Impedance Matching in Patient Interface Systems
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Solution Overview
Problem
The application of electrical stimulation in medical devices for treating movement disorders and neurodegenerative impairments interferes with the sensing of neurological bioelectrical signals, causing amplifier saturation and limiting the ability to measure desired electrical signals due to impedance mismatch issues at the electrode-tissue interface.
Innovation Solution
A system and method that measure the relative impedance difference between electrodes and apply a sub-therapeutic stimulation pulse to adjust and match the impedance, allowing for simultaneous therapeutic stimulation and monitoring of physiological activity by reducing impedance differences and improving the common-mode rejection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical stimulation is applied to treat movement disorders, then therapeutic effect is achieved, but amplifier saturation occurs and sensing of neurological bioelectrical signals becomes unreliable
Solution Approach 1:
The patent extracts the harmful stimulation signal from the sensing path by using separate electrode pairs: one pair for delivering electrical stimulation and another pair for sensing neurological bioelectrical signals. This separation removes the interference source from the measurement path, preventing amplifier saturation while maintaining therapeutic stimulation.
Solution Approach 2:
The patent introduces impedance matching circuitry as an intermediary between the electrodes and the amplifier. This intermediary component conditions the sensing signals by matching impedances, thereby preventing signal distortion and amplifier saturation while allowing faithful reproduction of neurological signals during stimulation.
2Reliability
If sensing electrodes are blocked during stimulation to avoid saturation, then amplifier saturation is prevented, but useful information during stimulation is lost
Solution Approach 1:
The patent extracts the sensing function from the stimulation electrodes by implementing dedicated sensing electrodes that remain active during stimulation. This allows continuous monitoring of neurological bioelectrical signals throughout the stimulation period, capturing useful information that would otherwise be lost.
Solution Approach 2:
The patent implements electrodes with multiple functions: certain electrodes can serve both as stimulation delivery electrodes and as sensing electrodes simultaneously. This multi-functionality allows the system to perform both therapeutic stimulation and continuous physiological monitoring without interrupting either function.
3Measurement precision
If impedance matching is not performed between electrodes, then device complexity is reduced, but sensing precision deteriorates due to impedance mismatch
Solution Approach 1:
The patent applies impedance matching techniques to equalize the impedance levels between different electrode pairs. By adjusting the electrical characteristics of the electrode interfaces to be equivalent, the system achieves balanced signal levels that improve sensing precision and reduce distortion without requiring complex adaptive algorithms.
Solution Approach 2:
The patent modifies electrical parameters such as electrode impedance, gain settings, and filtering characteristics to optimize signal quality. These parameter adjustments are made based on measured impedance values, allowing the system to adapt to varying physiological conditions while maintaining measurement precision.
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 reliable sensing of neurological bioelectrical signals during electrical stimulation by stabilizing the electrode-tissue interface, reducing saturation, and providing real-time feedback on the efficacy of the stimulation, thereby enhancing the effectiveness of treatment and diagnostic procedures.
Implementation Method 1
a sub-therapeutic stimulation pulse may be applied to one of the first and second electrodes to reduce the relative impedance difference between the electrodes
Data Source
AI summary
Systems and method may be used for interfacing with a patient. Systems may include a plurality of electrodes in electrical communication with a processor. The processor may determine a relative impedance difference between a first electrode and a second electrode, and apply a sub-therapeutic stimulation pulse to one of the first and second electrodes to adjust the relative impedance difference therebetween. Systems may include a processor capable of one or both of providing therapeutic stimulation to a patient via at least one electrode, and receiving electrical signals indicative of the patient's physiological activity. In some examples, the processor may simultaneously provide therapeutic stimulation to a patient and receive electrical signals from the patient indicative of the patient's physiological activity.