A 28-week preterm infant born to a mother with incomplete antenatal corticosteroid coverage presents with respiratory distress within 2 hours of birth. Chest X-ray shows a ground-glass appearance with air bronchograms. Regarding the pathophysiology and management of Respiratory Distress Syndrome (RDS), all of the following are true EXCEPT:

Explanation

## Pathophysiology of RDS **Key Point:** Respiratory Distress Syndrome (RDS), formerly called Hyaline Membrane Disease, is caused by surfactant deficiency in preterm infants, leading to increased alveolar surface tension and progressive atelectasis. ### Surfactant and Alveolar Mechanics **High-Yield:** Surfactant is a lipoprotein complex (90% lipid, 10% protein) synthesized by type II pneumocytes. It reduces surface tension at the air-liquid interface, preventing alveolar collapse and reducing the work of breathing. - **Deficiency mechanism:** Immature lungs (especially <32 weeks gestation) produce insufficient surfactant, causing: - Increased alveolar surface tension - Progressive atelectasis (collapse) - Ventilation-perfusion mismatch - Hypoxemia and hypercapnia ### Antenatal Corticosteroids **Clinical Pearl:** Maternal corticosteroids (betamethasone or dexamethasone) given 24 hours to 7 days before preterm delivery significantly reduce RDS incidence and severity by: 1. Accelerating surfactant synthesis in fetal lungs 2. Promoting type II pneumocyte maturation 3. Reducing intraventricular hemorrhage and necrotizing enterocolitis **Mnemonic: CRIB** — **C**orticosteroids **R**educe **I**ncidence of **B**irth complications ### Exogenous Surfactant Replacement **Key Point:** Surfactant therapy is MOST EFFECTIVE when administered **early** — ideally within the **first 6–12 hours of life**, and certainly before 72 hours. Early treatment: - Prevents further alveolar damage - Reduces need for mechanical ventilation - Decreases mortality and morbidity (BPD, IVH) **Warning:** The statement "most effective after 72 hours" is **FALSE**. Surfactant given after 72 hours has diminished benefit because: - Hyaline membranes have already formed - Secondary surfactant deficiency develops - Lung injury is more established ### PEEP and Mechanical Ventilation **High-Yield:** Positive End-Expiratory Pressure (PEEP) is a cornerstone of RDS management: - Maintains alveolar patency during expiration - Prevents repetitive opening-closing of alveoli (atelectotrauma) - Reduces intrapulmonary shunting - Improves oxygenation and reduces FiO~2~ requirement **Clinical Pearl:** Even gentle ventilation with PEEP (5–6 cm H~2~O) is superior to no PEEP in RDS. ## Summary Table: RDS Management Principles | Intervention | Timing | Mechanism | Effectiveness | | --- | --- | --- | --- | | Antenatal corticosteroids | 24 hrs–7 days before delivery | Accelerate surfactant synthesis | ↓ RDS incidence by ~50% | | Exogenous surfactant | **First 6–12 hours of life** | Replace deficient surfactant | ↓ Mortality, BPD | | PEEP/CPAP | Immediately on presentation | Prevent alveolar collapse | ↑ Oxygenation, ↓ FiO~2~ | | Oxygen therapy | Titrate to SpO~2~ 90–95% | Correct hypoxemia | Avoid hyperoxia (ROP) |