Respiratory Distress Syndrome (RDS)

Pathophysiology & Diagnostics

• Primary deficiency of surfactant production by Type II alveolar cells (peaks at 32-34 wks) leading to increased high alveolar surface tension.
• Creates intense atelectasis, severe V/Q mismatch, and intra-pulmonary right-to-left shunting.
• Biochemical: Exact L/S ratio (Lecithin-to-Sphingomyelin) < 2.0 or absent Phosphatidylglycerol (PG) in amniotic fluid implies severe lung immaturity.
• Classic Radiograph: Diffuse, hazy, bilateral reticulogranular opacities ('ground-glass') with visible air bronchograms overriding the cardiac silhouette, and extremely low lung volumes (< 8 ribs expansion).

Initial Respiratory Protocol (Delivery Room & NICU)

• Initiate Continuous Positive Airway Pressure (CPAP) at 5 to 8 cm H2O immediately in delivery room for breathing preterm infants.
• Intubation indications: Apnea, pH < 7.20 with PaCO2 > 60-65 mmHg, or failure of CPAP requiring sustained FiO2 > 0.30 - 0.40 to keep SpO2 > 90%.
• Volume Guarantee (VG) Mechanical Ventilation limits barotrauma. Target tidal volumes of 4.5 to 5.5 mL/kg, PEEP 5-6 cmH2O.
• Target oxygenation index aggressively: Strict SpO2 targets 90-95% consistently. Do NOT exceed 95% in extreme preemies to minimize severe ROS toxicity.

Exogenous Surfactant Dosing & Administration

• Timing is critical: Rescue administration indicated strictly when CPAP is failing (FiO2 > 30%) or immediately if electively intubated.
• Poractant alfa (Curosurf) specifics: Initial dose is exactly 2.5 mL/kg (200 mg/kg), administered via specific dual-channel ET tube catheter.
• Calfactant (Infasurf) or Beractant (Survanta): alternative bovines; follow exact manufacturer mL/kg limits based on phospholipid concentrations.
• Methods to minimize ventilation span: Use INSURE technique (INtubate, SURfactant, Extubate to CPAP within 30-60 mins).
• Emerging Method: LISA/MIST (Less Invasive Surfactant Administration) via a thin angiocatheter placed through vocal cords while baby spontaneously breathes on CPAP.

Adjunctive Medical Therapy

• Antenatal Corticosteroids: Ensure maternal Betamethasone (12 mg IM q24h x 2 doses) administered > 48h and < 7 days before delivery accelerates pneumocyte maturation.
• Caffeine Citrate: Administer loading dose 20 mg/kg promptly within the first 24 hours of life to stimulate central respiratory drive, augment tidal volume, and facilitate extubation.
• Maintain strict thermoregulation (incubator humidity > 80% initially) and carefully restrict initial fluids (60-80 mL/kg/day) to prevent pulmonary edema.

Diagnostic & Management Algorithm

• MIST/LISA Surfactant Delivery Algorithm: [START] Infant < 30wks on CPAP 6cmH2O with FiO2 > 30% -> [ACTION] Positioning & Atropine 10mcg/kg -> [PROCEDURE] Direct laryngoscopy, insert thin angiocath through vocal cords -> [DELIVERY] Administer Poractant 200mg/kg over 1-3 mins while breathing spontaneously -> [END] Remove catheter, maintain CPAP

References

1. Sweet DG, Carnielli V, Greisen G, et al. European Consensus Guidelines on the Management of Respiratory Distress Syndrome - 2022 Update. Neonatology.
2. Polin RA, Carlo WA; Committee on Fetus and Newborn. Surfactant replacement therapy for preterm and term neonates with respiratory distress. Pediatrics.