| All infants(n = 41) | Infants with frequent symptoms(n = 21) | Infants with infrequent symptoms(n = 20) | |
| Birth weight (g), mean (SEM) | 914 (37) | 915 (51) | 913 (55) |
| Gestational age (weeks), mean (SEM) | 27.2 (0.2) | 27.3 (0.4) | 27.0 (0.3) |
| Hospital admissions in previous 6 months, n (%) | 14 (34) | 11 (52) | 3 (15)* |
| Inhaled glucocorticoids for ⩾6 months, n (%) | 22 (54) | 10 (48) | 12 (60) |
| Surfactant-treated newborns, n (%) | 28 (68) | 13 (62) | 15 (75) |
| Patent ductus arteriosus, n (%) | 12 (29) | 7 (33) | 5 (25) |
| Intrauterine growth retardation, n (%) | 6 (5) | 2 (10) | 4 (20) |
| Maternofetal infection, n (%) | 11 (27) | 6 (29) | 5 (25) |
| Postnatal infection, n (%) | 17 (41) | 7 (33) | 10 (50) |
| Duration of oxygen supplementation (days), mean (SEM) | 68 (6) | 65 (7) | 73 (8) |
| PMA at end of oxygen supplementation (weeks), mean (SEM) | 37.0 (0.7) | 36.5 (0.9) | 37.5 (1.1) |
| PMA at end of mechanical ventilation (days), mean (SEM) | 29.5 (0.4) | 29.1 (0.4) | 29.8 (0.7) |
PMA, postmenstrual age.
The study population was divided into two subgroups according to the intensity of clinical manifestations at the time of the study. Infants with frequent symptoms were those with one or more respiratory exacerbation a month.
*p<0.05 between the two subgroups.