Atelectasis

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Chapter 402 Atelectasis

Atelectasis, the incomplete expansion or complete collapse of air-bearing tissue, results from obstruction of air intake into the alveolar sacs. Segmental, lobar, or whole lung collapse is associated with the absorption of air contained in the alveoli, which are no longer ventilated.

Pathophysiology

The causes of atelectasis can be divided into five groups (Table 402-1). Respiratory syncytial virus (RSV) and other viral infections in young children can cause multiple areas of atelectasis. Mucous plugs are a common predisposing factor to atelectasis. Massive collapse of one or both lungs is most often a postoperative complication but occasionally results from other causes, such as trauma, asthma, pneumonia, tension pneumothorax (Chapter 405), aspiration of foreign material (Chapters 379 and 389), and paralysis, or after extubation. Massive atelectasis is usually produced by a combination of factors, including immobilization or decreased use of the diaphragm and the respiratory muscles, obstruction of the bronchial tree, and abolition of the cough reflex.

Table 402-1 ANATOMIC CAUSES OF ATELECTASIS

CAUSE CLINICAL EXAMPLES
External compression on the pulmonary parenchyma Pleural effusion, pneumothorax, intrathoracic tumors, diaphragmatic hernia
Endobronchial obstruction completely obstructing the ingress of air Enlarged lymph node, tumor, cardiac enlargement, foreign body, mucoid plug, broncholithiasis
Intraluminal obstruction of a bronchus Foreign body, granulomatous tissue, tumor, secretions, including mucous plugs, bronchiectasis, pulmonary abscess, asthma, chronic bronchitis, acute laryngotracheobronchitis
Intrabronchiolar obstruction Bronchiolitis, interstitial pneumonitis, asthma
Respiratory compromise or paralysis Neuromuscular abnormalities, osseous deformities, overly restrictive casts and surgical dressings, defective movement of the diaphragm, or restriction of respiratory effort