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

Abstract

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.