Respiratory System
RDS and surfactant
Respiratory distress syndrome reflects surfactant deficiency, most often in preterm infants. Signs include tachypnea, grunting, retractions, and increasing oxygen need; chest radiograph shows low volumes and ground-glass opacities. Early CPAP reduces the need for intubation. Surfactant is given through the ETT, often by INSURE (intubate-surfactant-extubate to CPAP). Antenatal corticosteroids accelerate surfactant production and reduce RDS severity.
Oxygen targets and ventilation
Target preductal SpO2 90-95% for preterm infants (alarm limits about 89-96%) and 92-97% for term infants. Avoid hyperoxia, which contributes to BPD and retinopathy of prematurity. CPAP is typically 5-8 cm H2O; volume-targeted ventilation 4-6 mL/kg; permissive hypercapnia with PaCO2 45-55 mmHg and pH above 7.20 is acceptable in some preterm infants. BPD is defined as supplemental oxygen or respiratory support at 36 weeks postmenstrual age, graded by FiO2 and mode.
Apnea and air leak
Apnea of prematurity is treated with caffeine citrate (20 mg/kg load, 5-10 mg/kg/day). Pneumothorax causes sudden desaturation, asymmetry, and shifted heart sounds; transilluminate and needle-decompress if tension.
Worked example
A 27-week infant on day 3 has FiO2 0.45, MAP 10, pH 7.18, PaCO2 70. Reasoning: hypoventilation plus evolving RDS. Check ETT position and patency, exclude pneumothorax, optimize volume and MAP, and consider repeat surfactant. Do not simply increase oxygen.
Traps
- Blaming desaturation on lung disease alone; consider PDA, sepsis, anemia, apnea, and congenital heart disease.
- Weaning CPAP too quickly in a 26-week infant.
- Missing a pneumothorax after sudden deterioration.