January 29, 2022

expert reaction to a preprint looking at lung abnormalities found in long COVID patients with breathlessness

A preprint, an unpublished non peer reviewed study, has looked at lung abnormalities found in long COVID patients with breathlessness.

Dr Jeremy Rossman, Honorary Senior Lecturer in Virology, University of Kent, said:

“This study by Grist et al. builds on recent work using hyperpolarized xenon gas MRI (Xe-MRI) to identify lung damage that may underly shortness of breath in Long Covid patients. In this new type of diagnostic imaging, patients breathe in xenon gas which allows the researchers and clinicians to assess the transfer of gas (i.e. oxygen) from the lungs to the blood vessels. Here the researchers found that in 7 of 11 non-hospitalised Long Covid patients, over 6-months from their initial infection, there was significantly reduced gas transfer (compared to healthy uninfected control participants), despite no evidence of lung damage seen by chest X-ray or CT imaging. A similar reduction in gas transfer was seen in previously hospitalised COVID-19 patients which is consistent with previously published Xe-MRI results from October. Unfortunately, the study did not examine gas transfer in recovered non-hospitalised patients, so we do not know if these defects in gas transfer are seen in all patients following COVID-19 infection, or just in patients with Long Covid or previous severe acute disease. In addition, this was a small study that looked only looked at 11 Long Covid patients and is a pre-print that has not yet been subjected to peer review, and so it is unclear how generalisable the results will be to the wider Long Covid community. 

“The biological mechanisms behind Long Covid disease are not known at present, though many data-driven hypotheses have been proposed. This study suggests that Long Covid patients have reduced oxygen transfer from lungs into the blood. The cause of this reduction is not clear from the current research but may be related to the presence of micro-clots or changes to blood vessel integrity. If this hypothesis is proven it may help to explain some aspects of Long Covid disease. Additionally, this current research highlights what many patients have experienced, that conventional diagnostic assays (e.g. chest X-ray and CT scans) do not identify damage in most Long Covid patients. This can result in incorrectly framing Long Covid as a psychological disease, with patients then struggling to obtain the care they need. New diagnostic methods, such as Xe-MRI, may help to identify the damage underpinning Long Covid, progressing our understanding of disease mechanisms and enhancing patient care.” 

Prof Colin Berry, Professor of Cardiology, University of Glasgow, said:

“This is an interesting finding and worth future study. Currently due to the small sample size, it should be considered as hypothesis generating at this stage. It is good that the authors are now expanding their study to include a larger number of patients including those without significant breathlessness alongside participants with prior proven COVID-19 infection who have fully recovered. This will help further our understanding of the cause of breathlessness in long COVID and whether these abnormalities play a role.”

Dr Louise Sigfrid, Clinical Research Fellow and Public Health Specialist, Centre for Tropical Medicine and Global Health, University of Oxford, said:

“These early findings are really interesting, and in line with other emerging data on lung perfusion defects post-SARS-CoV-2 infection seen in adults as well as adolescents (Buonsenso et al, 2021). 

“These preliminary findings further emphasis the need to ensure that adults and children who experience persistent symptoms following Covid-19 illness have access to comprehensive diagnostic assessments – informed by presenting symptoms, to inform care and support. 

“It also highlights an urgent need for further large scale studies including both adults and children to further our understanding of the aetiology behind the different clusters of long term Covid-19 sequelae documented,  to inform treatment trials and support strategies to improve long term Covid-19 outcomes.” 

Buonsenso et al: https://www.thelancet.com/journals/lanchi/article/PIIS2352-4642(21)00196-6/fulltext

The preprint: ‘The Investigation of Pulmonary Abnormalities using Hyperpolarised Xenon Magnetic Resonance Imaging in Patients with Long-COVID’ by James Grist et al. will be published at 00:01 UK time on Saturday 29 January, which is also when the embargo will lift.

Declared interests

None received.