Scientists have identified persistent damage in the lungs of COVID-19 patients at least three months after they were discharged from hospital, and for some patients even longer.
This damage was not detected by routine CT scans and clinical tests, and the patients would consequently normally be told their lungs are normal, according the researchers at the universities of Sheffield and Oxford in the UK.
The study, published in the journal Radiology, also shows that patients not hospitalised with COVID-19 but who experience long-term breathlessness may have similar damage in their lungs.
However, the researchers said a larger study is needed to confirm this.
They noted that hyperpolarised xenon MRI (XeMRI) scans had found abnormalities in the lungs of some COVID-19 patients more than three months -- and in some cases, nine months -- after leaving hospital, when other clinical measurements were normal.
"The findings of the study are very interesting," said Professor Jim Wild from the University of Sheffield.
The 129Xe MRI is pinpointing the parts of the lung where the physiology of oxygen uptake is impaired due to long standing effects of COVID-19 on the lungs, even though they often look normal on CT scans.
"Many COVID-19 patients are still experiencing breathlessness several months after being discharged from hospital, despite their CT scans indicating that their lungs are functioning normally," said Professor Fergus Gleeson, the study's principal investigator at Oxford.
"Our follow-up scans using hyperpolarised xenon MRI have found that abnormalities not normally visible on regular scans are indeed present, and these abnormalities are preventing oxygen getting into the bloodstream as it should in all parts of the lungs," Gleeson said.
The study has now begun testing patients who were not hospitalised with COVID-19 but who have been attending long COVID clinics.
"Although we are currently only talking about early findings, the XeMRI scans of non-hospitalised patients who are breathless -- and 70 per cent of our local patients with Long COVID do experience breathlessness --may have similar abnormalities in their lungs," Gleeson explained.
"We need a larger study to identify how common this is and how long it will take to get better," he added.
