An apparatus and method for non-invasively determining the blood oxygen saturation within a subject's tissue by near-infrared spectroscopy is disclosed. Embodiments of the apparatus and method use the multi-distance method and take into account the attenuation of the light signal due to light absorbers other than hemoglobin and deoxyhemoglobin and the scattering properties of a subject's tissue.
Apparatus and method for measuring the blood oxygen saturation in a subject's tissue