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Fick Principle Equation — FRCA Primary MCQ

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HardPhysiology - CardiovascularFick Principle EquationFRCA Primary

Oxygen consumption is 250 mL/min and the arterial–mixed venous oxygen-content difference is 50 mL/L. What cardiac output does the Fick principle give?

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Correct answer: A — 5.0 L/min after converting the content difference to mL/L

The best answer is “5.0 L/min after converting the content difference to mL/L”. The Fick equation is cardiac output = oxygen consumption divided by the arterial–mixed venous oxygen-content difference. Here 250 mL/min ÷ 50 mL/L equals 5 L/min. Unit discipline matters: treating 50 mL/L as 50 mL/dL would introduce a tenfold error. A normal-value estimate must not replace the calculation.

Reference: Resuscitation Council UK, Adult Advanced Life Support Guidelines 2025: https://www.resus.org.uk/cy/node/36438