System and method for a non-invasive medical sensor
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Publication Number
US-11350861-B2
Publication Date
2022-06-07
Expiration Date
Abstract
A method and system for measuring oxygen levels and various blood constituents utilizing a sensor having one or more light sources, and one or more light detectors is disclosed. The system is capable of using data collected by the one or more detectors from a non-monochromatic light source to provide accurate information during motion events occurring with an extremity the sensor. The system is also capable of detecting and providing an alert if the sensor is not properly placed on a patient or becomes disengaged therefrom.
Core Innovation
The invention is a non-invasive optical reflectance type sensor and system for oxygen saturation sensing on a human subject that uses both non-monochromatic light and monochromatic red light and infrared light. The system includes a first detector and a second detector having different spectral response curves, and a wavelength sensor with detectors configured to respond differently to the emitted red light. Detector signals and red/infrared detection are processed to generate oxygen saturation values.
A core part of eliminating error is generating a first oxygen saturation value based on a ratio involving red light detected by the non-invasive optical reflectance type sensors and infrared light detected by the first detector and the second detector. A second oxygen saturation value is generated based on non-monochromatic light detected by the first detector and the second detector. The system substitutes the first oxygen saturation value with the second oxygen saturation value when a determination indicates that a ratio of measured centroid wavelength of the red light by the first detector and the second detector is outside a threshold.
The invention further mitigates motion artifacts and detects fault conditions by using broadband/non-monochromatic spectral absorption relationships derived from detector signal ratios, while also using centroid-wavelength conditions and thresholding of broadband/detector-derived metrics. In response to detected motion events, oxygen saturation substitution is performed to provide a pulse-synchronized oxygen saturation value based on the broadband-derived data as a fallback during motion events. The system can issue alerts when improper placement/disengagement is detected or when centroid wavelength is outside an acceptable range, and it self-calibrates by determining operating wavelength of the red emitter using differing detector spectral responses to compensate for wavelength drift due to temperature/current aging.
Claims Coverage
The document contains two independent claims (a method and a system). Across these independent claims, the core coverage includes dual-detector spectral response sensing, use of both non-monochromatic and monochromatic red/infrared light, computation of two oxygen saturation values, and conditional substitution based on centroid wavelength ratios and motion-event determinations tied to detector-signal ratios.
Dual-detector spectral response wavelength sensing for error elimination
Providing a non-invasive optical reflectance type sensor including a first detector and a second detector with different spectral response curves, and using those detectors within a wavelength sensor to support wavelength- and ratio-based determinations for oxygen saturation accuracy.
Dual-light approach with non-monochromatic periodic emission and monochromatic red/infrared
Emitting non-monochromatic light periodically via one or more non-monochromatic light sources and emitting monochromatic red light and infrared light via one or more monochromatic light sources, transmitting a portion of the emitted light towards skin of a human subject.
First oxygen saturation from red/infrared ratio and second oxygen saturation from non-monochromatic detection
Generating a first oxygen saturation value based on a ratio involving red light detected by the first detector and/or second detector and infrared light detected by the first detector and the second detector, and generating a second oxygen saturation value based on non-monochromatic light detected by the first detector and the second detector (or based at least in part on first and second detector signals derived from sampled non-monochromatic light).
Conditional substitution of oxygen saturation using centroid wavelength ratio outside threshold
Substituting the first oxygen saturation value with the second oxygen saturation value in response to a determination that a ratio of a first measured centroid wavelength of the red light by the first detector and a second measured centroid wavelength of the red light by the second detector is outside a threshold.
Motion-event based oxygen saturation substitution tied to detector signal ratio
In the system, determining that a motion event has occurred based, at least in part, on a ratio of the first signal to the second signal, and substituting the first oxygen saturation value with the second oxygen saturation value in response to that motion event determination.
Overall, the independent claims cover an optical reflectance sensing approach that computes two oxygen saturation values from red/infrared ratio and non-monochromatic detection, and then conditionally substitutes the values when detector-derived centroid wavelength ratios indicate out-of-threshold conditions and/or when motion events are determined using detector-signal ratios.
Stated Advantages
Eliminates error when a determination indicates centroid-wavelength ratio conditions are outside a threshold by substituting a second oxygen saturation value.
Reduces motion artifacts by using a motion-event determination tied to detector signal ratios to trigger oxygen saturation substitution.
Detects and compensates for wavelength drift by determining operating wavelength of the red emitter using differing detector spectral responses to compensate for wavelength drift due to temperature/current aging.
Generates alerts for fault conditions such as improper placement/disengagement and out-of-range centroid wavelength.
Documented Applications
Non-invasive optical sensing of oxygen saturation (SpO2) on a human subject using a reflectance-type sensor.
Use during motion events where oxygen saturation substitution is used as a fallback during motion artifacts.
Fault detection related to probe/sensor placement/disengagement and out-of-range centroid wavelength, with optional alerting/notifications.
Self-calibration to compensate for wavelength drift of the red emitter due to temperature/current aging.
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