Pilot study of the effects of local pressure on microvascular function in the diabetic foot

Aim The aim of the study was to determine whether areas of the diabetic foot that experience high pressures during normal activity also demonstrate reductions in cutaneous microvascular flow and/or endothelial function. Methods Sixteen patients with diabetes mellitus and eight healthy, age-matched control subjects were recruited. Maps of dynamic pressure on the plantar aspect of both feet were recorded during a normal gait cycle, and the skin microvascular blood flow response to the endothelium-dependent vasodilator acetylcholine was assessed at the sites of highest and lowest plantar pressure over the metatarsal heads. Results Patients with diabetes had higher plantar pressures than control subjects (P = 0.002), but there were no significant differences in basal skin blood flow or acetylcholine response between the groups. In the patients, baseline flow was increased (P = 0.041) but the acetylcholine response reduced (P = 0.03) at the high-pressure compared with the low-pressure site; this was most apparent in those who were particularly at risk of ulceration due to high plantar pressures. Conclusions Chronically raised plantar pressure in the diabetic foot is associated with increased basal skin blood flow, compared with lower pressure areas on the same foot. Further work is required to determine whether, and under what conditions, this additional hyperaemia is protective or maladaptive. In addition, high-pressure areas have a reduced responsiveness to an endothelium-dependent vasodilator, although the clinical significance of these changes is not clear.