System and method for non-invasive monitoring of cerebral tissue hemodynamics

Inventors

Cheng, Xuefeng

Assignees

Mespere Lifesciences Inc

Abstract

A method and system are provided which are useful for the non-invasive determination and monitoring of cerebral tissue oxygenation. The method comprises the steps of generating at least first and second jugular venous output signals against time based on the reflection of at least first and second wavelengths of light, respectively, from an external tissue site on the patient in the proximity of the internal jugular vein; obtaining corresponding first and second cardiac arterial output signals for the first and second wavelengths of light, respectively, from the patient, and separating the first and second cardiac arterial output signals from the first and second jugular venous output signals, respectively, to generate first and second cerebral venous output signals; and determining cerebral tissue oxygenation based on the first and second cerebral venous output signals. A system useful to monitor cerebral tissue oxygenation may comprise a first module for optically generating at least first and second jugular venous output signals against time at at least first and second wavelengths of light, respectively, from the patient; a second module for generating first and second cardiac arterial output signals at the first and second wavelengths of light, respectively, from the patient; and a signal processing means adapted to separate the first and second cardiac arterial output signals from the first and second jugular venous output signals, respectively, to yield first and second cerebral venous output signals, for the determination of cerebral tissue oxygenation.

Core Innovation

The invention relates to a non-invasive optical method and system for determining cerebral tissue oxygenation in a patient. It generates at least first and second jugular venous output signals of change in blood volume over time using photodetector(s) based on reflection of at least first and second wavelengths of light from a neck of the patient, where the output signal is current or voltage. It also obtains corresponding cardiac arterial output signals of change in blood volume over time for the first and second wavelengths using a pulse oximeter, also with current or voltage output signals.

The invention further subtracts the first and second cardiac arterial output signals from the first and second jugular venous output signals to generate first and second cerebral venous output signals. A processor then determines cerebral tissue oxygenation based on the first and second cerebral venous output signals. In the described implementation, the system includes modules for optical generation of jugular venous output signals and generation of cardiac arterial output signals, together with signal processing adapted to perform the subtraction and determination.

The monitoring is expressed in terms of cerebral venous output signals derived from the differential contribution of cardiac arterial signals and jugular venous signals at multiple wavelengths. The document describes using first and second wavelengths of light applied to the neck, and forming oxygenation from the cerebral venous output signals using modified Beer Lambert’s law in at least one refined aspect. It also describes system components such as photodetectors, light sources, signal processing means implemented with microprocessors, and a display unit/monitor for presented waveforms and an oxygenation value.

Claims Coverage

The partial content provides two independent claims, a method claim and a system claim, that share the same core inventive concept: generating wavelength-dependent jugular venous and cardiac arterial blood-volume change signals, subtracting arterial from jugular to obtain cerebral venous output signals, and determining cerebral tissue oxygenation using a processor or signal processing means. The claims explicitly cover multiple wavelength signals and the arterial/venous subtraction approach, with additional refinements in dependent claims including wavelength constraints and oxygenation determination based on modified Beer Lambert’s law.

Across the two independent claims, the inventive coverage is centered on generating jugular venous and cardiac arterial blood-volume change output signals at first and second light wavelengths, subtracting arterial signals from jugular signals to obtain cerebral venous output signals, and using a processor or signal processing means to determine cerebral tissue oxygenation. Dependent refinements in the partial content include specifying wavelength ranges or values and determining oxygenation using modified Beer Lambert’s law.

Stated Advantages

Documented Applications