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  What is Congenital Diaphragmatic Hernia (CDH)?

CDH is a developmental defect in the diaphragm (most commonly on the left side), which occurs in 1 per 2200 births and results in protrusion of the abdominal contents into the developing chest cavity, restricting fetal heart and lung development. Infants born with CDH suffer from variable degrees of pulmonary hypoplasia (underdeveloped lungs) and pulmonary hypertension (elevated blood pressure in the lungs). They may require substantial levels of cardio­pulmonary support, including extra­corporeal membrane oxygenation (ECMO), a heart-lung bypass that circulates blood through a machine to be oxygenated in patients with total respiratory and cardiac failure. Surgical treatment involves reducing the protruding abdominal contents back into the abdomen, followed by closure of the diaphragmatic defect with either autologous tissue (diaphragmatic muscle) or a prosthetic "patch". Outcome is largely determined by the severity of pulmonary hypoplasia and accompanying pulmonary hypertension. The best current estimate of postnatal survival reported an overall survival of 63%. However, neonates who survive the postnatal period without major complications can be expected to have a good long term outcome, due to the lung’s postnatal growth potential.

CDH was once thought to represent a dire emergency requiring immediate surgical treatment. Over the past 2 decades, there has been a shift in ideas over treatment towards initial respiratory "stabilization" and delayed diaphragmatic repair, following a seminal Canadian report demonstrating equivalent outcomes in CDH infants treated by "delayed" surgery as compared to "urgent" surgery. The impact of delayed surgical treatment of CDH has been generally favourable, with most centres reporting improved survival. However this experience has not been universal, as some studies have failed to show a survival advantage as a result of delayed surgery. Another recent therapeutic trend has been the adoption of less aggressive ventilatory strategies to lessen lung injury among these patients. Some studies have reported that in comparison with historical controls, CDH patients treated with high frequency oscillatory ventilation (HFOV) and permissive hypercapnea to reduce barotrauma, demonstrate improved outcomes, while other studies have not. Other therapeutic controversies include the use of inhaled nitric oxide and other pulmonary vasodilators in treatment of pulmonary hypertension, the role of steroids and surfactant, the role of ECMO and the timing of surgical repair in relation to ECMO, and the use of new ventilatory adjuncts, including liquid ventilation. For all of these treatment modalities, clinical practices are not standardized, and vary tremendously from one institution to another.

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