Temperature- and Pressure-Regulating Insoles for Prevention of Diabetic Foot Ulcers

Abstract

Diabetic foot ulcers (DFUs) pose a major threat to the United States healthcare system as well as patients and their families. High ulcer recurrence rates indicate that existing preventive measures are not effective. A new generation of multimodal preventive devices may reduce ulceration and amputation rates. Because previous research has revealed that tissue maintained at cooler temperatures is more resistant to breaking down, the evaluated technology may prevent foot ulceration. The purpose of this study was to test previously designed Temperature and Pressure Monitoring and Regulating Insoles (TAPMARI) in diabetic neuropathic and healthy subjects. A cooling unit, a mini-water pump, a battery pack, and a microcontroller (or simply thermostat) were placed inside a box attached to the subjects’ calf, which provided cooling inside the shoe. The microcontroller was set at 28°C. Eight subjects provided informed consent, 3 of whom had diabetic neuropathy. Subjects used the instrumented shoe on the right foot and the matching control shoe on the left and walked on a treadmill for 5 minutes at self-selected speeds. Baseline and postwalking thermographs were obtained with a thermal camera. At the 2-hour midpoint, subjects again walked on the treadmill for 5 minutes at self-selected speeds. Second baseline and postwalking thermographs were captured. Plantar pressure distributions were also quantified. The TAPMARI successfully regulated foot temperatures at or below the target temperature. The mean baseline temperature of the right (regulated) and left (control) feet were 28.1 ± 1.9°C (mean ± standard deviation) for all subjects. The mean temperatures at the end of the study were 25.9 ± 2.5°C (right) and 31.7 ± 1.6°C (left) in all subjects. In the diabetic neuropathy group, the final mean temperatures were 27.5 ± 2.4°C (right) and 31.6 ± 0.8°C (left), which indicated that the temperature goal was met inside the instrumented shoe. By regulating temperatures, TAPMARI may reduce the metabolic demands in the foot and prevent cell autolysis by eliminating the imbalance between oxygen demand and supply. This study warrants further development and testing of TAPMARI as well as investigating the clinical effectiveness in preventing DFUs.