Monitoring apparatus and method
Inventors
WHITING, Stewart • MORELAND, Samuel • Carter, Hugh • Smith, Morgan
Assignees
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Publication Number
US-12611124-B2
Publication Date
2026-04-28
Expiration Date
Abstract
An apparatus for monitoring blood oxygen saturation of a subject is provided. The apparatus includes a unit configured for wearing on the subject's upper arm, the unit comprising first and second light sources configured to emit light of first and second wavelengths and a photodetector configured to detect light of the first and second wavelengths, where the light sources are arranged to direct light into the upper arm and the photodetector is arranged to detect light reflected from within the upper arm.
Core Innovation
The invention provides an apparatus for monitoring blood oxygen saturation of a subject by wearing a unit on the subject’s upper arm. The unit includes a first light source configured to direct light of a first wavelength towards the upper arm and a second light source configured to direct light of a second wavelength towards the upper arm, where the second wavelength is different from the first wavelength. One or more photodetectors output at least one detected light signal indicative separately of detection of light of the first wavelength and light of the second wavelength reflected from within the upper arm when the unit is worn on the upper arm.
The apparatus further includes one or more processors and a memory with instructions that cause the apparatus to determine an indicator of blood oxygen saturation of blood in the upper arm in dependence on the detected light signals, and to output the indicator. The detection of light of the first wavelength is determined independently from detection of the second wavelength, and the processing uses the at least one detected light signal to determine the indicator.
Reliability and output conditioning are incorporated by determining how much the indicator varies across a measurement period and outputting the determined indicator only when the indicator is indicative of a change of less than ±5 percent within a measurement period of at least 8 seconds. The described implementation also includes motion sensing to assess whether motion makes the indicator unreliable, temperature sensing with threshold temperature triggering an alert related to raising temperature, and output gating based on signal variation constraints or a determination that the indicator is not unreliable.
Claims Coverage
The independent claims identify a wearable upper-arm monitoring method/apparatus using two different-wavelength light sources with photodetectors that separately output detected light signals for each wavelength, followed by processing to determine and output an oxygen saturation indicator. Across the dependent claims, the inventive features emphasize output stability gating (±5% over at least 8 seconds), and additional refinements including motion-based reliability assessment, frequency-dependent ratio processing, temperature threshold alerting, and not-unreliable output conditioning.
Upper-arm two-wavelength reflected-light detection
A unit configured for wearing on the subject's upper arm, including a first light source directing light of a first wavelength towards the upper arm, a second light source directing light of a second wavelength different from the first wavelength towards the upper arm, and one or more photodetectors outputting at least one detected light signal indicative separately of detection of light of the first wavelength and light of the second wavelength reflected from within the upper arm, with detection of the first wavelength determined independently from detection of the second wavelength.
Indicator determination from separately detected wavelength signals
Determining an indicator of blood oxygen saturation of blood in the upper arm in dependence on the at least one detected light signal indicative separately of detection of the first wavelength and the second wavelength reflected from within the upper arm, and outputting the indicator of blood oxygen saturation.
Variation-based output gating over a measurement period
Determining how much the indicator of blood oxygen saturation varies across a measurement period and outputting the determined indicator of blood oxygen saturation only when the indicator is indicative of a change of less than ±5 percent within a measurement period of at least 8 seconds.
Motion-sensor-based reliability assessment
Using a motion sensor and the detected motion signal to assess whether motion makes the blood oxygen saturation indicator unreliable, and conditionally outputting the indicator based on that reliability determination.
Frequency-dependent component ratio processing
Processing the detected light signal by decomposing each wavelength signal component into frequency-dependent and frequency-independent parts, computing ratios for each, and determining the ratio of the first ratio to the second ratio.
Temperature sensing with threshold-triggered alert
Including a temperature sensor and generating an alert based on a temperature signal indicating a temperature below a predetermined threshold temperature, such that the alert causes the subject to raise their temperature.
Not-unreliable output conditioning
Outputting the determined indicator of blood oxygen saturation only if the determined indicator is determined to be not unreliable.
Measurement period limited to less than 25 seconds
Performing the method with a measurement period of less than 25 seconds.
The independent claim coverage centers on upper-arm monitoring using two different wavelengths and photodetectors that separately detect reflected light per wavelength, with processing to determine and output a blood oxygen saturation indicator. Dependent claims further narrow operation via reliability and conditioning features, including output stability based on <±5% variation over at least 8 seconds, motion-based reliability assessment, detailed frequency-dependent ratio processing, temperature-threshold alerting, and restricting output to not-unreliable indicators, with an additional time constraint of less than 25 seconds.
Stated Advantages
Provides an output of an indicator of blood oxygen saturation of blood in the upper arm based on separately detected signals for different wavelengths.
Improves reliability by outputting the indicator only when it shows less than ±5 percent change within a measurement period of at least 8 seconds.
Improves reliability by conditioning output based on motion-sensor-determined reliability (reliable vs unreliable).
Improves reliability by conditioning output based on whether the indicator is determined to be not unreliable.
Supports detection/handling of signal issues using frequency-dependent component ratio processing for the two wavelength signals.
Provides temperature-related reliability support by generating an alert when the temperature is below a predetermined threshold temperature.
Documented Applications
Wearable upper-arm blood oxygen monitoring by directing first and second different-wavelength light into the upper arm, detecting reflected light separately for each wavelength, and outputting a blood oxygen saturation indicator.
Assessment and rejection/withholding of unreliable oxygen saturation indicators using stability over a measurement period and reliability conditioning based on motion and temperature sensing.
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