VV ECMO Cardiac Output Measurement Using CO2 Mass Balance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for measuring cardiac output in patients undergoing veno-venous extracorporeal membrane oxygenation (VV ECMO) are invasive and often inaccurate, particularly in cases of high recirculation, which can lead to missed diagnoses of cardiac insufficiency and inadequate treatment.

Innovation Solution

A non-invasive method and apparatus for calculating cardiac output using carbon dioxide content measurements before and after an oxygenator in the extracorporeal blood oxygenation circuit, adjusting for recirculation by varying sweep gas flow rates and employing mass balance equations to determine cardiac output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If current standard methods (pulmonary artery thermodilution, transpulmonary thermodilution) are used to measure cardiac output, then cardiac output measurement is achieved, but the measurement becomes invasive and inaccurate especially at high recirculation levels

Engineering Contradiction:

Improvecardiac output measurement accuracyVSAvoidinvasiveness and measurement inaccuracy at high recirculation

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent uses carbon dioxide as an intermediary substance to measure cardiac output. By tracking CO2 removal rates in the extracorporeal circuit and using mass balance equations, the system calculates cardiac output without direct invasive measurement in the patient's cardiovascular system, thereby avoiding the harmful effects of invasiveness while maintaining accuracy even at high recirculation levels

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical/invasive measurement systems (thermodilution catheters requiring pulmonary artery access) with a biochemical measurement approach using CO2 content analysis. This substitution eliminates the need for invasive mechanical insertion while providing accurate cardiac output measurements through non-invasive blood gas analysis

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If recirculation occurs in the VV ECMO circuit, then oxygenated blood is returned to the patient, but some portion is withdrawn again without passing through the heart, reducing therapeutic effectiveness

Engineering Contradiction:

Improvetherapeutic effectiveness of oxygenationVSAvoidrecirculation loss of oxygenated blood

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent implements feedback by continuously measuring CO2 removal rates and using this information to calculate recirculation levels. The system uses mass balance equations that incorporate CO2 content measurements to determine the proportion of recirculated blood, providing real-time feedback on therapeutic effectiveness and enabling adjustment of ECMO settings to optimize oxygenation while minimizing recirculation losses

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

Provides accurate and non-invasive cardiac output measurement, enabling timely intervention for cardiac insufficiency and improving patient management during VV ECMO treatment.

Implementation Method 1

establishing a first removal rate of carbon dioxide from the blood in an oxygenator in the extracorporeal blood oxygenation circuit

Methodology Applied

Scientific EffectGas exchange: Diffusion

Data Source

PatentUS20250222184A1Calculating cardiac output of a patient undergoing veno-venous extracorporeal blood oxygenation

Publication Date: 2025.07.10 TRANSONIC SYSTEMS INC

AI summary

A system for calculating cardiac output of a patient on an extracorporeal blood oxygenation circuit, such as veno-venous extracorporeal membrane oxygenation, includes determining (i) a first arterial carbon dioxide content or surrogate and (ii) a first carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the first removal rate of carbon dioxide from the blood; establishing a second removal rate of carbon dioxide from the blood in the oxygenator in the extracorporeal blood oxygenation circuit; determining (i) a second arterial carbon dioxide content or surrogate and (ii) a second carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the second removal rate of carbon dioxide from the blood; and calculating a cardiac output of the patient corresponding to a blood flow rate through the extracorporeal blood oxygenation circuit, the first arterial carbon dioxide content or surrogate, the first carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the first removal rate of carbon dioxide from the blood; the second arterial carbon dioxide content or surrogate and the second carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the second removal rate of carbon dioxide from the blood.