In respiratory distress syndrome, the expiratory grunt is best understood as an effort to:

• A. Conserve energy
• B. Decrease upper airway resistance
• C. Maintain a normal functional residual capacity
• D. Increase inspiratory effort to improve oxygenation

Answer: (C)

The expiratory grunt in neonatal respiratory distress syndrome is best understood as a mechanism to keep the lungs from collapsing at the end of exhalation. In RDS, surfactant deficiency makes the lungs stiff and alveoli tend to collapse during expiration, reducing functional residual capacity (FRC). By partially closing the glottis during expiration, the infant generates a small positive pressure in the airways (self-induced PEEP), which helps maintain airway and alveolar patency and preserves FRC. This preservation of end-expiratory lung volume improves gas exchange. It is not primarily about conserving energy, decreasing upper airway resistance, or increasing inspiratory effort.