Additive manufacturing experts at the University of Sheffield Advanced Manufacturing Research Centre (AMRC) recently made crucial parts for a protective respirator prototype within a week to help a small design company develop novel PPE to keep clinicians safe while working in intensive care units (ICUs) battling to save the lives of Covid-19 patients.

The Bubble PAPR is a low-cost Powered Air-Purifying Respirator developed by Designing Science, a ‘med-tech’ design consultancy, working with clinicians at Wythenshawe Hospital, part of Manchester University NHS Foundation Trust (MFT), and specialists at Manchester University, to protect front-line healthcare staff during the resurgent Covid-19 pandemic.

The simple low-cost device consists of a re-usable collar that sits around the neck and a single-use plastic hood that can be easily recycled. The collar contains a fan to draw in air through a virus filter and delivers a cooling airflow around the face.

It is designed to be compatible with stringent infection control practices but be comfortable to wear for the duration of a shift in and intensive care unit (ICU), or other high-risk areas. The wearer’s face is also clearly visible to improve communication between staff and patients.

Rapid polymer prototypes for critical components including the Bubble PAPR’s ventilation system, impeller and fan housing, were created by Mark Cocking, the AMRC’s polymer additive technical lead at the Design and Prototyping Group, using funding from the High Value Manufacturing (HVM) Catapult to get the job done even quicker.

He said: “Designing Science approached us for assistance with additive manufacture (AM) design, material and process selection. As the request was in relation to development for advanced Covid-19 PPE it was essential to provide functional components in a reduced time frame.

“To do this we implemented a custom support solution using the FormLabs SLA platform with resin suited to the required mechanical properties. Because of the urgency of the request, we used a bank of printers to speed up the production.

“We were able to deliver an optimised AM print strategy enabling challenging, first-time print components to be delivered for testing by the customer within the week.”

Patrick Hall, managing director of Designing Science, said the AMRC’s expertise and rapid response allowed them to complete the design successfully. The project is one of hundreds that the AMRC and the HMV Catapult fund as part of their commitment to small- and medium-size UK businesses.

“It really helped to get us over a financial hurdle at a time when the project was under a lot of financial pressure. We needed advice on the design of a fan for use in our Powered Air Purifying Respirator (PAPR) but we also needed to create five sets of fan parts for our first prototypes to be used in evaluations at Wythenshawe Hospital.

“Unfortunately, we had very little funding. We approached the AMRC for help and the engineers there reviewed our fan design and offered advice; they also offered to 3-D build the parts for us at zero cost. It meant we were able to complete the design successfully; the AMRC delivered the parts and we were able to assemble them into our prototypes and successfully carry out the testing and launch the product.

“The AMRC team was really helpful and professional. Their breadth of experience and resources was of great help for us at a time when the project was under strain.”

Develop new solutions
The Bubble PAPR is a collaboration between MFT, Designing Science and the University of Manchester to identify unmet clinical needs and work collaboratively to develop new solutions.

Mr Hall, who has more than 30 years’ experience in product design and medical innovation, said: “Most current PAPRs are repurposed industrial devices not designed for clinical use and are expensive. We have taken a user-centred design approach to engineer and develop the Bubble PAPR to be as simple as possible while meeting key functional and ergonomic requirements.

“This means it can be easily and cheaply manufactured in large volumes so it can be made available right across the healthcare system, wherever clinical and support staff are interacting with patients who have confirmed or suspected Covid-19 or other serious infections.”

He explained how the PPE concept came to be. “Early on in the Covid-19 crisis we asked our long-time collaborator Dr Brendan McGrath, an intensive care consultant at Wythenshawe Hospital, whether there was anything Designing Science could do to help. The answer came back swiftly: ’design a better PAPR’.

“We began a crash programme to develop something better, and we quickly focused on the concept of a simple, head-worn device which minimised the exposure of re-usable parts to Covid-19 bearing aerosols by containing, nearly everything, within a disposable hood.

“Weeks of intensive iterative design and prototyping followed where we refined the concept, developing a custom impeller which could be driven by a 5V DC motor and capable of generating the flows we needed to keep the hood inflated and the wearer cool and ventilated.

“Donning and doffing PPE in Covid-19 wards is an exacting and intricate process which must be carried out with discipline. Lockdown restricted our user research to video-conferencing, but we were able to understand user and environmental needs and design a solution which supported good practice.”

The team had to overcome many design challenges to create a working design, such as regulations dictating the need for a low-flow indicator, but their intention to avoid electronics meant developing a mechanical solution. That led to the creation of the mechanical low-flow sensor, consisting of a handful of mechanical parts, which is sensitive enough to respond to reductions in airflow and alerts the wearer when flow drops below a threshold.

Mr McGrath, who has been the clinical lead throughout the development and testing process, said: “We have tested Bubble PAPR and we know it performs its primary function which is to protect staff against inhalation of airborne viruses.

“We have also now tested it in a simulated clinical environment. The reaction from staff has been overwhelmingly positive — they saw something that was not restrictive on their face, that allowed them to communicate with their colleagues, that was pleasant to wear and will allow them to interact with their patients.”

Dr Glen Cooper, programme director for Mechanical Engineering Design (School of Engineering), at the University of Manchester, said: “The Bubble PAPR is both ergonomically and mechanically the right product to meet the need to protect NHS staff during the Covid-19 crisis and beyond.”

A patent has been filed and the development team are now working with manufacturing partners to produce Bubble PAPR in large volumes and are also busy signing up distribution partners. The aim is to have it widely available for front line staff, before the end of 2020.