Respiratory System
Core concepts
Neonatal respiratory disorders dominate this domain: respiratory distress syndrome (RDS) from surfactant deficiency, transient tachypnea of the newborn (TTN), meconium aspiration syndrome, and bronchopulmonary dysplasia. Understand signs of respiratory distress - tachypnea, grunting, nasal flaring, retractions, cyanosis - and the role of antenatal corticosteroids in accelerating surfactant production. Know the physiology of fetal lung fluid clearance and why TTN occurs (delayed clearance, often after cesarean delivery without labor). Understand oxygen therapy hazards, including retinopathy of prematurity and oxygen toxicity. For the high-risk mother, recognize how maternal conditions (diabetes, hypertension, smoking) affect fetal lung maturity and growth.
Traps
Questions often contrast RDS (surfactant deficiency, preterm, ground-glass infiltrates) with TTN (term or late preterm, rapid resolution, fluid in fissures). A frequent trap is assuming all tachypnea is RDS. Another trap: forgetting that oxygen must be titrated to target saturations, not maximized.
Worked example
A late preterm infant born by elective cesarean has tachypnea and grunting that resolves within 48 hours with supportive care. Rule of thumb: TTN is a diagnosis of exclusion that improves quickly; RDS worsens over the first hours and responds to surfactant and CPAP. Antenatal steroids are the single most effective prevention for RDS.
Study focus
Differentiate the common neonatal respiratory disorders by onset, risk factors, and radiographic pattern.