Introduction: The etiology of bronchopulmonary dysplasia (BPD) is multifactorial. Barotrauma has been implicated in the pathogenesis of BPD, but there is no data concerning ventilatory indices as predictors. Ureaplasma urealyticum airway colonization has been also been identified as a risk factor.
Objective: Identification of risk factors during the first week of life for the development of severe BPD in very-low birth weight infants (≤1250g) (VLBW).
Methodology: Records of all VLBW infants admitted to the neonatal intensive care unit (NICU) during 1996 and 1997 were reviewed. Infants with congenital anomalies, overwhelming sepsis, outborn infants, and infants whose records were unavailable were excluded. The requirement for mechanical ventilation on the 28th day of life was used to define severe BPD. Mild to moderate BPD was defined as the requirement for supplemental oxygen (FiO2>30%) on the 28th day of life. Infants who developed severe BPD were compared to those without BPD or those with mild to moderate BPD (non-severe BPD). Demographic, time-weighted averages of ventilatory [mean airway pressure (MAP), oxygenation index (OI=(MAP × FiO2)/PaO2), ventilator index (Vrl=MAP × rate), and ventilation index (Vnl=(PCO2 × PIP × Rate)/1000)], and clinical data were collected. The statistical analysis included chi-square, Student t, Mann-Whitney U, and logistic regression analysis.
Results: 179 VLBW infants were admitted to the NICU. 41 infants were excluded. Of the remaining 138 patients, 69 (50.0%) developed severe BPD. The infants who developed severe BPD had a lower birth weight (764±192 v. 1029±160 g, p<0.0001), were more premature (26± 2 v. 28±2 weeks gestation, p<0.0001), and had a longer length of stay (85±53 v. 56±20 days, p<0.0001) than the non-severe BPD group. (Table)
MAP, OI, VrI, and VnI were significantly higher in the severe BPD group. After controlling for birth weight, OI and total intravenous fluids in a logistic regression analysis, U. urealyticum tracheal cultures (p=0.0019) and moderate to large PDA (p=0.0125) were independently associated with the development of severe BPD.
Conclusions: High ventilatory indices, endotracheal colonization of U. urealyticum, and moderate to large PDA are associated with severe BPD. Strategies to decrease barotrauma, early treatment of U. urealyticum and early PDA closure may decrease the severity of BPD in VLBW infants.
(Spon by: John Moore)