Impaired xenon gas transfer observed two years after COVID-19 hospitalisation in patients with signs of interstitial lung disease

Introduction: Interstitial lung changes persist in some patients after COVID-19 hospitalisation. Aim: To characterise longitudinal pulmonary changes due to COVID-19 using ¹²⁹Xe and ¹H MRI. Methods: Patients with abnormal CT or ¹H MRI underwent MRI and PFTs up to 106 weeks after hospitalisation. MRI protocol: ¹²⁹Xe gas transfer (key metric: red blood cell to membrane fraction, RBC:M), ¹²⁹Xe ventilation, lung perfusion and structural imaging. Longitudinal comparisons (24 vs 52 weeks) and correlations were assessed using Wilcoxon Signed Rank and Spearman9s rank. Results: 23 patients (median age: 68(range: 53-78) years, 87% male) underwent MRI at 23(6-33)(n=13), 54(42-71)(n=18) and 106(98-117)(n=7) weeks after hospital admission. Patients had decreased RBC: M compared to older controls and low transfer factor Z-score at 24, 52 and 106 weeks (median TLCOz<-2.2 at all visits). Ventilation defect percentage was <6% for all patients. There was no longitudinal change (n=8) in ¹²⁹Xe gas transfer or TLCOz between 24 and 52 weeks. There was a significant decrease in FEV1/FVC Z-score and an increase in FVC Z-score (p=0.018; p=0.043). At 24 and 52 weeks, RBC:M correlated with TLCOz (r=0.661, p=0.038; r=0.709, p=0.015). Conclusion: Xenon gas transfer remains impaired two years post hospitalisation in this cohort. Fig 1: RBC:M alongside healthy control data (57(41-68)years, 67% male).