What is the primary pathophysiologic consequence of surfactant deficiency in RDS?

What is the primary pathophysiologic consequence of surfactant deficiency in RDS?

• A. Increased surface tension causing alveolar collapse
• B. Decreased surface tension causing overinflation
• C. Increased airway perfusion without edema
• D. Decreased work of breathing

Answer: (A)

Surfactant lowers surface tension at the air–liquid interface in the alveoli, which keeps them open during expiration and makes inflation easier. When surfactant is deficient, surface tension remains high, so alveoli tend to collapse at end expiration (atelectasis). This collapse reduces lung compliance and functional residual capacity, increasing the work of breathing and causing hypoxemia from uneven ventilation. Therefore, the primary consequence is increased surface tension leading to alveolar collapse.

Surfactant lowers surface tension at the air–liquid interface in the alveoli, which keeps them open during expiration and makes inflation easier. When surfactant is deficient, surface tension remains high, so alveoli tend to collapse at end expiration (atelectasis). This collapse reduces lung compliance and functional residual capacity, increasing the work of breathing and causing hypoxemia from uneven ventilation. Therefore, the primary consequence is increased surface tension leading to alveolar collapse.