CPAP Mask Vent Orifice Design for Noise Reduction
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Solution Overview
Problem
Current CPAP treatment systems for sleep disordered breathing suffer from excessive noise due to the washout vents, which can lead to non-compliance and discomfort for patients and their bed partners, and existing quiet vent designs face challenges in manufacturability, durability, and maintenance.
Innovation Solution
A vent assembly with surface characteristics such as roughening and scalloping on slotted vent apertures, featuring curvilinear shapes and a conic orifice design, is used to reduce noise by promoting turbulence and mixing of exiting gas with atmospheric air, thereby minimizing noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed vent design is used, then the vent is simple and inexpensive to make and operate, but the vent flow varies with mask pressure leading to excessive noise at high pressure
Solution Approach 1:
The patent applies a variable impedance vent design where the vent opening changes size based on mask pressure. At low pressure, the vent is larger to provide adequate washout flow, while at high pressure, the vent automatically closes or reduces to minimize turbulence and noise. This dynamic adjustment resolves the contradiction by maintaining simplicity while adapting to varying operating conditions.
Solution Approach 2:
The vent design changes its geometric parameters (opening size, shape) in response to pressure variations. The vent opening area is modified based on the operating pressure to optimize both washout effectiveness and noise reduction, transforming a static vent into a pressure-responsive structure that maintains optimal performance across different CPAP pressure levels.
2Object-generated harmful factors
If a variable vent design is used, then noise is reduced across a range of mask pressures, but the vent becomes difficult to manufacture, assemble, clean and maintain
Solution Approach 1:
The variable vent design uses a flexible diaphragm or movable component that automatically adjusts vent opening based on pressure differential. This dynamic mechanism reduces noise by providing appropriate vent flow at each pressure level while maintaining a relatively simple structure that can be manufactured using standard techniques, thus balancing noise reduction with manufacturability.
Solution Approach 2:
The patent employs a flexible membrane or thin-walled structure for the variable vent that can deform with pressure changes. This flexible approach allows the vent to adapt its opening size automatically, reducing noise without requiring complex mechanical assemblies, thereby improving ease of manufacture and cleaning while maintaining noise reduction benefits.
3Productivity
If the vent opening is enlarged to improve gas washout at low pressure, then washout flow is adequate, but noise increases at high pressure
Solution Approach 1:
The vent opening dynamically adjusts its size based on operating pressure. At low pressure, the opening is large to maximize washout flow and effectiveness. At high pressure, the opening automatically reduces or closes to minimize gas velocity and turbulence, thereby reducing noise. This dynamic adaptation allows the system to optimize washout performance across the entire pressure range without compromising noise levels.
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 proposed vent assembly effectively reduces noise levels during CPAP treatment, enhancing user comfort and compliance while being relatively inexpensive and easy to maintain, thus improving the affordability and effectiveness of CPAP therapy.
Implementation Method 1
A vent assembly with surface characteristics such as roughening and scalloping on slotted vent apertures, featuring curvilinear shapes and a conic orifice design, is used to reduce noise by promoting turbulence and mixing of exiting gas with atmospheric air
Data Source
AI summary
A washout vent for a mask for use with a system for supplying breathable gas pressurized above atmospheric pressure to an airway of a mammal for treatment of sleep disordered breathing, includes a solid mask section and a vent orifice extending through a thickness of the solid mask section and adapted for gas washout. The vent orifice includes opposed side walls providing a flow passage that allows gas to flow along the opposed side walls from an interior of the mask to atmosphere in use, and the opposed side walls defining at least a portion of a conic section having a length substantially greater than its width. The vent orifice includes an orifice inlet at the interior of the mask and an orifice exit open to atmosphere, and the opposed side walls converge from the orifice inlet to the orifice exit to reduce noise of gas washout.