<title>Calf muscle blood flow and oxygen consumption measured with near-infrared spectroscopy during venous occlusion</title>

Abstract

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: 1 10 MHz, wavelengths: 758 and 830 nm) to measure in real time (acquisition time: 0.64 s) the hemoglobin concentration and saturation. After 1-mm of baseline acquisition, we achieved venous occlusion by inflating a pneumatic cuff on the subject's thigh to a pressure of 60 mmHg. The cuffwas released after 1 mm. 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=O.73 ml/(lOOml)/min and OC=O.1O ml/(lOOg)/min. The corresponding average values found in legs affected by PVD are BF=1 .39 ml/(lOOml)/min and 0C0. 16 ml/(lOOg)/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.

Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

“…Baseline calibration values for these quantities are all comparable to the physiological norms found in other studies, 5,9,18,28,40,51 indicating fidelity of our instrumentation and methods for quantifying these parameters. For example, baseline BF values observed by NIRS and SGVP with the VO protocol in this study (0.88 AE 0.4 and 1.13 AE 0.6 ml∕100 ml∕ min) fell in the range of 0.7 to 4.0 ml∕100 ml tissue∕ min, reported in the literature.…”

“…The overall sampling rate was ∼1 Hz to produce one data point for DCS and five data points for Imagent. Baseline absolute BF was obtained by fitting the slope of the THC increase measured by Imagent during VO, 18,28,35,40 while baseline absolute _ VO 2 was calculated by fitting the slope of the difference between [HbO 2 ] and [Hb] during the first minute of AO. 9,41 Following baseline calibrations, sampling for the hybrid DCS/Imagent was changed to a one-to-one with 1 Hz overall sampling rate for use in the exercise protocol: 600 ms for DCS correlation plus 300 ms for Imagent sampling.…”

“…NIR spectroscopy (NIRS) oximetry is widely accepted to be reliable in the determination of oxy-hemoglobin (HbO 2 ), deoxy-hemoglobin (Hb), total hemoglobin concentration (THC), and blood oxygen saturation (StO 2 ) in deep tissues. 8,[26][27][28][29][30] Diffuse correlation spectroscopy (DCS) flowmetry is a more recent application of dynamic NIRS, which has been developed to examine relative blood flow (rBF) changes within deep tissue microvasculature. 6,22,31 DCS operates on the principle that photons injected into biological tissues diffuse and generate timevarying light speckle fluctuations due to the motion of moving scatterers in the tissue (e.g., red blood cells).…”

Intraoperative evaluation of revascularization effect on ischemic muscle hemodynamics using near-infrared diffuse optical spectroscopies

“…Using NIRS, researchers have found that muscle oxygenation responses to exercise were associated with the severity of muscle vascular diseases. 19,[21][22][23][24][25][26][27] NIRS was also used to monitor gluteal tissue oxygenation index during bypass of bilateral hypogastric artery (HA) 3 and assess bypass graft patency in large vessels. 8,28 Skeletal muscle blood flow can be indirectly estimated by NIRS through applying venous occlusion to a limb at several discrete time-points.…”

“…8,28 Skeletal muscle blood flow can be indirectly estimated by NIRS through applying venous occlusion to a limb at several discrete time-points. 25 Unfortunately, the occlusion interrupts blood flow and makes it difficult for continuous measurement of blood flow during revascularization. A novel technology, the NIR diffuse correlation spectroscopy (DCS) flowmeter, was recently developed for noninvasive and direct measurement of relative change of blood flow (rBF) in deep tissues, [29][30][31][32][33][34][35][36][37][38][39][40] including skeletal muscles.…”