Carbon monoxide poisoning — co-oximetry and hyperbaric oxygen viva

Diagnosis. Simultaneous household flu-like illness that improves outdoors in winter is carbon monoxide poisoning until proven otherwise. Do not be reassured by normal SpO2. Measure venous COHb by co-oximetry in every symptomatic member; arrange environmental source check (faulty heater/flue) before anyone returns home.^[2]

Mechanism. CO binds haemoglobin far more avidly than oxygen → COHb; impairs oxygen delivery and utilisation; delayed neurological sequelae may follow days to weeks later.^[1]

Initial therapy. 100% oxygen for all from first contact until asymptomatic with COHb cleared; ECG and troponin for cardiac injury; pregnancy test in women of childbearing age.^[1]

HBO. Father's syncope/LOC is a hyperbaric indication regardless of absolute COHb. Other indications include ongoing neuro deficit, cardiac ischaemia, severe acidosis and high COHb. Discuss transfer early.^[1]

Evidence. Weaver 2002 tested HBO against sham with cognitive sequelae as the outcome.^[1] Scheinkestel 1999 (Australia): randomised double-blind HBO versus normobaric oxygen with sham chamber treatments — underpins more conservative ANZ use focused on severe cases.^[3]

Discharge counselling. All patients need written advice about delayed neurological sequelae and safe housing/source remediation.^[2]