CO Poisoning SpO₂ — RACP Adult Medicine MCQ

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EasyEmergency MedicineCO Poisoning SpO₂RACP Adult Medicine

A 55-year-old man in a house fire has COHb 35%. SpO₂ reads 98%. Why the discrepancy?

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Correct answer: D — Pulse oximetry cannot distinguish COHb from oxyHb – falsely normal readings

Standard pulse oximeters read COHb as oxyHb. Co-oximetry (ABG) required for accurate saturation. Treat with 100% O₂.

Reference: eTG – 2025 – Toxicology; ARC – 2024