Variable Geometry Cannula for Airway Flushing
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Solution Overview
Problem
Conventional nasal cannulas struggle to maintain a high velocity of breathing gas flow at low volumetric flow rates, leading to suboptimal airway flushing, especially in non-hospital settings where high flow rates are not available, and require costly or confusing cannula size changes.
Innovation Solution
The development of nasal cannulas with variable geometry prongs that adjust their cross-sectional area in response to flow rate changes, incorporating shape memory materials or piezoelectric properties, and internal protrusions to introduce turbulence, ensuring constant velocity and effective flushing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the volumetric flow rate is decreased for patient comfort and reduced noise, then patient comfort is improved, but the velocity of the gas through the cannula is decreased, lowering the ability to flush the airways
Solution Approach 1:
The cannula incorporates a compliant distal end with radial slits that can dynamically change geometry in response to flow rate variations. At lower flow rates, the compliant material allows the distal end to collapse, reducing the cross-sectional area and maintaining gas velocity. At higher flow rates, the distal end expands to accommodate increased flow while preventing excessive velocity. This dynamic adaptation resolves the contradiction between patient comfort at low flow rates and adequate airway flushing velocity.
Solution Approach 2:
The invention changes the physical parameter of the cannula's cross-sectional area by incorporating a compliant distal end made of elastomeric or shape memory material. This material allows the cannula to automatically adjust its geometric parameters (cross-sectional area) in response to changes in flow rate, thereby maintaining relatively constant gas velocity across varying flow conditions without requiring manual intervention or multiple cannula sizes.
2Stress or pressure
If the cannula is sized properly for maximum flow rate to maintain reasonable pressure drop, then pressure drop is optimized, but at lower flow rates the velocity falls and causes suboptimal flush
Solution Approach 1:
The compliant distal end with radial slits creates a dynamically adjustable cross-sectional area that responds to pressure and flow rate changes. At maximum flow rates, the cannula maintains its full cross-sectional area to optimize pressure drop. At lower flow rates, the compliant material allows partial collapse of the distal end, reducing the cross-sectional area and maintaining gas velocity despite the lower overall flow, thus resolving the contradiction between pressure drop optimization and velocity maintenance.
3Ease of operation
If the cross-sectional area of the lumen is increased to reduce gas velocity for patient comfort, then patient comfort is improved, but the ability to flush the airways is reduced
Solution Approach 1:
Rather than using a fixed large cross-sectional area that would reduce velocity and flushing effectiveness, the invention employs a compliant distal end that dynamically adjusts the cross-sectional area based on flow rate. This allows the cannula to present a smaller effective area at low flow rates to maintain velocity for effective flushing, while providing a larger area at high flow rates to reduce velocity for patient comfort, thus resolving the contradiction between these two requirements.
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
These cannulas maintain high velocity and effective airway flushing at variable flow rates, improving patient comfort and efficiency, reducing energy consumption, and minimizing noise, while allowing for use with limited gas sources.
Implementation Method 1
incorporating shape memory materials or piezoelectric properties
Implementation Method 2
incorporating shape memory materials or piezoelectric properties
Implementation Method 3
internal protrusions to introduce turbulence
Data Source
Figure 1~3
Figure 4A~4B
Figure 5
AI summary
A cannula for providing respiratory therapy to a patient includes a first nasal prong having a proximal end attached to a cannula body and a distal end for insertion into a nare of the patient. The first nasal prong defines a lumen for a flow of breathing gas from a source of breathing gas to the nare of the patient, and the first nasal prong has a variable geometry such that a cross- sectional area of the lumen at the distal end of the first nasal prong varies with a flow rate of the breathing gas. Varying the cross-sectional area of the first nasal prong lumen with the flow rate of the breathing gas enables the first nasal prong to maintain a high velocity flow to the nare for effective flushing of the patient's airway.