Cardiovascular: Fick principle: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Cardiovascular: Fick principle

Sample item

In a resting patient, oxygen consumption is 300 mL/min, arterial oxygen content is 19 mL/dL, pulmonary artery oxygen content is 14 mL/dL and heart rate is 75 per minute. What is the stroke volume?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. 80 mL

Cardiac output = oxygen consumption / arteriovenous oxygen difference = 300 / (19 - 14) = 300 / 5 = 60 dL/min, which is 6 L/min (the difference is per dL, so 5 mL/dL = 50 mL/L and 300 / 50 = 6). Stroke volume = 6000 mL/min divided by 75 per minute = 80 mL.

Option by option

  • A. 800 mL

    This results from forgetting to convert dL to litres, giving 60 L/min.

  • B. 80 mL (correct)

    Correct. 6 L/min divided by 75 beats per minute gives 80 mL.

  • C. 40 mL

    This would result from an arteriovenous difference of about 10 mL/dL, giving 3 L/min.

  • D. 120 mL

    This would need an arteriovenous difference near 3.3 mL/dL, giving 9 L/min.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, 80 mL. Cardiac output = oxygen consumption / arteriovenous oxygen difference = 300 / (19 - 14) = 300 / 5 = 60 dL/min, which is 6 L/min (the difference is per dL, so 5 mL/dL = 50 mL/L and 300 / 50 = 6).

Why is "800 mL" not the answer?

This results from forgetting to convert dL to litres, giving 60 L/min.

Why is "40 mL" not the answer?

This would result from an arteriovenous difference of about 10 mL/dL, giving 3 L/min.

Why is "120 mL" not the answer?

This would need an arteriovenous difference near 3.3 mL/dL, giving 9 L/min.

What concept does this question test?

It tests Cardiovascular: Fick principle in Physiology. Stroke volume = 6000 mL/min divided by 75 per minute = 80 mL.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiovascular: Fick principle?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.