De Novo Powered Air-Purifying Respirator Design and Fabrication for Pandemic Response

Abstract

The rapid spread of COVID-19 and disruption of normal supply chains has resulted in severe shortages of personal protective equipment (PPE), particularly devices with few suppliers such as powered air-purifying respirators (PAPRs). A scarcity of information describing design and performance criteria for PAPRs represents a substantial barrier to mitigating shortages. We sought to apply open-source product development (OSPD) to PAPRs to enable alternative sources of supply and further innovation. We describe the design, prototyping, validation, and user testing of locally manufactured, modular, PAPR components, including filter cartridges and blower units, developed by the Greater Boston Pandemic Fabrication Team (PanFab). Two designs, one with a fully custom-made filter and blower unit housing, and the other with commercially available variants (the “Custom” and “Commercial” designs, respectively) were developed; the components in the Custom design are interchangeable with those in Commercial design, although the form factor differs. The engineering performance of the prototypes was measured and safety validated using National Institutes for Occupational Safety and Health (NIOSH)-equivalent tests on apparatus available under pandemic conditions at university laboratories. Feedback was obtained from four individuals; two clinicians working in ambulatory clinical care and two research technical staff for whom PAPR use is standard occupational PPE; these individuals were asked to compare PanFab prototypes to commercial PAPRs from the perspective of usability and suggest areas for improvement. Respondents rated the PanFab Custom PAPR a 4 to 5 on a 5 Likert-scale 1) as compared to current PPE options, 2) for the sense of security with use in a clinical setting, and 3) for comfort compared to standard, commercially available PAPRs. The three other versions of the designs (with a Commercial blower unit, filter, or both) performed favorably, with survey responses consisting of scores ranging from 3 to 5. Engineering testing and clinical feedback demonstrate that the PanFab designs represent favorable alternatives to traditional PAPRs in terms of user comfort, mobility, and sense of security. A nonrestrictive license promotes innovation in respiratory protection for current and future medical emergencies.

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“…The initial value of the test signal is the value of the PWM pulse width, which is supplied to the electronic speed controller, can be left zero (for the electronic speed controller of the brushless motor, this signal ranges from 800 μs to 2,300 μs at a frequency of 50 Hz) (Kothakonda et al, 2021). The final value of the test signal is selected considering the permissible value of the air pressure in the mask (up to 370 Pa, accordingly).…”

Mathematical model of air flow movement in a motorized filter respirator

“…One of such tasks is to ensure effective regulation of sup plying the necessary volume of air to the user, taking into ac count the pressure limitations in the MFR mask [5,6], based on changes in working conditions, the degree of physical exer tion on the user or their emotional state during the perfor mance of professional functions, contamination of MFR fil ters, and increase in their resistance to airflow [7,8], climatic conditions (temperature and humidity of the air) in the work ing area [9], and other parameters that characterize the influ ence on the quality indicators of RPE and may reduce their protective efficiency and level of comfort during the perfor mance of tasks of varying intensity [10].…”