Monitoring apparatus and method
Inventors
WHITING, Stewart • MORELAND, Samuel • Carter, Hugh • Smith, Morgan
Assignees
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Publication Number
US-11911155-B2
Publication Date
2024-02-27
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 using an upper-arm wearable unit. The unit includes a first light source and a second light source configured to direct light of first and second wavelengths towards the upper arm when worn, with the second wavelength different to the first. One or more photodetectors output detected light signals indicative separately of detection of reflected light of the first and second wavelengths from within the upper arm.
One or more processors determine an indicator of blood oxygen saturation of blood in the upper arm in dependence on the detected light signals, and the apparatus outputs the indicator. The unit further comprises a housing having an arm-facing portion with an incurvate surface for facing the upper arm, where the arm-facing portion includes a sensitive region protruding from the incurvate surface. The first and second light sources and the one or more photodetectors are exposed to the upper arm at the sensitive region, arranged so that light passes from the light sources into the upper arm and is received by at least one photodetector from within the upper arm when the unit is worn.
The described wearable system further incorporates signal processing for determining an oxygenation indicator from wavelength-dependent photoplethysmography, including AC/DC components and ratio-of-ratios, and includes device-specific calibration. In addition, the system uses motion sensing and temperature sensing to reject unreliable measurements during high motion and cold-induced vasoconstriction, and can generate alerts to prompt the subject to reposition/tighten and/or increase temperature when predetermined motion and temperature thresholds indicate unreliable readings.
Claims Coverage
The partial content includes two independent claims, each covering an upper-arm wearable blood oxygen saturation monitoring arrangement with different wavelengths projected into the upper arm and separately detected reflected signals to determine an oxygenation indicator. Across the independent claims, the main inventive features are the specific exposed optical arrangement using an incurvate housing surface and a protruding sensitive region, and the inclusion of a charger and power source as part of a kit of parts.
Upper-arm wearable unit with exposed first and second wavelength optics
A unit configured for wearing on the subject's upper arm, comprising a first light source configured to direct light of a first wavelength towards the upper arm when the unit is worn on the upper arm, a second light source configured to direct light of a second wavelength towards the upper arm when the unit is worn on the upper arm, the second wavelength being different to the first wavelength, and one or more photodetectors each configured to 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.
Incurvate housing with protruding sensitive region
A housing comprising an arm-facing portion having an incurvate surface for facing the upper arm, the arm-facing portion comprising a sensitive region protruding from the incurvate surface, wherein the first and second light sources and the one or more photodetectors are exposed to the upper arm at the sensitive region, being arranged such that light can pass from the first and second light sources into the upper arm, and light can be received by at least one of the one or more photodetectors from within the upper arm, when the unit is worn on the upper arm.
Determining and outputting a blood oxygen saturation indicator
One or more processors and a memory including instructions which, when executed, cause the apparatus to determine an indicator of blood oxygen saturation of blood in the upper arm, in dependence on the at least one detected light signal, and output the indicator of blood oxygen saturation.
Kit of parts including power source and charger
A kit of parts comprising an apparatus with a unit configured for wearing on the subject's upper arm, the apparatus comprising a power source, the first light source and second light source with different wavelengths, and one or more photodetectors outputting separately detected signals indicative of reflected light from within the upper arm, a strap configured to hold the unit on the subject's upper arm, and a charger for charging the power source.
The independent claims cover an upper-arm wearable optical arrangement projecting first and second wavelengths into the upper arm and separately detecting reflected light signals from within the upper arm, a housing geometry with an incurvate arm-facing portion and protruding sensitive region, and determination and output of a blood oxygen saturation indicator. The kit claim additionally specifies a power source, a strap holding the unit, and a charger for charging the power source.
Stated Advantages
Rejecting unreliable measurements during high motion.
Rejecting unreliable measurements during cold-induced vasoconstriction.
Avoiding false low readings by using correlation checks between motion and photoplethysmography-related behavior and between green and red/infrared signals (as described).
Providing alerts when temperature is below a predetermined threshold to prompt the subject to increase temperature.
Providing alerts to prompt the subject to reposition/tighten (as described).
Documented Applications
Wearable upper-arm blood oxygen monitoring for determining and outputting an oxygenation indicator based on blood oxygen saturation.
Use in conditions involving high motion where unreliable measurements are rejected using motion sensing (as described).
Use in cold-induced vasoconstriction conditions where unreliable measurements are rejected using temperature sensing (as described).
A kit of parts for monitoring blood oxygen saturation using an upper-arm unit including a charger for charging the power source (as described).
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