Abstract
BACKGROUND: Bronchopulmonary dysplasia (BPD) is the most common neonatal lung parenchymal disease characterized by obstructive and restrictive lung abnormalities. Evaluation of neonatal BPD lung disease using MRI has been shown to be more sensitive to short-term outcomes than standard clinical measures. However, the longitudinal trajectory of parenchymal disease remains poorly characterized. RESEARCH QUESTION: What is the 1-month trajectory of lung parenchymal disease in infants with moderate to severe BPD, as assessed by quantitative MRI measures of lung volume and tissue density? STUDY DESIGN AND METHODS: Thirty-six infants with grade 2 or 3 BPD (median postmenstrual age, 39.5 weeks [interquartile range (IQR), 37.4-40.9 weeks] at baseline MRI; female to male ratio, 19:17; median gestational age at birth, 26.5 weeks [IQR, 25.1-28.0 weeks]) underwent pulmonary MRI at 2 visits an approximately mean (SD) 5 (2) weeks apart. One-month changes in height, weight, whole-lung volume, and density as well as hypodense, normal density, or hyperdense tissue were compared between patients who did and did not require invasive mechanical ventilation. Changes in MRI results were compared with ventilator settings. RESULTS: Seventeen of 36 patients required ventilation at both visits, and 19 patients were nonventilated at either visit. One-month changes in lung volume were larger in ventilated patients (median, +52.9 mL [IQR, 38.7-83.2 mL]) than nonventilated patients (median, +29.5 mL [IQR, 16.9-37.9 mL]; P = .002). The hypodense lung volume of the ventilated patients significantly increased (median, +192 mL/m(2) [IQR, 32.2-322 mL/m(2)]; P = .002) despite stable mean airway pressure (median, +0.1% [IQR, -2.3% to 2.3%]; P = .93), but was unchanged in nonventilated patients (P = .10). Although hyperdense lung volume decreased in ventilated infants (median, -78.0 mL/m(2) [IQR, -170 to -28.5 mL/m(2)]; P = .015), those decreases were spatially separate from hypodensity increases, which mostly originated from normally dense or hypodense tissue. INTERPRETATION: Serial MRI captured global 1-month increases in hypodense lung specifically in invasively ventilated patients with BPD, suggesting global lung hyperexpansion and potential regional progression of parenchymal disease.