Flexible HMX Frame for CPAP Mask Fit and Humidity Retention

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Solution Overview

Problem

Existing respiratory therapy devices and interfaces, such as CPAP masks, suffer from discomfort, poor fit, and reduced compliance due to inadequate seal-forming structures, cumbersome stabilizing mechanisms, and noise, which impact patient adherence to therapy.

Innovation Solution

A patient interface with a plenum chamber, seal-forming structure, and positioning and stabilizing structure that allows for a comfortable fit, uses a heat and moisture exchanger (HMX) to maintain therapeutic pressure and humidity, and includes a vent structure to minimize noise and discomfort, while allowing mouth exposure for ambient breathing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a seal-forming structure is used to maintain therapeutic pressure, then therapy effectiveness is improved, but patient comfort deteriorates due to poor fit and discomfort

Engineering Contradiction:
Improvetherapy effectivenessVSAvoidpatient comfort
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The headgear incorporates flexible elements including elastic bands and adjustable straps that allow dynamic adaptation to different patient head shapes and sizes. The stabilizing structure includes flexible positioning elements that can move and conform to accommodate patient movement and anatomical variations, maintaining both seal integrity and comfort throughout therapy.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The headgear allows adjustment of multiple parameters including strap tension, band elasticity, and component positioning to optimize both the sealing pressure and comfort level. The system enables parameter modification to suit different patient anatomies and preferences while maintaining therapeutic effectiveness.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If stabilizing mechanisms are added to improve fit, then patient compliance is improved, but device complexity increases

Engineering Contradiction:
Improvepatient complianceVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The headgear is divided into separate functional components including adjustable straps, elastic bands, and stabilizing elements that can be independently adjusted and maintained. This segmentation allows for simpler individual components rather than one complex integrated system, facilitating easier manufacturing and patient adjustment.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The headgear components serve multiple functions: the elastic bands provide both sealing pressure and stabilization, the adjustable straps facilitate both positioning and comfort, and the flexible elements accommodate both anatomical variations and patient movement. This multi-functionality reduces the need for separate dedicated components for each function.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Ease of operation

If noise is reduced to improve patient comfort, then compliance is improved, but device complexity may increase due to additional noise reduction components

Engineering Contradiction:
Improvepatient comfortVSAvoiddevice complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The flexible headgear components that were originally designed for comfort and fit adjustment also serve as natural acoustic dampeners. The elastic materials and flexible structures absorb and reduce noise generated by mask movement and breathing, converting potential harm (noise) into a benefit (noise reduction) without requiring additional active noise control components.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

4Ease of operation

If mouth exposure is allowed for ambient breathing, then patient comfort is improved, but seal integrity may be compromised

Engineering Contradiction:
Improvepatient comfortVSAvoidseal integrity
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The headgear and mask system incorporates dynamic elements that automatically adjust to maintain seal integrity regardless of mouth position. The flexible straps and elastic bands adapt their tension and positioning in response to patient movement and mouth opening, ensuring the seal remains effective whether the mouth is closed or open for ambient breathing.

Inventive Principle:
Principle #15Dynamics

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

Enhances patient compliance and comfort by reducing noise, improving fit, and eliminating the need for humidifiers and water reservoirs, thereby simplifying use and reducing device complexity and cost.

Implementation Method 1

The material is configured to adsorb water vapour from gases exhaled by the patient and desorb water vapour into the flow of air at the therapeutic pressure

Methodology Applied
Scientific EffectAdsorption: Adsorption

Implementation Method 2

the flow of air at the therapeutic pressure... is heated by heat released from the HMX material(s)

Methodology Applied
Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentEP4225411B1Heat and moisture exchanger with flexible frame for patient interface
Publication Date: 2025.11.26 RESMED PTY LTD
  • EP4225411B1 patent drawingFigure 1
  • EP4225411B1 patent drawingFigure 2
  • EP4225411B1 patent drawingFigure 3

AI summary

A patient interface may include a plenum chamber pressurisable to a therapeutic pressure, the plenum chamber further comprising two plenum chamber connectors; a seal-forming structure constructed and arranged to seal with a region of the patient's face; a positioning and stabilising structure comprising two conduits configured to connect to a corresponding one of the plenum chamber connectors; a vent assembly having a plurality of vent holes configured to allow a continuous flow of gases exhaled by the patient from within the plenum chamber to ambient throughout the patient's respiratory cycle; and a heat and moisture exchanger (HMX) assembly including an HMX frame and a material positioned on the HMX frame, the material being supported by the HMX frame such that at least a portion of the flow of air entering the plenum chamber from the plenum chamber connectors passes through the material before entering the patient's airways.