Accelerometer-Based Motion Artifact Detection in Pulse Oximetry

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Solution Overview

Problem

Pulse oximetry and photoplethysmographic measurements face accuracy issues due to low-perfusion and motion artifacts, leading to false alarms and reduced reliability in calculating oxygen saturation and other physiological parameters.

Innovation Solution

A system that integrates an accelerometer with a pulse oximetry probe to detect movement and label corresponding physiological parameter measurements, allowing only motion-free data to be used for calculations and alarming, thereby reducing false alarms and improving measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If photoplethysmographic measurements are performed using a pulse oximetry probe, then oxygen saturation and pulse rate can be monitored non-invasively, but measurement accuracy is reduced due to motion artifacts and low-perfusion conditions

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidreliability of measurements

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

An accelerometer is introduced as an intermediary device to detect motion artifacts separately from the PPG signal. The accelerometer measures motion independently, and this motion information is used to identify and exclude artifact-contaminated PPG segments, thereby improving measurement accuracy without compromising reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The PPG signal is segmented into motion-free segments and motion-artifact segments based on accelerometer data. By dividing the continuous signal into distinct segments with different quality characteristics, the system can selectively process only the clean segments for physiological parameter calculation, improving both accuracy and reliability

Inventive Principle:

Principle #1Segmentation

2Reliability

If PPG signal analysis is performed to identify motion artifacts, then measurement reliability can be improved, but the complexity of signal processing increases

Engineering Contradiction:

Improvereliability of measurementsVSAvoidcomplexity of signal processing

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The accelerometer serves as an external intermediary that simplifies the detection of motion artifacts. Instead of relying solely on complex analysis of the PPG signal itself to detect motion, the accelerometer provides direct motion information, reducing the complexity of signal processing while improving reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Instead of analyzing the PPG signal to detect motion artifacts (which is complex and challenging), the system inverts the approach by using an accelerometer to detect motion and then using that information to identify artifact-free PPG segments. This reversal simplifies the overall processing complexity

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If motion artifacts are identified and excluded from analysis, then false alarms are reduced, but more data points are discarded

Engineering Contradiction:

Improvereliability of alarmingVSAvoiddata utilization efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The signal is segmented into motion-free and motion-artifact portions, allowing selective use of only the clean segments for physiological parameter calculation and alarm generation. This ensures that alarms are based on reliable data, improving alarming reliability while efficiently utilizing available good-quality data

Inventive Principle:

Principle #1Segmentation

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

The system effectively reduces false alarms and enhances the accuracy of oxygen saturation and pulse rate measurements by directly identifying and accounting for motion artifacts, ensuring reliable data presentation and alarming.

Implementation Method 1

an accelerometer positioned on, proximate to, or integrated with the probe measures acceleration

Methodology Applied

Scientific EffectAcceleration measurement: Accelerometer

Implementation Method 2

Light at red (e.g., around 660 nm) and infrared (e.g., around 940 nm) wavelengths is then passed sequentially through the patient to a photo-detector. The changing absorbance at each of the two wavelengths is measured to create a photoplethysmogram

Methodology Applied

Scientific EffectLight absorbance: Absorption (EM radiation)

Implementation Method 3

Using the ratio of changing absorbance of the red and infrared light caused by the difference in color between oxygen-bound (bright red) and oxygen-unbound (dark red or blue in severe cases) blood hemoglobin, a determination of oxygen saturation (SpO2) can be made

Methodology Applied

Scientific EffectAbsorbance ratio analysis: Absorption (EM radiation)

Data Source

PatentUS9788793B2Method and system to identify motion artifacts and improve reliability of measurements and alarms in photoplethysmographic measurements

Publication Date: 2017.10.17 KONINKLIJKE PHILIPS NV

AI summary

A system (10) and method to identify motion artifacts. Measurements of a physiological parameter of an associated patient are received from a probe (12) positioned on or proximate to the associated patient. Further, measurements of acceleration are received from an accelerometer (26) positioned on, proximate to, or integrated with the probe (12). Measurements of the physiological parameter are labeled based on the measured acceleration, such as being with or without motion.