Bronchiolitis
Peter F. Wright MD1
1 Professor of pediatrics; Department of Pediarics, and Chief, Division of Infectious Diseases, Vanderbilt University Medical School, Nashville, TN 37232
Bronchiolitis is an acute respiratory disease of early childhood characterized clinically by upper respiratory tract signs of rhinitis and congestion and by lower respiratory tract signs of tachypnea, retractions, wheezing, and rales. The presence of wheezing differentiates bronchiolitis from many of the other entities to be considered in the child with respiratory distress. Fever and other systemic signs are not prominent components of bronchiolitis. Radiographically, there is evidence of hyperexpansion of the chest, thickening of the bronchial walls, and areas of atelectasis or interstitial pneumonia. Physiologically, there is evidence of hypoxia and hypercarbia with disequilibrium of perfuson-ventilation. Pathologically, there is evidence of damage to the mucosal epithelium with loss of ciliary function. There is an increased production of mucus, with a proliferation of goblet cells. Submucosal edema and lymphocytic infiltration are common. These changes are seen throughout the respiratory tract but are particularly prominent in the cells and submucosal lining of the bronchioles, with resultant obstruction of the small airways (Fig 1).
The pathologic events are obviously central to the whole process of the illness. An understanding of the mechanisms by which the pathologic changes in bronchiolitis evolve, and their implications for diagnosis, therapy, prognosis, and, ultimately, prevention, will be the focus of this review.
