Date: January 2024 (Published).
Source: International Society for Respiratory Protection (ICRP) Conference 2022 -Submission ID: 123.
Abstract: The effectiveness of respiratory protection against an inhalation hazard for a user is a function of the efficacy of the device, means for the user to access the right device, adherence with its use instructions, and a commitment by manufacturers to produce the needed products. N95 filtering facepiece respirators (FFRs) are made in discrete sizes, which are limited in accommodating the size, gender, and ethnic diversity in the user population. Additionally, the pressure exerted by the generally stiff edges of an FFR on the face can affect user comfort. The pressure can also change during use, potentially compromising the fit of the FFR Thus, there is a need to design and develop a respiratory protective device (RPD) customized to a user’s facial features, which (1) flexes and moves with facial movements during use, (2) continuously monitors fit, and, (3) when needed, alerts the user to adjust the device. Additionally, reusability of RPDs is an important consideration for maintaining supplies during diseases outbreaks.

The primary objective of this research has been to develop a next-generation custom-fit reusable respiratory protective device (RPD) with continuous fit monitoring by bringing together advancements in 3D digital scanning, flexible materials, additive manufacturing, fabric-based sensor networks, and application software. This capability would give the user confidence that the device has been donned correctly, is maintaining a good faceseal, and will provide the specified degree of protection. The customizability of such a device is intended to provide effective respiratory protection to a wide range of users, including children, for whom RPD designs are currently limited.

As the first step in customizing the prototype, a set of 21 facial anthropometric landmarks and 15 dimensions was selected for the design. Landmarks relevant to respirator fit were selected based on previous literature studies. The faces of three members of the research team were scanned using a 3dMD digital scanning system. From these scans, algorithms were developed to create digital representations of the contours of the RPD frame.

For fit monitoring, a fabric-based sensor network with five sensors distributed around the frame and placed at the interface with the user’s face was developed. The number of sensors in the network can be varied. Bench testing of pressure loads showed their responsiveness to increasing pressure loads. Algorithms were then developed to standardize the locations of the sensors and a data bus conduit in the RPD frame. To hold the sensors and data bus in their positions, a “covering piece” was designed to mate with the base RPD frame. An interlocking mechanism was created to enhance the fit between the base frame and the covering piece to hold the filter. Based on an in-depth evaluation of 3D-printable materials to effectively balance RPD custom fit with comfort, materials were chosen and physical prototypes produced. The fit monitoring sensor network was integrated into the prototype. Initial tests of prototypes demonstrated that the customized RPD continuously monitors fit and responds effectively to changes in facial movement during use.

Article: Next-Generation Custom-Fit Reusable Respiratory Protective Device with Continuous Fit Monitoring.
Authors: Dr. Sungmee Park, Ms. Yuanqing Tian – Georgia Institute of Technology; Michael Bergman, Dr. Ziqing Zhuang, Jonisha Pollard – CDC/NIOSH/NPPTL; Prof. Sundaresan Jayaraman – Georgia Institute of Technology.