Predictors of outcome of prematurely born infants with pulmonary interstitial emphysema

Aim: To determine how oxygenation, ventilation efficiency and tidal volume requirements changed with the development of pulmonary interstitial emphysema (PIE) and whether in affected patients a composite gas exchange index predicted death or bronchopulmonary dysplasia (BPD). Methods: Infants who developed PIE from 2010 to 2016 were identified. The oxygenation index (OI), ventilation efficiency index (VEI), ventilation to perfusion ratio and inspiratory tidal volume were calculated before radiological evidence of PIE (pre-PIE) and at the worst PIE radiographic appearance (PIE-worst). Results: Thirty infants, median (IQR) gestational age of 24.6 (24.3–26.7) weeks were assessed. Their age at pre-PIE was 11 (6–19) days and 23 (13–42) days at PIE-worst. Compared to pre-PIE, at PIE-worst, the OI was higher [14.5 (10.7–19.2) vs 4.8 (3.1–6.1), respectively, p < 0.001], VEI was lower [0.01 (0.01–0.11) vs 0.16 (0.13–0.19), respectively, p < 0.001], ventilation to perfusion ratio was lower [0.15 (0.11–0.40) vs 0.26 (0.20–0.37), p = 0.033] and tidal volume was higher [9.9 (7.2–13.1) vs 6.4 (5.5–6.8) mL/kg, p = 0.007]. An OI >11.4 at PIE-worst predicted death or BPD with 80% sensitivity and 100% specificity. Conclusion: Development of PIE was associated with poorer oxygenation and ventilation efficiency despite increased tidal volumes. The OI at PIE-worst predicted death or BPD.