Cuffless Blood Pressure Estimation Using Differential Pulse Transit Times
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Solution Overview
Problem
Conventional blood pressure measurement methods, such as the pressure cuff method, are non-continuous and not suitable for wearable devices, and cuffless methods relying on pulse transit time (PTT) measurements are limited by errors due to pre-ejection period and lack of continuous monitoring.
Innovation Solution
A wearable apparatus with ECG and pulse wave sensors at multiple sites, using differential pulse transit times (DPTTs) and reflected wave characteristic analysis to estimate diastolic and systolic blood pressure, and calibrating biometric information with personal and vascular resistance data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure cuff method is used for blood pressure measurement, then measurement accuracy is improved, but the device complexity and suitability for wearable devices worsen
Solution Approach 1:
The patent replaces the mechanical pressure cuff system with an optical sensing system. Specifically, it uses photodetectors to detect pulse wave signals at multiple measurement sites, and ECG sensors to detect electrocardiogram signals, substituting the mechanical inflation/deflation mechanism with electronic signal processing to achieve blood pressure estimation without a physical cuff
Solution Approach 2:
The patent integrates multiple sensing functions into a single wearable device platform. The device simultaneously performs ECG signal acquisition, pulse wave signal acquisition at multiple sites, and blood pressure estimation, making the device versatile and suitable for continuous monitoring while eliminating the need for separate measurement tools
2Device complexity
If a single pulse transit time measurement is used, then device complexity is reduced, but measurement precision worsens due to pre-ejection period errors
Solution Approach 1:
The patent segments the pulse wave measurement into multiple independent measurement sites (e.g., wrist and finger). By measuring pulse waves at different locations and calculating differential pulse transit times between these sites, the system eliminates the pre-ejection period component that affects single-site measurements, thereby improving accuracy without requiring complex additional hardware
Solution Approach 2:
The patent introduces the ECG signal as an intermediary reference to identify the precise timing of ventricular depolarization. By using the ECG R-wave as a synchronized start point for measuring pulse wave arrival times at multiple sites, the system accurately separates the pre-ejection period from the actual pulse transit time, enabling precise blood pressure estimation
3Ease of operation
If non-pressure cuffless measurement is used, then ease of operation and wearability are improved, but measurement precision worsens
Solution Approach 1:
The patent transitions from single-point measurement to multi-dimensional measurement by acquiring pulse wave signals at multiple spatial locations (different measurement sites on the body). This dimensional expansion provides additional independent data streams that, when processed together, compensate for the lack of mechanical pressure application and improve the reliability of cuffless blood pressure estimation
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
Enables continuous, accurate estimation of blood pressure with reduced errors, using multiple sensors and advanced signal processing to improve measurement precision and user-specific models.
Implementation Method 1
an electrocardiogram (ECG) sensor configured to measure an ECG signal of a user
Implementation Method 2
a pulse wave sensor configured to emit light to a measurement site, detect the light returning from the measurement site, and obtain a pulse wave signal
Data Source
AI summary
An apparatus for estimating biometric information is provided. According to one exemplary embodiment, the apparatus may include a sensor comprising an electrocardiogram (ECG) sensor configured to measure an ECG signal of a user and a pulse wave sensor configured to measure two or more pulse wave signals at two or more measurement sites of the user; and a processor configured to obtain biometric information based on the ECG signal and the two or more pulse wave signals measured by the sensor.