Paediatric

Question 1

12 characteristics of neonatal airway & respiratory system

Answer 1

1. Neonate and infant have narrower airways (narrowest at subglottic region) – risk of post-extubation sub-glottic oedema. Increased airways resistance until aged 8
2. Greater vagal innervation of upper airway – more bradycardia at intubation + laryngospasm
3. Surface area for gas exchange is reduced.
4. Surfactant production begins at 24-26 weeks
5. Breathing is essentially diaphragmatic
6. Resting O2 consumption is higher (7ml/kg/min; adult = 3)
7. Minute volume is essentially rate dependent due to less developed musculature
8. At birth each terminal bronchiole opens into single alveolus instead of fully developed alveolar cluster
9. Smaller FRC, closing volume occurs within TV
10. CPAP effective at reducing work of breathing – triggers stretch receptors on chest wall
11. Rate of onset and emergence from volatiles is faster
12. Neonatal compliance = 5ml/cmH2o (adult = 100)

Question 2

9 characteristics of fetal / neonatal CVS

Answer 2

1. Fetal circulation: has foramen ovale and ductus arteriosus as shunts from R to L.
2. SVR increases as umbilical cord is clamped.
3. At first breath pulmonary vascular resistance decreases, pulmonary blood flow increases.
4. Consequent change in LA and RA pressures functionally closes foramen ovale.
5. By 10-15 hours after birth, PaO2 has risen and muscular contraction (+ closure) of ductus begins
6. Ductus is usually irreversibly closed by 3 weeks (due to drop in PGE2)
7. Hypoxia and acidosis increase (or keep) PulmVR high so can cause R-L shunt
8. Neonatal ECG has R axis
9. 5-10% fetal cardiac output goes to lungs