Body-worn pulse oximeter
Inventors
Moon, Jim • McCOMBIE, Devin • Dhillon, Marshal • Banet, Matthew
Assignees
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Publication Number
US-11638533-B2
Publication Date
2023-05-02
Expiration Date
Abstract
The invention provides a body-worn system that continuously measures pulse oximetry and blood pressure, along with motion, posture, and activity level, from an ambulatory patient. The system features an oximetry probe that comfortably clips to the base of the patient's thumb, thereby freeing up their fingers for conventional activities in a hospital, such as reading and eating. The probe secures to the thumb and measures time-dependent signals corresponding to LEDs operating near 660 and 905 nm. Analog versions of these signals pass through a low-profile cable to a wrist-worn transceiver that encloses a processing unit. Also within the wrist-worn transceiver is an accelerometer, a wireless system that sends information through a network to a remote receiver, e.g. a computer located in a central nursing station.
Core Innovation
The invention provides a body-worn thumb base finger-ring pulse oximeter integrated with a wrist transceiver that continuously measures RED/IR photoplethysmogram (PPG) waveforms and determines SpO2. The system uses thumb-specific processing of the RED and IR signals, including AC/DC separation and ambient light subtraction, to compute a ratio-of-ratios (RoR) mapped to SpO2.
The invention also provides continuous noninvasive blood pressure (cNIBP) by measuring an electrical signal indicative of a pulse pressure wave launched by the patient's heart using an ECG sensor and measuring an optical signal indicative of the pulse pressure wave at an extremity using the thumb base finger-ring PPG sensor. A time-dependent pulse transit time value is calculated from the measured ECG and PPG signals, and a blood pressure value is calculated from an averaged pulse transit time.
To support continuous operation, the system iterates measurement and pulse transit time calculation for a pre-determined period to form an average pulse transit time value, discarding time-dependent pulse transit time values that differ from the average by more than one standard deviation and recalculating the average without the discarded values. The rolling average is updated at each pulse pressure wave. Motion-aware artifact rejection and filters are applied using motion/posture/activity information derived from accelerometers at multiple body locations, including heuristic alarm/alert suppression for walking, convulsing, and falling.
Claims Coverage
The document provides one independent claim (clm-00001). It covers a continuous noninvasive blood pressure measurement method based on repeatedly measuring electrical and optical signals to calculate time-dependent pulse transit time, forming an averaged pulse transit time with outlier rejection, and converting the averaged value into blood pressure via recursive rolling-average updates.
Recursive electrical and optical pulse pressure wave measurement
A method that measures an electrical signal indicative of a pulse pressure wave recursively using an electrical sensor worn noninvasively on the patient's body, and measures an optical signal indicative of the pulse pressure wave at an extremity using a photoplethysmogram sensor worn noninvasively on the patient's body.
Time-dependent pulse transit time from electrical and optical signals
A method that calculates a time-dependent pulse transit time value from the measured electrical signal and the measured optical signal.
Averaged pulse transit time with standard deviation outlier rejection
A method that iterates the measurement and calculation steps for a pre-determined period to calculate an average pulse transit time value from a series of the time-dependent pulse transit time values, discards values that differ from the average by more than one standard deviation, and recalculates the average without the discarded values.
Blood pressure from averaged pulse transit time
A method that calculates a blood pressure value from the average pulse transit time value.
Rolling average updated at each pulse pressure wave
A method that recursively performs the steps such that the average pulse transit time value is a rolling average updated at each pulse pressure wave.
The claim scope is centered on recursive, noninvasive measurement of pulse pressure wave signals (electrical and PPG), time-dependent pulse transit time calculation, averaging over a period with outlier rejection using more than one standard deviation, converting the averaged pulse transit time into a blood pressure value, and maintaining a continuous rolling average updated at each pulse wave.
Stated Advantages
Continuous noninvasive blood pressure measurement (cNIBP) value.
Documented Applications
A clinical correlation is described by comparing SpO2 against a blood gas analyzer (gold standard).
Interested in licensing this patent?