Objective: Respiratory Severity Score (RSS), the product of Mean Airway Pressure (MAP) and Fraction of Inspired Oxygen (FiO2) may estimate severity of neonatal lung disease. We aimed to determine if RSS on the first day of life is associated with mortality and/or comorbidities in infants born less than or equal to 1,250 grams.
Methods: Data were extracted from the NYS Perinatal Data System for premature inborn infants from 2006-2016 born between 400-1,250 grams (N=730). RSS was divided into three categories: less than 2 (Low, n=310), 2-5 (Moderate, n=265), greater than 5 (High, n=155). The primary outcome was mortality. Logistic regression determined associations with composite outcomes of death or Respiratory Morbidity [respiratory support after 36 weeks post menstrual age (PMA)], death or Neurologic Morbidity [periventricular leukomalacia (PVL) or high grade intraventricular hemorrhage (IVH)], and Death/Severe Morbidity [death or Neurologic Morbidity or Respiratory Morbidity or stage ≥III retinopathy of prematurity (ROP) or necrotizing enterocolitis (NEC)] by RSS category.
Results: Birthweight and gestational age were lower with increasing RSS category (p<0.001 for both). Mode of delivery, antenatal steroids, and maternal age did not differ by RSS. In adjusted analyses, there were increased odds of mortality in infants with Moderate RSS (OR [95% Confidence Intervals] 3.1 (1.7-5.4) and High 4.5 (2.5-8.2). These groups had higher odds of death or Respiratory Morbidity, death or Neurologic Morbidity, and Death/Severe Morbidity.
Conclusion: Higher RSS (greater than or equal to 2) is associated with increased risk of mortality and morbidities in infants born less than or equal to1,250 grams.