A firefighter is rescued from a house fire with facial burns, singed nasal vibrissae, carbonaceous sputum and hoarseness. He is drowsy. Arterial gas shows PaO2 90 mmHg, PaCO2 38 mmHg and pH 7.30. Which statement about this patient's assessment is correct?

• A Pulse oximetry reading above 95 percent reliably excludes significant carbon monoxide poisoning
• B Intubation should be withheld until stridor appears
• C Hyperbaric oxygen is mandatory for all patients with suspected smoke inhalation
• D Carboxyhaemoglobin level should be measured, and 100 percent oxygen started immediately ✓

Explanation

Smoke inhalation causes both thermal injury to the airway and systemic carbon monoxide poisoning. Pulse oximetry cannot distinguish oxyhaemoglobin from carboxyhaemoglobin, so a normal saturation is dangerously reassuring and does not exclude poisoning. Co-oximetry measures carboxyhaemoglobin directly. One hundred percent oxygen is given immediately since it shortens the carboxyhaemoglobin half-life from about four hours on room air to under one hour. Intubation should be early when hoarseness and soot are present, before oedema obstructs the airway.

Reference: Sabiston Textbook of Surgery, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.