Pulse Oximeter Probe Third Wavelength Probe-Off Detection

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Solution Overview

Problem

Pulse oximeters face challenges in reliably detecting 'probe-off' conditions due to factors like incorrect probe placement, interference from nail polish, and motion artifacts, which can lead to erratic operation and misclassification of noise as a probe-off event.

Innovation Solution

Incorporating a third wavelength that is less penetrating through human tissue, such as green or blue light, to differentiate between proper attachment and misalignment by comparing the contrast ratio (CTR) across multiple wavelengths, allowing for more accurate detection of probe attachment status.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If only two wavelengths (660 nm and 940 nm) are used for pulse oximetry measurement, then the device complexity is low and the measurement is simple, but the reliability of probe-off detection is insufficient and false positives occur

Engineering Contradiction:

Improveprobe-off detection reliabilityVSAvoidnumber of light wavelengths

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The optical measurement is segmented into three distinct wavelength channels: two traditional wavelengths (660 nm red and 940 nm infrared) for hemoglobin measurement, and a third wavelength (e.g., 530 nm green) specifically for probe-off detection. This segmentation allows independent optimization of each wavelength's function, improving overall system reliability without significantly increasing complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A third wavelength light source and detector channel are introduced as an intermediary mechanism to mediate between the traditional two-wavelength pulse oximetry and the probe-off condition detection. This intermediary channel provides additional information that resolves the ambiguity in determining whether the probe is properly attached, eliminating false positives without requiring major system redesign

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If traditional two-wavelength pulse oximetry is used, then the device is cost-effective and simple to manufacture, but it cannot reliably distinguish between probe-off conditions and motion artifacts or noise

Engineering Contradiction:

Improvedetection accuracyVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The system dynamically adjusts the intensity of the third wavelength light source based on the detected signal levels. When motion artifacts or noise are detected in the traditional two-wavelength channels, the third wavelength channel provides dynamic compensation by comparing its signal characteristics, enabling reliable probe-off detection even in the presence of dynamic interference

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the optical parameter space by adding a third wavelength dimension to the measurement. This parameter change transforms the probe-off detection from a binary decision based on two wavelengths to a multi-dimensional analysis, improving detection accuracy while maintaining manufacturing simplicity through the use of standard LED technologies

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If the probe placement is not reliably verified, then the device operation is simple, but erratic operation occurs and false probe-off events are generated

Engineering Contradiction:

Improveoperation simplicityVSAvoidprobe attachment detection

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The third wavelength channel provides continuous feedback about probe attachment status independent of the traditional hemoglobin measurement channels. This feedback mechanism allows the system to distinguish between genuine probe-off conditions and artifacts caused by poor probe placement, motion, or noise, maintaining simple operation while improving reliability through additional verification

Inventive Principle:

Principle #23Feedback

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 approach significantly enhances the reliability of probe-off detection, reducing false positives and negatives, and is cost-effective due to its simplicity.

Implementation Method 1

light absorption by the tissue can be determined

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

Light transmission through an ideal absorbing sample is determined by the known Lambert-Beer equation as follows: Iout=Iine−sDC

Methodology Applied

Scientific EffectLambert-Beer law: Absorption (EM radiation)

Implementation Method 3

Pulse oximetry is at present the standard of care for the continuous monitoring of arterial oxygen saturation (SpO2)

Methodology Applied

Scientific EffectPulse oximetry: Absorption (EM radiation)

Data Source

PatentUS8126525B2Probe and a method for use with a probe

Publication Date: 2012.02.28 GE HEALTHCARE FINLAND

AI summary

The invention relates to a probe and a method for use with a probe, which produces signals indicative of the light absorption of arterial blood at least at a first light wave-length and at a second light wavelength. In order to indicate if the probe is not properly attached to a tissue site the method comprises measuring with at a third wave-length. The third wavelength is chosen so that human tissue is less transparent than at the first and second wavelengths.