Toxicology: 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 · Toxicology

Sample item

Why can carbon monoxide poisoning be difficult to recognize from pulse oximetry alone?

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

The answer and the reasoning

A. Standard pulse oximeters may misread carboxyhaemoglobin as oxyhaemoglobin

Conventional pulse oximeters cannot reliably distinguish oxyhaemoglobin from carboxyhaemoglobin, so readings may appear falsely reassuring; co-oximetry and exposure history are important when carbon monoxide is suspected.

Option by option

  • A. Standard pulse oximeters may misread carboxyhaemoglobin as oxyhaemoglobin (correct)

    Correct: standard oximetry can overestimate oxygenation in carbon monoxide poisoning.

  • B. It always produces severe cyanosis

    Cyanosis may be absent despite dangerous poisoning.

  • C. Pulse oximetry measures only blood pressure

    Pulse oximetry estimates oxygen saturation, not blood pressure.

  • D. Carbon monoxide never affects haemoglobin

    Carbon monoxide binds haemoglobin strongly and impairs oxygen delivery.

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 A, Standard pulse oximeters may misread carboxyhaemoglobin as oxyhaemoglobin. Conventional pulse oximeters cannot reliably distinguish oxyhaemoglobin from carboxyhaemoglobin, so readings may appear falsely reassuring; co-oximetry and exposure history are important when carbon monoxide is suspected.

Why is "It always produces severe cyanosis" not the answer?

Cyanosis may be absent despite dangerous poisoning.

Why is "Pulse oximetry measures only blood pressure" not the answer?

Pulse oximetry estimates oxygen saturation, not blood pressure.

Why is "Carbon monoxide never affects haemoglobin" not the answer?

Carbon monoxide binds haemoglobin strongly and impairs oxygen delivery.

What concept does this question test?

It tests Toxicology in Forensic Medicine. The correct option holds because: Correct: standard oximetry can overestimate oxygenation in carbon monoxide poisoning.

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 Toxicology?

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.