The 'PLUG' odyssey: adventures in experimental fetal tracheal occlusion

In animal experiments, it has been shown that tracheal occlusion counteracts the pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH). Successful clinical implementation requires a reliable, reversible, and atraumatic technique of occluding the fetal trachea. With this clinical goal in mind, the authors evaluated the following three methods of tracheal occlusion in a fetal lamb CDH model: (1) an occluded foam-cuffed endotracheal tube, (2) a foam-cuffed endotracheal tube with a magnetically controlled flow valve, and (3) a tracheal insert constructed of a water-impermeable, expandable, polymeric foam, which is placed by a translaryngeal approach. The foam-cuffed endotracheal tube did not provide consistently reliable fetal tracheal occlusion. Although the magnetically triggered flow valve functioned well, it was not necessary to open the valve in utero (to prevent overdistension of the lungs), and the presence of the valve contributed to several occlusive failures. In contrast, the foam insert was easy to position and to remove from the trachea, while providing reliable tracheal occlusion for several weeks with consequent enlarged fetal lungs, increased lung fluid volumes, complete reduction of abdominal viscera, and improved pulmonary gas exchange after birth. Bronchoscopic evaluation of the foam-occluded neonatal tracheas showed little or no tracheal damage, which was confirmed during necropsy by gross and histological examination. Translaryngeal placement of a compressible, water-impermeable polymeric foam appears to be a simple and safe technique to achieve fetal tracheal occlusion.