Loss of lung volume due to the collapse of part of or the entire lung. Caused by airway obstruction, infection, tumor, sedation / general anesthesia, or inadequate ventilation. Atelectasis can be reversible or fixed, depending on the etiology. Characterized by cough, dyspnea, low grade fever, decreased breath sounds, dullness to percussion, tachypnea, and tachycardia.

Management focuses on underlying cause and includes manual chest physiotherapy, mechanical insufflation-exsufflation, mechanically assisted cough, intrapulmonary percussive ventilation, and intermittent positive pressure breathing. Surgery may be necessary for severe compressive atelectasis.