Reference — Emergency Nursing
Carbon Monoxide Poisoning Reference
Carbon monoxide is the silent killer — odorless, colorless, and invisible to a standard pulse oximeter. It binds hemoglobin ~200× harder than oxygen, starving tissues while the SpO₂ reads reassuringly normal. The fix is high-flow oxygen and a high index of suspicion.
Educational use only. CO exposure is a medical emergency. Oxygen therapy, hyperbaric referral, and disposition follow provider orders and poison-control guidance. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Why It’s Dangerous (and Sneaky)
CO binds hemoglobin to form carboxyhemoglobin (COHb), displacing oxygen and shifting the oxyhemoglobin curve left — so tissues can’t get or release oxygen. Sources: smoke/fire, faulty furnaces and heaters, generators or cars running in enclosed spaces, and indoor grills.
A standard pulse oximeter cannot tell COHb from oxyhemoglobin — the SpO₂ reads falsely normal. Diagnosis requires co-oximetry / a COHb level (ABG with co-oximetry). Symptoms are nonspecific and flu-like, and whole households presenting together is a classic clue.
Symptoms by COHb Level
| COHb level | Typical signs |
|---|---|
| < 5% (nonsmokers normal; up to ~10% in smokers) | Usually none |
| 10–20% | Headache, fatigue, dyspnea on exertion |
| 20–30% | Throbbing headache, nausea/vomiting, dizziness, impaired judgment |
| 30–40% | Severe headache, confusion, weakness, visual changes |
| 40–50% | Syncope, tachycardia, ataxia |
| > 50% | Seizures, coma, dysrhythmias, cardiac/respiratory failure, death |
The classic “cherry-red” skin is LATE and unreliable — don’t wait for it. Levels correlate loosely with severity; clinical picture guides treatment.
Treatment
Remove from the source and give 100% oxygen via non-rebreather (or via ETT) immediately — it slashes the half-life of COHb from hours on room air to under ~90 minutes. Continue until COHb normalizes and symptoms resolve.
Hyperbaric oxygen (HBO) is considered for severe cases: very high COHb, loss of consciousness, neurologic signs, cardiac involvement, or pregnancy (fetal hemoglobin binds CO avidly). Monitor the ECG and cardiac status, treat acidosis and seizures, and consider concurrent cyanide toxicity in smoke/fire victims.
Warn about delayed neurologic sequelae (cognitive and personality changes days-to-weeks later) and arrange follow-up.
NCLEX Pearls
- ✦Pulse ox reads FALSELY NORMAL in CO poisoning — diagnose with a carboxyhemoglobin (co-oximetry) level.
- ✦Treatment = remove from source + 100% oxygen by non-rebreather; HBO for severe cases/pregnancy.
- ✦The cherry-red skin sign is late and unreliable — don't rely on it.
- ✦Suspect CO when a whole household has flu-like symptoms that improve away from home.
- ✦Watch for delayed neurologic sequelae; consider cyanide co-toxicity in fire/smoke victims.
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with Emergency Nurses Association (ENA) · AHA ACLS / PALS Guidelines · Advanced Trauma Life Support (ATLS). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →