̽��ֱ�� of Cambridge - Vilas Navapurkar

Air filter significantly reduces presence of airborne SARS-CoV-2 in COVID-19 wards

cjb250 — Tue, 16 Nov 2021 08:36:58 +0000

While the discovery could have implications for improving the safety of repurposed ‘surge wards’, the researchers say it also opens up the possibility of being able to set standards for cleaner air to reduce the risk of airborne transmission of infections.

Over the duration of the pandemic there has been a steady rise in the evidence that the SARS-CoV-2 virus can be transmitted through the air in small droplets (aerosols). But as hospitals have seen their capacity overwhelmed, they have been forced to manage many of their COVID-19 patients in repurposed ‘surge’ wards, which often lack the ability to change the air with a high frequency. While the use of appropriate personal protective equipment (PPE) protects staff and patients significantly reduces the risk of transmission, there are still reports of patient-to-healthcare worker transmission of the virus, potentially through the inhalation of viral particles.

A team at the ̽��ֱ�� of Cambridge and Cambridge ̽��ֱ�� Hospitals (CUH) NHS Foundation Trust investigated whether portable air filtration/UV sterilisation devices could reduce airborne SARS- CoV-2 in general wards that had been repurposed as a COVID ward and a COVID Intensive Care Unit (ICU). ̽��ֱ��results are published in Clinical Infectious Diseases.

Dr Vilas Navapurkar, a Consultant in Intensive Care Medicine at CUH, who led the study, said: “Reducing airborne transmission of the coronavirus is extremely important for the safety of both patients and staff. Effective PPE has made a huge difference, but anything we can do to reduce the risk further is important.”

“Because of the numbers of patients being admitted with COVID-19, hospitals have had to use wards not designed for managing respiratory infections. During an intensely busy time, we were able to pull together a team from across the hospital and ̽��ֱ�� to test whether portable air filtration devices, which are relatively inexpensive, might remove airborne SARS-CoV-2 and make these wards safer.”

̽��ֱ��team performed their study in two repurposed COVID-19 units in Addenbrooke’s Hospital. One area was a surge ward managing patients who required simple oxygen treatment or no respiratory support; the second was a surge ICU managing patients who required ventilation either through non-invasive mask ventilation or invasive respiratory support, such as involving the use of an invasive tube and tracheostomy.

̽��ֱ��team installed a High Efficiency Particulate Air (HEPA) air filter/UV steriliser. HEPA filters are made up of thousands of fibres knitted together to form a material that filters out particles above a certain size. ̽��ֱ��machines were placed in fixed positions and operated continuously for seven days, filtering the full volume of air in each room between five and ten times per hour.

In the surge ward, during the first week prior to the air filter being activated, the researchers were able to detect SARS-CoV-2 on all sampling days. Once the air filter was switched on and run continuously, the team were unable to detect SARS-CoV-2 on any of the five testing days. They then switched off the machine and repeated the sampling – once again, they were able to detect SARS-CoV-2 on three of the five sampling days.

On the ICU, the team found limited evidence of airborne SARS-CoV-2 in the weeks when the machine was switched off and traces of the virus on one sampling day when the machine was active.

Additionally, the air filters significantly reduced levels of bacterial, fungal and other viral bioaerosols on the both the surge ward and the ICU, highlighting an added benefit of the system.

First author Dr Andrew Conway Morris, from the Department of Medicine at the ̽��ֱ�� of Cambridge, said: “We were really surprised by quite how effect air filters were at removing airborne SARS-CoV-2 on the wards. Although it was only a small study, it highlights their potential to improve the safety of wards, particularly in areas not designed for managing highly infectious diseases such as COVID-19.”

Crucially, the research team developed a robust technique for assessing the quality of air, involving placing air samplers at various points in the room and then testing the samples using PCR assays similar those used in the ‘gold standard’ COVID-19 tests.

Professor Stephen Baker, from the Cambridge Institute of Therapeutic Immunology and Infectious Disease at the ̽��ֱ�� of Cambridge, said: “Cleaner air will reduce the risk of airborne disease transmission, but it’s unlikely to be the case that just installing an air filter will be enough to guarantee the air is clean enough. Every room and every situation will be different. A key part of our work has been developing a robust way of measuring air quality.”

Dr Navapurkar added: “We’re all familiar with the idea of having standards for clean water and of hygiene standards for food. We need now to agree standards for what is acceptable air quality and how we meet and monitor those standards.”

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

Reference
Conway Morris, A, et al. ̽��ֱ��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

Image: Dr Vilas Navapurkar in ICU beside an air filter

When a team of doctors, scientists and engineers at Addenbrooke’s Hospital and the ̽��ֱ�� of Cambridge placed an air filtration machine in COVID-19 wards, they found that it removed almost all traces of airborne SARS-CoV-2.

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

Vilas Navapurkar

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DNA test can quickly identify pneumonia in patients with severe COVID-19, aiding faster treatment

sc604 — Fri, 15 Jan 2021 06:00:00 +0000

For patients with the most severe forms of COVID-19, mechanical ventilation is often the only way to keep them alive, as doctors use anti-inflammatory therapies to treat their inflamed lungs. However, these patients are susceptible to further infections from bacteria and fungi that they may acquire while in hospital – so called ‘ventilator-associated pneumonia’.

Now, a team of scientists and doctors at the ̽��ֱ�� of Cambridge and Cambridge ̽��ֱ�� Hospitals NHS Foundation Trust, led by Professor Gordon Dougan, Dr Vilas Navapurkar and Dr Andrew Conway Morris, have developed a simple DNA test to quickly identify these infections and target antibiotic treatment as needed.

̽��ֱ��test, developed at Addenbrooke’s hospital in collaboration with Public Health England, gives doctors the information they need to start treatment within hours rather than days, fine-tuning treatment as required and reducing the inappropriate use of antibiotics. This approach, based on higher throughput DNA testing, is being rolled out at Cambridge ̽��ֱ�� Hospitals and offers a route towards better treatments for infection more generally. ̽��ֱ��results are reported in the journal Critical Care.

Patients who need mechanical ventilation are at significant risk of developing secondary pneumonia while they are in intensive care. These infections are often caused by antibiotic-resistant bacteria, and are hard to diagnose and need targeted treatment.

“Early on in the pandemic we noticed that COVID-19 patients appeared to be particularly at risk of developing secondary pneumonia, and started using a rapid diagnostic test that we had developed for just such a situation,” said co-author Dr Andrew Conway Morris from Cambridge’s Department of Medicine and an intensive care consultant. “Using this test, we found that patients with COVID-19 were twice as likely to develop secondary pneumonia as other patients in the same intensive care unit.”

COVID-19 patients are thought to be at increased risk of infection for several reasons. Due to the amount of lung damage, these severe COVID-19 cases tend to spend more time on a ventilator than patients without COVID-19. In addition, many of these patients also have a poorly-regulated immune system, where the immune cells damage the organs, but also have impaired anti-microbial functions, increasing the risk of infection.

Normally, confirming a pneumonia diagnosis is challenging, as bacterial samples from patients need to be cultured and grown in a lab, which is time-consuming. ̽��ֱ��Cambridge test takes an alternative approach by detecting the DNA of different pathogens, which allows for faster and more accurate testing.

̽��ֱ��test uses multiple polymerase chain reaction (PCR) which detects the DNA of the bacteria and can be done in around four hours, meaning there is no need to wait for the bacteria to grow. “Often, patients have already started to receive antobiotics before the bacteria have had time to grow in the lab,” said Morris. “This means that results from cultures are often negative, whereas PCR doesn’t need viable bacteria to detect – making this a more accurate test.”

̽��ֱ��test – which was developed with Dr Martin Curran, a specialist in PCR diagnostics from Public Health England’s Cambridge laboratory – runs multiple PCR reactions in parallel, and can simultaneously pick up 52 different pathogens, which often infect the lungs of patients in intensive care. At the same time, it can also test for antibiotic resistance.

“We found that although patients with COVID-19 were more likely to develop secondary pneumonia, the bacteria that caused these infections were similar to those in ICU patients without COVID-19,” said lead author Mailis Maes, also from the Department of Medicine. “This means that standard antibiotic protocols can be applied to COVID-19 patients.”

This is one of the first times that this technology has been used in routine clinical practice and has now been approved by the hospital. ̽��ֱ��researchers anticipate that similar approaches would benefit patients if used more broadly.

This study was funded by the National Institute for Health Research Cambridge Biomedical Research Centre.

Reference:
Mailis Maes et al. ‘Ventilator-associated pneumonia in critically ill patients with COVID-19.’ Critical Care (2021). DOI: 10.1186/s13054-021-03460-5

Researchers have developed a DNA test to quickly identify secondary infections in COVID-19 patients, who have double the risk of developing pneumonia while on ventilation than non-COVID-19 patients.

Using this test, we found that patients with COVID-19 were twice as likely to develop secondary pneumonia as other patients in the same intensive care unit

Andrew Conway Morris

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Lt. Cmdr. Michael Heimes checks on a patient connected to a ventilator at Baton Rouge General Mid City campus

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