Kher Lik Ng, Laura Saunders, Guilhem Collier, James Grist, Nina Kainth, Victoria Harris, Laurie Smith, Scarlett Strickland, Lotta Gustafsson, Paul Hughes, Ionitiana Evans, Leizl Alvarez, Avianna Laws, Siby Thomas, Alberto Biancardi, Jennifer Rodgers, Samantha Jones, Demi Jakymelen, Martin Brook, Thomas Newman, Megan Plowright, Lily Dryhurst-Pearce, Amany Elbehairy, Kenneth Jacob, Anthony McIntyre, David Capener, Jonathan Bray, Marianne Durrant, Kylie Yeung, Huw Walters, Violet Matthews, Lisa Watson, Gavin Vuddamalay, Gabriele Abu-Eid, Viktorie Madhusudhan Stisova, Mark Cox, Maja Lachut, Nina Mulvey, William Hickes, Alexander Horsley, Helen Davies, Alfred A Roger Thompson, Fergus Gleeson, Jim Wild, Emily Fraser
Most nonhospitalised LC participants exhibited no detectable pulmonary abnormalities, including those with breathlessness. However, ∼13% of breathless individuals demonstrated minor reductions in T L CO and 129Xe-MRI gas exchange suggesting a potential pulmonary contribution for symptoms in this subgroup.
BACKGROUND: Breathlessness is a common symptom in long COVID (LC). Using hyperpolarised xenon magnetic resonance imaging (129Xe-MRI), we assessed whether this symptom could be attributed to abnormalities in the alveolar-capillary membrane not detected by standard investigations. We focused on never-hospitalised individuals without an identified cause for breathlessness.
METHODS: In this prospective, multicentre study, we compared 129Xe-MRI, lung function, exercise capacity and symptom questionnaires in LC patients with breathlessness (BLC) to those without breathlessness (NBLC) and healthy controls. Primary outcome was whether BLC demonstrated measurable impairments in gas exchange focusing on dissolved-phase 129Xe-MRI metrics: red blood cell to membrane ratio (RBC:M) and red blood cell to gas ratio (RBC:Gas). We also explored associations between symptoms and physiological measures.
RESULTS: Of 269 participants recruited, 196 were included in the analysis (109 BLC, 43 NBLC, 44 controls), with age and sex well matched across groups. BLC had a significantly longer interval from infection to MRI (median 632 days; p<0.001). No significant differences in global or regional RBC:M or RBC:Gas were observed across groups. BLC showed lower forced expiratory volume in 1 s, forced vital capacity, transfer factor of the lung for carbon monoxide (T L CO), and carbon monoxide transfer coefficient (K CO) z-scores compared to controls, though >90% of values remained within normal range. A subset of BLC participants with low T L CO (14 out of 109) showed reduced 129Xe-MRI metrics and higher breathlessness scores.
INTERPRETATION: Most nonhospitalised LC participants exhibited no detectable pulmonary abnormalities, including those with breathlessness. However, ∼13% of breathless individuals demonstrated minor reductions in T L CO and 129Xe-MRI gas exchange suggesting a potential pulmonary contribution for symptoms in this subgroup.