Box plots of the respective lung function values by subject groups.

<p>Subjects were grouped according to post-conceptional age at birth (term-born and preterm) and according to disease state based on ATS definition of BPD (healthy preterm, mild, moderate and severe BPD) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004635#pone.0004635-Jobe1" target="_blank">[6]</a>. The boxes indicate the median and the 25^th and 75^th percentile, the whiskers the upper and lower adjacent values. Outside values are shown as separate dots. Box plots are shown for FRC at airway opening per weight in mL/kg.