Surfactant therapy primarily serves to do which of the following in neonates with respiratory distress?

• A. Increase alveolar edema
• B. Decrease surface tension
• C. Decrease pulmonary blood flow
• D. Increase lung compliance

Answer: (B)

Surfactant therapy works by lowering the surface tension at the air–liquid interface inside the alveoli. When surface tension is reduced, especially in the very small alveoli of preterm lungs, these air sacs are less prone to collapse during expiration. Keeping more alveoli open improves gas exchange, reduces the work needed to breathe, and enhances lung compliance. While increased compliance is a beneficial consequence, the direct, primary action is lowering surface tension. The other options describe effects that aren’t the primary purpose of surfactant therapy (edema, decreased pulmonary blood flow), and while surfactant does help lung mechanics, its key mechanism is reducing surface tension.