Demographics
| Responders | Non-responders | p-value | |
| Subjects, n | 59 | 34 | |
| Gestational age (weeks) | 25.7 (24.4–27.0) | 25.3 (24.6–27.0) | 0.90 |
| Birth weight (g) | 698 (585–883) | 724 (589–920) | 0.53 |
| PMA at iPFT (weeks) | 51 (45–57) | 53 (47–70) | 0.10 |
| Post-partum age at iPFT (months) | 5.8 (4.7–10.3) | 5.8 (4.4–7.5) | 0.17 |
| Weight at iPFT (kg) | 4.5 (3.7–5.4) | 4.5 (3.7–6.7) | 0.38 |
| Growth velocity (g·day−1)# | 10.5 (8.9–12.7) | 9.3 (7.2–12.3) | 0.07 |
| Length at iPFT (cm) | 53 (49–57) | 54 (50–62) | 0.27 |
| Length z-score at iPFT¶ | −2.11 (−3.05– −1.18) | −1.80 (−3.81– −1.00) | 0.70 |
| Respiratory support at iPFT | |||
| Noninvasive | 22 (37%) | 17 (50%) | 0.28 |
| Endotracheal tube | 20 (34%) | 6 (18%) | 0.15 |
| Tracheostomy | 17 (29%) | 11 (32%) | 0.82 |
| Family history of asthma | 23 (41%)+ | 8 (27%)ƒ | 0.24 |
| Pregnancy tobacco exposure | 20 (36%)+ | 14 (42%)## | 0.65 |
| Antenatal steroids | 48 (84%)§ | 27 (79%)¶¶ | 0.58 |
| Race | |||
| Black | 15 (25%) | 11 (32%) | 0.48 |
| White | 41 (69%) | 19 (56%) | 0.26 |
| Severe IVH | 4 (7%) | 4 (12%) | 0.46 |
| PDA ligation | 23 (41%) | 14 (41%) | 1.0 |
| NEC | 5 (8%) | 1 (3%) | 0.41 |
| Grade 3 BPD | 39 (66%) | 19 (56%) | 0.38 |
| Grade 2 BPD | 14 (24%) | 10 (29%) | 0.63 |
| Grade 1 BPD | 1 (2%) | 1 (3%) | 1.0 |
| Unknown at 36 weeks | 5 (8%) | 4 (12%) | 0.72 |
| RSS at 36 weeks | 6.2 (4.1–8.9)++ | 7.5 (3.8–9.1)§§ | 0.59 |
Data shown as median (interquartile range) or n (%), unless otherwise indicated. PMA: post-menstrual age; iPFT: infant pulmonary function test; IVH: intraventricular haemorrhage; PDA: patent ductus arteriousus; NEC: necrotising enterocolitis; BPD: bronchopulmonary dysplasia; RSS: respiratory severity score. #: from birth to iPFT using the exponential calculation; ¶: calculated from Centers for Disease Control and Prevention-National Center for Health Statistics length curves for 0–36 months of age; +: n=56; §: n=57; ƒ: n=30; ##: n=33; ¶¶: n=34; ++: n=49; §§: n=25.