Cross-cut: `algo-spo2-estimation`

Axis: algorithms

14 corpus entries disclose this tag.

Earliest disclosure: 1974

Listed in chronological order. Each entry’s prior_art_notes and disclosure_citation constitute the citeable prior art material.

Aoyagi (1974) — two-wavelength pulse oximetry principle (1974)

id: aoyagi-1974-two-wavelength-pulse-oximetry
corpus: private
form factor: other
creator: Takuo Aoyagi (Nihon Kohden)
disclosure: Aoyagi T, et al. — the pulsatile two-wavelength (red/infrared) ratio method for non-invasive arterial oxygen saturation, presented at the 13th Annual Meeting of the Japan Society of Medical Electronics and Biological Engineering (1974); commercialized as the Nihon Kohden ‘Ear Oximeter OLV-5100’ (1975) and Minolta ‘Oximet MET-1471’ (1977). History documented in Severinghaus JW, Honda Y. ‘History of blood gas analysis. VII. Pulse oximetry.’ J Clin Monit 1987;3(2):135-138.
ip status: patented
sensors: sensor-spo2, sensor-ppg, sensor-multi-wavelength-ppg
algorithms: algo-spo2-estimation
prior art notes: Discloses the pulsatile two-wavelength ratiometric method that underlies every non-invasive SpO2 device: comparing the AC/DC ratios of light absorbance at (typically) red ~660 nm and infrared ~940 nm through pulsatile tissue to compute arterial oxygen saturation. Any wearable claim reciting ‘a first and second light source at distinct wavelengths and a photodetector configured to compute oxygen saturation from a ratio of pulsatile components’ reads on this. § 102 prior art for the SpO2 principle from 1974; the wrist/ring/earbud form-factor variants are obvious combinations under [[obviousness-template]].

Mendelson & Ochs (1988) — reflectance-mode pulse oximetry / skin-reflectance PPG (1988-10)

id: mendelson-ochs-1988-reflectance-pulse-oximetry
corpus: academic
form factor: other
creator: Yitzhak Mendelson / Burt D. Ochs
disclosure: Mendelson Y, Ochs BD. ‘Noninvasive pulse oximetry utilizing skin reflectance photoplethysmography.’ IEEE Transactions on Biomedical Engineering 1988;35(10):798-805.
ip status: public-domain
sensors: sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg
algorithms: algo-spo2-estimation, algo-hr
prior art notes: Establishes pulse oximetry by reflectance (light source and detector on the same side of the tissue) rather than transmission — the geometry every wrist, forehead, ring, chest, and earbud PPG/SpO2 wearable uses, since those sites cannot be transilluminated. Any wearable-SpO2 claim reciting ‘a reflectance photoplethysmography sensor’ or ‘a light source and photodetector arranged on a common surface against the skin’ reads on Mendelson & Ochs 1988. Anchor for the reflectance-PPG/SpO2 cross-cut on non-fingertip sites.

Webster (ed.) (1997) — ‘Design of Pulse Oximeters’ (1997)

id: webster-1997-design-of-pulse-oximeters
corpus: academic
form factor: other
creator: John G. Webster (ed.)
disclosure: Webster JG (ed). ‘Design of Pulse Oximeters.’ Series in Medical Physics and Biomedical Engineering, IOP Publishing / Institute of Physics, 1997. ISBN 0-7503-0467-7.
ip status: public-domain
sensors: sensor-spo2, sensor-ppg
algorithms: algo-spo2-estimation, algo-hr
prior art notes: The standard engineering reference on pulse oximeter design as of 1997 — LED selection and drive, photodiode front-ends, the ratio-of-ratios calibration, motion-artifact handling, low-perfusion behavior, calibration-curve construction. Prior art for wearable-SpO2 claims to the extent they recite implementation details (wavelength choice, AC/DC ratio computation, calibration-curve mapping, artifact rejection) covered here; these were textbook-level public knowledge by 1997.

MIT wearable ring sensor (Rhee, Yang, Asada) — finger-ring PPG for ambulatory monitoring (2001-07)

id: asada-mit-wearable-ring-sensor-2003
corpus: academic
form factor: ring
creator: Sokwoo Rhee / Boo-Ho Yang / Haruhiko Harry Asada (MIT d’Arbeloff Lab)
disclosure: Rhee S, Yang B-H, Asada HH. ‘Artifact-resistant power-efficient design of finger-ring plethysmographic sensors.’ IEEE Transactions on Biomedical Engineering 2001;48(7):795-805 (and Asada HH, Shaltis P, Reisner A, Rhee S, Hutchinson RC. ‘Mobile monitoring with wearable photoplethysmographic biosensors.’ IEEE Engineering in Medicine and Biology Magazine 2003;22(3):28-40).
ip status: patented
sensors: sensor-ppg, sensor-accelerometer
algorithms: algo-hr, algo-spo2-estimation
prior art notes: Discloses a finger-ring-form-factor wearable PPG sensor with motion-artifact-resistant optical/mechanical design, low-power operation, on-body processing, and wireless telemetry of heart rate and SpO2 for ambulatory monitoring — i.e. the smart-ring physiological monitor, ~14 years before the commercial smart-ring wave. Directly anticipates ring-form claims combining ‘a ring body’, ‘a PPG emitter/detector at the inner ring surface’, ‘motion-artifact compensation’, and ‘wireless transmission of derived vitals’. Anchor for the ring × PPG cross-cut; [[oura-ring-gen1-2015]] and similar products descend from it.

Allen (2007) — ‘Photoplethysmography and its application in clinical physiological measurement’ (2007-02-20)

id: allen-2007-ppg-review
corpus: academic
form factor: other
creator: John Allen (Freeman Hospital / Newcastle)
disclosure: Allen J. ‘Photoplethysmography and its application in clinical physiological measurement.’ Physiological Measurement 2007;28(3):R1-R39. doi:10.1088/0967-3334/28/3/R01.
ip status: public-domain
sensors: sensor-ppg
algorithms: algo-hr, algo-hrv, algo-respiratory-rate, algo-spo2-estimation, algo-pwv-bp-estimation
prior art notes: Canonical review collecting the state of PPG measurement and the physiological parameters derivable from a PPG signal as of 2007 — heart rate, HRV, respiratory rate, SpO2, blood-pressure surrogates, arterial-stiffness/aging indices, vasomotor assessment. Relevant to wearable claims that recite ‘deriving [parameter X] from a photoplethysmography signal’ for any X covered here: the derivation was a published, enabled technique by 2007, defeating novelty of the bare derivation and supplying § 103 motivation for the form-factor+PPG+algorithm combinations. The single most-cited anchor for PPG-derived-metric wearable patents.

Dead Space — ‘RIG’ (suit with body-mounted health display and projected holographic UI) (2008-10-13)

id: dead-space-resource-integration-gear
corpus: fictional
form factor: garment
creator: EA Redwood Shores (Visceral Games) / Electronic Arts
disclosure: Dead Space (EA Redwood Shores / Electronic Arts, released 13 October 2008); the ‘Resource Integration Gear’ suit with a segmented LED strip on the wearer’s back/spine displaying current health (visible to others), oxygen monitoring, a holographic inventory/menu projected in front of the wearer, and a ‘stasis’ module.
ip status: fictional
algorithms: algo-spo2-estimation
prior art notes: Discloses a worn suit with (a) a body-mounted (spinal) physiological-status display readable by third parties, (b) oxygen-level monitoring, and (c) a holographic interface projected in the wearer’s view. Relevant to wearable-with-externally-visible-status-display claims combining ‘a body-worn garment’, ‘a sensor measuring a physiological parameter (e.g. SpO2 or general health state)’, and ‘a display on the garment surface presenting that parameter to onlookers’, and to body-projected holographic-UI claims. § 103 motivation as of 2008. Cf. [[logans-run-lifeclock]] (body-worn color status display), [[mass-effect-omni-tool]] (projected UI).

Pantelopoulos & Bourbakis (2010) — survey on wearable sensor-based systems for health monitoring and prognosis (2010-01)

id: pantelopoulos-bourbakis-2010-wearable-health-survey
corpus: academic
form factor: other
creator: Alexandros Pantelopoulos / Nikolaos G. Bourbakis
disclosure: Pantelopoulos A, Bourbakis NG. ‘A survey on wearable sensor-based systems for health monitoring and prognosis.’ IEEE Transactions on Systems, Man, and Cybernetics, Part C (Applications and Reviews) 2010;40(1):1-12.
ip status: public-domain
sensors: sensor-ecg, sensor-ppg, sensor-spo2, sensor-accelerometer, sensor-skin-temperature, sensor-respiration-impedance
algorithms: algo-hr, algo-arrhythmia-classification, algo-spo2-estimation, algo-fall-detection, algo-activity-classification
prior art notes: Surveys, as of 2010, the architecture and components of wearable health-monitoring systems — sensors (ECG, PPG, SpO2, accelerometry, temperature, respiration), garment- and patch- and watch-based form factors, on-body processing, wireless body-area networking, and the analytics (arrhythmia, fall, activity, deterioration prediction). Prior art establishing that the general ‘multi-sensor wearable + body-area network + cloud analytics’ system architecture and its building blocks were collected and published by 2010 — useful against later claims to the bare system architecture. General anchor.

ISO 80601-2-61 — particular requirements for basic safety and essential performance of pulse oximeter equipment (2011/2017) (2011-08-15)

id: iso-80601-2-61-pulse-oximeter-equipment-2011
corpus: standards
form factor: other
creator: ISO/IEC (TC 121/SC 3 and IEC SC 62D)
disclosure: ISO 80601-2-61:2011 (revised 2017). ‘Medical electrical equipment — Part 2-61: Particular requirements for basic safety and essential performance of pulse oximeter equipment.’ ISO, 2011.
ip status: standards
sensors: sensor-spo2, sensor-ppg, sensor-multi-wavelength-ppg
algorithms: algo-spo2-estimation
prior art notes: Publicly-adopted standard defining pulse oximeter equipment (a device estimating SpO2 and pulse rate from light at two or more wavelengths through perfused tissue) and the accuracy/validation requirements for it. Prior art for wearable-SpO2 claims to the extent they recite the multi-wavelength pulsatile method or the SpO2-and-pulse-rate output described here; the equipment definition and method have been a published standard since 2011 (building on the [[aoyagi-1974-two-wavelength-pulse-oximetry]] principle).

Bragi Dash (2014) — the first true ‘hearable’: in-ear PPG heart rate, accelerometer, storage and touch control inside wireless earbuds (2014-02-25)

id: bragi-dash-2014
corpus: private
form factor: earbud
creator: Bragi GmbH
disclosure: Bragi GmbH. ‘The Dash’ wireless smart earphones, crowdfunded February 2014 (shipped 2016) — fully wireless in-ear earbuds with a reflectance-PPG heart-rate sensor and oxygen-saturation estimation against the ear-canal wall, a 3-axis accelerometer (head-gesture and step/activity tracking), 4 GB onboard music storage, bone-conduction microphone, and capacitive touch control.
ip status: patented
sensors: sensor-ppg, sensor-spo2, sensor-accelerometer, sensor-microphone-bone
algorithms: algo-hr, algo-spo2-estimation, algo-step-count, algo-activity-classification
prior art notes: Discloses fully-wireless in-ear earbuds with a reflectance-PPG heart-rate and SpO2 sensor against the ear-canal wall, an accelerometer for head-gesture and step/activity tracking, onboard music storage, a bone-conduction microphone, and capacitive touch control — i.e. physiological sensing integrated into wireless earbuds. Anticipates hearable claims combining ‘a wireless earbud housing’, ‘an in-ear PPG/SpO2 sensor’, ‘an accelerometer for activity or head gesture’, and ‘on-device media and controls’ from 2014. Product-side anchor for the earbud × PPG cross-cut.

Withings ScanWatch (2020) — hybrid analog watch with PPG, SpO2 pulse oximetry, single-lead ECG, and accelerometer (2020-01-05)

id: withings-scanwatch-2020
corpus: private
form factor: watch
creator: Withings SA
disclosure: Withings (Nokia/Withings). ‘ScanWatch’, announced January 2020 (CE-marked 2020; FDA cleared 2022) — a hybrid analog wristwatch integrating a reflectance-PPG sensor (heart rate, irregular-rhythm screening), an SpO2 (pulse-oximetry) measurement, a single-lead ECG (back electrode plus a bezel electrode touched by the opposite hand, with AF detection), a 3-axis accelerometer, and an altimeter — with sleep and activity tracking.
ip status: patented
sensors: sensor-ppg, sensor-spo2, sensor-ecg, sensor-accelerometer, sensor-barometer
algorithms: algo-hr, algo-spo2-estimation, algo-afib-detection, algo-arrhythmia-classification, algo-sleep-staging, algo-step-count, algo-respiratory-rate
prior art notes: Discloses a wristwatch combining reflectance-PPG heart rate, pulse-oximetry SpO2, a single-lead ECG with AF detection, accelerometry, and an altimeter, with sleep-apnea screening (from the SpO2/respiration signals) — multiple regulated cardiorespiratory measurements in one consumer watch. Anticipates multi-modal medical-smartwatch claims reciting combinations of wrist PPG-HR + wrist SpO2 + single-lead ECG from 2020. Product-side anchor for the watch × {PPG, SpO2, ECG} multi-sensor cross-cut.

Open-Watch (Salar Motlaqolahi, 2021) — fully documented open STM32 smartwatch (BSc thesis) (2021)

id: smotlaq-open-watch-2021
corpus: open
form factor: watch
creator: Salar Motlaqolahi
disclosure: Motlaqolahi S. ‘Open-Watch’ — fully open-source smartwatch released as BSc thesis output (MIT license). Hardware: STM32 ARM Cortex-M MCU, MPU6050 6-axis IMU, MAX30102 reflectance PPG + SpO2, 4-layer PCB sponsored by PCBWay, full schematics + Gerbers + firmware published. https://github.com/SMotlaq/open-watch
ip status: open-permissive
sensors: sensor-ppg, sensor-spo2, sensor-accelerometer, sensor-gyroscope
algorithms: algo-hr, algo-spo2-estimation, algo-step-count
prior art notes: Discloses, as an MIT-licensed open-hardware smartwatch with full PCB design files (4-layer, PCBWay-sponsored fabrication) and firmware published, a wrist-worn device with reflectance PPG + SpO2 + 6-axis IMU + MCU + display. Demonstrates that the entire smartwatch design — schematic, layout, firmware — can be reproduced from undergraduate-thesis-level public work, defeating any claim that the integrated smartwatch is novel as a combination.

Masimo W1 (2022) — first FDA-cleared continuous wrist medical-grade pulse oximetry watch (2022-05)

id: masimo-w1-2022
corpus: private
form factor: watch
creator: Masimo Corp.
disclosure: Masimo Corp. ‘Masimo W1’ health-tracking watch, announced May 2022 — a wrist-worn device performing continuous medical-grade pulse oximetry (SpO2), pulse rate, perfusion index (PI), pleth variability index (PVi), respiratory rate from the PPG, and HRV, using Masimo’s SET/rainbow signal-extraction algorithms. (FDA cleared as a continuous-monitoring medical device.)
ip status: patented
sensors: sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg, sensor-accelerometer
algorithms: algo-spo2-estimation, algo-hr, algo-hrv, algo-respiratory-rate
prior art notes: Discloses a wrist-worn device performing continuous medical-grade pulse oximetry — SpO2, PR, perfusion index, PVi, RR-from-PPG, HRV — using established signal-extraction methods, distinguished from consumer spot-check SpO2 by continuous operation and clearance for medical use. Anticipates wrist-continuous-medical-SpO2 claims from 2022; the underlying two-wavelength SpO2 method is much older ([[aoyagi-1974-two-wavelength-pulse-oximetry]], [[mendelson-ochs-1988-reflectance-pulse-oximetry]], [[iso-80601-2-61-pulse-oximeter-equipment-2011]]). Product-side anchor for the watch × continuous-SpO2 cross-cut.

HealthyPi Move (ProtoCentral, 2026) — open-source medical-grade smartwatch (2024)

id: healthypi-move-2026
corpus: open
form factor: watch
creator: ProtoCentral Electronics
disclosure: ProtoCentral Electronics (Bengaluru, India). ‘HealthyPi Move’ fully open-source AMOLED smartwatch — Crowd Supply campaign launched 2024, units shipping 15 May 2026. Sensors: single-lead ECG, dual-site PPG (wrist + finger), SpO2, blood-pressure trending, EDA/GSR, heart rate, HRV, respiration rate (derived), body temperature, 6-axis IMU. Compute: Nordic nRF5340 (dual ARM Cortex-M33). Display: AMOLED, 300 mAh battery. Companion app: Flutter, runs on Android/iOS/macOS/Windows/Linux, all data stored locally. Hardware design, firmware (Zephyr RTOS on nRF Connect SDK), and companion app all open-source. https://www.crowdsupply.com/protocentral/healthypi-move
ip status: open-permissive
sensors: sensor-ecg, sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg, sensor-gsr, sensor-accelerometer, sensor-gyroscope, sensor-skin-temperature
algorithms: algo-hr, algo-hrv, algo-spo2-estimation, algo-respiratory-rate, algo-pwv-bp-estimation, algo-sleep-staging, algo-activity-classification, algo-step-count
prior art notes: Discloses, as fully open-source hardware and firmware (CC and MIT-style licensing across components), a wrist-worn smartwatch with the full consumer-medical sensor stack: single-lead ECG between back-of-watch electrode and a finger-touch electrode; multi-wavelength reflectance PPG with SpO2 and BP-trending; EDA/GSR; skin temperature; 6-axis IMU; on-device Zephyr-RTOS application; AMOLED display; all-local data storage via cross-platform Flutter app. Anticipates wrist-multi-sensor-watch claims from 2024-2026 to the extent they recite combinations of these elements; as open prior art it is unencumbered and any patent claim reciting these combinations must distinguish over HealthyPi Move’s specific implementation. The product-side anchor for the ‘open watch with the full sensor stack’ cross-cut.

H-Watch (Magno et al., 2024) — open-source ARM Cortex-M4F + ML + NB-IoT + energy-harvesting research smartwatch (2024)

id: h-watch-magno-2024
corpus: academic
form factor: watch
creator: Michele Magno et al. (ETH Zürich and collaborators)
disclosure: Magno M, et al. ‘H-Watch: A Multi-Sensor Smart Wearable for COVID-19 Symptom Monitoring with ML and Energy Harvesting.’ arXiv:2407.21501 (2024). Fully open-source smartwatch hardware + firmware for symptom monitoring: ARM Cortex-M4F MCU, on-device ML inference, NB-IoT cellular connectivity, integrated energy harvesting + battery. https://arxiv.org/abs/2407.21501
ip status: public-domain
sensors: sensor-ppg, sensor-spo2, sensor-skin-temperature, sensor-accelerometer
algorithms: algo-hr, algo-spo2-estimation, algo-respiratory-rate, algo-activity-classification
prior art notes: Discloses a fully open-source research smartwatch combining multi-sensor vitals (PPG/SpO2/temperature/IMU), on-device ML inference, NB-IoT direct cellular connectivity (no phone required), and integrated energy harvesting to extend battery life — published with full hardware design and firmware. Prior art for symptom-monitoring smartwatch claims reciting any of those elements from 2024. Establishes that the cellular-connected open-hardware ML-enabled smartwatch is a published research design.

Cross-cut: algo-spo2-estimation