Patent Publication Number: US-7717869-B2

Title: Pressure maintained inflatable boot

Description:
FIELD OF THE INVENTION 
   This invention relates to an inflatable boot, and more particularly to an inflatable boot used in the treatment of a human lower extremity. 
   BACKGROUND OF THE INVENTION 
   Inflatable boots have been employed in the rehabilitation of injured lower extremities for several years. In recent years, therapeutic inflatable boots which include a massaging feature have been developed. Two such massaging therapeutic boots are disclosed in U.S. Pat. Nos. 4,805,601, and 5,868,690, the complete disclosures of which are incorporated herein by reference for all purposes. 
   In these inflatable boots, air moves between a first fluid chamber, located on the sole of the inflatable boot, and two or more fluidically connected chambers dimensioned to surround the injured area. When a user pushes down on the first fluid chamber, while walking or pushing against a solid surface, compression of the first chamber moves air or fluid into the fluidically connected chambers and thus, causes a pressure increase in the connected chambers. Such pressure increase is maintained until the user releases the first fluid chamber to its expanded, pre-compressed configuration by lifting the sole during the walking stride or by relaxing the applied force against a stationary surface. Thus, these inflatable boots function to providing recurrent compression, or increased pressure, to an injured area by varying the fluid pressure imparted by the first chamber onto the fluidically connected chambers. 
   Recurrent compression of these inflated chambers creates a variation of pressures, or massaging, upon the injured lower extremity encased within the inflatable boot, and results in improved blood flow to the injured area. Efficient blood flow through the lower extremity is partially dependent upon the contraction of muscles. When a foot or ankle is injured, muscle contractions are often limited because it is painful and/or harmful to put weight on the extremity. The massaging action of the therapeutic inflatable boots improves blood flow by mimicking the pumping effect of muscle contractions in forcing pooled blood out of the veins. Such an improved blood flow promotes healing by taking away damaged cell waste products and providing a steady supply of cellular nutrients. 
   A massaging pressure variation may only promote blood flow if the pressure within the therapeutic boot is maintained within a certain therapeutic range. If the pressure in the inflatable boot is too low, the compression of the first chamber may not result in an increased pressure in the fluidically connected chambers that is sufficient to apply an external therapeutic pressure onto the encased injured extremity. If the boot-provided external pressure is too high, optimized healing may be inhibited. Conventional therapeutic inflatable boots are incapable of insuring that a proper therapeutic range of pressures is maintained at all times and under all atmospheric conditions. 
   SUMMARY OF THE INVENTION 
   An inflatable boot used in the rehabilitation of lower extremities is disclosed in the present application. The boot includes a bladder for encasing at least a portion of a lower leg, an ankle, and a foot. The bladder may be defined by an inner and an outer layer of substantially gas impermeable material, and may include at least one wall portion and a sole portion. The at least one wall portion and the sole portion may be fluidically interconnected. 
   The boot additionally includes a pressure control system, consisting of a pump and a pressure release valve. The pump is configured to draw air into the bladder upon ambulatory motion. The pressure release valve is adapted to limit the pressure within the bladder, such that the pressure may not exceed a maximum therapeutic pressure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a boot having a pump located within the bladder according to the present disclosure. 
       FIG. 2  is an isometric view of the boot of  FIG. 1  inflated and compressed. 
       FIG. 3  is a cut-away perspective view of a boot having a structural interconnection of noninflation according to the present disclosure. 
       FIG. 4  is a plan view of the top of the boot shown in  FIG. 3 . 
       FIG. 5  is a cross-sectional view of the boot shown in  FIG. 3  along line  5 - 5 . 
       FIG. 6  is a cut-away frontal view of the boot shown in  FIG. 4 , cut-away generally along line  6 - 6  of  FIG. 4 . 
       FIG. 7  is a plan view of the right side of the boot shown in  FIG. 3 , shown without an inserted lower extremity and uninflated. 
       FIG. 8  is a frontal view of the boot shown in  FIG. 7 . 
       FIG. 9  is a cross-sectional view of the boot of  FIG. 3  with an inserted lower extremity and partially inflated. 
       FIG. 10  is a cut-away rear view of the boot shown in  FIG. 4 , cut-away generally along line  10 - 10  of  FIG. 4 . 
       FIG. 11  is a cut-away rear view of the boot shown in  FIG. 10  with the boot inflated and in a neutral condition. 
       FIG. 12  is a cut-away rear view of the boot shown in  FIG. 11 , with the boot in its pressurized condition. 
       FIG. 13  is a cut-away view of the right side of an inflatable boot with an internal sling according to the present disclosure. 
       FIG. 14  is a frontal view of the boot shown in  FIG. 13 . 
       FIG. 15  is a cut-away view of the boot shown in  FIG. 13  with a lower extremity inserted. 
       FIG. 16  is a cut-away perspective view of the boot shown in  FIG. 13 , showing the boot partially inflated and with a lower extremity inserted. 
       FIG. 17  is a cut-away frontal view of the boot shown in  FIG. 13 , illustrating a sling portion with a lower extremity inserted. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , a boot is identified generally with the numeral  10 . Boot  10  is intended to encase a portion of a human lower extremity. Boot  10  may be specifically designed to treat lower extremity injury or disease and be utilized to promote healing of one or more portions of the lower extremity encased within the boot. Boot  10  may encase all or a portion of a lower leg  14 , an ankle  19 , and a foot  12 , including heel  18 , and toes  16 . Alternatively, boot  10  may include openings to expose portions of the lower extremity, such as the heel, toes, or other region of the extremity not requiring treatment. 
   Boot  10  may include a cover or outer layer  20  joined, or sealed, to a liner or inner layer  22 . Cover  20  and liner  22  may each be constructed from flexible material that is completely, or substantially, gas impermeable, or air-tight. In addition to being flexible and gas impermeable, the material of cover  20  and liner  22  may be durable, easily sealed, and generally non-irritating to an inserted human foot. Such flexible gas impermeable materials may include coated nylon cloth, coated canvas, ether-based polyurethane, rubbers, plastics, or other suitable materials. Cover  20  and liner  22  may be formed, or constructed from the same material, or from two or more different materials. For example, cover  20  may be constructed of coated 200 denier nylon oxford, and liner  22  may be constructed of ether-based polyurethane. Cover  20  and liner  22  may be constructed out of a single, contiguous sheet of such suitable material so as to avoid piecing, seams, and seals and to preserve the air impermeability throughout, or alternatively, may be pieced together using one or more pieces of material. 
   Cover  20  and liner  22  may collectively define a bladder  24  of boot  10 . Bladder  24  may be contiguous throughout boot  10 , such that a pressure change within any portion of bladder  24  may be communicated to the remaining portions of bladder  24 . Portions of bladder  24  may be fluidically connected to allow contiguous fluid or pressure communication throughout the bladder  24  of boot  10 . 
   In some embodiments of boot  10 , bladder  24  may have a number of fluidically connected portions, including a leg portion, indicated generally at  26 , and a sole portion, indicated generally at  28 . The bladder leg portion  26  may be sized and shaped for encasing at least a portion of lower leg  14 , and the bladder sole portion  28 , may be sized and shaped for encasing at least a portion of the foot  12 . Accordingly, the bladder leg portion  26  may encase, or wrap around one or more sides of the leg and ankle, and the bladder sole portion may wrap around one or more sides of the foot, including the sole  66 . In some embodiments, the bladder sole portion  28  may be adapted to be disposed beneath the sole  66  without wrapping one or more sides of the foot. 
   Bladder leg portion  26  and bladder sole portion  28  may be fluidically connected to each other via passageways including  68   a  and  68   b . A passageway, indicated generally as  68 , may be any open-flow connection between one or more bladder portions. Such passageways may be general flow areas between portions of a contiguous bladder  24  or alternatively, passageways  68  may be sealed partitions, columns or openings permitting flow between two distinct bladder portions. Air, or other fluid, may move in either direction in passageways  68 , in order to maintain an equalized pressure throughout all portions of bladder  24 . 
   A pump  29  may be located within one or more bladder portions. Pump  29  may include a first member  31 , a second member  33 , a reciprocating compression body  35 , a pump intake system  37 , and a pump outflow system  39 . Air, or other fluid, may be contained within pump  29  in one or more locations, including the body, air intake system, or the air outflow system. 
   The pump intake system  37  and/or pump outflow system  39  may include a one-way check valve  41  to assist in moving air from the exterior of the boot into bladder  24 . One-way valve  41  may function to prevent, or substantially limit, any movement of air out of the bladder to the boot exterior through the pump  29 . Accordingly, exterior air may be taken into pump  29  through the pump intake system  37 , and moved through the pump in only one direction, moving external air, or air from the boot&#39;s exterior, into the bladder  24 . 
   When in a neutral position, the first pump member  31  and the second pump member  33  may be separated by body  35 . As shown in  FIG. 1 , first and second pump member  31 ,  33  may be separated by a distance A. When a force is applied to pump  29  in the direction of arrow B, the first pump member  31  and the second pump members  33  may move closer together, which may compress body  35 . In such a compressed position, the first pump member  31  and the second pump member  33  may be separated by a distance A′. 
   When the compressing force applied in the direction of arrow B is removed, pump  29  may return to a neutral position. During a return to the neutral position of pump  29 , a negative pressure may be created within the pump which may draw external air into the pump through the pump intake  37 . Subsequent compression of pump  29  may expel air from the pump through pump outflow system  39  and into bladder  24 . The amount of negative pressure created in pump  29  may, in part, determine the volume of air that is moved into the bladder  24  by pump  29 . The design and size of the pump, as well as the amount of force applied by the user, may also affect the volume of air that is moved into the bladder  24  by pump  29 . 
   It should be appreciated that while  FIG. 1  shows pump  29  located in the bladder sole portion directly below the foot heel  18 , alternative embodiments may include a pump in the sole portion directly below any other aspect of the foot including the toes  16 , ball of foot  17 , and/or may include a pump located within the bladder leg portion. While pump  29  is schematically shown as a two part cylinder-shaped pump, it should be appreciated that pump  29  may be configured in any shape, including a wedge, an elongated platform, a circle, or a block. Further, pump  29  may occupy all, or any portion of, the bladder sole portion. 
   Additionally, schematically shown pump  29  may be any type of pump capable of drawing air into the bladder. While  FIG. 1  shows a compression pump, alternative embodiments may include cylinder and piston pumps, rubber bulb pumps, encased sponge pumps, and or multipart resin pumps. Regardless of the type of pump utilized, pump  29  may be constructed from lightweight materials, such as aluminum, titanium, or resins in order to maintain a low overall weight of boot  10 . 
   Pump  29  may also be disposed exterior to bladder  24  but in fluid communication therewith. For example, in some embodiments boot  10  may include an outsole or tread disposed between the cover of boot  10  and the ground surface. In these embodiments, pump  29  may be disposed between the cover and the outsole. Pump  29  may be disposed in operative association with bladder  24  such that external air can be pumped into bladder  24 . In some embodiments pump  29  may be disposed such that the pump is compressed with each step of the user, for users that are able to walk. In other embodiments, pump  29  may be configured to be repeatedly compressed through alternative user interaction. 
   Pump  29  may be utilized to inflate bladder  24 . When pump  29  is located within the bladder sole portion  28 , air exiting the pump may enter the sole portion  28 . Because the sole portion  28  may be in fluid connection with the remainder of bladder  24 , including the leg portion  26 , this air may flow out of sole portion  28  and into other bladder portions so that air pressure is equal in all connected bladder portions. Air may flow out of the sole bladder portion to the leg bladder portions via passageways  68 . Repetitive compressions of pump  29  may be required to inflate the bladder to the desired air volume. 
   Alternative means of inflating bladder  24  may also be utilized. Boot  10  may include an inlet valve  64  which may serve as an alternative location for the intake of air, or fluid, into bladder  24 . Inlet valve  64  may be adapted to selectively couple with various inflation devices, including inflation tubing  63 , mouthpiece  65 , hand pump  79 , or other auxiliary mechanical or electrical pumps  67 . 
   A user may utilize any of such inflation devices to manually inflate bladder  24 . A boot user may blow up, or inflate, bladder  24  of boot  10  by blowing air into inflation tubing  63  at mouth piece  65 . Thus, the user may blow through the inflation tubing, through inlet valve  64 , and into bladder  24 . The inflation tubing may be elongated so as to allow a user to blow into mouth piece  65  at a level above the boot  10 . 
   A user may also pump-up, or inflate, bladder  24  using hand pump  79 . A user may compress and release the bulb of hand pump  79  to create a negative pressure within the hand pump  67 , which may draw air into hand pump intake, through inlet valve  64 , and into bladder  24 . Thus, bladder  24  of boot  10  may be inflated using one or more mechanisms, including a pump  29  located within the bladder, inflation tubing  63 , mouthpiece  65 , hand pump  79 , or other auxiliary electrical or mechanical pumps, illustrated generally at  67 . 
   Once inflated, bladder  24  may protect the extremity by maintaining a space, or cushion, of pressurized air around the lower extremity. This inflated bladder  24  may provide some degree of protection in the event the encased lower extremity collides with, or bumps against, external objects. In some embodiments, the inflated bladder may conform to at least some portions of the lower extremity. By conforming to the lower extremity, inflatable boot  10  may also protect open wounds on the lower extremity from dirt and/or germs. 
   Pumping external air into bladder  24  may transition boot  10  from a deflated, storage configuration into an inflated operating configuration. The operating configuration of boot  10  may partially immobilize the encased lower extremity including the ankle joints and toe joints. This immobilization may be therapeutically advantageous in the treatment of some lower extremity injuries, including torn or surgically reconstructed tendons or ligaments, muscle tears, and ankle or foot sprains. Additionally, the inflated, operating configuration of boot  10  may provide compression to an injured lower extremity, which may decrease swelling in the injured lower extremity. 
   With continued reference to  FIG. 1 , some embodiments of boot  10  may include a pressure release valve  70 . Pressure release valve  70  may permit air to exit bladder  24  when the pressure within the bladder exceeds a maximum therapeutic pressure. A maximum therapeutic pressure may be a pressure above that which a clinical practitioner deems to be therapeutically beneficial. 
   The maximum predetermined therapeutic pressure may vary depending on the user and the type of lower extremity injury or disease being treated with the application of boot  10 . The maximum therapeutic pressure may be as high as 100 mm Hg, or approximately 2 psi. In some applications of inflatable boot  10 , the maximum therapeutic pressure may be higher than 100 mm Hg. A clinician may select a maximum therapeutic pressure to be a pressure ranging from about 25 mm Hg to about 125 mm Hg, such as 40, 50, 60, 75, 90, 100, or 110 mm Hg, or any other pressure in the range. 
   Boot  10  may be provided with a clinician-selectable maximum therapeutic pressure in a number of ways. For example, boot  10  may be provided in a plurality of configurations or sizes, each size being equipped with a pressure release valve of a different maximum therapeutic pressure. Alternatively, boot  10  may be provided with pressure release valve having an adjustable release pressure such that the clinician can modify the pressure release valve to release at air at the maximum therapeutic pressure. Some embodiments may include features to allow the clinician to adjust the pressure release valve while preventing the user from later modifying the release pressure. 
   Pressure release valve  70  may prevent a user from inflating bladder  24  beyond a predetermined maximum therapeutic pressure. Without such a pressure control, a user may, intentionally or unintentionally, inflate boot  10  beyond the maximum therapeutic pressure for a variety of reasons. For example, a user may unintentionally over-inflate bladder  24  because it may be difficult to determine the pressure during inflation. Alternatively, a user may find that inflation beyond the maximum therapeutic pressure feels more comfortable to the user because the increased pressure may reduce blood flow to the nerves, which may decrease pain sensation. Additionally, atmospheric changes, such as changing elevations or changing ambient temperatures, may result in an increased pressure within bladder  24  of boot  10 . Pressure release valve  70  thus prevents elevated bladder pressures that may exceed a maximum therapeutic pressure. 
   Pressure release valve  70  and intake valve  64  are illustrated as separate valves in  FIGS. 1 and 2 . Boot  10  may also omit intake valve  64  relying on the internal pump for inflation of the bladder. Alternatively, intake valve  64  and pressure release valve  70  may be integrated into a single valve assembly. 
   Pump  29  and pressure release valve  70  may function together to maintain a proper therapeutic pressure within the bladder, thus acting as a pressure maintenance system. The pressure maintenance system may operate to maintain the pressure in the boot within a predetermined therapeutic pressure range. The minimum therapeutic pressure on the lower extremity may be between 20 mm Hg and 60 mm Hg. When combined with the maximum therapeutic pressure, the therapeutic pressure range may fall somewhere between 20 mm Hg and 125 mm Hg depending on the type of lower extremity injury or disease being treated with the boot. 
   While the pressure release valve  70  may insure that a maximum therapeutic pressure is not exceeded, pump  29  may insure that a minimum therapeutic air pressure is maintained within bladder  24 . Pressure may drop within the bladder over time for a number of reasons. For example, air may slowly escape from the bladder through seams, seals, or through the cover or liner material. Additionally, the internal pressure may change for the same atmospheric reasons discussed above for pressure increases. A boot that is inflated in a warm environment may provide much less pressure when worn in a cold environment. 
   As discussed above, pump  29  may be configured to draw air into bladder  24 . Depending on the location of pump  29 , pump activation may occur during ambulatory motion when a user steps, walks, or runs or while a user pushes the pump against a solid surface. If the air drawn into bladder  24  by pump  29  causes the pressure inside bladder  24  to exceed the predetermined maximum therapeutic pressure, air may exit bladder  24  out of the pressure release valve  70  in order to decrease the bladder pressure to be within the therapeutic range. Thus, the therapeutic range may be maintained within bladder  24  by continuous inflation of pump  29  held in check, or controlled, with the pressure limiting effect of pressure release valve  70 . 
     FIG. 2  illustrates the compression of boot  10  which may occur during ambulation. While compression during ambulation is illustrated, boot  10  may be compressed through other methods of applying pressure on the boot, such as a user pressing the sole of his foot towards a wall or by automated mechanical means. During ambulation, boot  10  may be pressed against a surface  72  with a downward force in the general direction of arrow B. In addition to compressing pump  29 , as discussed above, such a downward force may cause bladder sole portion  28  to be pressed against, and compressed by, surface  72 . When sole portion  28  is pressed against surface  72 , the flexible material of cover  20  and liner  22  surrounding sole portion  28  may be deformed so as to compress or slightly flatten sole portion  28 . 
   Upon such compression, the volume of sole portion  28  may be significantly reduced increasing the air pressure within the sole portion. As sole portion  28  may be contiguously connected to other portions of bladder  24  by passageways  68 , the increased pressure in sole portion  28  may cause air to move out of compressed sole portion  28  and into leg portion  26  in order to achieve an equalized pressure throughout bladder  24 . The equalized bladder pressure is higher than the bladder pressure that existed when boot  10  was in the neutral state shown in  FIG. 1 . It should be noted that while  FIG. 2  illustrates a boot with a compressed sole portion, compression of any portion of bladder  24  may result in pressure increase throughout the boot. 
   In this compressed state, boot  10  may exert an increased pressure on the encased lower extremity. This increased pressure may move blood out of the venous system of the injured area, so as to improve blood flow. It may be appreciated that as the pressure is equalized in all parts of bladder  24 , boot  10  exerts approximately equal amounts of pressure throughout the encased portions of the lower extremity. Thus, any pressure increase may be distributed throughout the entire encased lower extremity, including leg  14 , ankle  19 , and foot  12 . 
   Once the compressive force is removed, sole portion  28  may return to a neutral state and the bladder pressure may return to an original, non-compressed pressure. When sole portion  28  returns to the non-compressed neutral state illustrated in  FIG. 1 , the relative pressure in sole portion  28  decreases, and air flows into sole portion  28  via passageways  68  to again equalize the pressure throughout bladder  24 . The recurrent or repetitive compression of boot  10  may cause recurrent pressure variation, or massaging of the injured encased lower extremity. Such massaging may increase the blood flow to this area and may promote healing. 
   The amount of pressure elevation that occurs upon any compression of boot  10  may be dependent upon a number of factors, including the relative volumes of air contained within the respective bladder portions, the compressibility of the bladder, and the amount of compressive force applied. Compression of a large volume of sole portion may cause a correspondingly larger volume of air to be moved out of the sole portion and into leg portion  26  in order in equalize the pressure throughout bladder  24 . The flexibility of the materials used to construct cover  20  and liner  22  may contribute to the compressibility of the boot  10 , and thus to the compressibility of sole bladder  28 . 
   Depending on a number of factors, including the relative volumes of the sole and leg portions, the materials of the bladder, and the compressive force applied, the increase of pressure during boot compression may vary. For example, the bladder pressure, and thus, the pressure exerted by the boot onto the encased lower extremity, may increase from 40 mm Hg to 90 mm Hg. Alternatively, other boots may increase from 50 mm Hg to 60 mm Hg. The degree of pressure change may be customized to provide the user with a desired therapeutic massaging effect. For example, some injuries treated by the inflatable boot may require large pressure differences to provide a deep massaging effect. Alternatively, a surface wound may require only gentle massaging for which a very minor pressure change may be preferred. As described above, pressure check valve  70  and pump  29  may be configured to maintain the pump in a desired therapeutic pressure range, including providing a desired therapeutic massaging effect. 
   With reference to  FIG. 3 , inflatable boot  10  is illustrated with a plurality of seals and seams which may function to maintain boot  10  in a desired configuration. As used herein, a seal is the joining of boot cover  20  to liner  22  to define bladder  24 , and a seam is the joining of two portions of bladder  24  to define a boot. Seals and seams may also be directly interconnected, and thus, may be united at some junctions. 
   A bladder seal  34  may be along the circumference of the entire, or substantially the entire bladder  24 . Several segments of bladder seal  34  are illustrated in  FIG. 3 , including a pair of top seals  36 , a toe seal  38 , and a heel seal  40 . In its entirety, bladder seal  34  may function to substantially maintain inflated air inside bladder  24  formed between gas impermeable cover  20  and liner  22 . Boot  10  may also include a structural interconnection seal  46  that is isolated from bladder seal  34 , and may function to form a structural support as described in further detail below. 
   Boot  10  may include one or more seams including a front seam  42 , and a rear seam  44 . The front seam and the rear seam may be the joining of two portions of bladder seal  34  into proper orientation to form a boot  10 . The seams may hold boot  10  in a lower extremity encasing boot shape. 
   Seals and seams may be made by a variety of methods, including heat sealing, radio frequency sealing, stitching, etc. More than one method may be used in the construction of each boot  10 . All of the seals may be formed before any of the seams are formed in some boot constructions. Furthermore, it may be possible to form some seams concurrently with the seals, so that in essence, the seals and the seams may overlap, or fuse in those portions of the bladder. While multiple seals and seams are illustrated in  FIG. 3 , it may be appreciated that alternative embodiments may be constructed without the use of any seams. Such alternative embodiments may be constructed from a single piece of material, be constructed from extruded material, or may be molded, for example. 
   As discussed above, boot  10  may include one or more structural interconnection seals  46  which may be substantially separate, or isolated, from bladder seal  34 . A structural interconnection seal  46  may join or interconnect cover  20  directly to liner  22  at a location that is interior to the bladder seal  34 , and thus, is interior to any edge of the boot cover or liner. The structural interconnection seal may be located interposed sole bladder portion  28  and leg bladder portion  26 , intermediate front seam  42  and rear seam  44 , and independent of bladder seal  34 . A first structural interconnection seal  46  may be formed on the right side of boot  10 , and a second structural interconnection seal may be formed on the left side of boot  10  (not shown). 
   As the structural interconnection seal  46  may be isolated from bladder edge  34 , any area within the interconnection seal  46  may not get inflated when bladder  24  is inflated. These uninflatable areas may function to provide support to the encased lower extremity. As shown in  FIG. 3 , by joining cover  20  and liner  22  in a region within the interior of bladder  24  between leg portion  26  and sole portion  28 , structural interconnection  46  may create a foot-supporting contour for sole portion  28  of bladder  24  by causing a fluid-filled inflated cushion to form under foot  12  when bladder  24  is inflated. Thus, liner  22  within sole portion  28  may form a platform  48  for the foot when bladder  24  is inflated. 
   The geometrical configuration of the structural interconnection seal  46  used may vary depending on the choice of materials used, the desired ornamental appearance, and the desired level of support desired. The elongated oval structural interconnection seal  46  illustrated in  FIG. 3  may provide a joining of cover  20  to liner  22  that is of sufficient strength to prevent material failure or delamination. However, other geometrical configurations may be used. For example, a series of isolated structural interconnection seals in a row, or simply a liner seal may be used, in alternative embodiments. 
   Still referring to  FIG. 3 , the formation of platform  48  under foot  12  may be further defined by one or more inwardly extending notches  50  included in the periphery of bladder  24  of boot  10 . Each notch  50  may be included in both cover  20  and liner  22 , and may generally extend along a bladder seal  34 , with an upper seam portion  52 , and a lower seam portion  54 . The upper seam portion  52  may be the lower end portion of rear seam  44 , while the lower seam portion may be formed independently of rear seam  44 . 
   Independently formed lower seal portion  54  may function to create what may be referred to as an open-looped heel for bladder  24 . Independently formed lower seal portion  54  may cause bladder  24  to fold over below rear seam  44 , without being closed by seam  44 . The open-loop heel feature is not clearly visible in  FIG. 3 . The inclusion of notches  50  as part of the open-looped heel may allow bladder  24  to further expand outwardly immediately below heel  18  of foot  12 , forming gas-filled auxiliary lobes  56 . Such auxiliary lobes  56  may augment the pressure-increasing volume of sole portion  28  of bladder  24 . 
   Toe seal  38  may similarly be formed independently of front seam  42 , so as to form an open-looped toe  58  for boot  10 . Open-looped toe  58  may be similar to the open-looped heel of boot  10 , in that a loop may be formed by a portion of bladder  24  that is folded over below front seam  42 , as seen in  FIG. 3 . Both an open-looped heel and an open-looped toe  58  may provide some ventilation of some portions of boot  10 . 
   A number of the features discussed above and illustrated in  FIG. 3  may also serve as visual reference indicating the proper placement of the lower extremity into boot  10 . As the lower extremity is placed into boot  10  prior to boot inflation, such placement may be challenging. A user may be assisted in proper placement by aligning their heel  18  with notch  50 , and/or by placing the arch of foot  12  over the structural interconnection  46 , as discussed below with respect to  FIG. 5 . If foot  12  is properly positioned before inflation of bladder  24 , an inflated cushion in sole portion  28  may form properly under foot  12  when bladder  24  is inflated. 
   Before leaving discussion of  FIG. 3 , it may be noted that boot  10  may include one or more pockets  60  each sized, shaped, and positioned to accommodate a thermal treatment device  62 . Pocket  60  may be included on or attached to liner  22  in any position of boot  10 . Pocket  60  may facilitate the placement of a thermal treatment device  62 , such as an ice pack or heat pack, adjacent to an injured area. Thermal treatment device  62  may be sandwiched between bladder  24  and at least a portion of lower leg  14 , ankle  19  or foot  12 , that may be inserted into boot  10 , when bladder  24  is inflated. 
   Referring briefly to  FIG. 4 , it may be appreciated that top seal  36  may define an opening, through which portions of the lower extremity, including leg  14 , may be inserted into boot  10 . As illustrated in  FIG. 4 , boot  10  may completely circumscribe the portions of the lower extremity encased within boot  10 . Alternative embodiments may leave sides, or parts of the encased lower extremity exposed. For example, alternative embodiments may be configured to expose the toes or the heel when the lower extremity is placed within boot  10  and bladder  24  is inflated. 
     FIG. 5  more clearly illustrates the orientation of foot  12  within boot  10 . Heel  18  of foot  12  may be relatively near to notches  50 , and toes  16  of foot  12  may be relatively adjacent to liner  22  on the portion of the boot distal from notches  50 . The sole of foot  12 , indicated generally at  66 , may be aligned approximately with a right sided structural interconnection  46 . 
   When foot  12  is positioned within boot  10  as shown in  FIG. 5 , sole bladder portion  28  may be of substantial thickness. Platform  48  therefore may be spaced a significant distance above the lowermost portion of cover  20  within sole bladder portion  28 . Auxiliary lobes  56  may function to augment sole portion  28 . Passageways  68  may remain open between structural interconnection  46  and bladder seal  34  so that fluid within bladder  24  may pass easily from sole bladder portion  28  into leg bladder portion  26 , and then back into sole bladder portion  28 . 
   Similar aspects of boot  10  are illustrated in  FIG. 6 . Front seam  42  and rear seam  44  (not visible here) may divide leg bladder portion  26  to form a pair of opposing leg bladder chambers  26   a  and  26   b , which may be fluidically interconnected to sole bladder portion  28  via passageways  68 . The interconnection between leg bladder chambers  26   a  and  26   b  and sole bladder portion  28  may be better appreciated referring collectively to  FIGS. 3 ,  5 , and  6 . The interconnection may be such that the inflatable interior of bladder  24 , encompassed by cover  20  and liner  22 , may be relatively unobstructed. Structural interconnections  46  preferably may be the only obstructions within the interior of bladder  24 . 
   This extensive interconnectiveness between relative proportions of leg bladder portion  26 , sole bladder portion  28 , structural interconnections  46 , and, passageways  68 , may be of such significance that any increase in pressure within any portion of bladder  24  acts substantially immediately on any other portion of bladder  24 . The pressure within bladder  24  is indicated visually within  FIGS. 1 through 6  by the bulging of cover  20 , and the fact that liner  22 , pocket  60 , and thermal treatment device  62  are each pressed against foot  12  and lower leg  14 . 
   Unlike  FIGS. 1 through 6  discussed above,  FIGS. 7 and 8  illustrate a boot  10  without an inserted human lower extremity.  FIG. 7  shows boot  10  in an uninflated, flattened condition. Such a condition may be suitable for storage. Several elements of boot  10  discussed above are identified in  FIG. 7 , including structural interconnection  46 , notches  50 , and intake valve  64 .  FIG. 8  shows the flattened boot  10  of  FIG. 7 , with open-looped toe  58  shown slightly opened for clarity. 
     FIG. 9  illustrates foot  12  and lower leg  14  inserted into a mostly uninflated boot  10 . Toes  16  may be positioned relatively close to front seam  42  and heel  18  of foot  12  may be positioned relatively close to notches  50 . Sole  66  of foot  12  may be aligned approximately with structural interconnection  46 . Thus, it may be appreciated that foot  12  is positioned approximately as shown in  FIG. 5 , with respect to each of these elements of boot  10 . In comparison of  FIG. 9  to  FIG. 5 , the primary difference may be that in  FIG. 9  bladder  24  hangs uninflated below sole  66  of foot  12 , while in  FIG. 3  bladder  24  is filled with air or other fluid so that cover  20  is forced into a more rounded configuration, encircling foot  12 . 
     FIG. 10  also illustrates boot  10  in a mostly uninflated state. In such an uninflated state liner  22  and thermal treatment device  62 , within leg bladder portion  26 , may press slightly against lower leg  14 , and liner  22  within sole bladder portion  28  may hang below sole  66  of foot  12 . Boot  10  may include an open-looped heel caused by independently formed heel seal  40 , as indicated generally at  40   a . The portion of liner  22  that hangs below sole  66  may be the portion that forms a foot-supporting contour for sole portion  28  when bladder  24  is inflated, as seen best in  FIG. 11 . 
     FIG. 11  illustrates boot  10  in an inflated state, and further depicts the interactions between structural interconnection  46 , cover  20 , and liner  22 . As bladder  24  is inflated, liner  22  within sole portion  28  may fold up around structural interconnection  46 , forming a foot-conforming contour of boot  10 . The fluid within bladder  24  may press relatively evenly on foot  12  and lower leg  14 , as indicated by the pressure-indicating arrows  71 . 
   Referring now to  FIG. 12 , boot  10  is shown in a compressed condition, as when bladder  24  is inflated to within a therapeutic range, and an applied force has pressed bladder  24  against surface  72 . In such a compressed, or pressurized condition, the volume of sole bladder portion  28  may be substantially diminished increasing the fluid pressure within sole bladder portion  28 . 
   As discussed above, a pressure increase within one portion of bladder  24  may be communicated to the remaining portions of bladder  24 . Thus, a pressure increase within sole bladder portion  28  may cause a pressure increase within leg bladder portion  26 . This pressure increase is indicated by the increased size of pressure-indicating arrows  71  in  FIG. 12  as compared to those in  FIG. 11 . It also may be noted that cover  20  of boot  10  may be forced into a much more rounded configuration in  FIG. 12 , when compared to  FIG. 11 . 
     FIGS. 13 through 17  illustrate an alternative embodiment of the inflatable boot of the present disclosure. Many of the elements illustrated in boot  110  are substantially similar to elements discussed above with respect to boot  10 . Accordingly, rather than reintroducing these elements, they are referred to below, and identified in  FIGS. 13 through 17  with the reference characters used in prior Figs., each preceded by a “1.” 
     FIGS. 13 through 17  illustrate a boot  110  which includes a support sling  174 . Boot  110  may include a sling  174  for supporting the encased lower extremity. Sling  174  may be made of any flexible sheet material, such as, nylon fabric, webbing, polyurethane, canvas, rubber, etc. Sling  174  may be undersized relative to cover  120  and liner  122  so that sling  174  hangs substantially above cover  120  within sole bladder portion  128 , as shown in  FIGS. 13 and 14  by fold line  174   a  of sling  174 . 
   Because of this size difference between sling  174  and liner  122  it may be difficult to attach sling  174  to liner  122 . In some embodiments, sling  174  may be attached to liner  122  after front and rear seams  142  and  144  are formed, and may be adhered to liner  122  using a variety of adhesives, sealants, or fasteners. Portions of sling  174  may be attached to liner  122  in combination with pocket  160 . 
   Some embodiments of boot  110 , or of boot  10 , may also include a tread  176 , illustrated in  FIGS. 13 through 16 . Tread  176  may be placed on the bottom of the boot  110  and may increase the wear resistance of an inflatable boot. This tread  176  may made from of rubber, plastic, resin, neoprene, or any other suitable flexible wear resistant material. 
     FIG. 15  also illustrates a sling  174  around a portion of a foot  12  inserted into boot  110  while boot  110  is in its mostly uninflated condition. A wall portion  126  of boot  110  may be held by a user hand  178 , while the foot is being inserted into the sling, and/or when the boot  110  is inflated. Upon insertion into bladder  124 , foot  12  may contact sling  174  substantially before contacting sole portion  128 . Thus, sling  174  may provide a positive-positioning element for boot  110 , operating as a platform-defining element suspended within bladder  124 , located inwardly of liner  122 . Foot  12  may therefore be supported by a cushion formed by sole portion  128  of bladder  124  when bladder  124  is inflated, the cushion being defined between sling  174  and cover  120 . 
     FIGS. 16 and 17  show boot  110  with foot  12  and lower leg  14  inserted, and with boot  110  partially inflated. As best seen in  FIG. 17 , when boot  110  is partially inflated sling  174  may be substantially adjacent to liner  122 . A pocket  160  containing a thermal treatment device may also be included in boot  110 . The pocket  160  may be formed out of portion of sling  174 , or alternatively may be independent of sling  174 . 
   It is believed that the disclosure set forth above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. Where the disclosure or subsequently filed claims recite “a” or “a first” element or the equivalent thereof, it should be within the scope of the present inventions that such disclosure or claims may be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. 
   Applicant reserves the right to submit claims directed to certain combinations and subcombinations that are directed to one of the disclosed inventions and are believed to be novel and non-obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of those claims or presentation of new claims in that or a related application. Such amended or new claims, whether they are directed to a different invention or directed to the same invention, whether different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of the inventions of the present disclosure.