesive removal force so that the vacu-seal  108  does not pull off hair or skin and create pain when it is removed. For example, the releasable adhesive may be a single use adhesive. In addition, the adhesive material may be thick and malleable so that it can deform or give, in order to fill gaps. Adhesives with water suspended in a polymer gel, e.g., a hydrogel, are generally effective. One example of such an adhesive is Tagaderm branded 3M adhesive (part No. 9841) which is a thin (5 mm) breathable adhesive that is typically used for covering burns and wounds. Another example is an electrocardiogram (EKG) adhesive such as 3M part No. MSX 5764, which is a thicker adhesive (25 mm). The vacu-seal should fasten such that there is no leakage of the vacuum. Once a vacuum is applied, the pressure differential pulls the vacu-seal  108  closer to the foot  130  such that the vacu-seal  108  around the foot  130  is enhanced, and there is no leakage. 
     The backing of the vacu-sealing portion  120  may be a thin, non-elastic, flexible material. The backing supports the adhesive and keeps it from being pulled under vacuum into the appendage opening. The backing also allows the adhesive to conform to both the shape of the foot and the shape of the top opening  128  of the hard or soft chamber  150 , as well as to fold in on itself to fill gaps that may be present in the vacu-seal around the foot. Furthermore, the backing prevents the adhesive from sticking to other surfaces. Commercially available polyethylene in thicknesses up to about 10 millimeters may be used for the backing. Polyethylene that is thicker than about 10 millimeters may limit the adhesive&#39;s ability to fold on itself and fill in gaps. The backing may also comprise any polymer that may be fabricated into a thin, non-elastic, flexible material. 
     In one embodiment, the vacu-sealing portion  120  comprises a backing surrounded by an adhesive such that the vacu-sealing portion  120  comprises two opposing adhesive faces. For example, 3M EKG adhesive product MSX 5764 contains a supportive backing in between multiple layers of adhesive. Multiple layers of backing can also be used to provide support for the vacu-seal  108 . 
     Although an elastic backing may be used in the vacu-seal  108 , an elastic support backing generally creates an inferior seal compared to a non-elastic support backing because the elastic support backing reduces the ability of the adhesive to fold against itself to fill gaps and to take up excess adhesive material. Also, the elastic backing creates a greater chance that the user will over tension the vacu-seal  108  and thereby reduce blood flow. 
     The top opening  128  of the hard or soft chamber  150  is preferably close to the size of the patient&#39;s foot to minimize the difference in dimensions that the vacu-seal  108  must cover. The smallest opening size that will accommodate the range of acceptable foot sizes is preferred. Minimizing the opening size reduces the force on the foot created by the pressure differential between the outside of the hard or soft chamber and the inside of the hard or soft chamber since the force caused by the pressure differential is approximately equal to the area of the top opening times the pressure differential. The vacu-seal  108  is typically able to be formed of different sizes to accommodate foot sizes down to the foot size of a small adult and up to various foot sizes of a large adult. For example, multiple opening sizes, such as small, medium, and large may be used to accommodate a wider range of foot sizes. 
     Alternatively, the top opening  128  may be fabricated to contract within a size range without constricting blood flow in the foot to further minimize this force and make vacu-sealing easier. For example, one or more strings may be used to tighten the top opening  128  to a foot. In another embodiment, external buckles, velcos, and straps, among others, may also be used to surround the top opening  128  of the hard or soft chamber  150  secure the top opening  128  around a foot. 
     In another embodiment of the invention, the hard or soft chamber  150  may be collapsible for easy storage and for ease of transportation, such as to remote locations. The collapsible hard or soft chamber may be disposable. The hard or soft chamber  150  may lay flat for storage and then expand or deploy to create a three dimensional hard or soft chamber that resists collapse by negative pressure and may be made from any flexible material including polymers such as nylons, polyesters, polystyrene, polypropylene, high density polyethylene (HDPE) or any other appropriate polymer. The flexibility of the hard or soft chamber material allows the hard or soft chamber  150  to be folded for storage and expanded for use. The hard or soft chamber may be strengthened by adding supports after expansion to prevent it from collapsing against the appendage under negative pressure. 
     In addition, one or more portions of the hard or soft chamber body  102  may be made from transparent materials such that the functioning of the device and the condition of the foot may be monitored during use of the device. In an alternative embodiment, the hard or soft chamber body  102  may be divided into two or more body sections to be assembled into the hard or soft chamber  150  and secured by one or more fastening units, such as velcos, snaps. 
       FIG. 3  is an example of the thermal exchange unit  104  of the invention. The thermal exchange unit  104  includes a thermal exchange body  146 . One side of the thermal exchange body  146  includes a plurality of thermal contact domes  148  for providing thermal contact surfaces  147  directly to the vacu-seal  108  and indirectly to the foot  130 . The diameter of the thermal contact surfaces  147  and the shapes or sizes thereof can vary such that the sum of the total area of the thermal contact surfaces  147  can be increase to the maximum. The thermal exchange unit  104  may further include a thermal fluid supply line  142  and a thermal fluid return line  144  connected to a thermal fluid source for circulating a thermal fluid medium therethrough the thermal exchange body  146  of the thermal exchange unit  104 . 
     The material of the thermal exchange main body  146  may be any durable material which provides thermal conductivity for the thermal fluid medium flown therein and can be, for example, any of the materials suitable for hard or soft chamber body  102 . In one embodiment, the thermal exchange main body  146  is made of a flexible material which can easily conform to the shape of the foot  130 . In another embodiment, the thermal contact domes  148  are made of a rigid material to provide rigid contacts to the foot  130 . 
     In addition, the material of the thermal contact domes  148  may be a material which provides high thermal conductivity, preferably much higher thermal conductivity than the material of the thermal exchange main body  146 . For example, the thermal contact domes  148  may be made of aluminum, which provides at least 400 times higher thermal conductivity than plastics or rubber. 
     In one embodiment, the thermal exchange unit  104  can be formed and assembled through RF welding. In another embodiment, the thermal exchange unit  104  may be formed and assembled through injection molding. There are many possible ways to design and manufacture the thermal exchange unit to provide a flexible thermal exchange unit that does not leak. 
       FIG. 4  is another example of a thermal exchange unit  204  of the invention. The thermal exchange unit  204  may include a thermal exchange body  246 , a thermal fluid supply line  242  and a thermal fluid return line  244  connected to a thermal fluid source for circulating a thermal fluid medium through the thermal exchange body  246  of the thermal exchange unit  204 . It is contemplated that a thermal exchange unit manufactured into layers of several materials bonded together to form internal fluid flow paths for thermal fluids to be flown therein may result in uneven surfaces, due to the presence of the internal fluid flow paths, resulting in bumpy surfaces and less contacts, thereby reducing surface area needed for maximum thermal transfer. In addition, the material for the thermal exchange main body  146 , such as polyurethane, etc., may not be good conductor for thermal transfer. Thus, the thermal exchange body  246  may be covered by one or more backing sheets  248  such that flat and even contact surfaces to the foot, resulting in a large total contact area, can be provided. In addition, the backing sheet  248  can be made of high thermal conductive material to provide high thermal conductivity between the thermal exchange unit  204  and the foot  130  via the vacu-seal  108 . For example, the backing sheets  248  may be made of a thin metal sheet, such as aluminum (like a foil) or other metal sheets. In general, aluminum or other metal materials may provide higher thermal conductivity than plastics or rubber, e.g., at least 400 times higher. 
       FIG. 5  is another example of a thermal exchange unit  504  of the invention. The thermal exchange unit  504  may be an electric pad having one or more electric wires  542 ,  544  connected to a power source. For example, the power source may be a low voltage DC current power source. In addition, the thermal exchange unit  504  may include a thermocouple  502  for monitoring the temperature and a thermoswitch  514 , which can automatically shut off the electric power when the temperature of the electric pad passes a safety level. 
     The thermal exchange units  104 ,  204 ,  504  according to embodiments of the invention generally provide thermal exchange surfaces which heat and/or regulate the temperature of an extremity of a mammal to be kept at a temperature of about 20° C. or higher, such as between about 10° C. and about 42° C. or between about 15° C. and about 40° C. It is found that different temperatures can cause blood flow to increase at different rates depending on the temperature of the skin that the device is applied to. 
     It is noted that one or more thermal exchange units  104 ,  204 ,  504 , individually or in combination, can be positioned and attached to one or more portions of the hard or soft chamber body  102  to provide thermal exchange and regulate the temperature of a mammal&#39;s extremity provided inside the hard or soft chamber  150 . In one embodiment, one or more thermal exchange units can be pre-assembled inside the hard or soft chamber  150 . In another embodiment, one or more thermal exchange units can be assembled into the hard or soft chamber  150  upon the use of a foot device. 
     In addition, the thermal exchange units  104 ,  204 ,  504  of the invention may include one or more temperature sensors and thermocouples to monitor the temperature of a mammal&#39;s extremity and provide temperature control feedback. For example, a tympanic temperature probe may be inserted to other body portions, such as ear canal, etc., of a mammal to monitor core body temperature and provide the core temperature feedback to the controller unit  160 . 
       FIG. 6  is a perspective view of one example of another foot device  600 . The foot device  600  includes a hard or soft chamber body  602 , a supply line  642 , a return line  644 , and a vacuum port  612 . As shown in  FIG. 6 , one or more tubings, lines, and ports can be bundled together into a tubing set  670  and connected to a controller unit (not shown) for easy transportation and operation. 
       FIG. 7  is a perspective view of two exemplary foot devices  700  and  710  which can be about the same size and fitted for a right or a left foot. Alternatively, the foot devices  700  and  710  can be manufactured into different sizes suitable for various foot sizes. 
       FIG. 8  illustrates another example of a leg device  800  of the invention. The leg device  800  may include an upper hard or soft chamber body  802 A and a lower hard or soft chamber body  802 B which form an upper hard or soft chamber  850 A and a lower hard or soft chamber  850 B, respectively. The leg device  800  may also include a flexible portion  803 , providing a flexible connection between the upper hard or soft chamber body  802 A and the lower hard or soft chamber body  802 B. In addition, there can be pressure air line and fluid tubing inside the flexible portion  803  connecting through the upper hard or soft chamber  850 A and the lower hard or soft chamber  850 B. The flexible portion  803  may be made of a flexible material to provide flexibility for a leg  830  of a mammal to be positioned inside the leg device  800 . For example, the flexible portion  803  may be snugly fitted near the ankle section of the leg  830 . Alternatively, the upper hard or soft chamber  850 A and the lower hard or soft chamber  850 B may be formed into one single vacuum hard or soft chamber. In another embodiment, the leg device  800  may include two or more individual devices, such as a foot device and a calf device, having the upper hard or soft chamber  850 A and the lower hard or soft chamber  850 B, respectively. 
     The leg device  800  may also include one or more thermal exchange units (not shown) and flexible membranes attached to one or more portions of the upper hard or soft chamber body  802 A and the lower hard or soft chamber body  802 B. A vacu-seal can be detachably or permanently installed inside the leg device  800  as a liner for the leg  830  and may include a vacu-sealing portion  820  near a top opening of the leg device  800  for sealing the leg device to the leg  830  under vacuum. 
     In addition, the leg device  800  may include one or more compression pads  860  around one or more portions of the upper hard or soft chamber  850 A and the lower hard or soft chamber  850 B. Each compression pad  860  may include one or more air pockets connected to gas lines and gas sources to be filled with air or various fluids when the leg  830  is positioned inside the leg device  800 . In addition, the air pockets on the compression pad  860  can alternatively be pumped with air or fluids to provide a bellow-like motion to apply various compression pressures or pressurized forces on portions of the leg  830  intermittedly, consecutively, or otherwise in a time appropriate manner. It is believed that applying pneumatic compression pressure or pressurized force on portions of the leg  830  may increase blood flow within the leg, prevent clotting and blood pooling in the veins, and prevent deep vein thrombosis. 
     One or more thermal fluid supply lines, return lines, electric lines, sensor lines, gas lines, temperature sensor ports, vacuum ports, and vacuum sensor port, can be provided to the leg device  800  via one or more apertures in the upper hard or soft chamber body  802 A and/or the lower hard or soft chamber body  802 B. These tubings, fluid lines, electric lines, gas lines and vacuum ports can be bundled together into a tubing set  870  through an aperture  872  on the hard or soft chamber body and connected to the controller unit  160  for easy transportation and operation. 
       FIG. 9  is another example of a leg device  900  of the invention. The leg device  900  may include a hard or soft chamber body  902  and an occlusion cuff  920  proximate the top portion of the hard or soft chamber body  902 . The hard or soft chamber body  902  can be conveniently assembled through fasteners  980 ,  982 ,  984 ,  986 ,  988  before or after a leg is positioned therein. The fasteners of the invention can be, for example, snaps, tabs, clips, tongs, adhesives, Velcro, among others, to join the hard or soft chamber body  902  together. 
     The leg device  900  may be used together with a vacu-seal having a sealing portion for attaching to the occlusion cuff  920  and providing a vacu-seal between the leg device  900  and the leg. The leg device may also be used without a vacu-seal and the occlusion cuff  920  is provided for sealing the leg device  900  to the leg. 
     The hard or soft chamber body  902  defines a hard or soft chamber  950  having one or more thermal exchange units  904  positioned therein. The one or more thermal exchange units  904  may be a fluid pad having a thermal fluid medium flown therein, an electric pad, or any other suitable thermal exchange units, individually or in combination. Thermal energy can be transferred from the thermal exchange unit  904  to the leg for heating or cooling the leg. 
     The leg device  900  further includes one or more compression pads  960 A,  960 B,  960 C, each having one or more air pockets connected to air lines and air sources for applying pneumatic compression pressure onto portions of the leg. The one or more thermal exchange units and compression pads of the leg device  900  can be positioned overlappingly or separately on one or more portions of the hard or soft chamber body  902  inside the hard or soft chamber  950 . 
     In operation, a foot, a leg, or a lower extremity is fitted into a vacu-seal and then the lower extremity covered with the vacu-seal is positioned in a lower extremity device. Alternatively, a detachable vacu-seal may first be assembled inside a lower extremity device before a lower extremity is fitted to the assembled lower extremity device. In addition, one or more detachable thermal exchange units may be pre-assembled inside a lower extremity device or may be assembled upon positioning a lower extremity into the lower extremity device. Then, a vacu-sealing portion of the vacu-seal is wrapped around a top opening of the foot device to form a tight seal and prevent air from entering the space between the foot and the foot device. 
       FIG. 10  illustrates one embodiment of the control unit  160  connected to various parts of a device  300  of the invention. A controller module  360  having the controller unit  160  therein houses all the electronics and mechanical parts which are required to regulate the temperature, vacuum pressure level, and compression pressurized force provided to the hard or soft chamber  150  of the device  300 . The controller module typically includes, for example, a vacuum pump  332 , a vacuum pump  334 , a thermal exchange medium source  336 , a fluid flow sensor  352 , a thermal exchange medium pump, a heater, a cooler, thermocouples, a heating medium pump, a proportional-integral-derivative (PID) controller for process control of the vacuum and the temperature, one or more power supplies, display panels, actuators, connectors, among others, to be controlled by the controller unit  160 . The settings of the controller unit  160  may be conveniently positioned onto a display panel which provides an operator interface. The controller unit  160  may contain additional electronics for optimal operation of the device  300  of the invention. In alternative embodiments, the vacuum control and temperature control may be controlled by two different controllers. 
     The controller unit  160  may provide safety features including a device shutdown feature that is activated if the device sensors, such as the temperature and pressure sensors, fail or become disconnected. The controller unit  160  may also include an alarm circuit or an alert signal if the temperature of the apparatus is not regulated correctly. A relief valve may be provided within the vacuum loop of the device such that the hard or soft chamber may be vented if the vacuum within the hard or soft chamber exceeds a certain level. 
     In one embodiment, a temperature probe  362  can be provided to measure the temperature of a portion of a mammal other than a foot, leg, or other extremity where the device is attached to. For example, a tympanic membrane can be attached to the ear canal as a temperature probe to provide core temperature reading. As such, a reference temperature for the human, such as a patient, can be obtained. Other sensors may include patient&#39;s blood flow and blood pressure and heart rate. These data are important to proper patient health care in keeping DVT from forming and keeping the patient at normal temperature range. 
     As shown in  FIG. 10 , the vacu-sealing portion  120  can be connected to the vacuum pump  332  via a vacuum port  324  to provide a vacu-seal pressure, F vacu-seal , thereto. The hard or soft chamber  150  can be connected to the vacuum pump  334  via a vacuum port  312  and a vacuum sensor return line  322  to provide a vacuum pressure or a negative pressure inside the hard or soft chamber  150 . 
     In addition, the hard or soft chamber having one or more thermal exchange units therein may be connected to the thermal exchange medium source  336  via a thermal exchange medium supply line  342  and a thermal exchange medium return line  344 . Further, the flow of a thermal exchange medium flown inside the thermal exchange medium supply line  342  can be monitored and regulated by the fluid flow sensor  352 . 
     These lines and ports of the invention may be bundled, contained, and strain-relieved in the same or different protective sheaths connected to the controller unit  160 . The lines may also be contained in the same or different tubing set with different enclosures for each medium used, such as fluid, vacuum, electric heat, and air lines. 
     In one embodiment, the thermal exchange units are coupled in a closed loop configuration with the thermal exchange medium source which provides a thermal exchange medium. For example, the thermal exchange unit may be coupled in a closed liquid loop configuration with a liquid tank housed within the controller module  360 . The closed loop configuration reduces the maintenance requirements for the operator because it minimizes the loss of thermal exchange medium that typically occurs if the thermal exchange unit is detached from the thermal exchange medium source. Contamination of the thermal exchange medium source is also minimized by the closed loop configuration. Contamination of the thermal exchange medium such as water can also be reduced by adding an antimicrobial agent to the thermal exchange medium source. In different embodiments, the thermal exchange medium may be either a liquid or a gas. In practice, the thermal exchange medium flow rate should be as high as possible, within practical limits of mechanics and noise. A high flow rate allows better temperature consistency, results in less thermal loss, and creates better thermal exchange. In a closed loop configuration including the thermal exchange unit and the thermal exchange medium source, with a total system volume of 0.75 liters, a flow rate of 2 liters a minute transfers twice as much fluid through the thermal exchange unit than a flow rate of 0.35 liters per minute. 
     In an alternative embodiment, the thermal exchange unit and vacuum lines may be connected to the control unit using actuated fittings such as quick release fittings with an automatic shut off mechanism. The automatic shut off mechanism halts the vacuum application and the heating medium flow as soon as the vacuum lines are disconnected. Actuated fittings may also allow the operator to change thermal exchange units. 
     The embodiments of the apparatus described above provide a method of increasing blood flow in one or more extremities of a mammal and decreasing clots within the veins in order to prevent deep vein thrombosis (DVT). The method includes providing one or more devices of the invention to the mammal and regulating the temperature of the one or more extremities of the mammal using the devices. As a result, one or more arteriovenous anastomoses (AVAs) blood vessels inside an extremity of a mammal are vasodilated, and constriction of the AVA blood vessels is reduced, thereby increasing blood flow and blood volume in the one or more extremities, decreasing the vessel wall contact time of the blood flow, and decreasing clots in the veins due to pooling. In one embodiment, a suitable portion of an extremity, preferably an extremity with vasculature that can be vasodilated by the device, such as a foot, may be placed into a device and sealed therein. 
     Once the foot is enclosed in the hard or soft chamber, negative pressure is applied to a vacuum port thereby lowering the pressure within the hard or soft chamber and exposing the foot to decreased pressure in the range of zero to about −120 mm-Hg, such as from about −10 mmHg to about −50 mm-Hg below atmospheric pressure. Simultaneously or sequentially, the thermal exchange medium is introduced into the thermal exchange unit positioned inside the hard or soft chamber body. The flow rate of the vacuum pump may be greater than about 4 liters per minute, and preferably about 12 liters per minute or more. In one aspect, the flow rate of the vacuum pump is between about 4 liters and about 20 liters per minute and is preferably between about 12 and about 20 liters per minute to minimize leakage of the apparatus. The negative pressure also enhances the sealing of the device by increasing the closing pressure on the sealing portion of the device and between the hard or soft chamber and the foot. 
     In one embodiment, the controller unit manages the thermal exchange medium and negative pressure for the duration of the treatment, which may be about 30 minutes, for example. The duration may be longer or shorter depending on the size of the foot or leg treated and the temperature of the foot or leg, and may be repeated. In some cases, the duration of the treatment may be cycled time period, for example, a time period of 1-5 minutes or longer for 5 cycles or longer. The controller is configured to halt the treatment after each treatment period. A “stop” button on the control unit may be used to turn off both the thermal exchange medium supply and the vacuum. 
     Embodiments of the invention may be used to increase blood flow of a patient in order to prevent DVT. Embodiments of the invention may also be used to regulate the temperature of a patient. In such a method, the temperature of the thermal exchange medium should be as high as possible without burning the patient. In a healthy patient, burning of the cells on the appendage can occur if the cell temperature exceeds about 43 degrees Celsius (° C.), but this may vary with exposure time and rate of thermal transfer. Therefore, the temperature of the thermal exchange medium is preferably calibrated such that skin temperature is maintained at less than 43 degrees Celsius. For example, different people have different tolerance levels for different temperature ranges, according to their ages, health conditions, etc. In addition, the device can be used for heating and maintaining the temperature of a patient as well as cooling. In general, a temperature range between about 10° C. to about 42° C. can be maintained. 
     Furthermore, the negative pressure is preferably as great as possible to maximize vasodilation, without restricting blood flow to the extremity. However, higher levels of temperature and negative pressure may cause pain in some patients because of sensitivity to temperature and sensitivity to negative pressure. Additionally, sensitivity to temperature and negative pressure may be increased with extended treatment time or repeated treatments. Furthermore, some patients may be prone to petechia, a condition in which capillaries microburst under negative pressure. 
     Consequently, in order to reduce patient discomfort, the controller may be configured with different temperature and vacuum settings. In one embodiment, one treatment setting is “High”, which includes the highest temperature and negative pressure setting. “Medium” and “Low” settings have progressively lower settings for temperature and/or negative pressure. Patients who are at high risk for petechia or who are being treated for an extended amount of time may be treated on the “Low” setting. The vacuum setting may be adjusted to provide less negative pressure in patients that are under anesthesia since they are already vasodilated, while the temperature is kept at a higher setting. In a further aspect, the device may use between about 5 watts and about 250 watts of energy power to raise a body core temperature at a rate of between about 4° C./hour and about 12° C./hour. Preferably, the power applied is between about 5 watts and about 80 watts, although a power of up to about 250 watts may be used. In contrast, a convective warming blanket that heats the whole body may use about 500 watts. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.