Localized irregularities in hemoglobin flow and oxygenation in calf muscle in patients with peripheral vascular disease detected with near-infrared spectrophotometry

Purpose: Near-infrared spectrophotometry is used to measure flow, concentration, and oxygenation of hemoglobin in arterioles, capillaries, and venules several centimeters deep in tissue. The purpose of this study was to investigate the distribution of flow, concentration, and oxygenation of hemoglobin in calf muscle in patients with documented peripheral arterial occlusive disease (PVD), patients with risk factors for PVD, and healthy younger subjects at rest. Method: With a frequency-domain near-infrared spectrophotometer and a specially designed probe, we generated maps at 22 locations simultaneously of hemoglobin flow, concentration, and oxygenation, with the venous occlusion method. Eight legs of 7 patients with diagnosed PVD (PVD group), 10 legs of 8 patients with normal ankle-brachial index but with risk factors for PVD (RF group), and 16 legs of 8 healthy subjects (H group) were studied. Results: Global mean values were significantly (P < .05) different between the three groups for oxygen consumption (PVD group, 0.027 ± 0.009 mL/100 g/min; RF group, 0.038 ± 0.017 mL/100 g/min; H group, 0.022 ± 0.020 mL/100 g/min), venous oxygen saturation (PVD, 59.7% ± 15.4%; RF, 69.6% ± 10.5%; H, 80.8% ± 4.5%), and, at 60 s of venous occlusion, concentration changes in oxyhemoglobin (PVD, 4.48 ± 3.25 μmol/L; RF, 8.44 ± 2.33 μmol/L; H, 6.85 ± 4.57 μmol/L), deoxyhemoglobin (PVD, 3.60 ± 0.73 μmol/L; RF, 4.39 ± 1.30 μmol/L; H, 2.36 ± 1.79 μmol/L), and total hemoglobin (PVD, 8.07 ± 3.83 μmol/L; RF, 12.83 ± 2.75 μmol/L; H, 9.21 ± 6.34 μmol/L). No significant difference was found between the three groups for hemoglobin flow (PVD, 0.92 ± 0.69 μmol/100 mL/min; RF, 1.68 ± 0.50 μmol/100 mL/min; H, 1.44 ± 1.17 μmol/100 mL/min) and blood flow (PVD, 0.45 ± 0.28 mL/100 g/min; RF, 0.77 ± 0.21 mL/100 g/min; H, 0.62 ± 0.50 mL/100 g/min). All parameters featured a distribution dependent on location. Conclusion: Mean value for venous oxygen saturation was higher in healthy subjects compared to patients with documented PVD. In patients with PVD, areas of lower oxygenation were clearly discernible. At distal locations of calf muscle, significant correlations between reduced hemoglobin flow, venous oxygen saturation, oxyhemoglobin, and total hemoglobin and reduced ankle-brachial index were found. Maps revealed localized irregularities in oxyhemoglobin, total hemoglobin, and venous oxygen saturation in patients with PVD. Near-infrared spectrophotometry is a noninvasive bedside technique that can enable determination of blood flow and oxygenation in tissue and may provide a method for evaluating patients with PVD.