Exhaled breath condensate: Measuring inflammation and oxidative stress in preterm infants

Abstract

Background and Aim: Pulmonary inflammation and oxidative stress contribute to the pathogenesis of bronchopulmonary dysplasia (BPD) following preterm birth. We aimed to measure inflammation and oxidative stress non-invasively, using exhaled breath condensate (EBC), in neonates with and without BPD. We also aimed to determine if markers of inflammation and oxidative stress were present later in infancy and relate biomarker levels to disease severity. Methods: EBC was collected from very preterm infants (GA < 32 weeks (w)) with and without BPD at 36 w postmenstrual age (PMA) and 12-15 months corrected. Inflammatory and oxidative stress markers were measured using enzyme-linked immuno-sorbent assay (ELISA). Untargeted metabolomic profiles were generated using gas chromatography/mass spectrometry (GC/MS). Results: EBC collection is feasible in preterm infants at 36w PMA (N=5) and 12-15 months (N=20) at a volume that allows metabolomic profiling (215.0 ± 121.2 μL). Markers of inflammation and oxidative stress were detected above 3.9 pg.mL^-1 and 0.8 pg.mL^-1 respectively (ELISA) in all infants, regardless of BPD classification. Surprisingly, biomarker levels were higher in infants without BPD (48.8 ± 28.0 pg.mL^-1) than in infants with BPD (17.8 ± 14.1 pg.mL^-1; p < 0.05). Distinctive metabolomic EBC profiles were identifiable between infants. However, all infants displayed alterations in surfactant metabolism and oxidative stress. Conclusion: EBC is a non-invasive technique capable of determining the lung metabolome in preterm infants. Preterm infants exhibit on-going inflammation and oxidative stress at 12-15 months corrected age, regardless of BPD classification.