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Publication Number
US-10694958-B2
Publication Date
2020-06-30
Expiration Date
Abstract
A wearable device and the accompanying method for the determination of continuous pulsatile BP are described. The absolute values can be obtained in the initial phase and how a transfer function can transform the BP-signal obtain at the finger or wrist to correct BP-values corresponding to the brachial artery and at heart level. The wearable device contains an orthostatic level-correcting element, which can measure the vertical distance between heart level and finger/wrist level, where the actual measurement takes places. The wearable device may be in the form of a ring, a watch, or a bracelet. Further, the wearable device has elements for wirelessly transmitting signals to host devices such as a smart phone, tablet or other computers.
Core Innovation
A wearable device for measuring hemodynamic parameters uses a photoplethysmographic system having one or more light sources and one or more light detectors that generate the photoplethysmographic signal, and a mounting element for attaching the photoplethysmographic system to a body part containing an artery having an actuator. The actuator and a control system control the contact pressure of the photoplethysmographic system, while the photoplethysmographic signal and contact pressure are used together to derive hemodynamic parameters. The hemodynamic parameters are further derived from a transfer function applied to the photoplethysmographic signal and the contact pressure.
Heart level correction is performed using an accelerator or motion sensor placed next to the photoplethysmographic system. The control system implements modes of operation including continuous measurement, initialization mode, and idle mode, with continuous measurement in which the contact pressure is adjusted by the control system and the actuator according to mean arterial pressure multiplied by a constant factor, and wherein the transfer function is applied to the photoplethysmographic signal and the contact pressure.
Initialization mode adjusts the contact pressure to different pressure levels, determines the amplitude of the photoplethysmographic signal, and determines mean blood pressure at the contact pressure where the highest amplitude is measured. Mean blood pressure multiplied by a constant factor is used as the starting point for the measurement modus. In idle mode, the contact pressure is adjusted to a constant pressure around 30-40 mmHg, the system waits for user interaction to bring the system in initialization and further into the measuring mode, and thereafter allows mode changes when heart rate increases over or decreases under a predefined threshold.
Claims Coverage
The document includes one independent claim (clm-00001) directed to a wearable hemodynamic measuring device, with dependent claims clm-00002 through clm-00006 adding further structural and functional refinements. Across these claims, the coverage centers on actuator-controlled contact pressure applied to a photoplethysmographic system, derivation of hemodynamic parameters from a transfer function, and heart level correction using an accelerator or motion sensor, supported by multiple operational modes.
Transfer-function derivation from photoplethysmographic signal and contact pressure
The hemodynamic parameters are further derived from a transfer function, wherein the transfer function is applied to the photoplethysmographic signal and the contact pressure.
Actuator-controlled mounting element for contact pressure control
A mounting element for attaching the photoplethysmographic system to a body part containing an artery having an actuator, wherein a control system controls the actuator and the contact pressure of the photoplethysmographic system.
Heart level correction using an accelerator or motion sensor
An accelerator or motion sensor placed next to the photoplethysmographic system used for heart level correction.
Continuous measurement mode with mean arterial pressure-scaled contact pressure
A mode for continuous measurement of hemodynamic parameters, wherein the contact pressure is adjusted by the control system and the actuator according to mean arterial pressure multiplied by a constant factor, and wherein the transfer function is applied to the photoplethysmographic signal and the contact pressure.
Initialization mode using varying pressure levels and highest PPG amplitude
A mode for the initialization of the continuous measurement of hemodynamic parameters, wherein the contact pressure is adjusted by the control system and the actuator to different pressure levels, wherein the amplitude of the photoplethysmographic signal is determined, wherein mean blood pressure is determined at the contact pressure where the highest amplitude of the photoplethysmographic signal is measured, and wherein the mean blood pressure multiplied by a constant factor is used as the starting point for the measurement modus.
Idle mode with constant contact pressure and threshold-based mode transition
An idle mode, wherein the contact pressure is adjusted to a constant pressure around 30-40 mmHg, wherein the system waits for user interaction in order to bring the system in initialization and further into the measuring mode, wherein the photoplethysmographic signal is measured for obtaining heart rate, and wherein the system can be further brought in initialization and thereafter into the measuring mode if heart rate increases over or decreases under a predefined threshold.
Pressure sensor for measuring contact pressure
The wearable device includes a pressure sensor for measuring the contact pressure.
Transmitting hemodynamic parameters to an Internet-connected host device
A transmitter that sends obtained hemodynamic parameters to an Internet-connected host device.
Multi-wavelength photoplethysmography for oxygen saturation
Uses at least two light sources or wavelengths and a light detector that generates multiple photoplethysmographic signals to calculate oxygen saturation.
Ring form factor with actuator-adjustable circumference
The device elements are arranged in a ring whose circumference is adjustable by an actuator.
Wrist bracelet/watch implementation with actuator changing contact pressure at radial artery
Implemented in a bracelet or watch, with an actuator changing the contact pressure at the wrist where the radial artery can be palpated.
Overall, the claim set covers a wearable hemodynamic sensor that uses actuator-controlled contact pressure applied to a photoplethysmographic system, derives hemodynamic parameters using a transfer function of photoplethysmographic signal and contact pressure, and performs heart level correction using an accelerator or motion sensor. The control system supports continuous measurement, initialization based on highest photoplethysmographic amplitude to set a starting mean blood pressure (scaled by a constant), and an idle mode with constant contact pressure around 30-40 mmHg, including transitions based on user interaction and heart rate thresholds.
Stated Advantages
Documented Applications
No documented applications found
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