Chronic respiratory morbidity following premature delivery--prediction by prolonged respiratory support requirement?

Abstract

Neonatal chronic lung disease (CLD) is usually diagnosed if an infant remains oxygen dependent beyond 36 weeks postconceptional age (PCA). Our aim was to determine whether a shorter duration of respiratory support accurately predicted subsequent respiratory morbidity. A total of 103 infants, median gestational age 29 weeks (range 23-35), were followed prospectively for 5 years. They had a birth weight of < 1500 g or, if a birth weight of between 1500 and 2000 g, had required neonatal ventilatory support. Parents completed diary cards; their child had positive symptom status if, in any one year, they coughed and/or wheezed on at least 3 days per week for a 4-week period or for at least 3 days following each upper respiratory tract infection. Subsequent respiratory morbidity, positive symptom status in years 1 and 2 or all 5 pre-school years, was related to various definitions of prolonged respiratory support: intermittent positive pressure ventilation dependence > 7 days; oxygen dependence > 28 days and oxygen dependence > 36 weeks PCA. In years 1 and 2, 25 children were symptomatic and 22 in all 5 years. The patients with subsequent respiratory morbidity were distinguished from those without by requiring longer respiratory support (P < 0.05). Logistic regression analysis demonstrated only oxygen dependence beyond 28 days was independently related to subsequent respiratory morbidity (P < 0.01). The positive predictive values and likelihood ratios (95% confidence intervals) for positive symptom status in all 5 years were for intermittent positive pressure ventilation > 7 days 35% (16-53) and 19.5 (1.01-3.76), for oxygen dependency > 28 days 42% (23-61) and 2.20 (1.45-5.02) and for oxygen dependency >36 weeks PCA 35% (13-58) and 1.67 (0.65-4.31).

Conclusion: Oxygen dependency at 28 days of age remains a useful criterion on which to diagnose "neonatal" chronic lung disease.