Surfactant kinetics in preterm infants on mechanical ventilation who did and did not develop bronchopulmonary dysplasia

Objective: To characterize surfactant kinetics in vivo in two groups of premature infants on different levels of mechanical ventilation and at different risk of developing bronchopulmonary dysplasia. Design: Controlled observational study in two independent groups of infants. Setting: Neonatal intensive care unit. Patients: Thirteen preterm infants (26 +/- 0.5 wks, birth weight 801 +/- 64 g) on high ventilatory setting and who finally all developed bronchopulmonary dysplasia (MechVentBPD), and eight (26 +/- 0.5 wks, birth weight 887 +/- 103 g) who had minimal or no lung disease and of whom none developed bronchopulmonary dysplasia (MechVentNoBPD). Measurements and Main Results: Endotracheal C-13-labeled dipalmitoyl-phosphatidylcholine was administered and subsequent measurements of the C-13 enrichment of surfactant-disaturated phosphatidylcholine (DSPC) from serial tracheal aspirates were made by gas chromatography-mass spectrometry. We calculated disaturated phosphatidylcholine pharmacokinetic variables in terms of half-life and apparent pool size from the enrichment decay curves over time. DSPC concentration from tracheal aspirates was expressed as milligrams/milliliter epithelial lining fluid (ELF-DSPC). Data are presented as mean +/- SE. In MechVentBPD infants vs. MechVentNoBPD, ELF-DSPC was much reduced, 2.9 +/- 0.6 vs. 9.4 +/- 3.0 mg/mL ELF (p =.03), half-life was shorter, 19.4 +/- 2.8 vs. 42.5 +/- 6.3 hrs (p = .002), and apparent pool size larger, 136 +/- 21, vs. 65.8 +/- 16.0 mg/kg (p = .057). In MechVentBPD, apparent DSPC pool size positively correlated with mean airway pressure x F10(2) and inversely correlated with ELF-DSPC. ELF-DSPC was inversely correlated with mean airway pressure x F10(2). No significant correlations were found in the MechVentNoBPD group. Conclusions: MechVentBPD infants showed profound alteration of surfactant kinetics compared with preterm infants with minimal; lung disease, and these alterations were correlated with severity of ventilatory support.