Congenital high airway obstruction syndrome
What is CHAOS, and how is it diagnosed and treated?
Congenital high airway obstruction syndrome (CHAOS) results from obstruction of the trachea above the level of the carina, usually from laryngeal or tracheal stenosis, but it can be from any cause of obstruction or severe stenosis high in the airway. As a result, the lungs become markedly expanded by the secretions normally exhaled by the fetus.
The hyperexpansion of the lungs flattens or everts the diaphragm and compresses the mediastinal structures, restricting venous return and potentially causing hydrops.
Diagnostic US features include enlarged hyperechoic lungs, distended bronchi and trachea, and a compressed heart. Polyhydramnios is often present along with other findings of nonimmune hydrops. Fetal MRI may be useful to show the location and length of the atretic tracheal segment.
Treatment makes use of EXIT as for other conditions with airway obstruction. Once the airway is established, the EXIT delivery is completed, and the neonate is cared for by a respiratory care team.
