Question 7

Describe how the respiratory system of a newborn differs from that of an adult.

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College Answer

This question required anatomical detail relating to the upper airway and bronchial tree, 
which was generally answered well. The functional implications of a highly compliant chest 
wall in defending FRC and the relationship of FRC to closing volume was less clearly 
explained. Better answers mentioned the high physiological dead space, oxygen 
consumption and work of breathing. Additional points were awarded for discussing the 
immaturity of the respiratory control centre and propensity for apnoea.
Common omissions included not providing comparative adult data or a written description 
of how neonates differed from adults (or the significance of this). Candidates confused chest 
wall compliance (increased in newborns) with lung compliance (reduced in newborns but 
rapidly approaches normal adult values as “specific compliance”). Increased oxygen 
consumption necessitates increased minute ventilation (with tidal volumes equivalent to 
adults on a weight basis) via respiratory rate.
Functional Residual Capacity FRC (equivalent to adults) and Closing Capacity (increased 
relative to adults) were often confused. Better answers provided responses often in tabular format. Discussion of cardiovascular responses and response to drugs were not requested and gained no marks.