Obstructive atelectasis (most common): airway obstruction (e.g., by a foreign body, mucus plug, malignancy) → nonventilated alveoli → reabsorption of gas in the poststenotic space → lung collapse
Nonobstructive atelectasis
Compression atelectasis: external space-occupying lesion (e.g., pleural effusion) that compresses the lung → forcefully pushes air out of the alveoli
Cicatrization (contraction) atelectasis: parenchymal scarring that leads to contraction of the lung (due to chronic destructive lung processes such as tuberculosis, sarcoidosis, and fibrosis, e.g., secondary to radiation therapy)
Relaxation atelectasis: loss of contact between parietal and visceral tissue (e.g., pneumothorax, pleural effusion)
Postoperative atelectasis: one of the most common post-operative complications (especially after chest or abdominal surgery); often occurs within 72 hours of surgery
Atelectasis is often precipitated by postoperative pain (poor cough) and poor lung compliance, retained airway secretions, posterior tongue prolapse, airway edema, or anesthetic effects, which can all interfere with spontaneous deep breathing and coughing.
Pathophysiology
Clinical features
Symptoms depend on the acuity and extent of atelectasis.
Large number of affected alveoli or rapid onset → acute dyspnea, chest pain, tachypnea, tachycardia, and cyanosis
Dull percussion note, diminished breath sounds, and decreased fremitus over the affected lung
Possibly tracheal deviation towards the side of lesion
