Table 2 Lung function data for the study population (n = 74)

Lung function variables	Bronchopulmonary dysplasia		p Values (t test)
Lung function variables	None and mild (n = 53)Mean (95% CI)	Moderate and severe (n = 21)Mean (95% CI)	p Values (t test)
FEV₁	89.8 (86.0 to 93.6)	80.9 (76.2 to 85.7)	0.004
FEF₅₀	83.4 (77.8 to 88.9)	68.1 (56.4 to 79.8)	0.021
TLC	102.1 (98.1 to 106.2)	102.4 (97.0 to 107.8)	0.935
RV/TLC	21.2 (19.6 to 22.8)	25.3 (22.0 to 28.5)	0.026

Lung function variables are expressed as percentages of predicted, except the ratio RV/TLC. The criteria for classification of bronchopulmonary dysplasia are given in the text.
FEV₁, forced expiratory volume in 1 s; FEF₅₀, forced expiratory flow at 50% of forced vital capacity; RV, residual volume; TLC, total lung capacity.