Active Low Impedance Electrode for ECG Artifact Reduction
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Solution Overview
Problem
Standard electrodes for ECG/EEG monitors exhibit high contact impedance, leading to significant artifact signals due to electrostatic coupling, particularly in environments with substantial electrostatic sources, such as ambulances, which compromises measurement quality and requires shielding of cables, limiting their use in emergency situations.
Innovation Solution
An active low impedance electrode system comprising an electrical activity sensor, a voltage sense contact, a current flow contact, and an active electrode coupler, which reduces skin electrode contact impedance by controlling the directional flow of sensor current to match patient voltage, eliminating the need for shielding in ECG/EEG cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard electrodes are used for ECG/EEG monitoring, then the electrode interface impedance varies dramatically (10K to 10M ohms), but this high impedance leads to significant artifact signals due to electrostatic coupling
Solution Approach 1:
The patent introduces an active electrode coupler as an intermediary component between the patient's skin and the measurement system. This coupler actively drives current through the skin-electrode interface to compensate for high contact impedance, thereby reducing artifact signals while maintaining measurement accuracy
Solution Approach 2:
The electrode system employs feedback control where the electrical activity sensor continuously monitors the patient's electrical signals and the active electrode coupler adjusts its output accordingly. This feedback mechanism ensures that the coupler compensates for impedance variations in real-time, minimizing electrostatic coupling artifacts
2Object-affected harmful factors
If shielded wires are used to minimize electrostatic coupling, then artifact signals are reduced, but the system complexity and cost increase
Solution Approach 1:
The patent extracts the electrostatic coupling problem from the cable shielding solution by addressing it at the electrode interface itself. The active electrode coupler compensates for electrostatic effects locally at the skin contact point, eliminating the need for extensive cable shielding and simplifying the overall system
3Reliability
If high contact impedance electrodes are used, then the electrode interface impedance varies between 10K and 10M ohms, but this requires the ambulance to pull over for 12-lead static-free ECG measurement
Solution Approach 1:
The active electrode coupler performs preliminary compensation for electrostatic coupling effects during patient transport. By actively driving current through the interface before measurement, it pre-establishes low-impedance contact conditions, allowing continuous ECG monitoring during ambulance transport without requiring stops for static-free measurements
4Object-affected harmful factors
If active feedback loop is used to force common mode current through reference electrode, then common mode signal is minimized, but the reference electrode impedance still affects measurement quality
Solution Approach 1:
The active electrode coupler serves as an intermediary that actively compensates for reference electrode impedance effects. By driving current through the skin interface and establishing an equivalence between patient voltage and sensor voltage, it neutralizes the impact of high reference electrode impedance on measurement quality
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 solution significantly improves ECG/EEG measurement quality by minimizing electrostatic coupled signals, allowing for low-cost disposable cables and maintaining measurement accuracy even in environments with substantial electrostatic sources.
Implementation Method 1
the electrical activity sensor controls a directional flow of a sensor current between the electrical activity sensor and the anatomical region to establish an equivalence between a patient voltage at voltage sense contact and a sensor voltage at active electrode coupler
Implementation Method 2
any electrostatic coupling into a wire that connects the electrode to an amplifier input of a ECG/EEG monitor will result in current flow across the patient impedance, and any artifact signal generated by such an electrostatic coupling is directly proportional to the impedance of the electrode skin interface
Data Source
AI summary
An active low impedance electrode (20) employing an electrical activity sensor (21) connected to a voltage sense contact (22), a current flow contact (23) and an active electrode coupler (24). In operation, responsive to the voltage sense contact (22) and the current flow contact (23) being attached to the anatomical region (13) of the patient, the electrical activity sensor (21) controls a directional flow of a sensor current between the electrical activity sensor (21) and the anatomical region (13) to establish an equivalence between a patient voltage at voltage sense contact (22) and a sensor voltage at active electrode coupler (24), and/or a patient contact impedance between the voltage sense contact (22) and the current flow contact (23) is greater than an active electrode impedance at the active electrode coupler (24).