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Carbon monoxide poisoning — DIPIMC MCQ

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ModerateEnvironmental MedicineCarbon monoxide poisoningDIPIMCDipIMC

A family is rescued from a house with a faulty boiler, complaining of headache, nausea and dizziness. Their pulse oximetry reads 99%. Why might the oximeter be misleading, and what is the appropriate action?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Oximetry cannot detect carboxyhaemoglobin; give high-flow oxygen

Standard pulse oximetry cannot distinguish carboxyhaemoglobin from oxyhaemoglobin, so it can read falsely normal in carbon monoxide poisoning; the correct action is to give high-flow oxygen to speed carbon monoxide elimination and transfer for assessment and carboxyhaemoglobin measurement. Relying on the oximeter to exclude poisoning is dangerous. A cluster of people with headache and nausea in one building strongly suggests carbon monoxide. Pearl: high-flow oxygen shortens the half-life of carboxyhaemoglobin, and hyperbaric oxygen is considered in severe cases.

Reference: TOXBASE; JRCALC Clinical Guidelines