Capnography Cannula Oxygen Delivery and Breath Sampling
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Solution Overview
Problem
Existing capnography cannulas often mix oxygen with exhaled breath, leading to inaccurate carbon dioxide readings due to dilution, which can result in erroneous capnography analysis, especially when oxygen is supplied simultaneously with exhalation sampling.
Innovation Solution
The design of capnography cannulas with elongated oxygen delivery openings and a distribution section that separates oxygen inflow from exhalation outflow, ensuring oxygen is delivered symmetrically and evenly to the nostrils while preventing mixing with exhaled breath, using a cannula body with a prong lumen and oxygen delivery openings that face radially outward to enhance separation and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxygen is delivered through conventional cannula openings, then oxygen delivery is provided, but mixing with exhaled breath occurs leading to inaccurate carbon dioxide readings
Solution Approach 1:
The cannula is divided into functionally separate zones: an oxygen delivery region with openings positioned to deliver oxygen anteriorly, and an exhalation sampling region with a port positioned to capture exhaled breath posteriorly. This spatial segmentation prevents mixing between the two gas flows, ensuring accurate carbon dioxide measurements while maintaining effective oxygen delivery.
Solution Approach 2:
The invention utilizes the longitudinal dimension of the cannula by positioning oxygen openings and exhalation ports at different locations along the cannula's length. Oxygen is delivered through openings facing forward while exhalation is sampled through a port positioned posteriorly, creating spatial separation along the longitudinal axis that prevents gas mixing.
2Productivity
If oxygen delivery openings are made larger or more numerous, then oxygen delivery efficiency improves, but mixing with exhaled breath increases
Solution Approach 1:
The cannula incorporates multiple oxygen delivery openings distributed along its length, with each opening positioned in a region where oxygen flow does not interfere with exhalation sampling. This segmented arrangement allows increased total oxygen delivery while maintaining separation from the exhalation port, preventing dilution of the breath sample.
Solution Approach 2:
Different regions of the cannula are assigned different functions with optimized characteristics: anterior regions contain oxygen delivery openings configured for efficient oxygen supply, while posterior regions contain the exhalation sampling port. This local optimization allows high oxygen delivery efficiency in the anterior region without compromising measurement precision in the posterior region.
3Productivity
If oxygen flow velocity is increased, then oxygen delivery effectiveness improves, but mixing with exhaled breath increases causing dilution
Solution Approach 1:
The invention resolves the velocity-concentration conflict by separating oxygen delivery and exhalation sampling along the longitudinal dimension of the cannula. High-velocity oxygen flow is directed anteriorly through openings positioned away from the posterior exhalation port, allowing effective oxygen delivery without diluting the breath sample captured for analysis.
Data Source
AI summary
An example cannula may include a cannula body defining an exhalation lumen configured to receive a volume of exhalation from a patient. The cannula body defines an oxygen inlet at a surface of the cannula body. The cannula body defines a plurality of elongated oxygen delivery openings fluidically coupled to the oxygen inlet and being arranged and sized to deliver substantially symmetrical oxygen flow to nostrils of the patient.