Pressure ulcers are common debilitating complications of diabetes that are caused by tissue ischemia. Skin blood flow in response to locally applied pressure might be impaired in diabetic patients because of the combined effects of a typically low skin temperature and alterations in microcirculatory function, and could be worsened by neuropathy. We measured skin blood flow by laser Doppler flowmetry over the internal anklebone in response to local pressure applied at 5.0 mmHg/min in three groups of diabetic patients (with clinical and subclinical neuropathy and without neuropathy) and in healthy matched control subjects at usual room temperature. Compared with in matched control subjects with comparable skin temperatures (29.3 ؎ 0.4 vs. 28.7 ؎ 0.4°C), in diabetic patients the skin blood flow response to locally applied pressure was further impeded, even in those without neuropathy. Indeed, skin blood flow decreased significantly from baseline at much lower applied pressure (7.5 mmHg) in diabetic subjects, again even in those without neuropathy, than in control subjects (48.8 mmHg). The large difference between these pressures could partially explain diabetic patients' high risk of developing decubitus and plantar ulcers. Diabetes 51:1214 -1217, 2002 P ressure ulcers are common debilitating complications of diabetes (1). Diabetes disturbs the autonomic regulation of skin microcirculation, even in the absence of neuropathy. Moreover, sensory diabetic neuropathy mainly affects unmyelinated primary afferent fibers (2) and impairs the vasodilation related to normally functioning unmyelinated C fibers (3,4). We recently reported on cutaneous pressure-induced vasodilation (PIV) in humans (5,6) and rats (7) as a physiological response to an increase in nonnoxious progressive local pressure. This mechanism allows skin blood flow to increase in response to locally applied pressure, whereas in its absence, skin blood flow is progressively decreased with application of increased local pressure. Although it results from nonpainful stimulation, this mechanism has been shown to disappear after chronic treatment with capsaicin in animals and humans (5,7), suggesting that it is dependent on the normal function of capsaicin-sensitive primary nervous afferents. Because temperature and blood flow in cutaneous microcirculation are highly correlated (8), skin temperature may have a major effect on skin blood flow response to applied pressure. Therefore, we hypothesized that the skin blood flow response to locally applied pressure would be impaired in diabetic patients because of the combined effects of their typically low skin temperature and diabetes-induced alterations of the vascular and nervous systems. To verify this hypothesis, we measured the effects of locally applied pressure on skin blood flow over the internal anklebone in diabetic patients with clinically apparent or subclinical neuropathy and without neuropathy and in healthy matched control subjects at usual ambient temperature.
RESEARCH DESIGN AND METHODSSubjects. Subj...