Development of a new instrument to measure oxygen saturation and total hemoglobin volume in local skin by near-infrared spectroscopy and its clinicalapplication

The oxygen saturation (StO(2)) and total hemoglobin volume in cutaneous blo od are closely related to cutaneous metabolism and are important factors in determining the skin color. Most conventional apparatuses for the measurem ent of cutaneous metabolism have been designed to evaluate qualitative chan ges in the oxyhemoglobin volume, deoxyhemoglobin volume, and their sum (tot al Hb volume) relative to their baseline values. In this study, we develope d an instrument for non-invasive evaluation of individual and regional diff erences in StO(2) and Hb volume, a system unaffected by melanin (Kao PSA sy stem model III), and examined the validity of its application. First, chang es in StO(2) and total Hb volume in the antebrachial region during venous o cclusion and devascularization by compression of the brachial region were e valuated. Changes in total Hb volume following Venous occlusion were found to reflect the cutaneous blood flow. Also, StO(2) was considered to reflect the state of oxygen consumption by the skin, because it was markedly reduc ed during devascularization. Next, the subjects were exposed to graded hypo baric conditions, and the relationships among StO(2), arterial blood oxygen saturation (SaO(2)), and venous blood oxygen saturation (SvO(2)) were stud ied. StO(2) showed significant positive correlations with SaO(2) (r=0.811, P<0.001) and SvO(2) (r=0.966, P<0.001), and its correlation with SvO(2) was particularly strong. Therefore, StO(2) was found to be closely dependent o n SvO(2). Lastly, StO(2), total Hb volume, and other parameters were measur ed in healthy women (aged 20-69 years), and their regional differences and age-associated changes were evaluated. These regional differences (angle of mouth > cheek > forehead) and age-associated decreases in StO(2) are consi dered to be caused by the age-associated decreases in the cutaneous blood f low.