A new pilot study has found abnormalities in the lungs of long Covid patients who had not experienced severe illness but experienced the symptom of breathlessness.

The Explain study used the gas xenon as part of MRI scans to investigate possible lung damage in the patients who had not been admitted to hospital, but continue to experience the symptom.

As part of the study patients were required to breathe in one litre of the gas which behaves similarly to oxygen in the lungs, so radiologists could observe how it moves from the lungs into the bloodstream.

The initial results of the study suggested there was significantly impaired gas transfer from the lungs to the bloodstream in the long Covid patients despite other tests including CT scans coming back as normal.

The study's chief investigator, consultant and Professor of Radiology at the University of Oxford Fergus Gleeson, said that similar abnormalities had been found in patients studied after having been in hospital.

"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.

"There are now important questions to answer. Such as how many patients with long Covid will have abnormal scans, the significance of the abnormality we've 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."

As these findings have not yet been peer reviewed, the Explain study will recruit about 400 participants to develop these early findings on a larger scale.