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Fick principle cardiac output — FRCA Primary MCQ

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HardPhysiologyFick principle cardiac outputFRCA Primary

During a research measurement, whole-body oxygen consumption is 250 mL/min, arterial oxygen content is 200 mL/L and mixed venous oxygen content is 150 mL/L. What is the most appropriate cardiac output?

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Correct answer: E — 5 L/min

By the Fick principle, cardiac output equals oxygen consumption divided by the arteriovenous oxygen content difference. The difference is 50 mL/L, so 250 mL/min divided by 50 mL/L gives 5 L/min. The tempting 10 L/min answer usually results from using a 25 mL/L difference. Fick calculations require consistent units.

Reference: Ganong Review of Medical Physiology; Primary FRCA physiology texts