Effect of prenatal diaphragmatic hernia on pulmonary arterial morphology.

Congenital diaphragmatic hernia (CDH) is a major cause of severe lung hypoplasia and pulmonary hypertension in the newborn. While the pulmonary hypertension is thought to result from abnormal vascular development and arterial vasoreactivity, the anatomical changes in vascular development are unclear. We have examined the 3D structure of the pulmonary arterial tree in rabbits with a surgically induced diaphragmatic hernia (DH). Fetal rabbits (n = 6) had a left-sided DH created at gestational day 23 (GD23), delivered at GD30, and briefly ventilated; sham-operated litter mates (n = 5) acted as controls. At postmortem the pulmonary arteries were filled with a radio-opaque resin before the lungs were scanned using computed tomography (CT). The 3D reconstructed images were analyzed based on vascular branching hierarchy using the software Avizo 2020.2. DH significantly reduced median number of arteries (2,579 (8440) versus 576 (442), p = .017), artery numbers per arterial generation, mean total arterial volume (43.5 ± 8.4 vs. 19.9 ± 3.1 µl, p = .020) and mean total arterial cross-sectional area (82.5 ± 2.3 vs. 28.2 ± 6.2 mm2 , p =.036). Mean arterial radius was increased in DH kittens between the eighth and sixth branching generation and mean arterial length between the sixth and 28th branching generation. A DH in kittens resulted in threefold reduction in pulmonary arterial cross-sectional area, primarily due to reduced arterial branching. Thus, the reduction in arterial cross-sectional area could be a major contributor to pulmonary hypertension infants with CDH.

Quantifying lung aeration in neonatal lambs at birth using lung ultrasound.

Background: Lung ultrasound (LUS) is a safe and non-invasive tool that can potentially assess regional lung aeration in newborn infants and reduce the need for X-ray imaging. LUS produces images with characteristic artifacts caused by the presence of air in the lung, but it is unknown if LUS can accurately detect changes in lung air volumes after birth. This study compared LUS images with lung volume measurements from high-resolution computed tomography (CT) scans to determine if LUS can accurately provide relative measures of lung aeration. Methods: Deceased near-term newborn lambs (139 days gestation, term ∼148 days) were intubated and the chest imaged using LUS (bilaterally) and phase contrast x-ray CT scans at increasing static airway pressures (0-50 cmH2O). CT scans were analyzed to calculate regional air volumes and correlated with measures from LUS images. These measures included (i) LUS grade; (ii) brightness (mean and coefficient of variation); and (iii) area under the Fourier power spectra within defined frequency ranges. Results: All LUS image analysis techniques correlated strongly with air volumes measured by CT (p < 0.01). When imaging statistics were combined in a multivariate linear regression model, LUS predicted the proportion of air in the underlying lung with moderate accuracy (95% prediction interval ± 22.15%, r 2 = 0.71). Conclusion: LUS can provide relative measures of lung aeration after birth in neonatal lambs. Future studies are needed to determine if LUS can also provide a simple means to assess air volumes and individualize aeration strategies for critically ill newborns in real time.