Transcutaneous Oxygen Tension in Legs and Feet of Diabetic Patients

Transcutaneous oxygen tension (tcPO₂) of the legs and feet was measured at 37 and 44°C in 21 patients with diabetes mellitus, 9 of whom had peripheral neuropathy. At 37°C, tcPO₂ in the legs and feet of diabetic patients with peripheral neuropathy was significantly higher (P < .02) than in control subjects and diabetic patients without neuropathy. Whereas tcPO₂ in the legs of control subjects and nonneuropathic diabetic patients was > in the feet (P < .02), this leg-to-foot difference was absent in diabetic patients with neuropathy. After an increase in skin temperature to 44°C, tcPO₂ increased in the legs and feet of all three groups, but the increase was smallest in diabetic patients with neuropathy and greatest in control subjects. In neuropathic (P < .02) and nonneuropathic (P < .02) diabetic patients, tcPO₂ was significantly lower than in control subjects. These data are consistent with a loss of vasoconstrictor tone in the blood vessels perfusing skin and subcutaneous tissue at 37°C and an inability of these vessels to vasodilate and increase blood flow at 44°C in diabetic patients in general and neuropathic diabetic patients in particular. This inability to increase tcPO₂ after an increase in temperature and possibly other vasodilatory stimuli may contribute to the pathogenesis of nonhealing ulcers, protracted infections, and gangrene, which characterize the diabetic foot.