Modulation of plantar circulation in physiological loading: An investigation of intermittent local hypoxia in the diabetic neuropathic foot

Plantar skin ulceration is a complication facing 15 percent of diabetic neuropathic individuals. In the United States (US), diabetic ulcers lead to over 80,000 amputations annually with the cost of treatment exceeding ;We hypothesize: if we apply a load simulating gait to the plantar foot and measure microvascular function, diabetic individuals will demonstrate an increased delay in reestablishing microvascular flow compared to healthy individuals. We challenged plantar microcirculation of the hallux by applying pressure and simultaneously assessing for blood flow. We developed a prototype device to test microvascular reaction to continuous and pulsed loads. Three diabetic individuals with a high risk of ulceration and five non-diabetic, non-neuropathic healthy controls enrolled in the study. The new device applied 90 seconds of controlled loading at levels adjusted for blanching in each individual, followed by 180 seconds of refractory time. Time values for response to occlusion were determined for each load/unload cycle.;We found mean latency between end of compression and initiation of response for each of two loading protocols: continuous in the diabetic group (0.479 seconds) versus healthy (0.055 seconds) and pulsed (at 1.0Hz) in diabetics (119.475 seconds) compared to (69.650 seconds) in the healthy. This study showed the effectiveness of the prototype in sequencing microvascular response to simulated gait loads demonstrating different reactions between the two groups. It also suggested a relationship between latency and elasticity in soft tissue. This study sheds new light on microvascular function in the diabetic foot. We theorize that gait modulation of microcirculation causes skin hypoxia that goes unnoticed by the diabetic individual resulting in skin ulcers. The study may allow for improved understanding of diabetic ulceration etiology and suggests the need for further investigation into microvascular function.