Noninvasive optoacoustic monitoring of blood oxygenation in large blood vessels



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Continuous monitoring of cerebral blood oxygenation is critically important for successful treatment of patients with severe traumatic brain injury and patients undergoing cardiac surgery. At present, the techniques for monitoring blood oxygenation are invasive. We propose the noninvasive monitoring of cerebral venous blood hemoglobin saturation (SvO2) by optoacoustic probing of blood circulating in the internal jugular vein (IJV). This thesis describes the tests of the optoacoustic system with three different probes in phantoms, in vitro, and in vivo in sheep along with different data processing algorithms. A LabView®-based scanning system, that automatically moves the optoacoustic probe across the IJV while continuously taking measurements, was developed and used for testing the optoacoustic probes. Automatic signal processing determined the signal with the best probe-vessel alignment which was then used for further processing. The scanning system was tested in phantoms using solutions with different absorption coefficients and with blood at various levels of hemoglobin saturation (SO2). Amplitudes and profiles of the optoacoustic signals recorded from the phantoms closely followed the SO2 changes in accordance with blood optical properties. These data indicate that the scanning system is capable of improving the accuracy of noninvasive monitoring of hemoglobin saturation by minimizing errors associated with lateral misalignment of the probe with respect to blood vessels.



optoacoustic, noninvasive, monitoring, large blood vessels, blood oxygenation