Nasal-Oral Cannula Partition Wall for Accurate Exhaled Gas Sampling
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Solution Overview
Problem
Existing nasal/oral cannulae suffer from void volumes that cause turbulence and backflow, leading to inaccurate analysis of exhaled gases, and conventional manufacturing methods are limited by material stiffness, complexity, and assembly issues.
Innovation Solution
A nasal/oral cannula design with a gas-tight inner wall adjacent to the inlet minimizes void volume, ensuring a smooth, laminar gas flow, combined with a manufacturing method using injection molding and solvent bonding for flexible production of various shapes and sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional nasal/oral cannulae are used for collecting exhaled gases, then the cannula structure is simple and easy to manufacture, but void volumes create turbulence and backflow that decrease the accuracy of gas analysis
Solution Approach 1:
The cannula is divided into multiple functional segments: a tubular body for gas collection, an internal partition wall separating inhalation and exhalation pathways, and distinct inlets/outlets for each function. This segmentation eliminates void volumes and prevents turbulence by creating dedicated flow paths for inhalation and exhalation gases, thereby improving measurement precision without excessive complexity
Solution Approach 2:
Different regions of the cannula are designed with different structural qualities: the tubular body has a smooth interior for laminar flow, the partition wall creates sealed compartments to eliminate dead spaces, and the inlet/outlet regions are optimized for gas entry and exit. This local optimization ensures smooth gas flow and accurate analysis while maintaining manufacturing feasibility
2Ease of operation
If stiff materials are used in cannula manufacturing, then the cannula maintains structural integrity, but the cannula is uncomfortable for patient use and difficult to adapt to different shapes and sizes
Solution Approach 1:
The material properties are optimized by selecting polymers with appropriate flexibility parameters that balance comfort and structural integrity. The injection molding process parameters (temperature, pressure, cooling rate) are adjusted to produce cannulae with the desired degree of flexibility while maintaining sufficient strength for structural integrity and patient comfort
3Productivity
If injection molding is used for manufacturing cannulae, then production efficiency is high and various shapes and sizes can be produced, but the process requires precise control of molding parameters to avoid defects
Solution Approach 1:
The mold design incorporates preliminary features such as appropriate gate locations, runner systems, and cooling channel configurations that are optimized before production begins. This preliminary optimization of the molding setup reduces the need for precise parameter adjustments during production, enabling high productivity while maintaining manufacturing precision through pre-engineered mold features
Data Source
AI summary
A nasal/oral cannula for collecting a flow of exhaled gases and its method of manufacture are disclosed. The cannula comprises an elongated tubular body having a first and a second end portion, a surface and an internal volume; a wall internally disposed within said tubular body, said wall defining a first subvolume of said internal volume in the lengthwise direction of the tubular body; and an inlet through said surface, for introducing exhaled gases into said first subvolume. The first end portion defines an exit port for exhaled gases from said subvolume, and said wall is arranged directly adjacent to said inlet.