Physiological Signal Sensing During Stimulation Therapy

Solution Overview

Problem

Sensing physiological signals in proximity to a stimulation site during electrical stimulation therapy is challenging due to the overwhelming amplitude of stimulation signals, which saturate the sensing circuits and obscure the smaller physiological signals, making it difficult to detect them effectively, especially during the recharge phase when the stimulation pulse is not present.

Innovation Solution

Applying a common mode voltage at the stimulation electrodes during the recharge period, approximating the peak of the stimulation pulse, allows continuous sensing of physiological signals, and using blanking techniques during large stimulation pulse amplitudes to minimize artifacts in the sensed signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If sensing electrodes are used to detect physiological signals during stimulation therapy, then physiological signal detection is enabled, but the sensing circuits are saturated by the large amplitude stimulation signals and cannot detect the small amplitude physiological signals

Engineering Contradiction:

Improvephysiological signal detection accuracyVSAvoidsignal saturation and obscuration

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent segments the sensing operation into two distinct phases: a first sensing phase during the stimulation pulse when the stimulation signal is present, and a second sensing phase during the recharge period when the stimulation signal is absent. This temporal segmentation allows the sensing circuits to detect physiological signals without being saturated by the large amplitude stimulation signals, as each phase is optimized for its specific signal characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by performing sensing during the recharge period before the next stimulation pulse begins. The recharge period provides a preliminary window where the sensing circuits can detect physiological signals while the stimulation circuits are not active, preventing saturation and allowing accurate detection before the next stimulation cycle starts.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If continuous sensing is attempted during both stimulation pulse and recharge period, then more physiological data is available, but the sensing circuits are overly saturated during the stimulation pulse and recharge phase

Engineering Contradiction:

Improvephysiological signal acquisition rateVSAvoidsensing circuit accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the sensing operation into two distinct phases: a first sensing phase during the stimulation pulse when the stimulation signal is present, and a second sensing phase during the recharge period when the stimulation signal is absent. This temporal segmentation allows the sensing circuits to detect physiological signals without being saturated by the large amplitude stimulation signals, as each phase is optimized for its specific signal characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by performing sensing during the recharge period before the next stimulation pulse begins. The recharge period provides a preliminary window where the sensing circuits can detect physiological signals while the stimulation circuits are not active, preventing saturation and allowing accurate detection before the next stimulation cycle starts.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If the recharge phase is blanked out to avoid saturation, then sensing accuracy is improved, but there is inadequate time remaining to sense physiological signals

Engineering Contradiction:

Improvephysiological signal detection accuracyVSAvoidsensing time window

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent segments the sensing operation into two distinct phases: a first sensing phase during the stimulation pulse when the stimulation signal is present, and a second sensing phase during the recharge period when the stimulation signal is absent. This temporal segmentation allows the sensing circuits to detect physiological signals without being saturated by the large amplitude stimulation signals, as each phase is optimized for its specific signal characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by performing sensing during the recharge period before the next stimulation pulse begins. The recharge period provides a preliminary window where the sensing circuits can detect physiological signals while the stimulation circuits are not active, preventing saturation and allowing accurate detection before the next stimulation cycle starts.

Inventive Principle:

Principle #10Preliminary 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 sensing of physiological signals during both stimulation and recharge periods, reducing saturation and artifacts, thereby improving the accuracy of signal detection and allowing for more effective tailoring of stimulation therapy.

Implementation Method 1

amplifying the differential mode signal during the stimulation pulse and the recharge period to produce an output signal

Methodology Applied

Scientific EffectDifferential mode signal amplification:

Implementation Method 2

applying a common mode voltage at the stimulation electrodes during the recharge period where the common mode voltage approximates the peak of the stimulation pulse

Methodology Applied

Scientific EffectCommon mode voltage approximation:

Data Source

PatentUS9717428B2Devices and methods for sensing physiological signals during stimulation therapy

Publication Date: 2017.08.01 MEDTRONIC INC

AI summary

Devices and methods provide for the sensing of physiological signals during stimulation therapy by preventing stimulation waveform artifacts from being passed through to the amplification of the sensed physiological signal. Thus, the sensing amplifier is not adversely affected by the stimulation waveform and can provide for successful sensing of physiological signals. A common mode voltage is applied to the stimulation electrodes while sensing during a recharge period where the common mode voltage approximates the stimulation pulse being received at the sensing electrodes. This common mode voltage is determined based on measuring a common mode signal for at least one of the inputs of the amplifier or by deriving the proper common mode from monitoring the output signal of the amplifier to observe the elimination of artifacts during stimulation. Blanking switches may be used to blank the sensing of the peak of the recharge period should that peak be relatively large.