Authors

Abstract:

Based on the ineffectiveness of N95s in high-risk environments (e.g. ICUs) and the shortage of PAPR technology, paPURE has designed a 3D printable solution to solve current and projected shortages in PAPR (Powered Air Purifying Respirators) devices for frontline healthcare providers. Our solution is highly scalable and adaptable to pre-existing technology in hospitals. It can be rapidly made in-house both simply and affordably, making it highly accessible.

I. Problem Overview / Relevant Clinical Background

Powered, air-purifying respirators (PAPRs) are currently the gold standard in medicine when treating patients diagnosed with COVID-19 and other highly infectious respiratory diseases[1] due to their positive pressure system that filters air extremely effectively before it reaches their airway. However, this technology package is costly, totalling $2000, if not more.[2] Additionally, PAPRs require highly specific motors, batteries and air filters, which are currently in short supply. Both well-established hospitals such as the Mayo Clinic (4500 physicians to 200 PAPRs)[2] and smaller county hospitals such as the Hunterdon Medical Center (where not a single PAPR is available to physicians) are facing critical shortages of this personal protective equipment (PPE). These barriers render the technology inaccessible for an immense number of people on the front line and consequently leaves them far more vulnerable to infection.     Other alternatives to PAPR include N95s, surgical masks, and currently, homemade masks due to a worldwide shortage of PPE.[3] Although they provide a barrier against aerosols, standard and surgical N95s are easily compromised with an improper fit and have an assigned protection factor (APF) of ten4, while PAPRs have an APF of 25 to 1000, rendering the latter far more effective at protecting HCPs. Physicians also prefer PAPRs over N95s because PAPRs are reusable, easier to breathe through, do not require fit testing, and make them feel safe. Additionally, surgical masks and homemade solutions are not designed or certified to prevent the inhalation of small airborne contaminants, resulting in HCP sickness and in extreme cases, death.[1][5]

II. Proposed Solution

In order to provide purified air to those in the most high risk environments, we have developed a novel, inexpensive, accessible PAPR device that is lightweight and 3D printable within 24 hours. Printed using ABS, PLA, or other filaments, paPURE is mounted to the user’s hip and contains an accessible hobby motor, available batteries (rechargeable 4 AA batteries and/or 4 9V batteries), a 3D-printed compressor fan, and aluminium foil wires. Additionally, changing battery configurations alters fan speed to ensure optimal flow rate. This motor drives the compressor fan which, with the help of a fan shroud , pulls air through attached filter(s) and into an output channel. After passing through the fan, the air flows through a customizable hosing adapter, entering an available  mask (e.g. traditional, adpt. N95, etc.) (See Appendix 2.5). Through this accessible technology, HCPs are given access to pure positive pressure air systems (in which airflow serves to seal any gaps in masks, as well as reduce respiratory fatigue in HCPs), drastically decreasing their infection risk in areas such as ICUs and ERs. Even N95’s have proven ineffective due to high viral particle concentrations associated with common procedures. In addition to some sealing tape, the motor and batteries are easily available. The device’s customizability allows for interoperability with existing masks, filters, and hosing (See Appendix 3.1), allowing hospitals, and possibly surrounding hobbyists/machinists (regulatory dependent), to produce PAPRs for their physicians and nurses, thus protecting frontline HCPs. For images and procedures: See Appendix 1 and 2.

III. Use Case

The intended users of this product are frontline HCPs caring for those affected with highly virulent pathogens such as COVID-19. In ICUs and ERs, hospitals see a high concentration of COVID-19 patients. When medical professionals treat patients in these areas, they are exposed to a high viral load. To properly protect these frontline workers—from nurses to the doctors—it is paramount that they be equipped with the gold standard of PPE. paPURE aims to modify the current PPE that medical professionals use, by adapting existing masks to PAPR technology. With our technology, an HCP would don their mask, clipping the paPURE device to their belt, and connecting to the mask via a hose.  Following paPURE assembly, the medical professional will need to use sucrose (saccharine) spray to test proper device assembly.[6] At most, we expect setting up the paPURE to add 5-10 minutes to a medical professional’s routine, but it would greatly improve safety and comfort.

IV. Evidence for Functionality/Efficacy

We were able to validate the efficacy and functionality of our solution through research into current PAPR and respirator technologies, which our design was modelled after. PAPRs are highly recommended by NIOSH and OSHA for use in the presence of aerosol transmitted diseases,[2] such as COVID-19. Numerous studies have also cited PAPR as being highly effective when used in past epidemics such as the H1N1 and Ebola outbreaks.[2] The PAPR provides greater protection than alternatives due to the positive pressure environment it creates within a mask such that the mask requires no fit testing.[4, 7] Furthermore, literature supports the use of existing filters (HEPA/CBRN/P100) (see Appendix 2) as well as our self-constructed filter design (see Appendix 3), which was based on existing filter technology.[8] According to a study assessing indoor air filtration, any effective air filter must balance adequate ventilation, the ability to filter small particles, and cost-effective maintenance within its design.[8] Our self-constructed filter should only be used if existing options are unavailable. That being said, it should be able to meet all requirements and is reusable (with sterilization using a sodium chloride solution).[9] One of the major challenges typically associated with the use of PAPR in healthcare is its low battery life.[4] Our solution involves replacing the expensive and specific lithium batteries traditionally used in PAPRs with easily rechargeable AA and/or 9V batteries. By maximizing battery compatibility, paPURE is more durable and accessible to HCPs than the current PAPR technologies.  Preliminary testing and analysis of our solution corroborate our literary findings. After 3D printing our solution using PLA at 0.16 mm layer height and 10% infill density, water-hold testing was utilized to ensure the absence of water-leaking pores in the tested material for an interval of 30 minutes, with a longer interval planned for the future. Additionally, the implementation of 4 AA, 4 9V batteries, and a hobby motor into the printed design ensured a good fit and strength/weight distribution analysis. Setup for bacteriophage filtering efficacy is currently underway using  E. coli K12 lawns and T4 Phage.

V. Further Design / Testing Work Required

We must more thoroughly test the filtration capability of paPURE, the porosity of the 3D-printed solution, and the battery life and longevity of the prototype. Filter integrity testing—in which a mineral oil spray can be cleanly distributed over the filter on the outside, followed by traditional aerosol photometry—is well validated and has been used for over 70 years in HEPA filter testing in cleanrooms. The same test should allow us to observe our filter’s capability of filtering out small particles.[12] Air leakage (e.g. bubble test[13]) tests can be easily performed. Regarding the porosity of PLA, our 3D printing filament, and the fine particles emitted while printing, evidence[9][10] suggests that thorough washing or paraffin coating should resolve the issue. Further testing is required in regards to the ideal filament, not only for porosity, but also for accessibility in hospitals. Finally, due to location limitations throughout this pandemic, we are yet to run the prototype through its full lifecycle to measure battery life (run until ~80% airflow). It is important we also perform this test before distribution so HCP can plan for when to recharge the device. In terms of general testing, if we are able to validate these requirements, our device is projected to pass barriers to FDA approval.

VI. Implementation Plan

paPURE’s solution is implementable almost immediately. After the preliminary testing summarized above, the only barrier between our tested prototype and implementation is FDA approval. We have, however, identified conditions that will allow us to expedite the regulatory pathway (such as the 501(k) pathway suggested to us by regulatory experts).[15] paPURE uses the same technology as existing PAPRs (and non-3D printable components such as the motor are sold individually). Thus, taking advantage of our additive manufacturing model will allow us to accelerate FDA approval. Additionally, Prisma Health’s 3D-printed ventilator-splitter received emergency use authorization from the FDA,[16] and we have drawn parallels between Prisma Health’s technology and paPURE’s. Therefore, from a regulatory perspective, we don’t anticipate major regulatory challenges. Concerns have been raised by the FDA regarding safety of 3D-printed technology for medical use,[15] but because any particles emitted from our 3D print will be purified through a filter, these concerns aren’t relevant for our prototype. Our technology eliminates the need for a middle-man manufacturer. The only required components are readily available to hospitals and clinics, allowing HCPs to produce the device as per their need. Local schools or universities with 3D printers can accommodate a lack of 3D printers at some hospitals. After FDA approval, our CAD model and assembly instructions will be sent to hospitals and clinics, who could print and assemble the device (See Appendix 3.1). Players involved in the production of this technology would be hospital assembly workers, but the design is truly assemblable by anyone (the only limitation being that assembly be done under a fume hood to prevent contamination). Physicians we’ve already talked to will be taking our design to the board of directors and have given us promising feedback regarding the need for this technology. We are looking into potential partnerships with PPE developers (See Appendix 3.2) and/or motor manufacturers. From hospital purchasing experts have communicated a need for affordable PAPRs. Our solution is over 10 times cheaper than current PAPR technologies (See Appendix 3.3), increasing likelihood of adoption. Experts we’ve talked to anticipate a surge of cases within the next two to three weeks and are already facing shortages of PPE. This has accelerated our timeline, but we are confident that it is feasible given the current state of emergency (See Appendix 3.4). With the support of Johns Hopkins Center of Bioengineering Innovation and Design, we anticipate the rollout of our CAD model and Assembly instructions to hospitals and clinics by Wednesday, April 13th (week of April 19th at the latest), which would hopefully enable healthcare providers around the country to prepare themselves for the surge in COVID-19 patients before it occurs.

VII. Resources Needed for Completion

Due to the few resources that we require, our team has considerable potential for excelling in efficiently producing and distributing our product. We have access to materials needed to build, design, and initially test the prototype (i.e. 3D printer, Glovebox, Fusion360, etc.), maintaining accessibility. We may need assistance communicating this idea to hospitals (and schools or businesses with 3D printers if need be). We will need some assistance in developing instructions for assembly and use of our technology, as well as in optimizing our 3D model to reduce printing time. Financial and/or technical guidance to navigate the regulatory pathways to obtain FDA approval for our product will also be necessary. Some aforementioned aspects of the testing protocol require additional resources currently unavailable to us (e.g., helium testing, viral particles, photometer). We have accessed personal connections in the clinical and regulatory space, as well as at JHU through our BME Design Teams.

Appendix and Citations

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Website

paPURE Website

Hackathons

Technologies

3dprinting, cad, cpap, p100

Devpost Software Identifier

258184