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Abstract Body

Chronic respiratory morbidity is unfortunately common in childhood, particularly in those born very prematurely and who had bronchopulmonary dysplasia (BPD). Affected infants can suffer lung function abnormalities even into adolescence and adulthood. They have airways obstruction which may not respond to bronchodilators. The lung function abnormalities are associated with wheeze and reduced exercise tolerance. Moderately and late prematurely born children may also have increased respiratory morbidity being more likely to asthma and have RSV lower respiratory tract infections than term born peers.
Being born small for gestational age (SGA) may reduce the likelihood of RDS, but SGA infants are more likely to develop BPD and have respiratory problems in the first two years. Antenatally administered endotoxin in animal models resulted in a reduced number of alveoli which were larger in volume. A systematic review of 158 studies has demonstrated that chorioamnionitis is significantly associated with BPD development. Males compared to females have worse outcomes on the neonatal unit and through childhood, for example at 11 to 14 years more males had low lung function. Interestingly, post puberty “BPD” women rather than men were more likely to have asthma and be short of breath on exercise. At an older age, women but not men, had an increased risk of obstructive lung disease and asthma with decreasing gestational age and birthweight. Increased exposure to antenatal corticosteroids, postnatal surfactant and non-invasive ventilation does not appear to have influenced lung function at follow up. Very few randomised controlled trials of ventilation modes have incorporated long term follow up. At 11 to 14 years of age, those entered into the UKOS trial had superior lung function and educational attainment if they had been supported by high frequency oscillation rather than conventional ventilation (CMV). An invitro study demonstrated the likely mechanism was that the CMV group had been exposed to greater cyclical mechanical stretch resulting in higher cytokine release which can decrease angiogenesis and alveolarization. At 16 to 19 years, however, there were no significant differences in lung function between the two groups suggesting that there had been catch up lung growth in the CMV group. Whether that is maintained merits testing. Postnatal corticosteroid exposure on the neonatal unit, however, has been associated with poorer lung function at 11 to 14 years and, between 11 to 14 and 16 to 19 years, a decline in lung function occurred rather than the increase expected through puberty. As prematurely born infants never reach the same level of lung function as those born at term, postnatal corticosteroid administration may put individuals at increased risk of the early onset of chronic obstructive lung disease. Long term follow up of prematurely born children is required if we are to understand their lung function trajectory and the impact of interventions.

Results

Of the 80,761 infants within the overall cohort, 1,237, 1,359 and 888 infants received PND at 2–3, 4–5 and ≥6 weeks old respectively with balanced variables after IPTW. Compared to infants receiving PND at 2–3 weeks old, infants in the ≥6 weeks group had higher odds of severe BPD and death (OR 1.44 (95% CI 1.12–1.86)), longer duration of invasive ventilation (mean difference 18.9 days (95% CI 16.6–21.3)) but similar respiratory support requirement at discharge (OR 1.24 (95% CI 0.99–1.55)) (Figure).