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Bronchopulmonary dysplasia (BPD)—sometimes called chronic lung disease of infancy—is a disorder of lung injury and repair in infants who developed respiratory failure after birth and is characterized by persistent respiratory signs and symptoms. The pathogenesis of BPD is related to prematurity and the treatment of the accompanying early respiratory failure; the treatment interacts with the immature developing lung, causing further injury and delayed repair. The injurious effects of treatment include barotrauma from positive-pressure ventilation and oxygen toxicity. However, other therapies developed in the past 40 years have led to a different clinical, histological, and radiographic presentation and have redefined the condition. For a more detailed discussion of the pathogenesis, risk factors and prevention of BPD see Chapter 59.

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In 1960, Wilson and Mikity described five premature infants1,2 who developed respiratory disease between 1 and 5 weeks of age; the radiographic and histological findings in these infants were similar to the first description of BPD. In 1967, Northway and colleagues3 described a chronic lung disease occurring in premature infants with respiratory distress syndrome treated with positive-pressure mechanical ventilation and supplemental oxygen. The original definition of BPD was based on clinical criteria, consisting of a set of historical facts: needing mechanical ventilation for a minimum of 3 days in the first 2 weeks of life; having an abnormal chest radiograph by 28 days of life; being oxygen dependent for greater than 28 days; and showing persistent signs of respiratory distress beyond 28 days.

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The definition and presentation of BPD has changed since the advent of surfactant replacement therapy. The classic histological findings of BPD—a patchy distribution of alveolar septal fibrosis and hyperinflated lung parenchyma—are now less common. Disruption of distal airway, blood vessel, and parenchymal development with impaired alveolar and vascular growth, in a more homogeneous distribution, are now more commonly found. New histological findings reflect an evolution in treatment and hence a change in the patient population that develops the disease; now BPD is found in very premature infants of a younger postconceptual age who are treated with surfactant. The differences between the original definitions of BPD and what has been termed the “new BPD” will be discussed in the following sections.

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Epidemiology, Specific Populations at Risk, and Associated Disorders

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Calculating the incidence of bronchopulmonary dysplasia (BPD) and defining populations at risk is made difficult by evolution and variation in definitions used in the literature and in the care of premature infants. Although the use of surfactant replacement therapy led to a decrease in the incidence of BPD, the overall incidence of this disorder has not changed much over the past decade.4 Neonatal centers vary widely in reported incidence of BPD, which is about 20% of all ventilated premature newborns.5 The reported incidence for all newborns is lower (2 to 3/1000 live births) than the incidence among premature infants surviving the neonatal period or those at 36 ...

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