ECG-PPG Sampling Synchronization for Accurate PWV Blood Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The precision of blood pressure measurement using the Pulse Wave Velocity (PWV) method is affected by deviations in sampling frequencies and times between electrocardiogram (ECG) and photoplethysmogram (PPG) signals, leading to errors in calculated Pulse Transit Time (PTT) and subsequently measured blood pressure values.
Innovation Solution
A method and apparatus that control ECG and PPG sampling modules to simultaneously sample a standard periodic signal, compensate for sampling frequency deviations and time differences, using a high-precision clock signal to ensure precise synchronization and frequency stability, thereby reducing errors in PTT and blood pressure measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ECG and PPG signals are sampled separately by independent sampling modules, then the sampling structure is simple and independent, but sampling time and frequency precision deviate, directly affecting blood pressure measurement precision
Solution Approach 1:
The patent merges the clock sources of ECG and PPG sampling modules into a single shared clock source. This ensures both modules operate under the same time base, eliminating sampling time and frequency deviations caused by independent clock sources, thereby improving blood pressure measurement precision without requiring complex synchronization hardware
Solution Approach 2:
The patent implements a feedback mechanism where the sampling end time difference and sampling frequency deviation are calculated based on sampled data, and compensation values are generated and fed back to adjust the sampling start times and frequencies of ECG and PPG modules. This closed-loop feedback system continuously corrects sampling synchronization errors, maintaining high measurement precision
2Measurement precision
If sampling frequencies and times are not compensated, then the sampling process is simple and fast, but the calculated Pulse Transit Time (PTT) contains errors, leading to inaccurate blood pressure values
Solution Approach 1:
The patent performs preliminary sampling of standard periodic signals by both ECG and PPG modules before actual blood pressure measurement. This preliminary action allows calculation of sampling end time differences and frequency deviations in advance, enabling pre-computation of compensation values that are applied before the main measurement, thus minimizing time loss during actual operation
Solution Approach 2:
The patent dynamically adjusts sampling parameters (start times and frequencies) of ECG and PPG modules based on calculated compensation values. By changing these parameters in real-time, the system corrects sampling synchronization errors without requiring complete re-sampling, thereby reducing time loss while improving PTT measurement precision
3Measurement precision
If a high-precision clock signal is used for synchronization, then sampling time precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent introduces a standard periodic signal as an intermediary reference that both ECG and PPG sampling modules sample independently. This intermediary signal serves as a common reference point, allowing calculation of sampling synchronization errors without requiring direct coupling or complex high-precision clock distribution systems, thus maintaining simplicity while improving time precision
4Measurement precision
If sampling frequency deviations are not compensated, then the sampling operation is straightforward, but the blood pressure mathematical modeling precision is affected
Solution Approach 1:
The patent replaces complex hardware frequency stabilization mechanisms with software-based frequency deviation calculation and compensation. By using digital signal processing to calculate frequency deviations from sampled standard periodic signals and applying computational compensation to sampling timing, the system achieves high modeling precision without requiring complex mechanical or electronic frequency control hardware
Data Source
AI summary
Blood pressure detection signal sampling and compensation methods and apparatuses, and an example blood pressure signal collection system are described. One example method described includes controlling an electrocardiogram (ECG) sampling module and a photoplethysmogram (PPG) sampling module to simultaneously sample a standard periodic signal. Sampling frequencies and sampling end times are separately obtained. A sampling start time and a sampling frequency of the ECG sampling module or the PPG module is then compensated so that a sampling frequency deviation is less than a preset frequency threshold and a sampling end time difference is less than a preset time threshold.