Embryology- <16 weeks: Pseudoglandular
- 16-24 weeks: Canalicular
- Some primitive gas exchange possible
- 24-36 weeks: Saccular
- Beginning of surfactant production
- >36 weeks: Alveolar
CXR- 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
- Cold
- Asphyxia
- C-section
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
Notes- 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
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