Atelectasis refers to which condition?

• A. Lung Collapse (Complete or Partial)
• B. Pneumonia
• C. Alveolar overdistension
• D. Fluid in the alveoli

Answer: (A)

Atelectasis is the collapse or non-aeration of lung tissue—parts of the lung aren’t filling with air, so those alveoli are deflated and not participating in gas exchange. This partial or complete collapse reduces oxygenation in the affected region and can happen after surgery, from airway obstruction (like mucus plugs), or from external compression (such as fluid or air pressing on the lung). It differs from pneumonia, which is an infection that fills alveoli with inflammatory fluid and causes consolidation; from alveolar overdistension, which is air sacs that are overly stretched or inflated; and from edema, where fluid collects in the alveoli. So the description that fits best is lung collapse (complete or partial).