1. A method for non-invasively determining the blood oxygen saturation level within a subject's tissue, using a spectrophotometric system that includes a processor, a visual display, and a plurality of sensors, each sensor having at least one light source operable to transmit a light signal into the subject's tissue, and at least one light detector operable to sense the light signal after passage through the subject's tissue and to produce signal data representative of the sensed light signal, the method comprising the steps of: positioning the sensors relative to the subject to sense separate regions of the subject; sensing the subject's tissue and determining an absolute oxygen saturation level for each region using sensed signal data from each region; displaying the oxygen saturation level for a selected region, or an average of the oxygen saturation levels of all of the regions, on the visual display; comparing the oxygen saturation level of each region to a predetermined value, and determining if the oxygen saturation level of each region represents an adverse condition relative to the predetermined value; replacing the oxygen saturation value of the selected region or average value then currently displayed with the oxygen saturation value of the region having the most adverse oxygen saturation value relative to the other regions.