Which description best defines atelectasis?

• A. Inflammation of the pleura
• B. Infection of alveoli with fluid
• C. Accumulation of pus in the pleural space
• D. Part or all of a lung collapses, preventing it from fully expanding

Answer: (D)

Atelectasis means the lung or part of it has collapsed and cannot fully expand, so air is not kept in those alveoli and gas exchange is reduced. This can happen when a blockage prevents air from entering a region of the lung (such as mucus plugging) or when external pressure (from fluid, a tumor, or a pneumothorax) compresses the lung. Clinically you may see decreased or absent breath sounds over the affected area and signs of hypoxemia with shallow breathing. It’s distinct from pneumonia, which is infection with alveolar filling; pleuritis, which is inflammation of the pleura; and empyema, which is pus in the pleural space.