Atelectasis

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Chapter 402 Atelectasis

Ranna A. Rozenfeld

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

Clinical Manifestations

Symptoms vary with the cause and extent of the atelectasis. A small area is likely to be asymptomatic. When a large area of previously normal lung becomes atelectatic, especially when it does so suddenly, dyspnea accompanied by rapid shallow respirations, tachycardia, cough, and often cyanosis occurs. If the obstruction is removed, the symptoms disappear rapidly. Although it was once believed that atelectasis alone can cause fever, studies have shown no association between atelectasis and fever. Physical findings include limitation of chest excursion, decreased breath sound intensity, and coarse crackles. Breath sounds are decreased or absent over extensive atelectatic areas.

Massive pulmonary atelectasis usually presents with dyspnea, cyanosis, and tachycardia. An affected child is extremely anxious and, if old enough, complains of chest pain. The chest appears flat on the affected side, where decreased respiratory excursion, dullness to percussion, and feeble or absent of breath sounds are also noted. Postoperative atelectasis usually manifests within 24 hr of operation but may not occur for several days.

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