Emphysema and Overinflation

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Chapter 384 Emphysema and Overinflation

Pulmonary emphysema is distention of air spaces with irreversible disruption of the alveolar septa. It can be generalized or localized, involving part or all of a lung. Overinflation is distention with or without alveolar rupture and is often reversible. Compensatory overinflation can be acute or chronic and occurs in normally functioning pulmonary tissue when, for any reason, a sizable portion of the lung is removed or becomes partially or completely airless, which can occur with pneumonia, atelectasis, empyema, and pneumothorax. Obstructive overinflation results from partial obstruction of a bronchus or bronchiole, when it becomes more difficult for air to leave the alveoli than to enter; there is a gradual accumulation of air distal to the obstruction, the so-called bypass, ball valve, or check valve type of obstruction.

Localized Obstructive Overinflation

When a ball-valve type of obstruction partially occludes the main stem bronchus, the entire lung becomes overinflated; individual lobes are affected when the obstruction is in lobar bronchi. Segments or subsegments are affected when their individual bronchi are blocked. Localized obstructions that can be responsible for overinflation include foreign bodies and the inflammatory reaction to them, abnormally thick mucus (cystic fibrosis, Chapter 395), endobronchial tuberculosis or tuberculosis of the tracheobronchial lymph nodes (Chapter 207), and endobronchial or mediastinal tumors. When most or all of a lobe is involved, the percussion note is hyperresonant over the area, and the breath sounds are decreased in intensity. The distended lung can extend across the mediastinum into the opposite hemithorax. Under fluoroscopic scrutiny during exhalation, the overinflated area does not decrease, and the heart and the mediastinum shift to the opposite side because the unobstructed lung empties normally.

Unilateral Hyperlucent Lung

Unilateral hyperlucent lung can be associated with a variety of cardiac and pulmonary diseases of children, but in some patients, it occurs without demonstrable underlying active disease. More than half the cases follow one or more episodes of pneumonia; a rising titer to adenovirus (Chapter 254) has been documented in several children. This condition can follow bronchiolitis obliterans and can include obliterative vasculitis as well, accounting for the greatly diminished perfusion and vascular marking on the affected side.

Patients with unilateral hyperlucent lung can present with clinical manifestations of pneumonia, but in some patients the condition is discovered only when a chest radiograph is obtained for an unrelated reason. A few patients have hemoptysis. Physical findings can include hyperresonance and a small lung with the mediastinum shifted toward the more abnormal lung. This condition has been labeled Swyer-James or Macleod syndrome. The condition is thought to result from an insult to the lower respiratory tract. Some patients show a mediastinal shift away from the lesion with exhalation. CT scanning or bronchography can demonstrate bronchiectasis. In some patients, previous chest radiographs have been normal or have shown only an acute pneumonia, suggesting that a hyperlucent lung is an acquired lesion. No specific treatment is known; it may become less symptomatic with time. Indications as to which children would benefit from surgery remain controversial.