The EXPLAIN study has used hyperpolarised xenon MRI scans to uncover evidence of lung damage in a small group of people who were not hospitalised with Covid-19 yet continue to experience breathlessness long after initial infection. These abnormalities had previously not shown up on standard Computed Tomography (CT) scans.
The work builds on an earlier study that used the same cutting-edge method of imaging to find persistent lung abnormalities in patients who had been admitted to hospital with Covid-19 several months after they were discharged.
Hyperpolarised xenon MRI is a safe scanning test that requires the patient to lie in the MRI scanner and breathe in one litre of the inert gas xenon that has been hyperpolarised so that it can be seen using MRI. As xenon behaves in a very similar way to oxygen, radiologists can observe how the gas moves from the lungs into the blood stream. The scan takes just a few minutes and, as it does not require radiation exposure, it can be repeated over time to see changes to the lungs.
These initial results show that there is “significantly impaired gas transfer” from the lungs to the bloodstream in these long COVID patients when other tests are normal.
DPAG Postdoctoral Research Scientist Dr James Grist, who has been running the scans and image analysis, said: “It’s real breakthrough that we can detect abnormalities in gas handling in the lungs of people that have never been hospitalised with COVID, yet now suffer from long COVID, in particular breathlessness. We cannot seem to find anything wrong on their normal CT scans, and yet here we can clearly see that there is something not right with our imaging technique. This is particularly useful because it may start to shed some light on why some people experience the symptom of breathlessness long after COVID, and will allow us quantitatively measure the effect of any therapies used to try and reverse this.”
Long Covid refers to a host of symptoms that continue for many weeks after a coronavirus infection and cannot be explained by another cause. 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.
A larger, more detailed study is under way to confirm the results. The full EXPLAIN study, supported by the NIHR Oxford Biomedical Research Centre (BRC), will recruit around 400 participants: 200 long COVID patients with breathlessness, along with 50 patients who have had COVID-19 but now have no symptoms at all; 50 patients who have no breathlessness, but do have other long COVID symptoms, such as ‘brain fog’; and 50 people who have never had long COVID who will act as controls for comparison. It is one of 19 studies that have received nearly £40 million investment from the National Institute for Health Research (NIHR) to improve understanding of long COVID, from diagnosis and treatment through to rehabilitation and recovery.
More information about the study and can be found on the NIHR Oxford BRC website.