Researchers used a novel xenon gas scan method to pick up lung abnormalities in coronavirus patients who have not been hospitalised but still experience breathlessness.
Breathlessness is a symptom in most long COVID patients, but it has been unclear whether this is linked to other factors such as changes in breathing patterns, tiredness, or something more fundamental.
The Explain study, a pilot study involving 36 patients, suggests there is significantly impaired gas transfer in the lungs to the bloodstream in long COVID patients – despite other tests including CT scans coming back normal.
“We knew from our post-hospital COVID study that xenon could detect abnormalities when the CT scan and other lung function tests are normal. What we’ve found now is that, even though their CT scans are normal, the xenon MRI scans have detected similar abnormalities in patients with long COVID,” said Fergus Gleeson, the study’s chief investigator.
“These patients have never been in hospital and did not have an acute severe illness when they had their COVID-19 infection. Some of them have been experiencing their symptoms for a year after contracting COVID-19,” said Gleeson, who is also a professor of radiology at the University of Oxford and consultant radiologist at Oxford University Hospitals NHS Foundation Trust.
The professor said there were important questions to answer such as how many patients with long COVID will have abnormal scans, the significance of the abnormality that has been detected, the cause of the abnormality, and its longer-term consequences.
“Once we understand the mechanisms driving these symptoms, we will be better placed to develop more effective treatments,” Gleeson said.
The study, which involves teams from Sheffield, Oxford, Cardiff and Manchester, had 36 participants split into three groups. The full study will recruit around 400 participants.
Emily Fraser, Respiratory Consultant who leads the Oxford Post-COVID Assessment Clinic, said these are interesting results and may indicate that the changes observed within the lungs of some patients with long COVID-19 contribute to breathlessness.
“However, these are early findings and further work to understand the clinical significance is key. Extending this study to larger numbers of patients and looking at control groups who have recovered from COVID should help us to answer this question and further our understanding of the mechanisms that drive long Covid,” Fraser said.
Professor Jim Wild, head of imaging and professor at the University of Sheffield, said Xenon MRI was uniquely placed to help understand why breathlessness persists in some patients post COVID-19 infection.
“Xenon follows the pathway of oxygen when it is taken up by the lungs and can tell us where the abnormality lies between the airways, gas exchange membranes and capillaries in the lungs.
“This multicentre study is very exciting, and I really look forward to it helping translate lung MRI methods that we have developed further towards clinical use in the UK,” Wild said.
“More than a million people in the UK continue to experience symptoms months after having COVID-19, with breathlessness one of the most commonly reported symptoms. This early research is an important example of both the committed effort the UK research community is taking to understand this new phenomenon, and the world-leading expertise that community contains,” said Professor Nick Lemoine, Chair of NIHR’s Long Covid funding committee and Medical Director of the NIHR Clinical Research Network.
The study received government funding and is being supported by the National Institute for Health Research’s (NIHR) Oxford Biomedical Research Centre. Its findings, which have not been peer-reviewed, were posted on the bioRxiv pre-print server.