PPG Blood Pressure Estimation with Posture Correction
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Solution Overview
Problem
Existing technologies face challenges in accurately estimating blood pressure using photoplethysmogram (PPG) signals, particularly due to variations in measurement posture which can affect the reliability of the estimates.
Innovation Solution
An apparatus and method that utilize a PPG sensor to measure PPG signals and a processor to extract cardiovascular features, calculate variations in these features, determine the measurement posture, and adjust the blood pressure estimation accordingly by correcting for posture changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If blood pressure is estimated using PPG signals without posture correction, then the estimation process is simple and fast, but the measurement precision deteriorates due to posture variations
Solution Approach 1:
The system performs preliminary posture detection and correction calculations before final blood pressure estimation. By detecting the user's posture state first and pre-calculating correction values based on the time interval between waveform components, the system prepares correction factors in advance to compensate for posture-induced measurement errors, thereby improving accuracy without adding significant complexity to the final estimation process.
Solution Approach 2:
The system implements feedback by continuously monitoring the time interval between two waveform components in the PPG signal to detect posture changes. This feedback mechanism triggers automatic correction value calculations that adjust the blood pressure estimation based on detected posture deviations from the reference posture, enabling dynamic compensation for measurement errors.
2Measurement precision
If posture correction is applied to improve blood pressure estimation accuracy, then measurement precision improves, but the calculation complexity increases
Solution Approach 1:
The system performs self-service by automatically detecting posture changes through intrinsic PPG signal characteristics (time interval between waveform components) and autonomously calculating correction values without requiring external sensors or manual intervention. The processor extracts cardiovascular features from the PPG signal itself to determine posture state and generate appropriate correction factors, eliminating the need for additional measurement devices or complex external monitoring systems.
Solution Approach 2:
The system changes measurement parameters by utilizing the time interval between two waveform components as a posture indicator parameter. By monitoring changes in this temporal parameter, the system infers posture state and adjusts the blood pressure estimation accordingly, transforming a simple time-based measurement into a multi-functional parameter that provides both physiological and positional information.
3Reliability
If the system monitors multiple cardiovascular features to detect posture changes, then the reliability of posture detection improves, but the processing time increases
Solution Approach 1:
The system extracts only the critical posture-indicating feature (time interval between two waveform components) from the PPG signal, separating this specific parameter from other cardiovascular features. By focusing on this single extracted parameter rather than analyzing all signal characteristics, the system achieves reliable posture detection while minimizing processing time and computational overhead.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate blood pressure estimation by accounting for changes in measurement posture, improving the reliability and precision of blood pressure monitoring using PPG signals.
Implementation Method 1
a light source configured to emit light to the user; and a detector configured to detect light scattered or reflected from the user
Implementation Method 2
a light source configured to emit light to the user; and a detector configured to detect light scattered or reflected from the user
Data Source
AI summary
An apparatus for estimating blood pressure may include: a photoplethysmogram (PPG) sensor configured to measure a PPG signal from a user; and a processor configured to: extract a cardiovascular feature from the PPG signal; calculate a first variation in the extracted cardiovascular feature compared to a reference cardiovascular feature measured at a reference time; determine a measurement posture of the PPG signal based on a time interval between two waveform components of the PPG signal; in response to the measurement posture corresponding to the reference posture, estimate the blood pressure based on the first variation; and in response to the measurement posture not corresponding to the reference posture, obtain a second variation by correcting the first variation; and estimate blood pressure based on the second variation.