Respiratory · Year 1 · from Respiratory
Case 2: Neonatal Respiratory Distress Syndrome
Case Presentation
A 28-week gestational age male infant is born via emergency cesarean section due to placental abruption. The infant weighs 1,100 grams. Within minutes of birth, the neonate develops grunting respirations, nasal flaring, and intercostal retractions. The infant appears cyanotic despite supplemental oxygen by hood. Vital signs show respiratory rate 72/min and heart rate 165 bpm. Oxygen saturation is 82% on 40% FiO2. Chest X-ray reveals diffuse bilateral ground-glass opacities with air bronchograms and low lung volumes, described as a "white-out" pattern. Arterial blood gas shows pH 7.22, PaCO2 58 mmHg, PaO2 45 mmHg, and HCO3 22 mEq/L.
The diagnosis of neonatal respiratory distress syndrome (RDS) is made based on prematurity, clinical presentation, and radiographic findings. The underlying pathophysiology is surfactant deficiency due to immature type II pneumocytes. Without adequate surfactant, surface tension at the air-liquid interface is high, leading to alveolar instability, atelectasis, and decreased lung compliance. According to LaPlace's law (P = 2T/r), smaller alveoli have higher collapsing pressure, causing them to empty into larger alveoli.
The infant is intubated and given exogenous surfactant replacement therapy via the endotracheal tube. Within hours, oxygenation improves significantly. The infant requires mechanical ventilation with low tidal volumes and appropriate PEEP to maintain alveolar recruitment. Over the following days, endogenous surfactant production increases as type II pneumocytes mature, and the infant is successfully weaned from mechanical ventilation.
Key Learning Points
- Pulmonary surfactant, produced by type II pneumocytes, reduces alveolar surface tension and increases lung compliance
- Surfactant deficiency leads to high surface tension, decreased compliance, atelectasis, and increased work of breathing
- LaPlace's law explains alveolar instability: without surfactant, small alveoli with higher collapsing pressure empty into larger alveoli
- Surfactant molecules concentrate during alveolar compression (expiration), further reducing surface tension and stabilizing alveoli
- Exogenous surfactant replacement therapy has dramatically improved outcomes in premature infants with RDS