Two-wavelength optoacoustic technique for accurate, noninvasive, and continuous measurement of blood oxygenation

Noninvasive monitoring of blood oxygenation (oxyhemoglobin saturation) offers great promise in the management of life-threatening illnesses including traumatic brain injury. We proposed and built a two-wavelength optoacoustic system to accurately and noninvasively monitor blood oxygenation in veins. The system includes nanosecond Nd:YAG and Alexandrite lasers and a specially designed optoacoustic probe. We tested the system in vitro in sheep blood with experimentally varied oxygenation and total hemoglobin concentration. Our results demonstrated that the system is capable of blood oxygenation measurements with high accuracy despite variation of total hemoglobin concentration. These results suggest that the two-wavelength optoacoustic technique can be used for patients with different or changing hemoglobin concentrations as may happen during infusion of blood-free fluids or as a consequence of hemorrhage.