Changes in magnetic resonance imaging scores and ventilation inhomogeneity in children with cystic fibrosis pulmonary exacerbations

Acute pulmonary exacerbations (aPEs) in patients with cystic fibrosis (CF) often result in incomplete recovery of lung function despite treatment, and are associated with lung function decline over time [1, 2]. Monitoring is therefore important to detect aPEs early and to track treatment responses. Recent studies testing pulmonary function with multiple breath washout (MBW) have shown that the Lung Clearance Index (LCI), the main outcome measure of MBW, is a sensitive tool to measure early changes in the CF lung [3, 4]. However, the potential role of MBW and LCI in more advanced CF lung disease is currently unclear. In fact, a recent study demonstrated heterogeneous responses in LCI, with a significant proportion of patients with CF showing worsening of LCI with treatment for aPEs [5]. Resolution of mucus plugging, resulting in recruitment of poorly ventilated areas of the lung to MBW, would potentially explain the discordant changes in pulmonary function testing by spirometry and LCI with treatment.