Characteristics of study participants
| Healthy | Asthma | Preterm | BPD | |
| Participants | 24 | 22 | 22 | 22 |
| Male/female | 12/12 | 9/13 | 10/12 | 11/11 |
| Age (years), median (range) | 20.5 (18.3–23.8) | 20.3 (18.6–23.3) | 19.2* (18.7–22.4) | 19.6* (18.2–21.2) |
| BMI (kg·m−2), median (range) | ||||
| Male | 21.6 (19.7–32.5) | 23.9 (20.6–29.4) | 20.3 (16.8–26.7) | 20.4 (17.9–29.8) |
| Female | 21.8 (18.1–37.9) | 21.2 (18.2–34.2) | 22.1 (17.0–27.7) | 22.1 (17.9–32.6) |
| Post-bronchodilator FEV1 (% pred) | 108.9 (99.7–114.1) | 101.8 (94.1–109.0) | 102.8 (96.9–113.3) | 85.0*** (76.2–99.1) |
| Post-bronchodilator FEV1 (z-scores) | 0.78 (−0.03–1.26) | 0.15 (−0.52–0.77) | 0.24 (−0.27–1.18) | −1.31*** (−2.00–−0.08) |
| Post-bronchodilator FEV1/FVC | 0.90 (0.86–0.93) | 0.86 (0.83–0.89) | 0.93 (0.89–0.95) | 0.80*** (0.74–0.88) |
| Post-bronchodilator FEV1/FVC (z-scores) | 0.42 (−0.26–0.89) | −0.19* (−0.43–0.32) | 0.87 (0.14–1.33) | −1.04*** (−1.86–0.18) |
| Post-bronchodilator reversibility (%) | 4.9 (2.0–6.3) | 5.9* (3.6–8.3) | 3.0 (1.8–7.6) | 6.9* (4.3–11.9) |
| Post-bronchodilator reversibility (positive)# | 0 | 2 (9) | 2 (9) | 5* (23) |
| DLCOadj (% pred) | 86.5 (80–96) | 81.5 (75–91) | 73*** (65–83) | 70*** (64–73) |
| RV (% pred) | 84.5 (68.5–105.5) | 72.5 (52–96) | 82 (65–132) | 87 (60–98) |
| RV/TLC | 19 (17–22.5) | 18.5 (14–23) | 21 (18–23) | 20 (17–24) |
| FeNO (ppb) | 10.9 (9.7–17.1) | 31.4** (11.6–49.2) | 13.3 (11.0–19.8) | 13.4 (9.2–21.8) |
Data are presented as n, median (interquartile range) or n (%), unless otherwise stated. BPD: bronchopulmonary dysplasia; BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; DLCOadj: diffusing capacity of the lung for carbon monoxide adjusted for blood haemoglobin; RV: residual volume; TLC: total lung capacity; FeNO: fractional exhaled nitric oxide. #: defined as increase in FEV1 of 12% and 200 mL. *: p<0.05, **: p<0.01, ***: p<0.001, comparing BPD, preterm and asthma groups to healthy control group.