• <16 weeks: Pseudoglandular
• 16-24 weeks: Canalicular
• Some primitive gas exchange possible
  
• 24-36 weeks: Saccular
• Beginning of surfactant production
  
• >36 weeks: Alveolar
  

• Hazy lung fields throughout
  
• Stuff obscured
• Heart borders
• Diaphragm if severe

Chronic lung disease (CLD)

• Used to be called bronchopulmonary dysplasia (BPD)
• Results from physical damage to lungs, by repeated forced opening
• Develops within 15 mins of birth
  
• => Usefulness of HFOV

Factors decreasing surfactant production

• Acidosis
• pH <7.25
• Cold
• < 35 degrees
• Asphyxia
• Damages vasculature
• C-section
• Esp. elective

Prevention

• Betamethasone 12 mg q. 24 hr to mum, for all deliveries <35 weeks
• Ideally for 7 days pre-delivery

Management

• Steroids to mum pre-delivery if possible
• Don't give multiple courses of steroids to baby
• Decreases myelination
• Decreases head circumference
• Judicious O2
• Beware:
• ROP
• Cerebral apoptosis
• Reduced blood flow
• Surfactant
• Reduces death (NNT 20)
• Reduces pneumothorax (NNT 50)
• Do it within 15 mins
• 2 doses better than 1
• Caffeine
  
• Extubate early, or use non-invasive CPAP
  

Prevalence

• 90% at 26 weeks
• 70% at 30 weeks
• 20% at 35 weeks
• 1-2% at term

Differentials

• Congenital pneumonia
• Congenital heart disease
• Lung malformation
  

• RDS is a resp rate of >60 at birth
• Key respiratory parameter to change is functional reserve capacity (FRC)
• i.e. can't establish the "open state" to breath over
  
• More than six anterior ribs in the mid-clavicular line shows hyperinflation
• Grunting serves the same purpose as pursed-lips breathing - keeps airways open
• Reduced CO2 causes cerebral vasoconstriction
• cf Over-ventilation