COVID-19: Looking at different ways in which aerosol research can support the fight against COVID-19
As Director of the EPSRC Centre for Doctoral Training in Aerosol Science and the Bristol Aerosol Research Centre, Professor Jonathan Reid’s approach to tackling COVID-19 is, naturally, focused on aerosols. ‘Aerosols’ is a term that is used to refer to a collection of particles that are airborne and with sizes typically smaller than the diameter of a human hair. When we speak, breathe, cough or even sing, we generate hundreds of these particles that someone else could breathe in, transmitting the virus responsible for COVID-19.
A key piece of work from Professor Reid has shown that there is significantly less risk of COVID-19 transmission from anaesthesia procedures than was previously thought. This is an important finding at a time when many operations and NHS procedures have been postponed or cancelled, causing problems for patients in the UK.
Since the outset of the COVID-19 pandemic, there has been much debate about the danger to hospital staff from anaesthetic procedures. Concerns include that inserting a tube in the patient’s airway (intubation) before surgery or removing it at the end (extubation) may produce a fine mist of small aerosol particles and spread the COVID-19 virus to nearby staff.
This risk was judged so high that the procedures are classified ‘aerosol generating procedures’ (AGPs) for which respirators and high-level personal protective equipment (PPE) are worn routinely, and after which surgery stops while the operating room is cleared of aerosols and special cleaning is undertaken. These requirements have dramatically slowed surgery and contributed to increases in NHS waiting lists for surgery, with similar problems in hospitals worldwide. Despite the presumed risk, no direct measurements of aerosols have ever been made during these potential anaesthetic procedures.
In a paper published in Anaesthesia(1) Professor Reid and fellow researchers at Bristol have shown that anaesthetic procedures may only produce a fraction of the aerosols previously thought, much less than would be produced during a single regular cough. This now brings into question whether the procedures should in fact be designated AGPs. These results should help inform future PPE guidelines by providing evidence on the relative risk of aerosol generation associated with tracheal intubation and extubation.
For safety reasons, this study was not performed on patients with COVID-19, but on other patients to demonstrate the aerosols produced during these procedures which are common during anaesthesia and in intensive care. While the evidence around aerosol generation during these procedures is reassuring, the risk of SARS-CoV-2 transmission has not been directly studied. The team’s interpretation rests on the widely accepted link between aerosol generation and infection risk. The paper detailing these research results has gone to the UK government, with the expectation that the information will support further studies and a change in guidance around AGPs. In the meantime, the team has moved on to doing similar work but looking at dental surgeries and orthopaedic operations.
‘Very few other universities are as collaborative as Bristol. I’m proud to have been part of a wider team working on almost every aspect of the pandemic.’
In another study led by Professor Reid – himself a keen singer and choir member – collaborative research has shown that singing does not produce substantially more respiratory particles than when speaking at a similar volume. These findings are crucial in providing COVID-19 guidance for live musical performances and the safe distancing of performers and audience. The performing arts have been badly affected during the coronavirus pandemic with live musical performances cancelled for many months because singing was identified as a potential higher-risk activity. This study was influential in changing government guidance on performance and opened up some elements of performing. The study has now been extended for a further 12 months.
In Professor Reid’s most recent work a team of researchers is suspending the virus in an aerosol to see how long it remains infectious for, working within a containment level-three laboratory designed to handle bacteria and viruses that cause severe human disease. They are also measuring how much aerosol a patient emits while infected with COVID-19 and whether this varies depending on the stage of the disease progression. This has implications for the current pandemic guidelines and especially rules around social distancing. It has been believed that COVID-19 is passed on through droplets released from the nose and mouth during activities such as breathing or coughing, where the droplets fall rapidly to the ground. However, there is a growing school of thought that in fact the virus may remain in aerosol droplets and collect in places that may be poorly ventilated. Professor Reid’s work in this field is expected to further inform government policy.
Reference
(1) Brown, J., Gregson, F. K. A. , Shrimpton, A., Cook, T. M., Bzdek, B. R., Reid, J. P., and Pickering, A. E. (2020) ‘A quantitative evaluation of aerosol generation during tracheal intubation and extubation’, Anaesthesia, 76(2), p174-181. doi: 10.1111/anae.15292.