Single Electrode Biopotential and Bioimpedance Signal Acquisition

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Solution Overview

Problem

Existing implantable medical devices require two separate electrode pairs to concurrently measure bioimpedance and biopotential signals, leading to increased device size and interference issues, which complicates the monitoring of physiological signals and therapy delivery.

Innovation Solution

An implantable medical device that uses a single pair of electrodes to simultaneously acquire bioimpedance and biopotential signals by synchronizing the drive signal for bioimpedance measurement with the sampling intervals of the biopotential signal, minimizing noise and artifact through advanced signal processing and control techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a single pair of electrodes is used to measure both bioimpedance and biopotential signals, then device size is reduced, but noise and artifact on biopotential signals increase due to drive signal interference

Engineering Contradiction:

Improvedevice sizeVSAvoidnoise and artifact on biopotential signal

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic action by using time-division multiplexing where the drive signal for bioimpedance measurement is applied periodically at specific intervals, and biopotential signals are sampled during intervals when the drive signal is not active. This periodic switching allows both measurements to share the same electrode pair while minimizing interference, as the biopotential sampling occurs during quiet periods between drive signal applications.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements preliminary action by applying the drive signal for a predetermined duration before sampling the biopotential signal, allowing the drive signal to settle and reach steady state. This preliminary application ensures that transient artifacts from signal switching are minimized, and the system is in a stable state when biopotential measurements are taken, reducing noise and artifact.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If two separate electrode pairs are used to avoid interference, then signal quality is improved, but device size and complexity increase

Engineering Contradiction:

Improvesignal interferenceVSAvoiddevice size

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

The patent applies merging by combining the functions of two separate electrode pairs into a single shared electrode pair. The same electrodes are used alternately for both bioimpedance measurement (by applying drive signal and measuring voltage response) and biopotential signal acquisition, thereby reducing the number of electrodes and associated feedthroughs from two pairs to one pair, which reduces device size and complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent implements universality by making the single electrode pair multi-functional, capable of performing both bioimpedance measurement and biopotential signal acquisition. The electrodes are not dedicated to a single function but are universally used for both purposes through time-division multiplexing, allowing the device to maintain comprehensive monitoring capabilities with fewer components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If drive signal is applied continuously for bioimpedance measurement, then measurement accuracy is improved, but biopotential signal quality deteriorates due to ongoing interference

Engineering Contradiction:

Improvebioimpedance measurement accuracyVSAvoidnoise on biopotential signal

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic action by implementing intermittent drive signal application rather than continuous application. The drive signal is applied in periodic bursts for bioimpedance measurement, followed by intervals where no drive signal is active and biopotential signals are sampled. This periodic on-off pattern maintains sufficient bioimpedance measurement accuracy through repeated measurements while ensuring biopotential signals are captured during artifact-free intervals.

Inventive Principle:

Principle #19Periodic action

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, uninterrupted monitoring of biopotential signals while acquiring bioimpedance data without increasing device size, reducing noise and artifact, and allowing for efficient therapy delivery.

Implementation Method 1

measure tissue impedance based on a voltage signal developed across the electrodes in response to the drive signal

Methodology Applied

Scientific EffectElectrical Impedance: Electrical Resistance

Implementation Method 2

acquire a biopotential signal from the electrodes. The biopotential signal may be generated by biological tissue during physiological activity

Methodology Applied

Scientific EffectBiopotential: Electric Field

Data Source

PatentEP3043704B1Apparatus and method for simultaneous capture of biopotential and tissue impedance signals

Publication Date: 2023.05.03 MEDTRONIC INC

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AI summary

A medical device and associated method acquire a biopotential signal from a pair of electrodes at a first sampling rate and a bioimpedance signal from the pair of electrodes at a second sampling rate. An onset and/or offset of the drive signal delivered to the pair of electrodes for acquiring the bioimpedance signal is synchronized to the first sampling rate.