Asphyxia: inert gas: practice question

A Forensic 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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Forensic Medicine · Asphyxia: inert gas

Sample item

A man is found dead with a plastic bag over his head connected by a tube to a cylinder of nitrogen. The face is only mildly cyanosed and there are no signs of struggle. Why would he feel little distress before losing consciousness?

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

The answer and the reasoning

B. Oxygen is displaced but carbon dioxide does not accumulate, so there is no air hunger

The urge to breathe is driven mainly by rising carbon dioxide, not falling oxygen. In an inert gas atmosphere, expired carbon dioxide is washed out, so hypoxia develops without hypercapnia and with little distress, and unconsciousness comes rapidly. Autopsy findings are often non-specific, so circumstances and gas analysis are important.

Option by option

  • A. Nitrogen binds haemoglobin more strongly than oxygen

    Binding to haemoglobin more strongly than oxygen is the mechanism of carbon monoxide, not nitrogen.

  • B. Oxygen is displaced but carbon dioxide does not accumulate, so there is no air hunger (correct)

    Correct. Oxygen lack without carbon dioxide build-up does not provoke air hunger.

  • C. Nitrogen causes immediate cardiac arrest

    Death is from hypoxia, not from direct cardiac poisoning.

  • D. The gas has a strong sedative action on the brain

    Nitrogen is physiologically inert and is not sedative at normal pressure.

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.

More Forensic Medicine questions

Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is B, Oxygen is displaced but carbon dioxide does not accumulate, so there is no air hunger. The urge to breathe is driven mainly by rising carbon dioxide, not falling oxygen.

Why is "Nitrogen binds haemoglobin more strongly than oxygen" not the answer?

Binding to haemoglobin more strongly than oxygen is the mechanism of carbon monoxide, not nitrogen.

Why is "Nitrogen causes immediate cardiac arrest" not the answer?

Death is from hypoxia, not from direct cardiac poisoning.

Why is "The gas has a strong sedative action on the brain" not the answer?

Nitrogen is physiologically inert and is not sedative at normal pressure.

What concept does this question test?

It tests Asphyxia: inert gas in Forensic Medicine. In an inert gas atmosphere, expired carbon dioxide is washed out, so hypoxia develops without hypercapnia and with little distress, and unconsciousness comes rapidly. Autopsy findings are often non-specific, so circumstances and gas analysis are important.

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 Asphyxia: inert gas?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic 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.