OBJECTIVEFoot ulceration remains a major health problem for diabetic patients and has a major impact on the cost of diabetes treatment. We tested a hyperspectral imaging technology that quantifies cutaneous tissue hemoglobin oxygenation and generated anatomically relevant tissue oxygenation maps to assess the healing potential of diabetic foot ulcers (DFUs).RESEARCH DESIGN AND METHODSA prospective single-arm blinded study was completed in which 66 patients with type 1 and type 2 diabetes were enrolled and followed over a 24-week period. Clinical, medical, and diabetes histories were collected. Transcutaneous oxygen tension was measured at the ankles. Superficial tissue oxyhemoglobin (oxy) and deoxyhemoglobin (deoxy) were measured with hyperspectral imaging from intact tissue bordering the ulcer. A healing index derived from oxy and deoxy values was used to assess the potential for healing.RESULTSFifty-four patients with 73 ulcers completed the study; at 24 weeks, 54 ulcers healed while 19 ulcers did not heal. When using the healing index to predict healing, the sensitivity was 80% (43 of 54), the specificity was 74% (14 of 19), and the positive predictive value was 90% (43 of 48). The sensitivity, specificity, and positive predictive values increased to 86, 88, and 96%, respectively, when removing three false-positive osteomyelitis cases and four false-negative cases due to measurements on a callus. The results indicate that cutaneous tissue oxygenation correlates with wound healing in diabetic patients.CONCLUSIONSHyperspectral imaging of tissue oxy and deoxy may predict the healing of DFUs with high sensitivity and specificity based on information obtained from a single visit.

Diabetic foot ulcers are known to have a biomechanical etiology. Among the mechanical factors that cause foot lesions, shear stresses have been either neglected or underestimated. The purpose of this study was to determine various plantar pressure and shear variables in the diabetic and control groups and compare them. Fifteen diabetic patients with neuropathy and 20 non-diabetic subjects without foot symptoms were recruited. Subjects walked on a custom-built platform capable of measuring local normal and tangential forces simultaneously. Pressure-time integral quantities were increased by 54% (p=0.013) in the diabetic group. Peak AP and resultant shear magnitudes were found to be about 32% larger (p<0.05), even though diabetic subjects walked at a slower velocity. Lower AP and ML stress range (peak-to-peak) values were observed in the control subjects (p<0.05). Shear-time integral values were increased in the diabetic group by 61% and 132% for AP and resultant shear cases, respectively (p<0.05). Plantar shear is known to be a factor in callus formation and has previously been associated with higher ulcer incidence. During gait, shear stresses are induced with twice the frequency of pressure characteristically. Therefore, plantar shear should be investigated further from a broader perspective including the temporal specifications and fatigue failure characteristics of the affected plantar tissue.

Despite their advantages, percutaneous coronary interventional procedures are less effective in diabetic patients. Changes in the mechanical properties of vascular walls secondary to long-term hyperglycemia as well as other factors such as age may influence coronary distensibility. This investigation is aimed at deciphering the extent of these effects on distensibility of postmortem human coronary arteries in a controlled manner. Excised human left anterior descending (LAD) coronary arteries were obtained within 24 h postmortem. With the use of intravascular ultrasound, vascular deformation was analyzed at midregions of 51 moderate lesions. Intraluminal pressure was systematically altered using a computerized pressure pump system and monitored by a pressure-sensing guidewire. Distensibility, a normalized compliance term, was defined as the change in lumen area normalized by the initial reference area over a given pressure interval. With the use of multivariate analysis and repeated-measures ANOVA, coronary distensibility was independently influenced by hyperglycemia and age (P < 0.05) through the entire pressure range. Within physiological pressure range, distensibility was significantly reduced with age in nonhyperglycemic coronary specimens (10.55 +/- 4.41 vs. 6.99 +/- 2.45, x10(3) kPa(-1), P = 0.01), whereas the hyperglycemic vessels were stiff even in the younger group (7.90 +/- 5.82 vs. 7.20 +/- 3.36, x10(3) kPa(-1), P = 0.79). Similar results were observed with stiffness index and elastic modulus of the arteries. Hyperglycemia and age independently influenced the distensibility of moderately atherosclerotic LAD coronary arteries. The stiffening with age was overshadowed in the hyperglycemic group by as-yet-undetermined factors.

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Most arterial mechanics studies have focused on excised non-coronary vessels, with few studies validating the application of ex-vivo results to in-vivo conditions. A method was developed for testing the mechanical properties of intact left anterior descending coronary arteries under a variety of conditions. Vascular deformation and pressure were simultaneously measured with intravascular ultrasound and a pressure transducer guidewire, respectively. Results suggest the importance of understanding in-vivo factors such as myocardial support, vascular tone and local pressure fluctuations when applying ex-vivo coronary characterization data. With further development, this method can more accurately characterize the true in-vivo constitutive behavior in normal and atherosclerotic coronaries.