Neonatal desaturation — FRCA Primary MCQ

Correct answer: D — High oxygen consumption and low FRC shorten safe apnoea time

Neonates have high oxygen consumption and limited oxygen reserves. Reduced haemoglobin lowers arterial oxygen content is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. ADH inserts aquaporin-2 channels in collecting ducts is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Central chemoreceptors respond to CSF hydrogen ion concentration is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Ventilation of poorly perfused alveoli increases dead space is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physiology, the correct answer is usually the variable that best explains the observed change in the anaesthetised patient.

Reference: West's Respiratory Physiology; Ganong Review of Medical Physiology; Primary FRCA textbooks