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Entonox contraindications — DIPIMC MCQ

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HardPharmacology (Pre-Hospital)Entonox contraindicationsDIPIMCDipIMC

You are considering Entonox (50% nitrous oxide and 50% oxygen) for pre-hospital analgesia. In which of the following situations is it most clearly contraindicated?

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

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Correct answer: D — A suspected pneumothorax following blunt chest trauma

Nitrous oxide diffuses into air-filled spaces faster than nitrogen can leave, so it expands trapped gas; Entonox is therefore contraindicated where a closed gas space may be present or enlarging, including pneumothorax, decompression illness, bowel obstruction, and a base-of-skull injury with possible intracranial air. A simple closed limb fracture, uncomplicated labour, a sprain and renal colic are all appropriate indications in a stable patient. The specific danger in a suspected pneumothorax is conversion to a tension pneumothorax. Pearl: ask about recent diving and exclude a pneumothorax before offering Entonox after chest trauma.

Reference: JRCALC Clinical Guidelines