PMC

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) . 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 lung clearance index (LCI).

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) . 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.

a) Tidal volume versus weight for term and preterm infants. The black line indicates the regression line with a coefficient of correlation of 0.31 for the term-born infants and a coefficient of correlation of 0.65 for the preterm infants and the respective R² values given in the figure. b) Variability in lung volume determined by weight depending on disease severity. The graph shows 1−R² value of the regression model between weight and FRC. The R² value indicates how much of the variability in lung volume can be explained by the weight, and thus the 1−R² is a measure of how much infants are able to change their lung volumes given their body size.

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) . 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 t _PTEF/t _E. The p-value for trend obtained by regression analysis was <0.001.

a) ROC curve comparing the ability of above mentioned lung function parameters to discriminate between healthy infants (term-born and preterm) and BPD infants using data of 221 healthy and 103 preterm infants. The resulting area under the curve is 0.58 for FRC_ao, 0.52 for LCI, 0.67 for respiratory rate and 0.76 for t _PTEF/t _E. b) ROC curve comparing the ability of above mentioned lung function parameters to discriminate between 179 term-born and 43 preterm healthy infants; BPD infants were not considered for this analysis. The resulting area under the curve is 0.43 for FRC_ao, 0.50 for LCI, 0.60 for respiratory rate and 0.64 for t _PTEF/t _E.