Oxygen Consumption Determination Using Optical Gas Sensing

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Solution Overview

Problem

Existing systems for measuring oxygen consumption volume (VO2) are limited by size, cost, and accuracy, particularly at high FiO2 levels, where the Haldane transformation becomes ill-conditioned, leading to erroneous calculations and restricted usage in clinical scenarios.

Innovation Solution

A method and apparatus that determine VO2 by receiving indications of oxygen fractions in inhalation and exhalation gases, using a gas concentration sensing system with oxygen and carbon dioxide sensors to calculate VO2 through precise measurements of gas flow rates and fractions, improving accuracy and reducing the need for time-aligned oxygen concentration and gas flow waveform alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the Haldane transformation is used to calculate VO2 at high FiO2 levels, then the calculation can be performed with moderate equipment, but the accuracy deteriorates because the transformation becomes ill-conditioned

Engineering Contradiction:

Improveequipment simplicityVSAvoidVO2 calculation accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameters from relying on nitrogen volume assumptions (Haldane transformation) to directly measuring oxygen concentration in both inhaled and exhaled gases using optical sensors. This parameter change enables accurate VO2 calculation across all FiO2 levels, including high FiO2 where the Haldane transformation fails.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If expensive O2 sensors are used for breath-by-breath measurements, then VO2 measurement accuracy is improved, but system cost increases

Engineering Contradiction:

ImproveVO2 measurement accuracyVSAvoidsystem cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent employs inexpensive optical oxygen sensors that can be easily manufactured and replaced, eliminating the need for expensive conventional O2 sensors. These cost-effective sensors provide sufficient measurement accuracy for clinical VO2 monitoring applications.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces traditional mechanical/electrochemical O2 sensing systems with optical sensing technology. This substitution reduces sensor cost while maintaining measurement accuracy, making the overall system more affordable and manufacturable.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If high-frequency O2 concentration measurements are performed, then breath-by-breath VO2 measurement capability is achieved, but the requirement for precise time alignment of waveforms increases measurement complexity

Engineering Contradiction:

Improvemeasurement frequencyVSAvoidwaveform alignment complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent implements self-synchronized measurement where the optical sensors naturally capture oxygen concentration data synchronized with the respiratory cycle without requiring external triggering or complex time alignment algorithms. The measurement system automatically adapts to the subject's breathing pattern.

Inventive Principle:

Principle #25Self-service

4Device complexity

If FiO2 is manually input from ventilator settings, then the measurement system remains simple, but accuracy deteriorates due to estimation errors

Engineering Contradiction:

Improvesystem simplicityVSAvoidFiO2 accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces an optical sensing intermediary that directly measures oxygen concentration in the inhaled gas mixture, eliminating reliance on manual FiO2 input or ventilator setting estimates. This direct measurement approach provides accurate FiO2 values regardless of the delivery system used.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution enhances the accuracy of oxygen consumption measurements across various FiO2 levels, reduces system costs, and provides a compact, reliable method for VO2 determination, overcoming limitations of existing systems.

Implementation Method 1

an oxygen concentration sensor configured to determine a difference between an oxygen concentration level in a sampled inhalation gas and an oxygen concentration level in a sampled exhalation gas

Methodology Applied

Scientific EffectOxygen concentration sensing: Absorption Spectroscopy

Implementation Method 2

a gas flow sensor configured to provide an indication of a flow rate of the exhalation gas

Methodology Applied

Scientific EffectGas flow measurement:

Data Source

PatentUS11678815B2Oxygen consumption determination

Publication Date: 2023.06.20 KONINKLIJKE PHILIPS NV

AI summary

A computer-implemented method is described. The method includes receiving an indication and determining a subject's oxygen consumption based on the indication. The indication refers to an oxygen fraction in a sample of inhalation gas delivered by a ventilator for inhalation by a subject. The indication further refers to an oxygen fraction in a sample of exhalation gas exhaled by the subject. The indication further refers a measurement of a flow rate of the exhalation gas.