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80 new air filter machines to help reduce hospital infection

Pioneering research by Addenbrooke's has resulted in air filter machines being installed across the Trust to help reduce the risk of Covid infection for patients and staff.

The installation of 80 machines follows research carried out on Covid wards at Addenbrooke's Hospital in January 2021, at the height of the second wave of the pandemic.

The study found that air filter machines remove almost all traces of airborne Covid virus and other viruses, bacteria and fungi that are also known to cause infection.

An airfilter machine and Dr Vilas Navapurkar, who conceived and led the study

We have proved these machines dramatically reduce air borne infections so it makes sense to have many more of them

Andrew Turner, CUH engineer

Andrew Turner is an engineer at Cambridge University Hospitals NHS Trust (CUH) and was part of the research team, working alongside doctors and scientists from the University of Cambridge.

"For the initial study we used two air filter machines, but the results were so dramatic it made sense to get many more and use them across the Trust to help reduce outbreaks of infection. Now we have a total of 80 machines, most of them bought by the Trust but many also donated by manufacturers."

A number of air filters units have been installed in clinics where air borne infection is a particular risk, including endoscopy, maxillofacial and lung function

The majority however are designated to particular areas by the infection control team, and moved around the site to where they are most needed.

This includes general wards being converted to treat patients with Covid and the emergency department.

Each machine has cost the Trust around £5,000 alongside maintenance costs.

Reducing airborne transmission of the coronavirus is extremely important for the safety of both patients and staff

Dr Vilas Navapurkar, consultant in intensive care medicine at CUH
Covid ICU
An intensive care Covid ward at CUH during the height of the pandemic second wave, January 2021

Dr Vilas Navapurkar led the study and is a consultant in intensive care medicine at CUH.

He said: “Effective PPE has made a huge difference, but anything we can do that could reduce the risk further is important.”

“Because of the numbers of patients being admitted with Covid, hospitals have had to use wards not designed for managing respiratory infections. Our study showed that portable air filtration devices, which are relatively inexpensive, remove airborne SARS-CoV-2 and other micro organisms that cause infection which may make these wards safer.”

The research was supported by Wellcome, the Medical Research Council and the National Institute for Health Research Cambridge Biomedical Research Centre.

A further study is now underway to assess how effective air cleaning is at reducing infection risk.

The Addenbrooke's Air Disinfection Study (AAirDS) aims to build on the research so far, and is co-led by Dr Matthew Butler and Dr Victoria Keevil.

This next study is the first of it's kind in the world to combine genomics, electronic health data, patient outcomes, microbiological air sampling and indoor air quality

Dr Matthew Butler, CUH consultant

CUH consultant Dr Butler added:

“We know now that air filter machines can reduce the amount of infectious particles in the air. What we don’t know is how much that reduction translates into our risk of getting sick. For instance how much of any pathogen needs to be inhaled or be exposed to in order to infect us?

"AAirDS aims to begin to answer these questions and is the first study of its kind in the world to combine genomics, electronic health data, patient outcomes, microbiological air sampling and indoor air quality sensing to quantify the effect of air filters in a hospital setting.”

The study will be deploying air filter machines on two wards, caring for older people at Addenbrookes for a year.

This will give data on how effective air cleaning might be at preventing outbreaks with SARS-CoV2, the virus causing Covid, but also other respiratory viruses, MRSA, clostridioides difficile (C diff) and norovirus.

AAirDS is funded by the UK Health Security Agency (formerly Public Health England).

Conway Morris, A, et al. The removal of airborne SARS-CoV-2 and other microbial bioaerosols by air filtration on COVID-19 surge units. Clin Inf Dis; 30 Oct 2021; DOI: 10.1093/cid/ciab933

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