A Pulmonary Score for Assessing the Severity of Neonatal Chronic Lung Disease

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Abstract
Background. Limited data are available to describe the spectrum of severity of neonatal chronic lung disease. In the multicenter Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity trial, all infants had some degree of pulmonary dysfunction, because eligibility required a median oxygen saturation of ≤94% with room air. Infants randomized to the supplemental oxygen group (oxygen saturation target of 96–99%) had more pulmonary morbidity than did those in the conventional group (oxygen saturation target of 88–94%). This prompted the retrospective development of a pulmonary severity score to compare the baseline status of the 2 groups. Objectives. To describe a pulmonary score that reflects the severity of neonatal lung disease and to evaluate the association of the score and its components with subsequent pulmonary morbidity through 3 months of corrected age. Design and Methods. A pulmonary score was developed empirically by a consensus panel of 3 neonatologists and was defined as the fraction of inspired oxygen (Fio2) × (support) + (medications), where Fio2 is the actual or “effective” (for nasal cannula) Fio2; support is 2.5 for a ventilator, 1.5 for nasal continuous positive airway pressure, or 1.0 for nasal cannula or hood oxygen; and medications is 0.20 for systemic steroids for bronchopulmonary dysplasia, 0.10 each for regular diuretics or inhaled steroids, and 0.05 each for methylxanthines or intermittent diuretics. The scores could range from 0.21 to 2.95. Pulmonary morbidity was defined as any of the following occurring from randomization at a mean of 35.4 weeks’ postmenstrual age through 3 months of corrected age: death or rehospitalization with a pulmonary cause; an episode of pneumonia/sepsis/exacerbation of chronic lung disease; or continued hospitalization, supplemental oxygen therapy, diuretic treatment, or systemic steroid therapy at 3 months. Between-group differences were tested with the Kruskal-Wallis or χ2 test. Results. Data through death or the 3-month corrected age examination were available for 588 infants. Enrolled infants represented a wide spectrum of severity of chronic lung disease, with baseline pulmonary scores at randomization ranging from 0.21 to 2.6. The median pulmonary score at enrollment did not differ between the conventional and supplemental groups (0.42 and 0.45, respectively). However, higher baseline pulmonary scores were observed for infants who did versus did not develop subsequent pulmonary morbidity (0.48 vs 0.38). The pulmonary score was associated with subsequent pulmonary morbidity. Regression analyses adjusting for Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity group assignment, gestational age at birth, race, gender, and postmenstrual age at randomization revealed that the score was a significant independent predictor of subsequent pulmonary morbidity (odds ratio: 7.2; 95% confidence interval: 3.6-14.4). Conclusions. The pulmonary score, calculated near term, reflects a wide spectrum of bronchopulmonary dysplasia severity and is associated with subsequent pulmonary morbidity through corrected age of 3 months. This simple score could prove useful in clinical and research settings. Validation of the score requires additional study.