Respiratory medicine: COPD: practice question

A General Medicine 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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General Medicine · Respiratory medicine: COPD

Sample item

A 65-year-old man with severe COPD presents with an acute exacerbation, breathlessness and drowsiness. His arterial blood gas on room air shows PaO2 52 mmHg and PaCO2 68 mmHg. What oxygen target is appropriate?

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

The answer and the reasoning

C. Controlled oxygen to keep saturation at 88 to 92%

In patients at risk of hypercapnic respiratory failure, uncontrolled high-flow oxygen can worsen carbon dioxide retention through loss of hypoxic ventilatory drive, worsened ventilation-perfusion matching and the Haldane effect. The aim is a saturation of 88 to 92% using a Venturi mask, with blood gas monitoring. Hypoxia kills faster than hypercapnia, so oxygen must not be withheld.

Option by option

  • A. High-flow oxygen to achieve 100% saturation

    Saturation of 100% risks worsening hypercapnia and acidosis.

  • B. No oxygen, because it will always worsen hypercapnia

    Withholding oxygen from a hypoxaemic patient is dangerous.

  • C. Controlled oxygen to keep saturation at 88 to 92% (correct)

    Correct. Titrated oxygen corrects hypoxaemia without causing dangerous hypercapnia.

  • D. Oxygen only after his PaCO2 normalises

    Hypoxaemia needs correction immediately and cannot wait for gas exchange to normalise.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is C, Controlled oxygen to keep saturation at 88 to 92%. In patients at risk of hypercapnic respiratory failure, uncontrolled high-flow oxygen can worsen carbon dioxide retention through loss of hypoxic ventilatory drive, worsened ventilation-perfusion matching and the Haldane effect.

Why is "High-flow oxygen to achieve 100% saturation" not the answer?

Saturation of 100% risks worsening hypercapnia and acidosis.

Why is "No oxygen, because it will always worsen hypercapnia" not the answer?

Withholding oxygen from a hypoxaemic patient is dangerous.

Why is "Oxygen only after his PaCO2 normalises" not the answer?

Hypoxaemia needs correction immediately and cannot wait for gas exchange to normalise.

What concept does this question test?

It tests Respiratory medicine: COPD in General Medicine. The aim is a saturation of 88 to 92% using a Venturi mask, with blood gas monitoring. Hypoxia kills faster than hypercapnia, so oxygen must not be withheld.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Respiratory medicine: COPD?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.