Abstract:
An inflatable foot cushion to reduce the force amplifications upon the heel of a foot received therein when the body is in a supine position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application 61/516,087, filed Mar. 29, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of inflatable devices for supporting the human body, and more particularly is concerned with a novel improved inflatable foot cushion to counter the force amplifications experienced by the foot, and particularly the heel area of the foot, when the body is in the supine position. 
     In the supine position, the foot assumes the shape of a wedge that tapers from the toes down to the heel. The mechanical force amplifications that are typically associated with a wedge are therefore also experienced by the wedge-shaped foot. The heel area, and more specifically the points of contact between the heel area and the substrate upon which the body is lying in the supine position, experiences mechanical force amplifications that are analogous to those experienced by the working edge of the typical wedge. In addition, when in the supine position, the lower legs function as levers with the heel areas serving as fulcrums, further amplifying the mechanical forces acting upon the heel areas. 
     The recognition that heel ulcers are caused by such mechanical forces (pressure, shear and frictional stresses) on the heel became clinically significant in the early 1980&#39;s. Since that time it has been found that offloading mechanical forces on the heel is the ideal way to prevent a pressure ulcer of the heel from developing (see NPUAP and EPUAP Guidelines). During the era of using pillows to offload mechanical forces on the heel, the occurrence of pressure ulcers of the heel continued to increase. Pressure ulcers of the heel are now running a close second to sacral pressure ulcers. When considering the deep tissue injury component of the pressure ulcer, pressure ulcers of the heel are now first in occurrence (see Vangilder, MacFarlane, Harrison, Lachenbruch and Meyer 254-261). 
     In 1994, a three-chambered Inflatable Foot Cushion was patented (U.S. Pat. No. 5,328,445). The prevention and treatment of pressure ulcers of the heel and other types of foot wounds have been exceptional when this patented inflatable foot cushion has been in use. The foot resting chamber of that device was constructed to resemble the keel of a boat. The objectives of the two main inflatable chambers of the patented Inflatable Foot Cushion that defined the foot resting chamber were the offloading the mechanical forces on the heel; the giving of symmetrical static air support to the calf, ankle and foot; and (3) the supporting of the sole of the foot to prevent foot drop and resultant injury. The third main chamber of that patented Inflatable Foot Cushion was an independent chamber (16) that was used beneath the two main chambers as an accessory chamber to elevate the inflatable foot cushion. 
     SUMMARY OF THE INVENTION 
     The present invention is a novel improved inflatable foot cushion that addresses and resolves issues that arose in the prevention of ulcers of the heel when using the three-chambered Inflatable Foot Cushion of U.S. Pat. No. 5,328,445, which is incorporated by reference herein. 
     One embodiment of the improved inflatable foot cushion of the present invention is an inflatable foot cushion to reduce the force amplifications upon the heel of a foot received therein when the body is in a supine position, comprising: an inflatable main chamber having two inflatable downwardly-sloping sides and a two-sided inflatable foot chamber with each side of the inflatable foot chamber being connected in fluid communication with one of the two downwardly-sloping sides that support with static air pressures the calf, ankle and foot of a body in a supine position, leaving the heel of the foot free of support, when they are positioned within the inflatable main chamber; a plurality of inflatable, adjustable calf straps connected in fluid communication at one end thereof with one of the downwardly-sloping sides and removably and adjustably affixed at the other end thereof to the other downwardly-sloping side that overlay the skin on a calf along the tibia when a calf is positioned within the inflatable main chamber; an inflatable, adjustable foot strap connected in fluid communication at one end thereof with one side of the inflatable foot chamber and removably and adjustably affixed at the other end thereof to the other side of the inflatable foot chamber that overlays the skin on the top of a foot when a foot is positioned within the inflatable main chamber; and an inflatable, adjustable two-sided foot sole cushion with one side of each side connected in fluid communication to one side of the inflatable foot chamber and with the other side of each side removably and adjustably affixed to each other, whereby the two-sided foot sole cushion overlays and adjusts to the contour of the sole of a foot positioned within the inflatable foot chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side elevation view of the novel inflatable foot cushion of the present invention. 
         FIG. 2  is a left side elevation view of the novel inflatable foot cushion of the present invention. 
         FIG. 3  is a top plan view of the novel inflatable foot cushion of the present invention. 
         FIG. 4  as a right side perspective view of the novel inflatable foot cushion of the present invention. 
         FIG. 5  is a right side perspective view of the novel inflatable foot cushion of the present invention. 
         FIG. 6  is a front perspective view of the novel inflatable foot cushion of the present invention. 
         FIG. 7  is a front end view of the novel inflatable foot cushion of the present invention. 
         FIG. 8  is an exploded top plan view of the inflated novel inflatable foot cushion of the present invention showing the relationships of its constituent parts. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 8 , which is an exploded top plan view of an inflated novel inflatable foot cushion ( 1 ) of the present invention, and which illustrates the relationships of its novel constituent parts, and which also illustrates how two pliable plastic sheets have been joined together by conventional means to form the novel inflatable chambers and straps of the inflatable foot cushion ( 1 ) of the present invention. Referring to  FIG. 2 , there is one inflation port ( 12 ) for all of the air inflatable chambers shown in  FIG. 8 , all of which are in fluid communication with each other, with one exception.  FIG. 2  also illustrates an inflation port ( 12 ) for independent air inflatable chamber ( 10 ), which is not in fluid communication with the other chambers illustrated in  FIG. 8 , and which is of the same size and has the same functionality as does independent air inflatable cushion  16  of the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445. The only difference between present independent inflatable chamber  10  and the inflatable cushion ( 16 ) of U.S. Pat. No. 5,328,445 is that the present invention&#39;s cushion ( 10 ) is kept in it adjustable positions by hook and loop fasteners ( 13 ,  14 ). Independent inflatable chamber  10  is not a part of the presently claimed invention. 
     The first novel improvement of the improved inflatable foot cushion ( 1 ) of the present invention is the addition of air-inflated, adjustable calf straps ( 2 ) that secure the novel inflatable foot cushion ( 1 ) to the calf, ankle and foot (“CAF”) of a patient, which air inflated calf straps effectively protect a patient&#39;s skin of the calf over the tibia when the calf is secured within the novel inflatable foot cushion ( 1 ) by the inflated adjustable calf straps ( 2 ). This is accomplished by filling the individual inflatable calf straps ( 3 ,  4 ,  5 ) with static air, each strap being formed, as are all other static air chambers of the novel inflatable foot cushion ( 1 ) of the present invention, by two pliable plastic sheets joined together by conventional means to form inflatable chambers within the calf straps ( 3 ,  4 ,  5 ). Filling the calf straps ( 3 ,  4 ,  5 ) with air moves the welded joints ( 7 ) of the two pliable plastic sheets that were joined together to form the air chambers within the calf straps ( 3 ,  4 ,  5 ) well away from a patient&#39;s skin of the calf over the tibia when the calf straps ( 3 ,  4 ,  5 ) are each independently snugged up against the skin of the calf over the tibia to secure the improved inflatable foot cushion ( 1 ) of the present invention about the CAF of the patient. The inflatable calf straps ( 3 ,  4 ,  5 ) are each connected at one end thereof to one downwardly-sloping side ( 16 ) of the main chamber ( 6 ) in fluid communication with the main chamber ( 6 ), and at the other end each calf strap ( 3 ,  4 ,  5 ) is adjustably attached to the opposite downwardly sloping side ( 17 ) of the main chamber ( 6 ) with hook and loop fasteners ( 13 ,  14 ). By this novel design of the secured inflated calf straps ( 3 ,  4 ,  5 ) of the improved inflatable foot cushion, the calf and ankle are fully supported and kept snug through 360 degrees by equalized static air pressures (cf., Boyles Law and Paschal Principles). Not only do the air-filled calf straps ( 3 ,  4 ,  5 ) deliver non-gradient air pressure to the calf, but as mentioned above, they also keep the sealed construction edges ( 7 ) of the air-filled straps ( 3 ,  4 ,  5 ) away from the skin of the calf over the tibia. Neither of these novel design features was present in the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445. 
     The second novel improvement of the inflatable foot cushion ( 1 ) of the present invention is the sloped-downward design of the sides ( 16 ,  17 ) of the main chamber ( 6 ), which slope downwardly from the calf to the ankle areas of the main chamber ( 6 ) (see  FIG. 1 ). The use of the air filled calf straps ( 3 ,  4 ,  5 ) allows this lower side profile of the sides ( 16 ,  17 ) of the main chamber ( 6 ) to be used effectively to provide for better ambient air circulation around the calf and ankle area, which in combination with through holes ( 11 ) in the sides ( 16 ,  17 ) provides for better ambient air control (both temperature and moisture control) around the calf and ankle. The novel inflatable foot cushion ( 1 ) of the present invention ( 1 ) thus permits more ambient air to enter the novel inflatable cushion and surround the calf and ankle areas. To improve ambient air circulation calf strap ( 5 ) may be freed from its securing hook and loop fasteners ( 13 ,  14 ) on side ( 17 ) of the main chamber ( 6 ) and temporarily the hook faster ( 14 ) of calf strap ( 5 ) may be attached to loop fastener ( 20 ) shown on side ( 17 ) ( FIG. 2 ) of main chamber ( 6 ). 
     In testing done to date, the lower side profile of the downwardly-sloping sides ( 16 ,  17 ) of the main chamber ( 6 ) also reduces the chance for lateral rotation of the CAF within the main chamber ( 6 ), and reduces the chances for an over extension or flexion of the patient&#39;s knee and a lateral rotation of the patient&#39;s hip. This is a major improvement over the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445, as that device is balloon-like in its overall structure, and it therefore has a tendency to roll from side-to-side when either over or under inflated with air. The lower profile, downwardly sloping sides ( 16 ,  17 ) of the present invention also allow patients wearing the novel inflatable foot cushion ( 1 ) to articulate their ankles and to move their foot fore and aft while it is snuggly embraced within the novel inflatable foot cushion ( 1 ) of the present invention. 
     The third and fourth novel improvements of the inflatable foot cushion ( 1 ) of the present invention, discussed below, relate to the prevention of the inflatable foot cushion ( 1 ) of the present invention from spinning on its longitudinal axis, which compromises the desired CAF positioning within the device, and which occurs at times when the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445 is in use. 
     The third novel improvement of the inflatable foot cushion ( 1 ) of the present invention is a novel air filled and adjustable foot strap ( 9 ) that is connected in fluid communication with the foot chamber cushion ( 19 ) of main chamber ( 6 ), and it passes from foot chamber cushion ( 19 ) to foot chamber cushion ( 18 ) where it is adjustably attached to foot cushion chamber ( 18 ) of the main chamber ( 6 ) with hook and loop fasteners ( 13 ,  14 ). In this manner, the air filled and adjustable foot strap ( 9 ) covers the skin on top of a foot positioned within the main chamber ( 6 ) which prevents the CAF from inadvertently slipping out of the novel inflatable foot cushion ( 1 ) of the present invention in use. The foot strap ( 9 ) also allows for a complete customizable fitting of a patient&#39;s within the novel inflatable foot cushion ( 1 ) of the present invention. This novel feature can be compared to the lacing or strapping of normal footwear to the foot. 
     The fourth novel improvement of the inflatable foot cushion of the present invention ( 1 ) is the novel design of the adjustable, inflatable foot sole cushion ( 8 ) that is adjustable in two parts (see  FIGS. 6 &amp; 7 ) with hook and loop fasteners ( 13 ,  14 ) to match the contours of the sole of a foot within the novel inflatable foot cushion ( 1 ) of the present invention. The adjustable and inflatable two-part foot sole cushion ( 8 ) has one part thereof in fluid communication with foot chamber cushion ( 18 ) and the other part in fluid communication with foot chamber cushion ( 19 ), and foot sole cushion ( 8 ) thereby allows a more custom fit of the inflatable foot cushion ( 1 ) of the present invention to the sole of a patient&#39;s foot. It is adjustable with large hook and loop fasteners ( 13 ,  14 ) ( FIGS. 6 &amp; 7 ) which also protects the sides of a foot from being too tightly fit within the novel inflatable cushion ( 1 ) of the present invention. The uniform shape of the foot sole cushion ( 14 ) of the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445 was not able to accomplish this custom fit to the sole of a foot. 
     The adjustable, inflatable two-part foot sole cushion ( 8 ) also creates a desirably larger hole ( 15 ) in main chamber ( 6 ) for a patient&#39;s heel to reside within, unsupported (see  FIGS. 1, 3 &amp; 6 ), than was created in the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445. This fact, coupled with the functionality of foot strap ( 9 ) and foot sole cushion ( 8 ), which keep a foot up, thereby preventing “foot drop” (see  FIG. 1 ), also effectively protects the entire Achilles heel area, as well. 
     Furthermore, when the two-part foot sole cushion ( 8 ) is opened completely by disassociating the adjustable hook and loop fasteners completely ( 13 ,  14 ) (see  FIG. 7 ), the patient&#39;s foot sole is fully exposed, and the patient could then become ambulatory, moving from a bed to a chair, for example, while still wearing the novel inflatable foot cushion ( 1 ) of the present invention, which was not a possibility with the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445. 
     In testing to date, the third and fourth novel improvements of the present invention also assisted in preventing the spinning of the inflatable foot cushion ( 1 ) of the present invention on its longitudinal axis, which occurred at times when the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445 is over or under inflated. 
     In summary, these foregoing novel improvements present within the inflatable foot cushion ( 1 ) of the present invention address the maintenance of proper anatomical positioning of the CAF when it is in use; they deliver a low profiled static air support through in 360 degrees to the CAF so that skin and soft tissue distortion, ischemia, lymphatic and interstitial fluid obstruction and reperfusion injuries are less likely to occur, when the novel inflatable foot cushion ( 1 ) of the present invention is in use. 
     The following two tables summarize in tabular format the differences between the novel inflatable foot cushion ( 1 ) of the present invention (“2011 Device”) and the Inflatable Foot Cushion of U.S. Pat. No. 5,328,445 (“1994 Device”). 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                 1994 Device 
                 2011 Device 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Delivers Static Air Support to the 
                 Yes 
                 Yes 
               
               
                 Calf/Ankle/Foot (“CAF”) 
               
               
                 Offloads the Heel 
                 Yes 
                 Yes 
               
               
                 Protects Achilles Tendon 
                 Yes 
                 Yes 
               
               
                 Has Air Filled, Adjustable Strapping 
                 No 
                 Yes 
               
               
                 Protects the Medial Malleolus 
                 Yes 
                 Yes 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 Rating of Effectiveness I-5 
               
               
                 (5 = Excellent-1 = Poor) 
               
             
          
           
               
                   
                 1994 Device 
                 2011 Device 
               
               
                   
                   
               
             
          
           
               
                 Unloads the Heel 
                 5 
                 5 
               
               
                 Delivers Non-Gradient Static Air 
                 5 
                 5 
               
               
                 Support 
               
               
                 Addresses Microclimate 
                 4 
                 5 
               
               
                 (Heat, Moisture) 
               
               
                 Prevents Foot Drop 
                 3 
                 4 
               
               
                 Prevents Lateral Rotation 
                 3 
                 4 
               
               
                 Prevents Over-Extension of the Knee 
                 4 
                 5 
               
               
                 Safety of the Adjustable Straps 
                 4 
                 5 
               
               
                 Foot Compartment Customizing 
                 2 
                 5 
               
               
                 Ability 
               
               
                 Prevention of the CAF Spinning, and 
                 3 
                 5 
               
               
                 Improper Positioning 
               
               
                 Ease of Use 
                 4 
                 5 
               
               
                 Cost Effective 
                 5 
                 5