Neonatal / Pediatric Respiratory Distress Syndrome (RDS)

Also called: Hyaline Membrane Disease (HMD) | Infantile RDS (IRDS) | Surfactant Deficiency Disorder

1. Introduction & Overview

• ~92% at 24-25 weeks gestation
• ~88% at 26-27 weeks
• ~76% at 28-29 weeks
• ~57% at 30-31 weeks

2. Fetal Lung Development - The Foundation

3. Surfactant - What It Is and What It Does

• ~90% phospholipids - mainly dipalmitoyl phosphatidylcholine (DPPC), the workhorse molecule
• ~10% proteins - SP-A, SP-B, SP-C, SP-D

Surface tension (T) = Pressure (P) × radius (r) / 2

• SP-B and SP-C - small hydrophobic proteins that are essential for surface tension reduction; present in commercial surfactant preparations
• SP-A and SP-D - larger hydrophilic proteins involved in host defense and maintaining surfactant pool size

4. Pathophysiology of RDS

The Core Problem: Surfactant Deficiency

Premature birth (< 34 weeks)
        ↓
Insufficient Type II pneumocytes → LOW SURFACTANT
        ↓
High alveolar surface tension
        ↓
Alveolar collapse (ATELECTASIS) at end-expiration
        ↓
Reduced functional residual capacity (FRC)
        ↓
V/Q mismatch → HYPOXIA + HYPERCAPNIA
        ↓
Pulmonary vasoconstriction → Pulmonary hypertension
        ↓
Right-to-left shunt (through PDA or foramen ovale)
        ↓
Worsened hypoxia → Acidosis
        ↓
Acidosis further damages Type II cells
        ↓
Even LESS surfactant produced → vicious cycle

The Hyaline Membrane

Factors That Worsen Surfactant Deficiency

5. Clinical Presentation

Classic Signs (TNRCG mnemonic):

• T - Tachypnea (respiratory rate > 60 breaths/min)
• N - Nasal flaring
• R - Retractions - subcostal, intercostal, sternal notch (use of accessory muscles)
• C - Cyanosis (central)
• G - Grunting (expiratory) - the HALLMARK sign

Why does the baby grunt?

Clinical Course

• Symptoms worsen over the first 48-72 hours
• Then gradually improve (natural surfactant production increases)
• With exogenous surfactant treatment, recovery is much faster

6. Radiology - Chest X-Ray

CXR Grade 1 (Mild)

CXR Grade 3-4 (Severe)

CXR Grading System (4 Grades)

Pathognomonic features:

1. Ground-glass reticulogranular pattern - diffuse microatelectasis
2. Air bronchograms - air-filled large airways visible against the opacified alveolar background
3. Low lung volumes - small, hypoexpanded chest
4. Note: Hyperinflation in a preterm infant without ventilation makes RDS highly unlikely

7. Diagnosis

Differential Diagnosis

8. Management

Antenatal Prevention (the most impactful intervention!)

• Betamethasone (preferred): 12 mg IM × 2 doses, 24 hours apart
  • OR Dexamethasone: 6 mg IM × 4 doses, 12 hours apart
• Given to mothers at risk of preterm delivery between 24-34 weeks gestation
• Extended to 34-37 weeks (late preterm) if delivery risk is present
• Also recommended for elective cesarean at term (reduces respiratory morbidity)
• Mechanism: Corticosteroids stimulate surfactant production by maturing Type II pneumocytes and increasing SP-B and SP-C gene expression
• A single rescue course is recommended if >7 days since first course and delivery still threatened
• Recent evidence (2025 meta-analysis, PMID 40418984): beneficial even for late preterm births

Postnatal Management - Step-by-Step

• Warm, neutral thermal environment (incubator or radiant warmer)
• Pulse oximetry monitoring; target SpO₂ 90-95% (avoid both hypoxia AND hyperoxia)
• PaO₂ target: 50-80 mmHg
• Screen for sepsis (blood culture, CBC); start empirical antibiotics × 48h until cultures clear

Mild RDS          →  Supplemental O₂ (nasal cannula/hood)
                          ↓
Moderate RDS      →  CPAP (nasal)  ← Start here for most preterm infants
                          ↓
Severe RDS        →  Intubation + Mechanical Ventilation

• Bubble CPAP (4-6 cm H₂O via nasal prongs) - keeps alveoli open, reduces work of breathing, reduces intubation need
• Gentle ventilation strategies are preferred to minimize barotrauma/volutrauma - the INSURE technique (INtubate, SURfactant, Extubate) aims to minimize ventilation time

• Delivered intratracheally via endotracheal tube
• Works immediately - increases lung compliance, reduces oxygen and pressure requirements
• Animal-derived surfactants (containing SP-B and SP-C) are the standard:
  • Beractant (Survanta) - bovine
  • Poractant alfa (Curosurf) - porcine (most widely used)
  • Calfactant (Infasurf) - calf lung
• Three strategies:
  1. Prophylactic - given before first breath to all at-risk infants (< 27-28 weeks)
  2. Early rescue - given within 2 hours of clinical diagnosis
  3. Late rescue - given when FiO₂ > 0.3-0.4 and X-ray confirms RDS
• Latest evidence (2024-2025 network meta-analysis, PMID 39736686 and 41430414): Poractant alfa + budesonide shows additional benefit in extremely preterm infants ≤28 weeks, reducing BPD rates
• Less invasive surfactant administration (LISA/MIST): surfactant given via thin catheter while baby breathes spontaneously on CPAP - avoids intubation, increasingly preferred

9. Complications

Acute Complications:

Chronic / Long-term Complication:

• Defined as oxygen dependency at 28 days of life (or 36 weeks corrected gestational age)
• Caused by: oxygen toxicity, barotrauma/volutrauma from mechanical ventilation, inflammation, infection
• Histology: simplified large alveoli, impaired capillary development, variable interstitial fibrosis
• Management: gradual weaning of O₂ and ventilatory support, pulmonary vasodilators (sildenafil, bosentan, nitric oxide) if pulmonary hypertension develops

10. Visual Summary

11. Quick Memory Mnemonics for MBBS

Risk Factors - "PDMCMG":

• Prematurity
• Diabetes (maternal)
• Male sex
• Caesarean (without labor)
• Multiple gestation (twins)
• Genetic (SP-B deficiency)

Signs - "TNCGR" (The Newborn Can't Get air Right):

• Tachypnea
• Nasal flaring
• Cyanosis
• Grunting (expiratory)
• Retractions

Management - "ASST":

• Antenatal steroids (prevention)
• Supplemental oxygen / SpO₂ targets
• Surfactant replacement
• Thermal environment + supportive care

12. Recent Evidence Update (2024-2026)

Key Take-Home Points for Exams

1. RDS = surfactant deficiency in preterm infants - Type II pneumocytes not mature enough
2. Hallmark sign = expiratory grunting (auto-PEEP mechanism)
3. CXR = ground-glass reticulogranular pattern + air bronchograms + low lung volumes
4. Pathology = hyaline membranes (eosinophilic) lining alveolar ducts on histology
5. Prevention = antenatal betamethasone (24-34 weeks, given to mother)
6. Treatment = CPAP + exogenous surfactant (intratracheal)
7. Key complication = BPD (chronic lung disease of prematurity)
8. RDS worsens over 48-72h then improves - surfactant accelerates this recovery

Sources: Creasy & Resnik's Maternal-Fetal Medicine, Fishman's Pulmonary Diseases and Disorders, The Developing Human: Clinically Oriented Embryology, Langman's Medical Embryology, StatPearls (NIH), LearningRadiology.com; supplemented with 2024-2025 PubMed meta-analyses (PMIDs: 39736686, 40418984, 41430414).