System and method for estimating the brain blood volume and/or brain blood flow and/or depth of anesthesia of a patient

A system for estimating the brain blood volume and/or brain blood flow and/or depth of anesthesia of a patient, comprising:

• at least one excitation electrode to be placed on a temple of the head of a patient for applying an excitation signal,
• at least one sensing electrode to be placed on the other temple of the head of the patient for sensing a measurement signal (VC) caused by the excitation signal,
• at least one electrode to be placed on the scalp of the patient's head to receive an EEG signal of spontaneous electrical activity of the brain of the patient, and
• a processor device for processing said measurement signal (VC) sensed by the at least one sensing electrode for determining an output indicative of the brain blood volume and/or the brain blood flow, said measurement signal (VC) being processed in the processor device in a first processing path comprising an amplification device for amplifying the measurement signal (VC) and an analog-to-digital converter for digitizing the measurement signal (VC), and said EEG signal received by the at least one EEG electrode being processed in the processor device in a second processing path for receiving and processing the EEG signal, wherein the processor device is constituted to reduce noise in the measurement signal (VC) by applying a non-linear noise-reduction algorithm based on a Poincare map analysis, and
• wherein the processor device is constituted to determine, based on the noise-reduced version of the measurement signal (VC), a correlate of the brain blood volume according to an area (A) obtained from integration of the measurement signal (VC), and wherein the area (A) is obtained from integration of the measurement signal (VC) over the left ventricular ejection time (LVET), which is estimated as the period from a point (B), defined as the minimum of the derivative of the measurement signal (VC) prior to a maximum point (C), to a point (X), defined as the minimum of the derivative of the measurement signal (VC) immediately after said maximum point (C), and
• wherein the processor device is further constituted (i) to determine a correlate of the brain blood flow by multiplying said correlate of the brain blood volume with a value indicative of the heart rate of the patient, (ii) to feed the correlate of the brain blood volume and/or the correlate of the brain blood flow into a first non-linear model comprising a fuzzy logic model or a quadratic equation model, to obtain output values indicative of the brain blood volume and/or the brain blood flow, and (iii) to feed features derived from the EEG signal and said output values into a second non-linear model to obtain final output values for the brain blood volume and/or the brain blood flow, and/or an output value indicative of a depth of anaesthesia.