The text was from Dr Ian Renfrew, an interventional radiologist at Barts Health NHS Trust in London, and it asked if anyone could help develop a ‘shield’ to prevent coronavirus particles from hospitalised patients reaching the medical workers caring for them.
As the head of programmes for manufacturing technology at Rolls-Royce, York knew exactly who could help. Members of his team are embedded at the Manufacturing Technology Centre (MTC) in Coventry, one of the country’s leading research and technology organisations. The dots started to join up.
“We had a phone call one evening. By about 12 o’clock the next afternoon we had a very, very Heath Robinson, hashed-together plastic model that we could talk around, and that’s when the design team started to put some meat on the bones,” says Danny McGee, chief engineer in advanced production systems at the MTC.
“The good thing with Danny’s team is they are really good, creative bunch of people. They are very good at sort of coming up with that conceptual engineering and literally walking around the MTC facilities there and just harvesting stuff… before you know it, it’s been taken off and borrowed,” says York.
The project, which also involves Dr Paolo Perella at Royal London Hospital and is supported by Innovate UK, was to build an Aerosol Generating Procedure (AGP) shield – in simple terms, a clear box to be placed around the upper half of patients being treated for Covid-19, giving medical staff access for ‘intubation and extubation’, or the insertion and removal of tubes for ventilation.
“If someone has been intubated and they cough, then obviously the droplets with the virus are carried, are expelled out, and without this box they go into the room. The box we’ve created captures the virus in a much smaller space,” says McGee.
Viral load
The shield started out as a square box, but the MTC’s first prototype revealed that a clear line of sight down the throat is critical for medical staff. The shape was adjusted to let doctors get as close as possible, and to see the path to get a laryngoscope down the patient’s airway. “There is a compromise between visibility and the ability to get implements in,” says McGee.
After the initial idea, a Tweet about the device got some attention. There was also some reticence, with concerns that the shield would simply concentrate the viral load and then release its contents when removed.
To tackle that issue the NHS doctors involved with the project contacted Arup, asking for some simulation expertise to prove the shield’s usefulness. The team, including IMechE fellow Dr Mohammad Tabarra, was contacted on Thursday before the Easter weekend.
“Although there was a long Easter weekend, they said ‘No, the NHS are working and we want to help,’” says Dr Tabarra.
The Arup experts – Amir Pournasr, Dr Ertan Hataysal and Edith Blennerhassett, alongside Dr Tabarra – used computational fluid dynamics to simulate the path of virus particles after a patient has coughed. The shield design also includes a placement position for a standard doctor’s suction tube, which can suck virus particles from the box. The team, which usually focuses on ventilation of underground rail tunnels, ran different simulations to find the ideal placement, and found it was having the tube standing vertically against one side of the box.
“We simulated for about eight minutes and the results were quite promising, that some 90% of particles of all sizes had been removed… so that was quite encouraging,” says Dr Tabarra.
The team ran further simulations, using different methods to prove the design’s success. They found that heavier virus particles that are similar in weight to water droplets stick to the sides of the box, while the suction tube removes smaller particles.
“It’s really a common sense idea, but you don’t get it until you’re in the thick of it,” says Dr Tabarra. “The doctors see patients who are coughing and sneezing. Even if they have their own garments on, it makes much more sense to contain the pollution at source. It’s a much smarter idea.”
Organic development
The MTC first partnered with Beacon International in Desborough, which built 120 PVC units from an early design. The CEO of Aston Martin then linked the team with nearby automotive supplier Multimatic, which is using vacuum forming to build the latest version in one piece. Earlier this week, 200 shields had been built and the team is making the designs open source for other manufacturers.
“It’s come out as a really good multi-disciplinary work,” says Dr Tabarra. “It’s a natural development, an organic development where everyone felt they could pitch in and help.”
The collaboration demonstrated throughout the project is “highly encouraging,” says York at Rolls-Royce. “It’s a completely different space for us but actually the principles are the same for any design, make, testing routine… you’re dealing with a clinical group describing things in terms of viral load and dealing with patients with certain symptoms and things like that, and that is quite technical as well. That was a challenge initially, but it’s quite apparent once you have got two pretty bright groups together you find a quick way of working.”
Frontline heroes
The consortium has an initial order for 250 shields, and dozens have already been trialled in 30 hospitals, delivered by a small fleet of Aston Martin SUVs.
As well as protecting staff during intubation and extubation, the device can speed up cleaning and turnaround between patients – a vital factor, both during and after the pandemic. With so many Covid-19 patients, many other surgeries and procedures have been delayed. Using the shield will help medical staff safely and efficiently deal with the backlog when the opportunity presents itself.
Dr Tabarra also stresses the simplicity of the device, which has “no instruments or gadgets”. Doctors use suction tubes in their work anyway, so can quickly adjust to using the shield.
“We are expecting orders and demand for this to go up,” says McGee. “The body for the design we have come up with could be used post-Covid. There are several other medical operations where this could be used as well.”
For now, the AGP shield can provide an extra layer of protection, and even comfort, for NHS staff who sorely need it. “Our driving factor behind all of this are these people who are called our frontline heroes,” says McGee. “This is our opportunity to give them our support and helping hand.”
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