Noninvasive monitoring of cerebral blood oxygenation in ovine superior sagittal sinus with novel multi-wavelength optoacoustic system.

Noninvasive monitoring of cerebral blood oxygenation with an optoacoustic technique offers advantages over current invasive and noninvasive methods. We report the results of in vivo studies in the sheep superior sagittal sinus (SSS), a large central cerebral vein. We changed blood oxygenation by increasing and decreasing the inspired fraction of oxygen (FiO(2)). Optoacoustic measurements from the SSS were performed at wavelengths of 700, 800, and 1064 nm using an optical parametric oscillator as a source of pulsed near-infrared light. Actual oxygenation of SSS blood was measured with a CO-Oximeter in blood samples drawn from the SSS through a small craniotomy. The amplitude of the optoacoustic signal induced in the SSS blood at lambda = 1064 nm closely followed the changes in blood oxygenation, at lambda = 800 nm was almost constant, and at lambda = 700 nm was changing in the opposite direction, all in accordance with the absorption spectra of oxy- and deoxyhemoglobin. The optoacoustically predicted oxygenation correlated well with actual blood oxygenation in sheep SSS (R(2) = 0.965 to 0.990). The accuracy was excellent, with a mean difference of 4.8% to 9.3% and a standard deviation of 2.8% to 4.2%. To the best of our knowledge, this paper reports for the first time accurate measurements of cerebral venous blood oxygenation validated against the "gold standard" CO-Oximetry method.

In vivo monitoring of blood oxygenation in large veins with a triple-wavelength optoacoustic system.

A noninvasive optoacoustic technique could be a clinically useful alternative to existing, invasive methods for cerebral oxygenation monitoring. Recently we proposed to use an optoacoustic technique for monitoring cerebral blood oxygenation by probing large cerebral and neck veins including the superior sagittal sinus and the internal jugular vein. In these studies we used a multi-wavelength optoacoustic system with a nanosecond optical parametric oscillator as a light source and a custom-made optoacoustic probe for the measurement of the optoacoustic signals in vivo from the area of the sheep neck overlying the external jugular vein, which is similar in diameter and depth to the human internal jugular vein. Optoacoustic signals induced in venous blood were measured with high resolution despite the presence of a thick layer of tissues (up to 10 mm) between the external jugular vein and the optoacoustic probe. Three wavelengths were chosen to provide accurate and stable measurements of blood oxygenation: signals at 700 nm and 1064 nm demonstrated high correlation with actual oxygenation measured invasively with CO-Oximeter ("gold standard"), while the signal at 800 nm (isosbestic point) was independent of blood oxygenation and was used for calibration.

Accurate, noninvasive measurement of total hemoglobin concentration with optoacoustic technique.

The measurement of total hemoglobin concentration is currently invasive and time consuming. The optoacoustic technique may provide accurate and noninvasive measurements of total hemoglobin concentration by probing blood vessels. We studied the influence of blood vessel diameter and lateral displacement of the optoacoustic probe on accuracy of total hemoglobin concentration measurements with this technique.