CO toxicity — pulse ox FALSELY normal
Carbon monoxide poisoning recognition
Mnemonic device
SpO2 lies — get co-oximetry
Mapping
Why
Pulse ox can't distinguish carboxyhemoglobin (HbCO) from oxyhemoglobin — reads ~100% even when HbCO is 50%
Hint
Cherry-red mucosa, headache, confusion, fire/smoke exposure, faulty heater
Lab
ABG with co-oximetry: PaO2 normal but HbCO elevated (>3% non-smoker, >10% smoker, >25% severe)
Tx
100% O2 via NRB (t½ HbCO drops 320 min → 80 min). Hyperbaric O2 if HbCO >25%, neuro symptoms, pregnant, LOC, cardiac ischemia.
Clinical note: Pulse ox reads ~100% even with severe CO toxicity — DO NOT rule out hypoxia by SpO2 in fire/smoke patients. Co-oximetry on ABG required.