Respiratory Flashcards
Meconium Aspiration Syndrome (MAS)
Respiratory condition where the newborn inhales (aspirates) meconium-stained amniotic fluid into the lungs, before or during delivery, from foetal distress (asphyxia → hypoxia → vagal stimulation → meconium release) or post-term delivery. Leads to:
- Airway obstruction (partial/complete) & respiratory distress
- Chemical pneumonitis (inflammatory reaction)
- Surfactant inactivation causing ↓ compliance
- Barrel-shaped chest (hyperinflation)
- PPHN
- HIE
What is the link between MAS and HIE?
The same hypoxic insult that causes MAS can cause HIE, both often co-exist.
- Perinatal asphyxia (impaired gas exchange) occurs before/during/after birth causing hypercapnia, acidosis, hypoxia.
- Asphyxia → hypoxia → vagal stimulation → meconium release → aspiration
- Sustained hypoxia/ischaemia during labour → impaired cerebral perfusion & O2 delivery → primary energy failure (HIE) → cell death cascade (latent phase, possibly secondary energy failure)
- MAS is the pulmonary consequence of hypoxia, HIE is the neurological consequence
What is the link between MAS and PPHN?
MAS can lead to PPHN by ↑ PVR
- Airway obstruction (air trapping, hyperinflation, alveolar collapse)
- Inflammation & damaged alveolar-capillary barrier
- Surfactant inactivation
- Severe hypoxia + acidosis → pulmonary vasoconstriction + ↑ PVR
- High PVR exceeds systemic vascular resistance, so blood is shunted right to left via PDA/PFO, bypassing the lungs, worsening hypoxia
What is the link between MAS and surfactant?
The elements that compose meconium inactivate surfactant causing inflammation and alveolar collapse, impaired gas exchange, ↓ lung compliance.
- Surfactant therapy given in mod-severe cases MAS to restore lung function & improve oxygenation until internal surfactant production re-starts
Respiratory Distress Syndrome (RDS)
Insufficient surfactant production in pre-term neonates within 6h of life, causing:
- Alveolar collapse
- Impaired gas exchange
- Respiratory distress.
- ↓ lung compliance
- Hypoxia & hypercapnia
- Formation of hyaline membranes (fibrin & necrotic cells lining alveoli)
Transient Tachypnoea of the Newborn (TTN)
Delayed clearance of foetal lung fluid causing tachypnoea in term neonates.
- Common in elective C-section, rapid delivery, maternal diabetes
- Normally in utero, lungs are filled with fluid and should be drained by lymphatics at birth
- Delayed drainage causes pulmonary oedema, ↓ lung compliance, ↓ gas exchange
- Leads to tachypnoea (>60 breaths/min) in first 2h of life
- No significant hypoxia or cyanosis
- Resolves in 24-72h
Process and effect of surfactant therapy
- Natural or synthetic surfactant
- Endotracheal tube (intubate) directly into lungs or thin catheter (less invasive).
- Spreads across alveoli ↓ surface tension, ↑ compliance, ↓ respiratory effort
- Improves oxygenation within minutes
