The EXPLAIN study, which involves teams at Sheffield, Oxford, Cardiff and Manchester, is using hyperpolarised xenon MRI scans to investigate possible lung damage in Long COVID patients who have not been hospitalised with COVID-19 but who continue to experience breathlessness
Researchers have identified abnormalities in the lungs of Long COVID patients who are experiencing breathlessness that cannot be detected with routine tests.
The EXPLAIN study, which involves teams at Sheffield, Oxford, Cardiff and Manchester, is using hyperpolarised xenon MRI scans to investigate possible lung damage in Long COVID patients who have not been hospitalised with COVID-19 but who continue to experience breathlessness.
The study, which received government funding in 2021, is supported by the NIHR Oxford Biomedical Research Centre (BRC). The findings were published on the medRxiv pre-print server. A previous study had used the same cutting-edge method of imaging to establish that there were persistent lung abnormalities in patients who had been hospitalised 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 bloodstream.
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.
While the full EXPLAIN study will recruit around 400 participants, this initial pilot had 36 people taking part, consisting of three groups:
- Patients diagnosed with Long COVID, who have been seen in Long COVID clinics and who have normal CT (computerised tomography) scans
- People who’ve been in hospital with COVID-19 and discharged more than three months previously, who have normal or nearly normal CT scans and who are not experiencing Long COVID
- An age- and gender-matched control group who do not have Long Covid symptoms and who have not been hospitalised with COVID-19
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.
The method, development and clinical applications of hyperpolarised xenon MRI was pioneered by Professor Jim Wild and the Pulmonary, Lung and Respiratory Imaging Sheffield (POLARIS) research group at the University of Sheffield. The team performed the first clinical research studies in the UK and the world’s first clinical diagnostic scanning with this technology.
EXPLAIN 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.
The full EXPLAIN study will recruit 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.