Nasal Cannula with Inflatable Cuff for CO2 Washout

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Solution Overview

Problem

High flow oxygen therapy (HFOT) systems face inefficiencies due to turbulent gas flow patterns that lead to CO2 rebreathing, increasing dead space and the risk of hypercapnia, as high flow rates mix CO2 with incoming respiratory gases, causing it to recirculate into the airway.

Innovation Solution

A nasal cannula design with a distal end positioned between the nasopharynx and oropharynx, incorporating an inflatable cuff to seal the nasal passageway and a CO2-permeable membrane for sidestream monitoring, which facilitates laminar gas flow and reduces CO2 rebreathing by directing exhaled CO2 out through the mouth, while maintaining oral exhalation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high flow oxygen therapy is delivered to increase oxygen delivery, then oxygen delivery is improved, but turbulent gas flow causes CO2 rebreathing and increases dead space

Engineering Contradiction:

Improveoxygen deliveryVSAvoidCO2 rebreathing

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The airway is segmented into nasal and oral pathways. The nasal cannula delivers oxygen through the nasal passage while the oral passage remains open for exhalation. This segmentation allows separate optimization of oxygen delivery (nasal) and CO2 elimination (oral), preventing CO2 rebreathing while maintaining high flow oxygen therapy.

Inventive Principle:

Principle #1Segmentation

2Productivity

If high flow rates are used to improve oxygen delivery, then oxygen delivery is improved, but CO2 mixes with incoming respiratory gases causing recirculation

Engineering Contradiction:

Improveoxygen deliveryVSAvoidgas composition

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The system transitions from a single-pathway approach to a multi-dimensional airflow pattern. Oxygen is delivered through the nasal passage while exhaled CO2 is directed through the oral passage. This spatial separation in different dimensions prevents mixing of CO2 with incoming oxygen, maintaining stable gas composition despite high flow rates.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of operation

If a nasal cannula is used for oxygen delivery, then ease of operation is improved, but CO2 monitoring accuracy deteriorates due to turbulent flow and rebreathing

Engineering Contradiction:

Improvedevice simplicityVSAvoidCO2 monitoring accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

A CO2-permeable membrane is introduced as an intermediary between the patient's airway and the CO2 monitoring system. This membrane selectively allows CO2 to pass through while blocking other gases, enabling accurate CO2 monitoring without disrupting the high flow oxygen therapy or requiring complex sampling systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Productivity

If the distal end of the nasal cannula is positioned in the pharynx region, then CO2 washout is improved, but device complexity increases due to cuff and membrane components

Engineering Contradiction:

ImproveCO2 washout efficiencyVSAvoidcannula structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The nasal cannula is designed with multi-functionality: the distal end positioned in the pharynx region serves both oxygen delivery and CO2 washout functions; the inflatable cuff provides both sealing for CO2 prevention and anchoring; the CO2-permeable membrane enables both monitoring and facilitates CO2 removal. This multi-functionality reduces the need for separate devices while achieving multiple therapeutic goals.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 nasal cannula design improves CO2 washout and reduces rebreathing by promoting laminar gas flow, enhancing respiratory gas delivery efficiency and allowing for accurate sidestream CO2 monitoring during HFOT.

Implementation Method 1

a CO2-permeable membrane disposed on the distal end of the conduit. The CO2 permeable membrane is configured to selectively allow passage of CO2 gas from the patient's airway into the conduit during exhalation, wherein the CO2-permeable membrane is selectively permeable to CO2 relative to oxygen

Methodology Applied

Scientific EffectSelective permeability: Semipermeable Membrane

Implementation Method 2

incorporating an inflatable cuff to seal the nasal passageway

Methodology Applied

Scientific EffectInflation: Pressure Increase

Implementation Method 3

facilitates laminar gas flow and reduces CO2 rebreathing by directing exhaled CO2 out through the mouth

Methodology Applied

Scientific EffectLaminar flow: Laminar Flow

Data Source

PatentUS11478596B2System and method for high flow oxygen therapy

Publication Date: 2022.10.25 COVIDIEN LP

AI summary

A method of method of high flow oxygen therapy (HFOT) and carbon dioxide (CO2) monitoring includes delivering high flow oxygen therapy (HFOT) via a central lumen of a nasal cannula, the nasal cannula comprising a proximal end, a distal end positioned within a pharynx region of a patient's airway, and the central lumen and a sampling lumen formed within a wall of the nasal cannula. The method also includes receiving sampled exhaled breath of the patient via the sampling lumen at a CO2 monitor, wherein the sampling lumen is configured to sample the exhaled breath at the pharynx region through the CO2-permeable membrane and direct the sampled exhaled breath to a CO2 monitor fluidly coupled to the sampling lumen and determining a level of CO2 in the exhaled breath using the CO2 monitor.