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.