The severity of muscle ischemia during intermittent claudication

PURPOSE: The degree of ischemia during intermittent claudication is difficult to quantify. We evaluated calf muscle ischemia during exercise in patients with claudication with near infrared spectroscopy. METHODS: A Critikon Cerebral Redox Model 2001 (Johnson & Johnson Medical, Newport, Gwent, United Kingdom) was used to measure calf muscle deoxygenated hemoglobin (HHb), oxygenated hemoglobin (O(2)Hb), and total hemoglobin levels and oxygenation index (HbD; HbD = O(2)Hb - HHb) in 16 patients with claudication and in 14 control subjects before, during, and after walking on a treadmill for 1 minute (submaximal exercise). These measures were repeated after a second maximal exercise in patients with claudication and after 7 minutes walking in control subjects. Near-infrared spectroscopy readings during maximal exercise were then compared with a model of total ischemia induced with tourniquet in 16 young control subjects. RESULTS: Total hemoglobin level changed little during exercise in both patients with claudication and control subjects. HHb levels rose, and O(2)Hb level and HbD falls were more pronounced in patients with claudication than in control subjects after submaximal and maximal exercise. During maximal exercise, HbD fell markedly by a median (interquartile range) of 210.5 micromol/cm (108.2 to 337.0 micromol/cm) in patients with claudication compared with 66.0 micromol/cm (44.0 to 101.0 micromol/cm) in elderly control subjects and 41.0 micromol/cm (36.0 to 65.0 micromol/cm) in young control subjects (P <.001). This fall also was greater than the HbD fall induced with tourniquet ischemia at 90.8 micromol/cm (57.6 to 126.2 micromol/cm; P =.006). CONCLUSION: Hemoglobin desaturation in exercising calf muscle is profound in patients with claudication, considerably greater even than that induced with three minutes of tourniquet occlusion. Further studies are necessary to investigate the relationship between the inflammatory response and near-infrared spectroscopy during exercise in patients with claudication.