System for noninvasive optical measurements of physiological properties in tissue
Embodiments of the present invention comprise systems and methods for noninvasion measurements of physiological properties of tissues. The system comprises a light emitter, an optical detector, a mechanical sensor and a processor. The light emitter is capable of emitting light of at least two different wavelengths and comprises at least one light source. The processor is capable of evaluating physiological properties of the tissues from measurements of the optical and the mechanical sensor. More precisely, the processor is capable of evaluating physiological properties of venous blood by using data measured by the mechanical sensor and the optical detector. For example, the oxygenation of venous blood can be measured. Furthermore, the systems can optionally comprise a light emitter which emits three wavelengths and/or the light emitter and the optical detector are arranged in reflection geometry and are located at a distance of at most 10 mm from each other.
1. A method for measurement of physiological properties of tissue comprising the steps of
a) emitting light with at least two wavelengths,
b) measuring an optical signal based on a light intensity after the emitted light has interacted with the tissue,
c) performing an accelerometer measurement synchronized with the step of measuring an optical signal,
d) evaluating a physiological property of venous blood from a combination of said optical signal and said accelerometer measurement,
wherein said step of evaluating the physiological property of venous blood comprises the step of statistically correlating said accelerometer measurement with said optical signal, and wherein said method further comprises the steps of determining portions of the optical signal correlated with the accelerometer measurement to be of venous origin and uncorrelated signal portions to be of arterial origin.