Reference Values of Regional Oxygen Saturation (rSO2) Determined by Near-Infrared Spectroscopy (NIRS) for 18 Selected Regions of Interest (ROIs) in Young and Elderly Healthy Volunteers

Regional oxygen saturation (rSO2) assessed by near-infrared spectroscopy (NIRS) reflects the perfusion and metabolism of the assessed tissue. The study aimed to determine the reference values of rSO2 for selected body areas, considering gender, age and body composition. We studied 70 healthy volunteers divided into two age groups (18–30 and >60 years). The rSO2 was measured using NIRS in eighteen selected regions of interest (ROIs). Body composition analysis was carried out using dual-energy X-ray absorptiometry (DXA). Significant differences in rSO2 values were found between almost all analyzed ROIs (p < 0.05) with a simultaneous lack of asymmetry between contralateral side of the body. The average rSO2 values from the ROIs analyzed ranged from 40.34 ± 17.65% (Achilles tendon) to 69.94 ± 6.93% (tibialis anterior muscle). Age and the values of adiposity indices and the fat mass content are factors that may significantly reduce the rSO2 value. In most ROIs, higher rSO2 values were recorded for the younger group (p < 0.0001). The rSO2 values at rest are area-specific in young and elderly healthy subjects. The changes in rSO2, both in clinical assessment and research, should be interpreted taking into account the body area being assessed and individual factors such as age and body fat content.