I. Introduction
Tissue oxygen saturation (StO2, the percentage of total hemoglobin that is saturated with oxygen) can be continuously monitored using near-infrared spectroscopy (NIRS) technology [1]–[8]. It provides an indirect indicator of perfusion adequacy by measuring the balance between oxygen supply and demand [6]–[16]. Due to the thinner scalp and skull, cerebral tissue oximetry (CTO) originally gained much interest in pediatric populations, but later on, it has also been utilized in various clinical and research studies involving adults, such as in cardiac and noncardiac surgery applications, intensive care, and anesthesia monitoring [6]–[16]. The specific oxygen saturation thresholds requiring intervention or prognostic value of desaturations measured by CTO on the clinical outcomes are still under investigation [6], [7], [16]–[18].