Patient Interface Venting With Plenum Diffusers for Lower Noise
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Solution Overview
Problem
Existing patient interfaces for obstructive sleep apnea treatment using continuous positive airway pressure (CPAP) systems face issues with carbon dioxide accumulation due to washout vents, which cause noise and drafts, disrupting patients and their bed partners.
Innovation Solution
A patient interface with a ball socket or swivel joint component featuring a vent with specific geometric designs, including exit holes, plenum chambers, diffusers, and fibrous media to minimize noise and drafts by controlling gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If washout vents are provided to remove carbon dioxide accumulation, then gas venting function is improved, but noise and drafts are generated causing disturbance to patient and bed partner
Solution Approach 1:
The vent is divided into multiple small exit holes (e.g., 10-20 holes) arranged in an array rather than a single large opening. Each hole has specific dimensional ratios (length-to-diameter ratio of 2:1 or greater, pitch-to-diameter ratio of 4:1 or greater) to control gas flow patterns. This segmentation distributes the gas flow across multiple points, reducing individual jet velocity and resulting noise/draft while maintaining total venting capacity
Solution Approach 2:
A plenum chamber is introduced as an intermediary space between the exit holes and the external environment. The plenum chamber allows gas to expand and equalize pressure before discharge, and may contain fibrous media to further diffuse the flow. This intermediary structure transforms the direct high-velocity jets from individual holes into a more distributed, lower-velocity flow pattern that reduces noise and draft disturbance
2Object-affected harmful factors
If multiple exit holes are arranged in an array with specific geometric ratios, then noise and drafts are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies optimal parameter ranges for the exit holes (length-to-diameter ratio ≥ 2:1, pitch-to-diameter ratio ≥ 4:1, specific diameter ranges of 0.5-1.5mm) that balance performance and manufacturability. These parameter specifications provide clear design guidelines that achieve noise and draft reduction while remaining feasible with standard manufacturing tolerances for medical devices
3Object-affected harmful factors
If plenum chamber with fibrous media is used to diffuse gas flow, then noise and drafts are minimized, but device complexity increases
Solution Approach 1:
The vent components (exit holes, plenum chamber, and fibrous media) are integrated into a single molded piece where feasible, combining multiple functions into one component. The exit holes are directly formed in the plenum chamber walls, and the fibrous media is positioned within the plenum chamber space, eliminating the need for separate assemblies and reducing overall device complexity while maintaining the noise and draft reduction benefits
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 design effectively reduces noise and drafts by optimizing vent geometry and flow redirection, ensuring a consistent and predictable leak rate, enhancing user comfort and reducing disturbances.
Implementation Method 1
The diffuser can have an expansion angle of at least about 4 degrees and/or less than or equal to about 8 degrees. The length to root diameter ratio of the diffuser can be at least about 1.5 to 1.
Implementation Method 2
The plenum space can also contain a fibrous media.
Data Source
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AI summary
Interfaces for positive pressure therapy having various vent designs are disclosed herein. The interfaces include a bias flow vent with design geometries that help reduce and/or minimize draft and noise levels of the fluids exiting the vents. Some of the vent designs include particular vent hole geometries, plenum spaces, diffusers and fibrous media.