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Publication Number
US-10470692-B2
Publication Date
2019-11-12
Expiration Date
Abstract
Provided are a method and systems for performing pulse oximetry. A light signal is emitted for a period of time and a modulated light signal is detected. The modulated light signal includes a red signal and an infrared signal. The modulated light signal is originated by an interaction of the light signal with a pulsatile tissue and a non-pulsatile tissue. The modulated light signal is processed to estimate an oxygen saturation in the pulsatile tissue during the period of time. The processing includes removing a non-pulsatile component resulting from the interaction of the light signal and the non-pulsatile tissue. The non-pulsatile component can be removed by removing a first parameter from an intensity of the infrared signal and a second parameter from an intensity of the red signal. The parameters are pre-determined using a calibration process to reproduce a true value for a ratio used to determine the oxygen saturation.
Core Innovation
The invention relates to pulse oximetry using a wearable device that emits a red signal and an infrared signal at human tissue, where the tissue includes pulsatile tissue and non-pulsatile tissue. The wearable device detects modulated red and infrared signals as intensities of interactions of the respective emitted signals with the human tissue, including both pulsatile and non-pulsatile contributions, where the non-pulsatile contribution is associated with reflection of the signal from the non-pulsatile tissue.
To address the non-pulsatile contribution, the invention shifts the first detected signal and the second detected signal by first and second parameters L_red and L_ir, respectively. The shifting accounts for a contribution due to reflection of the red signal from the non-pulsatile tissue and a contribution due to reflection of the infrared signal from the non-pulsatile tissue, and based on the shifted first signal and the shifted second signal, the invention determines a ratio used to obtain oxygen saturation and then determines a value of the oxygen saturation.
The invention further defines that L_red and L_ir are positive arbitrary scalars pre-determined in a calibration process. The calibration process includes determining L_red and L_ir based on a relationship that uses detected maxima and minima of the first and second signals to reproduce a true ratio R_true for obtaining oxygen saturation, and the resulting oxygen saturation value is used to provide reports on a symptom or a progression of one or more chronic diseases of a user.
Claims Coverage
The partial content includes three independent claims, one method, one system, and one computer-readable medium. The claims cover 3 main inventive features: emitting and detecting modulated red and infrared signals at tissue including pulsatile and non-pulsatile tissue; shifting the detected signals with calibrated positive parameters L_red and L_ir to account for non-pulsatile reflection; and determining oxygen saturation from a ratio and using it to provide reports on chronic disease symptom or progression.
Modulated red and infrared interactions with pulsatile and non-pulsatile tissue
Emitting a red signal and an infrared signal at human tissue including pulsatile tissue and non-pulsatile tissue, and detecting a first signal representing an intensity of a modulated red signal and a second signal representing an intensity of a modulated infrared signal, where each modulated signal results from interaction with the human tissue.
Calibration-based shifting of detected signals using Lred and Lir
Shifting the first signal by a first parameter L_red and shifting the second signal by a second parameter L_ir to account for contribution due to reflection of the red signal from the non-pulsatile tissue and reflection of the infrared signal from the non-pulsatile tissue, where L_red and L_ir are positive arbitrary scalars pre-determined in a calibration process.
Ratiometric oxygen saturation via true ratio Rtrue and maxima/minima-based calibration, then chronic disease reporting
Determining, based on the shifted first signal and the shifted second signal, a ratio to obtain an oxygen saturation and determining a value of the oxygen saturation based on the ratio, where the calibration process determines L_red and L_ir based on a relationship using maxima and minima to reproduce a true ratio R_true, and using the oxygen saturation value to provide reports on a symptom or a progression of one or more chronic diseases of a user.
Across the independent claims, the inventive coverage centers on generating and detecting modulated red and infrared signals at tissue with pulsatile and non-pulsatile components, removing non-pulsatile reflection effects by shifting with calibration-based positive scalars L_red and L_ir, and computing oxygen saturation from a ratio determined using a calibration relationship that yields a true ratio R_true, followed by reporting symptom or progression of one or more chronic diseases.
Stated Advantages
Provides reports on a symptom or a progression of one or more chronic diseases of a user based on the oxygen saturation value.
Documented Applications
Providing reports on a symptom or a progression of one or more chronic diseases of a user using the value of oxygen saturation.
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