Synopsis

 acute bronchopulmonary dysplasia

• necrotizing bronchiolitis (bronchiolar necrosis)
• alveolar epithelium necrosis
• persistence of pulmonary hyaline membranes
• extensive acinar damage
  • alveolar cell hyperplasia
  • alveolar cell regenrative aspects
  • septal edema

 pulmonary fibroplasia and pulmonary fibrosis

 chronic bronchopulmonary dysplasia

• bulky lungs, firm lungs
• macroscopic irregular fissures (association of hyperexpanded and atelelectatic acini)
• septal fibroplasia and septal fibrosis
• bronchial epithelial metaplasia
• bronchiolar epithelial metaplasia
• bronchiolar smooth muscle hypertrophy (brochiolar smooth muscle hyperplasia)
• marked bronchial secretion
• associations of clusters of hyperexpanded alveoli (dilated alveoli) and emphysematous alveoli with clusters of atelectatic alveoli

Etiology

 oxygen toxicity
 poor bronchial drainage
 mechanical ventilation