Dual Cannula Nasal Sampling for Breath Gas Dilution
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Solution Overview
Problem
Existing methods for delivering medicinal gases, such as oxygen, to patients often result in dilution of exhaled breath samples, making it difficult to accurately measure components like carbon dioxide, especially at high flow rates, due to the physical limitations of conventional cannula designs and positioning of gas delivery and sampling cannulae.
Innovation Solution
A system comprising a gas delivery cannula and an exhaled breath sampling cannula, where the sampling cannula is positioned deeper in the nostril than the gas delivery cannula, with adjustable depth and multiple apertures to minimize gas dilution, and optionally includes a capnograph for measuring CO2 levels, allowing for accurate sampling even during high gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high flow rate gas delivery is used to treat respiratory conditions, then oxygen therapy effectiveness is improved, but exhaled breath sample dilution increases making measurements inaccurate
Solution Approach 1:
The system divides the nasal cavity into two distinct functional zones using separate cannulae: one for gas delivery and another for breath sampling. The sampling cannula is positioned deeper in the nasal cavity beyond the gas delivery cannula, creating spatial segmentation that prevents delivered gas from contaminating the breath sample. This allows high flow rate oxygen therapy to proceed while maintaining accurate capnographic measurements.
Solution Approach 2:
The exhaled breath sampling cannula acts as an intermediary element that retrieves breath samples from a location (deeper in the nasal cavity) that is shielded from the direct path of delivered gas. This intermediary sampling mechanism enables the system to obtain accurate breath measurements without interrupting high flow rate oxygen delivery to the patient.
2Quantity of substance
If gas delivery cannula is positioned to deliver oxygen effectively, then oxygen therapy is improved, but exhaled breath sampling accuracy deteriorates due to sample dilution
Solution Approach 1:
The system transitions from a single-dimension approach (one cannula performing both delivery and sampling) to a two-dimensiona lapproach (separate cannulae positioned at different depths along the longitudinal axis of the nasal cavity). By extending the sampling cannula deeper than the delivery cannula, the system creates a depth dimension that isolates the sampling zone from the gas delivery zone, preventing dilution while maintaining effective oxygen therapy.
3Device complexity
If conventional single cannula design is used, then device simplicity is maintained, but both gas delivery and breath sampling functions cannot be performed simultaneously without dilution
Solution Approach 1:
The system implements multi-functionality by equipping each cannula with specific optimized functions: the gas delivery cannula is optimized for oxygen delivery, while the exhaled breath sampling cannula is optimized for capnographic measurements. This functional differentiation allows both oxygen therapy and breath sampling to occur simultaneously without interference, transforming the system from single-function to multi-functional capability.
Solution Approach 2:
The dual-function requirement is resolved by segmenting the single cannula structure into two separate cannulae, each optimized for its specific function. The gas delivery cannula handles oxygen delivery while the sampling cannula positioned deeper in the nasal cavity handles breath collection. This segmentation eliminates the functional conflict that would exist in a single cannula design, enabling simultaneous operation of both functions.
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 system enhances the reliability of exhaled breath measurements by reducing gas dilution, enabling more accurate assessment of respiratory conditions and ventilation status, even during high-flow gas delivery.
Implementation Method 1
to reduce dilution of sampled exhaled breath by delivered gas
Implementation Method 2
Since infrared light was found to be absorbed particularly well by CO2, capnographs usually measure infrared absorption in the breath gasses, which indicates the level of CO2 in these gasses.
Data Source
AI summary
A system for sampling exhaled breath and for supply of a gas, the system comprising: a gas delivery cannula comprising at least one nasal prong for insertion into a nostril, the nasal prong comprising a distal end; an exhaled breath sampling cannula for insertion into the nostril, the exhaled breath sampling cannula comprising a distal end; and a connector for coupling the gas delivery cannula to the exhaled breath sampling cannula, such that the distal end of the exhaled breath sampling cannula is disposed deeper in the nostril than the distal end of the nasal prong, to reduce dilution of sampled exhaled breath by delivered gas. The connected is configured to facilitate adjustability of an insertion depth of the exhaled breath sampling cannula into said nostril.