Airway muscle in infants with congenital diaphragmatic hernia: Response to treatment

Abstract

Background/Purpose: Airway muscle hyperactivity and chronic lung disease frequently follow congenital diaphragmatic hernia (CDH) treatment. The aim of this study was to compare the quantity of airway muscle and alveolar ductal artery muscle in CDH infants after various treatments. Methods: Five groups were studied postmortem: CDH, died within 24 hours, without high ventilatory assistance ( n = 3); CDH, various extracorporeal membrane oxygenation (ECMO) durations, without high ventilatory assistance ( n = 4); CDH, various ECMO durations, with high ventilatory assistance ( n = 7); no CDH, without high ventilatory assistance ( n = 12); and no CDH, with high ventilatory assistance and bronchopulmonary dysplasia (BPD) ( n = 5). Sections from standardized fixed lungs were immunohistochemically stained for α-smooth muscle actin. Muscle surrounding conducting airways from small preterminal bronchioles to bronchi was quantitated in both the ipsilateral and contralateral lungs with computerized image analysis. Similarly, muscle mass was quantitated in alveolar ductal arteries. Results: CDH infants with low ventilatory assistance, regardless of postnatal age, had the same quantity of airway muscle as low ventilatory assistance controls. Infants with CDH and prolonged high ventilatory assistance had significantly more muscle throughout the conducting airways, similar to BPD infants without CDH, even though the CDH infants had significantly less exposure to high ventilatory assistance. With both low and high ventilatory assistance, the quantity of muscle in both the ipsilateral and contralateral lungs was similar. In contrast, small acinar arteries in CDH infants have increased muscle mass at birth. This muscle is decreased by ECMO but persists in CDH infants with high ventilatory assistance. Conclusions: The authors show that postnatally, CDH infants acquire increased muscle quantity throughout the conducting airways, in both the ipsilateral and contralateral lungs, with relatively short exposure to high ventilatory assistance. The normal decrease in acinar arterial mass that occurs postnatally is delayed in CDH infants with high ventilatory assistance.