Intersection cross-cut: sensor-ppg ∩ algo-pwv-bp-estimation

Axes: sensors × algorithms

7 corpus entries disclose both tags.

Earliest disclosure: 1973

These entries are the direct inputs to OBVIOUSNESS_TEMPLATE.md. Any patent claim combining these two elements is anticipated or rendered obvious by the chain below.

Peñáz (1973) — the volume-clamp (vascular unloading) method of continuous finger blood pressure (1973)

  • id: penaz-1973-volume-clamp-finger-bp
  • corpus: academic
  • form factor: other
  • creator: Jan Peñáz
  • disclosure: Peñáz J. ‘Photoelectric measurement of blood pressure, volume and flow in the finger.’ Digest of the 10th International Conference on Medical and Biological Engineering, Dresden, 1973, p. 104. (Basis of the Finapres / volume-clamp continuous BP monitors.)
  • ip status: public-domain
  • sensors: sensor-ppg, sensor-cuffless-bp-volume-clamp, sensor-pressure-skin
  • algorithms: algo-pwv-bp-estimation
  • prior art notes: Discloses the volume-clamp / vascular-unloading method: a finger cuff servo-controlled by a photoplethysmographic feedback loop to hold the arterial volume constant, so the applied counter-pressure tracks the arterial pressure waveform continuously and non-invasively. Any cuffless/continuous-BP wearable claim reciting ‘a photoplethysmographic feedback loop controlling an applied pressure to maintain constant vascular volume’ reads on Peñáz 1973. Anchor for the volume-clamp cuffless-BP cross-cut (the finger/ring form-factor variants are obvious combinations under [[obviousness-template]]).

Geddes et al. (1981) — pulse transit time as an indicator of arterial blood pressure (1981-01)

  • id: geddes-1981-pulse-transit-time-bp
  • corpus: academic
  • form factor: other
  • creator: Leslie A. Geddes et al. (Purdue)
  • disclosure: Geddes LA, Voelz MH, Babbs CF, Bourland JD, Tacker WA. ‘Pulse transit time as an indicator of arterial blood pressure.’ Psychophysiology 1981;18(1):71-74.
  • ip status: public-domain
  • sensors: sensor-ecg, sensor-ppg, sensor-cuffless-bp-ptt
  • algorithms: algo-pwv-bp-estimation
  • prior art notes: Establishes that pulse transit time — the delay between a proximal timing reference (e.g. the ECG R-wave) and the arrival of the pulse at a distal site (e.g. a finger PPG) — varies inversely with arterial blood pressure, and can therefore be used to estimate BP without a cuff. Any cuffless-BP wearable claim reciting ‘estimating blood pressure from a pulse transit time (or pulse arrival time / pulse wave velocity) derived from two physiological signals’ reads on Geddes 1981. Earliest anchor for the PTT-cuffless-BP cross-cut; [[mukkamala-2015-ptt-cuffless-bp-review]] is the modern survey.

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.

Mukkamala et al. (2015) — ‘Toward Ubiquitous Blood Pressure Monitoring via Pulse Transit Time: Theory and Practice’ (2015-08)

  • id: mukkamala-2015-ptt-cuffless-bp-review
  • corpus: academic
  • form factor: other
  • creator: Ramakrishna Mukkamala et al.
  • disclosure: Mukkamala R, Hahn J-O, Inan OT, Mestha LK, Kim C-S, Töreyin H, Kyal S. ‘Toward Ubiquitous Blood Pressure Monitoring via Pulse Transit Time: Theory and Practice.’ IEEE Transactions on Biomedical Engineering 2015;62(8):1879-1901.
  • ip status: public-domain
  • sensors: sensor-ecg, sensor-ppg, sensor-cuffless-bp-ptt, sensor-cuffless-bp-tonometry
  • algorithms: algo-pwv-bp-estimation
  • prior art notes: Canonical 2015 review of cuffless blood-pressure estimation by pulse transit time / pulse arrival time / pulse wave velocity: the physiological models, the practical sensor configurations (ECG+PPG, dual PPG, ballistocardiogram+PPG), the calibration strategies, and the accuracy limitations. Prior art for cuffless-BP wearable claims reciting any of the configurations or calibration approaches surveyed here — they were collected, modeled, and published by 2015. Combined with watch/ring/patch form-factor disclosures, makes wearable PTT-based BP an obvious combination under [[obviousness-template]].

Samsung Galaxy Watch3 / Samsung Health Monitor (2020) — wrist single-lead ECG and optical-PPG cuffless blood pressure (2020-08)

  • id: samsung-galaxy-watch-bp-ecg-2020
  • corpus: private
  • form factor: watch
  • creator: Samsung Electronics Co., Ltd.
  • disclosure: Samsung Electronics. ‘Samsung Health Monitor’ app on Galaxy Watch3 / Watch Active2, 2020 — wrist single-lead ECG (between a back-crystal electrode and a side-button electrode touched by the opposite hand, with AF/sinus classification) and a cuffless blood-pressure feature using the optical (PPG) pulse-wave signal calibrated against a periodic conventional cuff reading. (Cleared in Korea 2020; subsequently in other markets.)
  • ip status: patented
  • sensors: sensor-ecg, sensor-ppg, sensor-cuffless-bp-ptt
  • algorithms: algo-afib-detection, algo-arrhythmia-classification, algo-pwv-bp-estimation, algo-hr
  • prior art notes: Discloses a wristworn device that takes a single-lead ECG with on-device AF classification and, separately, estimates blood pressure from the wrist optical-PPG pulse waveform after calibration against a periodic conventional cuff measurement (a calibrated-cuffless approach). Anticipates wrist-cuffless-BP claims reciting ‘estimating blood pressure from a wrist photoplethysmography signal calibrated by a reference cuff reading’ from 2020 — the underlying PTT/PWV-BP technique is much older ([[geddes-1981-pulse-transit-time-bp]], [[mukkamala-2015-ptt-cuffless-bp-review]]). Product-side anchor for the watch × cuffless-BP cross-cut.

Aktiia bracelet (2021) — optical-PPG-based continuous cuffless blood-pressure monitoring bracelet (2021-01)

  • id: aktiia-bracelet-cuffless-bp-2021
  • corpus: private
  • form factor: bracelet
  • creator: Aktiia SA
  • disclosure: Aktiia SA. ‘Aktiia bracelet’ (later ‘Hilo’), CE-marked and launched in Europe January 2021 — a slim wristband with optical photoplethysmography that, after a one-time initialization against a conventional cuff (and periodic re-calibration), estimates systolic and diastolic blood pressure several times a day automatically, day and night, from the wrist PPG pulse waveform.
  • ip status: patented
  • sensors: sensor-ppg, sensor-cuffless-bp-ptt, sensor-accelerometer
  • algorithms: algo-pwv-bp-estimation, algo-hr
  • prior art notes: Discloses a slim wristband that, after a one-time cuff initialization (and periodic re-calibration), automatically estimates systolic and diastolic blood pressure multiple times per day and night purely from the wrist optical-PPG pulse waveform — i.e. continuous, fully cuffless, calibration-initialized wrist BP monitoring. Anticipates continuous-cuffless-wrist-BP claims from 2021; the PPG-pulse-feature-to-BP mapping rests on the much older PTT/PWV-BP and pulse-contour literature ([[geddes-1981-pulse-transit-time-bp]], [[mukkamala-2015-ptt-cuffless-bp-review]]). Product-side anchor for the bracelet × cuffless-BP 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.

Public domain (CC0 1.0). The corpus IS the prior art commons.

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