Fick principle — FRCA Primary MCQ

Correct answer: B — Reduced haemoglobin lowers arterial oxygen content

The Fick principle relates oxygen consumption to cardiac output and arteriovenous content difference. Acidosis shifts the oxyhaemoglobin curve right is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Small myelinated fibres block relatively early is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Aldosterone increases sodium reabsorption and potassium secretion is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. High oxygen consumption and low FRC shorten safe apnoea time 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