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Less aerosol emission from respiratory support than breathing, speaking or coughing

 
 
Respiratory support used to treat patients with severe COVID-19 are associated with less aerosol emission than breathing, speaking or coughing, suggests new research funded by NIHR and UKRI.

Patients with severe COVID-19 receive respiratory support and oxygen delivery with continuous positive airways pressure (CPAP) and high-flow nasal oxygen (HFNO). Both procedures are considered high-risk for generating aerosols from SARS-CoV-2, which are the primary vehicle for transmitting the coronavirus. However the study found that CPAP is associated with less aerosol emission than breathing, speaking or coughing, and that aerosol emission from the respiratory tract does not appear to be increased by HFNO.
 
Although direct comparisons are complex to make, the study suggests coughing appears to generate significant aerosols in a size range compatible with airborne transmission of SARS-CoV-2. This means the risk of SARS-CoV-2 aerosolisation is likely to be high in all areas with COVID-19 patients.
 
This information is vital to show how best to organise operating theatres, medical procedures, out-patient clinics, wards and use of protective equipment, in order to protect patients and staff while maximising the ability of the NHS to resume life-saving work.
 
Dr James Dodd, senior author on the respiratory area of the study, said: “We were delighted to work with world-leading aerosol scientists to design and deliver this study which provides much needed, high quality data on the risk of aerosol emissions when caring for patients with severe COVID-19.
 
“Our study has shown that the use of CPAP actually reduces aerosol transmission rather than increases it. Although direct comparisons are complex, cough appears to generate significant aerosols in a size range compatible with airborne transmission of SARS-CoV-2. This will inform policy makers on appropriate PPE and ventilation in different hospital settings and ultimately how we can best protect our patients and staff.”

AERosolisation And Transmission Of SARS-CoV-2 in Healthcare Settings (AERATOR)’ is funded by the NIHR and UKRI COVID-19 rapid response call and is led by researchers from the University of Bristol and North Bristol NHS Trust. The study received urgent public health status to support the research team to rapidly deliver the study. The findings from the study have been presented to the NIHR Aerosol Generating Procedures (AGP) Task and Finish Group that feeds into the AGP subgroup which reports to SAGE.

The study results have been published on the pre-print server medRxiv, so the research has not been through peer-review or published in a scientific journal.