Bland–Altman comparison of lung clearance index (LCI) from multiple breath wash-out following open and modified closed circuit wash-in for both healthy controls and patients with cystic fibrosis (CF). #: open minus closed. Bland–Altman comparison of lung clearance index (LCI) from multiple breath wash-out following open and modified closed circuit wash-in for both healthy controls and patients with cystic fibrosis (CF). #: open minus closed. Alex R. Horsley et al. ERJ Open Res 2016;2:00042-2015 ©2016 by European Respiratory Society