In vivo measurements of regional hemoglobin oxygen saturation values and limb-to-arm ratios of near-infrared spectroscopy for tissue oxygenation monitoring of lower extremities in healthy subjects

OBJECTIVE: Near-infrared spectroscopy (NIRS) is a noninvasive technique that allows monitoring of regional hemoglobin oxygen saturation (rSO(2)) values and might have a role in the diagnosis of peripheral arterial disease. We assessed the reproducibility and inter-subject variability of rSO(2) values and rSO(2) limb-to-arm ratios (LARs) in lower extremities of healthy subjects. METHODS: The rSO(2) values and rSO(2) LARs were calculated in eight healthy subjects without peripheral arterial disease. The rSO(2) values were measured at rest at six fixed spots at each lower limb and a reference spot at each upper arm. NIRS provided the rSO(2) values without involvement of any other processing technique. After measurements were completed, rSO(2) LARs were calculated by dividing the rSO(2) value of a lower extremity spot by the rSO(2) value of the arm. Measurements were performed twice on 1 day and repeated on 4 different days. RESULTS: Mean coefficients of variation of measurements of rSO(2) values and rSO(2) LARs at the same spot in the same subject were respectively less than 6% and 8% for every measurement spot over time. Coefficients of variation of measurements at the same spot between different subjects were less than 15% and 19% for every measurement spot respectively. CONCLUSION: NIRS is an easily applicable, noninvasive tool for measurement of tissue oxygenation of lower extremities in healthy subjects. The reproducibility of rSO(2) values and rSO(2) LARs at the same measurement spot in the same subject is good.