ECG Electrode Impedance Measurement Using Variable DC Current
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Solution Overview
Problem
Existing ECG monitoring systems face challenges in accurately measuring contact impedance between electrodes and the patient's skin, which affects signal quality due to factors like electrode gel drying and skin moisture, and traditional methods introduce measurement errors with high current levels and lead-off detection issues.
Innovation Solution
The system injects small DC currents into ECG electrodes, measures voltages, and uses mathematical equations to determine impedance without known offset voltages or body voltage values, allowing for accurate impedance calculation by varying current levels and selecting reference electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional impedance measurement methods are used with high current levels, then measurement range is extended, but measurement errors increase and lead-off detection issues occur
Solution Approach 1:
The patent applies parameter changes by using variable current levels instead of fixed high current. The system dynamically adjusts the magnitude of injection currents based on electrode configuration and impedance characteristics, enabling accurate measurements across different impedance ranges while avoiding the harmful effects of consistently high current levels.
Solution Approach 2:
The measurement system is made dynamic by allowing current levels to vary during the measurement process. The system adapts current magnitudes based on real-time conditions and electrode configurations, transitioning from static high-current measurements to dynamic adaptive current injection for improved reliability and accuracy.
2Device complexity
If offset voltages and body voltage values are considered known, then impedance calculation is simplified, but measurement accuracy decreases due to voltage interference
Solution Approach 1:
The patent extracts and eliminates the interfering offset voltages and body voltage values from the measurement equations through mathematical manipulation. By selecting specific electrode combinations and current configurations, these unknown voltage terms are removed from the impedance calculation, allowing accurate measurement without requiring knowledge of these interfering voltages.
Solution Approach 2:
The system uses mathematical relationships and electrode configuration selections as intermediaries to eliminate the harmful voltage terms. By introducing specific measurement equations and selecting reference electrodes strategically, the offset and body voltages are mathematically cancelled out, enabling accurate impedance determination without direct measurement of these interfering parameters.
3Adaptability or versatility
If electrode gel dries or skin moisture changes, then contact impedance varies, but signal quality deteriorates
Solution Approach 1:
The system implements feedback by continuously monitoring contact impedance and using this information to assess signal quality. The impedance measurements provide real-time feedback about electrode-skin contact conditions, allowing the system to detect degradation from gel drying or skin moisture changes and take appropriate actions to maintain signal quality.
Solution Approach 2:
The system performs preliminary impedance measurements to assess contact quality before正式 ECG signal acquisition. By measuring contact impedance in advance, the system can identify poor electrode contact conditions and alert users to reposition electrodes or apply more gel, preventing signal quality deterioration during actual monitoring.
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
This method provides increased accuracy in impedance measurements, reduces measurement errors, and expands the operating range of ECG monitoring systems, improving signal quality and reducing distortion.
Implementation Method 1
The current sources can also be a Direct Current (DC) sources
Implementation Method 2
The resistance at the electrode-patient interface is known as contact impedance
Data Source
AI summary
Systems and methods are provided herein for monitoring electrocardiogram (ECG) electrodes. Each ECG electrode is electrically connected to a patient body and a corresponding current source. A reference ECG electrode of the monitored ECG electrodes is selected. Current is injected into each electrode. Each current has a respective predetermined level. Based on the injected currents, ECG electrode voltages are generated. The injected currents are adjusted after measuring the ECG electrode voltages while the predetermined level through the reference ECG electrode is maintained. An impedance associated with each non-reference ECG electrode is determined based on the ECG electrode voltage and the injected current.