Quantifying consistency in tissue oxygenation across anatomical landmarks in healthy individuals through near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a non-invasive optical technique that leverages NIR light penetration in tissues to measure tissue oxygenation levels. In the spatially-resolved (SR) configuration, NIRS devices can monitor regional oxygenation percentage (rSO₂). There has been a debate about the normal range of tissue rSO₂ and the reliable anatomical landmark as a control site for clinical NIRS studies. The primary objective of this research was to establish a baseline measure of average rSO₂ in healthy individuals and identify the most reliable anatomical landmark for NIRS measurements. Tissue rSO₂ was collected from 18 different body locations from a cohort of healthy adult participants using a clinical continuous-wave SR-NIRS device. Data was collected continuously at a sampling rate of 0.5 Hz for 30 seconds per site in a supine position. Twenty participants (15 males and five females), with a mean age of 29.5 years, participated in this study. The average body rSO₂ calculated as 74.2% ±1.6 among 20 participants. Among all 18 anatomical landmarks, the highest rSO₂ values were observed at the infraorbital region, with 79.0% on the left (SD ±3.7) and 78.6% on the right (SD ±3.7) and the lowest rSO₂ was observed in thenar eminence region with 67.9% (SD ±4.5) on the right and 68.2% (±3.8) on the left side. The sternum demonstrated a rSO₂ value of 74.8% (SD ±2.8), with the lowest standard deviation overall. Sternum has been identified as a reliable anatomical landmark for NIRS data collection in the human body.