Describe how the respiratory system of a newborn differs from that of an adult.
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.
Domain | Differences in the neonate | In the adult |
Airway |
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Airway resistance |
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Lung volumes and spirometry variables |
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Compliance |
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Gas exchange |
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Control of respiration |
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Respiratory enegetics |
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Davis, Ryan P., and George B. Mychaliska. "Neonatal pulmonary physiology." Seminars in pediatric surgery. Vol. 22. No. 4. WB Saunders, 2013.
Neumann, Roland P., and Britta S. von Ungern‐Sternberg. "The neonatal lung–physiology and ventilation." Pediatric Anesthesia 24.1 (2014): 10-21.
LoMauro, Antonella, and Andrea Aliverti. "Physiology masterclass: extremes of age: newborn and infancy." Breathe 12.1 (2016): 65-68.