Deformable CPAP Exhaust Vent for Stable Bias Flow
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Solution Overview
Problem
Current CPAP systems face challenges in maintaining a constant bias flow over a wide range of operating pressures, leading to noise and draft disturbances for patients and bed partners due to increasing carbon dioxide accumulation, which requires increased power consumption and physical dimensions in flow sources.
Innovation Solution
A bias flow control system with a valve configuration that includes a membrane with varying wall thickness and lobe structures, which constricts the flow opening as pressure increases, maintaining a relatively constant bias flow rate by altering the outlet and inlet geometries to regulate gas flow based on applied pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fixed dimension hole/array is used for washout vent, then carbon dioxide removal is enabled, but bias flow increases as CPAP pressure increases causing noise and draft disturbances
Solution Approach 1:
The patent employs a deformable membrane that dynamically changes its geometry in response to pressure variations. As CPAP pressure increases, the membrane deforms to constrict the flow opening, automatically regulating bias flow to remain relatively constant. This dynamic adaptation eliminates noise and draft disturbances while maintaining effective carbon dioxide removal across varying pressure conditions.
Solution Approach 2:
The invention changes the physical state and geometry of the vent opening through membrane deformation. The membrane transitions from a flat state at low pressure to a constricted state at high pressure, altering the flow characteristics. This parameter change enables the system to maintain constant bias flow despite pressure variations, resolving the contradiction between CO2 removal effectiveness and disturbance minimization.
2Object-affected harmful factors
If bias flow is increased to remove carbon dioxide, then carbon dioxide accumulation is countered, but physical dimension and power consumption of flow source increase
Solution Approach 1:
The deformable membrane vent operates passively, utilizing the existing CPAP pressure to regulate its own geometry and control bias flow. No additional power is required for the venting mechanism itself. The system self-regulates by allowing the pressure differential to naturally deform the membrane, thereby maintaining constant bias flow without increasing flow source power consumption.
Solution Approach 2:
The membrane acts as an intermediary between the CPAP pressure source and the exhaust flow. It mediates the relationship between pressure and flow by deformable geometry adjustment, enabling effective carbon dioxide removal while preventing the need for increased power consumption in the flow source.
3Object-affected harmful factors
If bias flow is increased to remove carbon dioxide, then carbon dioxide accumulation is countered, but physical dimension of flow source increases
Solution Approach 1:
The passive membrane-regulated vent eliminates the need for oversized flow sources. By using the existing CPAP pressure to deform the membrane and regulate flow, the system achieves effective carbon dioxide removal without requiring increased physical dimensions of the flow generating components.
4Ease of operation
If a deformable orifice is used to regulate flow, then constant bias flow is maintained, but the orifice may entirely collapse at high pressure
Solution Approach 1:
The membrane incorporates regions of varying wall thickness, creating local differences in structural rigidity. Thicker regions provide structural support to prevent complete collapse, while thinner regions allow sufficient deformability for flow regulation. This local quality variation enables the membrane to maintain its opening at high pressures while still achieving constant bias flow control.
5Strength
If wall thickness is increased to prevent orifice collapse, then structural integrity is improved, but flow regulation capability is reduced
Solution Approach 1:
The membrane features non-uniform wall thickness distribution, with thicker sections providing structural support and thinner sections enabling deformability. This local quality differentiation allows the membrane to simultaneously maintain structural integrity and achieve effective flow regulation across the full pressure range.
Solution Approach 2:
The membrane may utilize composite material structures combining materials with different mechanical properties. This composite construction enables simultaneous achievement of structural strength and controlled deformability, allowing the membrane to resist complete collapse while maintaining flow regulation capability.
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
This solution reduces variance in flow rate, minimizes noise and draft disturbances, and decreases the energy and size requirements of the flow source, enhancing the control over sound intensity and flow overhead in CPAP systems.
Implementation Method 1
A bias flow control system with a valve configuration that includes a membrane with varying wall thickness and lobe structures, which constricts the flow opening as pressure increases
Data Source
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AI summary
A patient interface includes a mask body, an elbow, a connector and a conduit. Any one or more of the mask body, the elbow, the connector and the conduit includes a bias flow vent. The bias flow vent is configured to deform with the application of pressure but not fully collapse such that an orifice size defined by the bias flow vent can vary with the application of pressure.