Validation in volunteers of a near-infrared spectroscope for monitoring brain oxygenation in vivo.

Cerebral oximeters based on near-infrared spectroscopy may provide a continuous, noninvasive assessment of cerebral oxygenation. We evaluated a prototype cerebral oximeter (Invos 3100; Somanetics, Troy, MI) in 22 conscious, healthy volunteers breathing hypoxic gas mixtures. Using the first 12 subjects (training group), we developed an algorithm based on the mathematic relationship that converts detected light from the field surveyed by the probe to cerebral hemoglobin oxygen saturation (CSfO2). To develop the algorithm, we correlated the oximeter result with the estimated combined brain hemoglobin oxygen saturation (CScombO2, where CScombO2 = SaO2 x 0.25 + SjO2 x 0.75 and SjO2 = jugular venous saturation). We then validated the algorithm in the remaining 10 volunteers (validation group). A close association (r2 = 0.798-0.987 for individuals in the training group and r2 = 0.794-0.992 for individuals in the validation group) existed between CSfO2 and CScombO2. We conclude that continuous monitoring with cerebral oximetry may accurately recognize decreasing cerebral hemoglobin oxygen saturation produced by systemic hypoxemia.