Investigation of oxygen saturation in regions of skin by near infrared spectroscopy

Background Oxygen is essential for life, and investigation of the skin's oxygen environment and identification of its effects on the skin may lead to the discovery of new antiaging targets. To understand individual skin differences and age-related changes, we developed a noninvasive method using near infrared spectroscopy (NIRS) to measure the regional saturation of oxygen (rSO(2)) of human skin. Materials and methods To construct an NIRS sensor probe specialized for skin measurement, the distance between the sensor transmitter and receiver was optimized based on data for the thickness of the facial skin to the subcutaneous fat layer. To analyze the relationship between skin oxygen saturation and body oxygen saturation, rSO(2) was measured by NIRS, oxygen saturation of peripheral artery (SpO(2)) was measured by pulse oximeter, and physical conditions were considered, such as body mass index (BMI) and muscle mass, in Japanese women (age 20s-60s). Results Both skin rSO(2) and SpO(2) varied among individuals and decreased with age. Only SpO(2) showed a relationship with BMI and muscle mass, whereas rSO(2) showed no relationship with these physical conditions. No relationship between rSO2 and SpO(2) was observed. Conclusion Individual and age-related differences in skin by rSO(2) values were found by NIRS optimized for local skin; however, the factors affecting rSO(2) differed from those affecting SpO(2), and further study is needed.