Assessment of Microcirculation and the Prediction of Healing in Diabetic Foot Ulcers

Globally, diabetes mellitus has grown to pandemic proportions, affecting 194 million people worldwide and is expected to increase in prevalence to 344 million by the year 2030 (Wild, et al., 2004). Of these patients, between 2 and 6% will develop a diabetic foot ulcer (DFU) yearly (Ramsey, et al., 1999). The onset of a DFU often precipitates a complex chain of events that may lead to limb loss. Infected DFUs account for 20% of hospital visits for this patient population (Bouter, et al. 1993) and precede roughly 85% of lower extremity amputations in patients with diabetes (Pecoraro, et al. 1990). The long-term outcome for a diabetic patient after a major limb amputation is grave with 50% of these patients deceased at 5 years (Moulik, et al. 2003). Additionally, the cost to treat this disease places a significant strain on the health-care system. The cost to manage these foot disorders is estimated at several billion dollars annually (Wild, et al. 2004), while the individual cost of a major limb amputation is estimated at almost $45,000 (Apelqvist, et al. 1994). With the combination of excessive cost to treat diabetes complications coupled with the major detrimental health effects on individual patients, it is necessary to develop and employ new technological methods to predict healing of diabetic foot ulcers. Once a diabetic patient develops a pedal ulceration it becomes incumbent on the physician to evaluate the ulcer’s healing potential. Much research has focused on the prediction of diabetic foot ulcer healing. Clinically, it has been shown that a 50% decrease in area over a 4week period with standard wound care adequately predicts ulcer healing at 12 weeks (Sheehan, et al., 2003). The disadvantage of this method, however, is the delay in treatment that occurs as a result of the natural time deferment in this process. As such, newer technologies have utilized the determination of microcirculation to predict ulcer healing. This chapter focuses on the application of these new technologies to determine microvascular circulation and predict diabetic foot ulcer healing. Large artery (macrocirculatory) disease has been well documented elsewhere with disease at the infrapopliteal region (Bembi, et al. 2006) causing loss of tissue perfusion and critical limb ischemia and gangrene. Various noninvasive vascular testing modalities exist to determine large vessel luminal disease. These include dual mode ultrasound, segmental leg pressures, ankle brachial indices, pulse volume recordings, toe pressures, and toe brachial indices. The above tests have been found to yield useful clinical data regarding large vessel disease and often function as safe precursors to more advanced imaging techniques such as magnetic resonance arteriography. These methods also assist with surgical revascularization