Bronchopulmonary Dysplasia
Bronchopulmonary dysplasia (BPD) is a chronic lung disorder that occurs in low birth weight infants who require mechanical ventilator support during the first weeks or months of life. Although the precise mechanisms that produce the severe pulmonary changes seen in BPD are unclear, several factors appear to contribute both to the lung injuries and the relatively non-specific responses of the lung to these injuries. In affected infants, the mechanical ventilator may cause volutrauma, resulting in hyperdistention of the alveoli and alveolar ducts. In the early stages of BPD, pulmonary inflammation and exudate are present, possibly as a result of oxygen toxicity, pulmonary inflammation due to infection or other irritants, pulmonary edema due to capillary damage or a patent ductus arteriosus or excessive fluid damage, and increased airway resistance. Later, as breakdown of the alveolar walls and scarring occurs, lung tissue demonstrates alternating areas of emphysema with hyperaeration and pulmonary scarring and atelectasis.
Infants with BPD demonstrate increased airway resistance resulting, in part, from hyperplasia of the bronchial epithelium. Increased mucus production, induced by trauma and infection, combined with secretion retention secondary to ciliary damage, can also contribute to airway obstruction.
Surviving infants frequently sustain permanent lung injury and persistent respiratory distress. Bronchopulmonary dysplasia is now the leading cause of lung disease in U.S. infants. As surviving babies mature, the initial respiratory distress syndrome requiring assisted ventilation gradually evolves into bronchopulmonary dysplasia (BPD). Although acute distress gradually resolves, reduced lung compliance and increased airway resistance may persist for years. Fortunately, for many low birth-weight children, lung function improves progressively. In others, especially those whose lungs are badly damaged, chronic pulmonary problems persist. In severe cases of BPD, lung transplantation may extend survival.
Children with BPD are at high risk for recurrent pulmonary infections, especially viral infections of the lower respiratory tract. Some rapidly develop respiratory decompensation, resulting in significant morbidity and mortality. Prevention and treatment of bacterial and viral infection are essential components in the care of infants and children with BPD. Retained secretions secondary to such complications create an ideal environment for growth and colonization of opportunistic organisms, leading to progressive pulmonary damage and, ultimately, respiratory failure. Effective treatment must include an appropriate combination of antibiotic, diuretic and, in those children with recurrent pulmonary infection, Airway Clearance Therapy to reduce the incidence and severity of those complications.
Sources
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Rush MG, Hazinski TA. Current therapy of bronchopulmonary dysplasia. Clin Perinatol 1992; 19(3): 563-590. Gaynor JW, Bridges ND, Clark BJ, Spray TL. Update on lung transplantation in children. Curr Opin Pediatr 1998; 10(3): 256-261.
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