Arup supports development of AGP shield for NHS frontline workers

Lessons from the underground 

Arup has considerable expertise in modelling how gases move. Our tunnel ventilation team have lent their expertise in Computational Fluid Dynamics (CFD), normally employed to simulate ventilation systems found in underground road and railway tunnels, to an innovative and important healthcare design project alongside doctors from the Royal London Hospital, the UK’s Manufacturing Technology Centre (MTC) and Rolls-Royce. Our team has used modelling techniques to replicate and measure the airflow patterns to reveal the likely trajectory of viral particles from COVID patients within a surgical setting.

These experiments have helped validate the effectiveness of a protective box, called an AGP (Aerosol Generating Procedure) shield that was manufactured to contain the viral load in a theatre environment collaboration with the MTC, Rolls-Royce, Dr Ian Renfrew, Consultant Interventional Radiologist at BARTS, Dr Paolo Perella, Anaesthetic Registrar at Royal London Hospital, and supported by Innovate UK.

By following patient breathing cycles at both normal, passive breathing rates and during episodes of coughing, the simulations were able to show how the virus in the air could be contained and removed, with additional work that optimised the location of the air extraction tube inside the shield box. Having the tube standing vertically against one side of the box, will maximise the capture of airborne particles, minimising the dispersion of the virus within the larger treatment room. Even with the correct PPE on, it makes much more sense to contain the virus at source using a shield.

Early models were based on assumptions and parameters from initial research by the team. Each iteration was refined with input from medical professionals and design changes to the box itself. The later simulations also discovered that heavier virus particles, similar in weight to water droplets, stick to the top and side surfaces of the box, while the suction tube effectively removes smaller particles. Our insights have resulted in improvements to the shield’s effectiveness for both clinical teams and patients alike.

One shield, many uses 

As with everything else in the response to the pandemic, work has been determined and rapid. The MTC has been receiving requests for a number of the shields, and dozens have already been trialed within hospitals.  

In addition to protecting hospital staff, the shield box has the potential to decrease cleaning times between patients, a vital factor to alleviate the consistent pressure on resources within hospitals and intensive care units during this pandemic. Treatments and surgeries not associated with COVID-19 have also been delayed following the outbreak. Implementation of the shield will help staff navigate this backlog effectively and efficiently post crisis. 

Additional potential uses for the AGP shield are also being investigated, including possible applications in dentistry and endoscopy where its use will be vital as these procedures are often carried out without the full benefit of sophisticated air handling capability that is found in operating theatres.