Quantification of cerebral oxygenation by full-spectrum near-infrared spectroscopy using a two-point method.

The aim of this study was to quantify the relative concentrations of oxyhemoglobin and deoxyhemoglobin within the light path of the brain and to estimate cerebral hemoglobin (Hb) oxygen saturation using full-spectrum near-infrared spectroscopy (fsNIRS). For this purpose, we developed a novel exponential correction equation as well as a two-point spectroscopy method to estimate the relative concentrations of Hb and Hb oxygen saturation in biological tissues. The results of evaluation of measurements using an in vitro model indicated that our fsNIRS method enables accurate and non-invasive measurements of Hb content and saturation in a highly scattered medium such as the human brain. According to the results of analysis using a hypoxic piglet model, the mean cerebral Hb oxygen saturation (SbO(2)) of newborn piglets at an inspired oxygen gas concentration of 0.21 was estimated to be 63+/-4% (mean+/-S.D.). Umbilical arterial and left internal jugular venous Hb oxygen saturation were simultaneously estimated to be 96+/-2% and 52+/-11%, respectively. SbO(2) and arterial Hb oxygen saturation values had a linear relationship. The average oxygenation state of cerebral tissue is comparable with that of the cerebral vein. The results of this study showed that our method can be used to monitor Hb oxygen saturation in the neonatal brain at the bedside in an intensive care unit.