Full Face Mask CO2 Rebreathing Reduction via Segmented Outlet
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Solution Overview
Problem
Full face masks for non-invasive mechanical ventilation suffer from significant CO2 rebreathing due to stagnation within the mask's rigid shell and increased volume caused by the ventilation tube, leading to elevated CO2 concentrations in the blood, which can result in serious health issues like hypercapnia.
Innovation Solution
A full face mask design featuring a transparent polycarbonate or copolyester shell with a thermoplastic elastomer gasket, a non-vented outlet fitting for CO2 evacuation, and a neckband with five attachment points to minimize CO2 stagnation and rebreathing without using anti-rebreathing valves that increase expiratory resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid plastic shell is used to receive the patient's face, then the mask structure is stable and can be sealed, but CO2 stagnation occurs inside the shell leading to high CO2 rebreathing
Solution Approach 1:
The mask shell is divided into separate functional zones: an inspiratory zone for fresh gas entry and an expiratory zone for CO2 removal. This segmentation allows independent optimization of gas flow paths, enabling CO2 evacuation through dedicated channels while maintaining structural stability of the overall mask assembly.
Solution Approach 2:
A neckband is introduced as an intermediary component between the mask shell and the patient's head. The neckband provides flexible adjustment and secure positioning without requiring the rigid shell to directly contact and conform to facial contours, thereby maintaining shell integrity while improving seal adaptability.
2Object-generated harmful factors
If anti-rebreathing valves are used to reduce CO2 rebreathing, then CO2 elimination is improved, but expiratory resistance increases worsening ventilation efficiency
Solution Approach 1:
The harmful CO2 is extracted from the mask interior through dedicated expiratory channels that provide a direct pathway from the expiratory zone to the external environment. This extraction system operates passively through pressure gradients and geometry-driven flow, eliminating the need for active valves that would impede breathing.
Solution Approach 2:
The mask utilizes pneumatic principles to drive CO2 removal through pressure differentials created during expiration. The expiratory channels are designed to exploit the natural pressure gradient between the expiratory zone and ambient atmosphere, enabling valveless CO2 evacuation that maintains low resistance to patient breathing.
3Reliability
If the ventilation tube section is extended to connect to the mask, then the connection is more secure, but the volume of CO2 stagnation increases
Solution Approach 1:
The ventilation tube connection is nested within the mask structure itself, with the tube integrated into the shell's internal geometry. This nesting eliminates the need for external extension tubes, securing the connection within the mask body while minimizing the additional volume that would contribute to CO2 stagnation.
4Stability of the object's composition
If five attachment points are used for the neckband, then the mask fixation is more stable, but the device complexity increases
Solution Approach 1:
The five attachment points are merged into a unified neckband system that distributes fixation forces across multiple locations. Rather than creating five separate adjustment mechanisms, the neckband integrates all attachment points into a single continuous structure that provides stable fixation while maintaining simplicity of adjustment.
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 mask significantly reduces CO2 rebreathing and associated health risks by effectively evacuating CO2 through a dedicated outlet fitting, as demonstrated by ventilation tests showing lower average CO2 re-breathed volumes and minimum inspiration concentrations compared to traditional masks.
Implementation Method 1
the outlet fitting (15) for the outlet of the air, rich in carbon dioxide, exhaled by the patient
Data Source
AI summary
A face mask (also called full face) for respiratory therapy, in particular for non-invasive mechanical ventilation, has a low value of CO2 rebreathing. The mask includes a shaped shell to cover at least the mouth, the nose and the eyes of a patient when the mask is worn, and includes, on said shaped shell an inlet fitting for the connection to a pipe through which a ventilation apparatus supplies the mask with a mixture of air and oxygen, and an outlet fitting, separate from said inlet fitting, for the discharge of air exhaled by the patient. With this arrangement, the mask allows drastically reducing the phenomenon of carbon dioxide rebreathing, which is very harmful for the patient subjected to ventilation.