Global and Regional Heterogeneity of Lung Aeration in Neonates with Different Respiratory Disorders: A Physiologic Observational Study

Abstract

Background Aeration heterogeneity affects lung stress and influences outcomes in adults with acute respiratory distress syndrome (ARDS). The authors hypothesize that aeration heterogeneity may differ between neonatal respiratory disorders and is associated with oxygenation, so its evaluation may be relevant in managing respiratory support. Methods This was an observational prospective study. Neonates with respiratory distress syndrome, transient tachypnea of the neonate, evolving bronchopulmonary dysplasia, and neonatal ARDS were enrolled. Quantitative lung ultrasound and transcutaneous blood gas measurements were simultaneously performed. Global aeration heterogeneity (with its intra- and interpatient components) and regional aeration heterogeneity were primary outcomes; oxygenation metrics were the secondary outcomes. Results A total of 230 (50 respiratory distress syndrome, transient tachypnea of the neonate or evolving bronchopulmonary dysplasia, and 80 neonatal ARDS) patients were studied. Intrapatient aeration heterogeneity was higher in transient tachypnea of the neonate (mean ± SD, 61 ± 33%) and evolving bronchopulmonary dysplasia (mean ± SD, 57 ± 20%; P < 0.001), with distinctive aeration distributions. Interpatient aeration heterogeneity was high for all disorders (Gini–Simpson index, between 0.6 and 0.72) except respiratory distress syndrome (Gini–Simpson index, 0.5), whose heterogeneity was significantly lower than all others (P < 0.001). Neonatal ARDS and evolving bronchopulmonary dysplasia had the most diffuse injury and worst gas exchange metrics. Regional aeration heterogeneity was mostly localized in the upper anterior and posterior zones. Aeration heterogeneity and total lung aeration had an exponential relationship (P < 0.001; adj-R2 = 0.62). Aeration heterogeneity is associated with greater total lung aeration (i.e., higher heterogeneity means a relatively higher proportion of normally aerated lung zones, thus greater aeration; P < 0.001; adj-R2 = 0.83) and better oxygenation metrics upon multivariable analyses. Conclusions Global aeration heterogeneity and regional aeration heterogeneity differ among neonatal respiratory disorders. Transient tachypnea of the neonate and evolving bronchopulmonary dysplasia have the highest intrapatient aeration heterogeneity. Transient tachypnea of the neonate, evolving bronchopulmonary dysplasia, and neonatal ARDS have the highest interpatient aeration heterogeneity, but the latter two have the most diffuse injury and worst gas exchange. Higher aeration heterogeneity is associated with better total lung aeration and oxygenation. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New