Calf muscle blood now and oxygen consumption measured with near-infrared spectroscopy during venous occlusion

We present non-invasive measurements of the calf muscle blood flow (BF) and oxygen consumption (OC) by near-infrared spectroscopy. We used a frequency domain tissue oximeter (modulation frequency: 110 MHz, wavelengths: 758 and 830 nm) to measure in real time (acquisition time: 0.64 s) the hemoglobin concentration and saturation. After 1-min of baseline acquisition, we achieved venous occlusion by inflating a pneumatic cuff on the subject's thigh to a pressure of 60 mmHg. The cuff was released after 1 min. The baseline/inflation/release procedure was repeated 3 times to verify reproducibility. We calculated the BF and OC from the initial rate of increase of the total hemoglobin and deoxy-hemoglobin concentration immediately after the onset of venous occlusion. We examined 8 healthy subjects and 18 patients affected by peripheral vascular disease (PVD) in 1 or 2 legs to investigate whether muscle BF and OC at rest can be useful indicators of vascular insufficiency. In healthy legs, we obtained average values of BF = 0.73 ml/(100ml)/min and OC = 0.10 ml/(100g)/min. The corresponding average values found in legs affected by PVD are BF = 1.39 ml/(100ml)/min and OC = 0.16 ml/(100g)/min. The ranges of values of BF and OC measured in the healthy legs broadly overlap with the corresponding ranges measured in the PVD legs.