Introduction  ¹²⁹Xe MRI provides sensitive measures of pulmonary function and microstructure and may be useful in monitoring disease progression.

Objective  To assess longitudinal changes in lung function and microstructure over a year in patients with asthma and/or COPD with ¹²⁹Xe MRI and pulmonary function tests (PFTs).

Methods  Patients with asthma and/or COPD taking part in the NOVELTY study [NCT02760329] were recruited from primary care and assessed post-bronchodilator with ¹²⁹Xe MRI (ventilation, acinar dimensions and gas transfer) and PFTs (spirometry, body plethysmography and gas transfer) at 2 visits 1 year apart.

Results  136 patients, aged 28?82 years, with asthma (72), asthma+COPD (41) or COPD (23) were assessed (60 weeks apart on average). Gas transfer decreased from visit 1 to visit 2; ¹²⁹Xe red blood cell/membrane (RBC/M) V1 = 0.321, V2 = 0.299, p<0.0001; transfer factor of the lung for carbon monoxide (TLco) z-score V1 = 0.028, V2 = -0.293, p<0.0001. MRI ventilation defect percent (VDP) increased from visit 1 to visit 2; VDP V1 = 4.2%, V2 = 4.5%, p=0.0027. Acinar dimensions, FEV₁ and residual volume (RV)/ total lung capacity (TLC) did not change between visits. Changes in VDP and TLco were greater for patients with COPD than patients with asthma; ?VDP COPD = 4.0%, asthma = -0.1%, p = 0.013, ?TLco z-score COPD = -0.500, asthma = -0.161, p = 0.013.

Conclusions  Gas transfer and ventilation worsened in patients with asthma and/or COPD over a period of 1 year, and changes were greater in patients with COPD than patients with asthma. No changes in acinar microstructure, FEV₁ or RV/TLC were detected over 1 year.