Carbon monoxide (CO) poisoning is a life-threatening condition caused by inhaling carbon monoxide gas — a colorless, odorless, and tasteless gas produced by incomplete combustion of fuels. Because it is undetectable without specialized equipment, CO poisoning is often called the “silent killer.”
In healthcare, rapid recognition and emergency intervention are crucial, as untreated CO poisoning can lead to severe hypoxia and death.
Pathophysiology of Carbon Monoxide Poisoning
Carbon monoxide binds to hemoglobin in red blood cells more strongly than oxygen — about 200–250 times more affinity. This forms carboxyhemoglobin (COHb), which:
- Displaces oxygen from hemoglobin
- Prevents oxygen transport to tissues
- Leads to severe tissue hypoxia, even if oxygen levels in the environment are normal
Because CO occupies hemoglobin binding sites, oxygen delivery to vital organs is reduced, causing cellular hypoxia and tissue damage.
Common Causes and Sources
CO is produced by incomplete burning of carbon-containing fuels. Common sources include:
- Automobile exhaust (e.g., working in a closed garage or auto repair shop)
- Gas stoves and heaters
- Fireplaces and wood-burning stoves
- Portable generators used indoors or in poorly ventilated spaces
- Furnaces with poor ventilation
High-risk environments:
- Poorly ventilated rooms
- Enclosed workspaces
- Areas with malfunctioning heating systems
Nursing Assessment – Key Questions (NCLEX Tip)
When assessing for possible CO poisoning, nurses should ask:
- “Are you a car mechanic or often around engine exhaust?”
- “How have you been keeping your house warm?”
These questions help identify exposure risk from common CO sources.
Signs and Symptoms
CO poisoning symptoms are often vague and may be mistaken for flu or fatigue.
Early Symptoms
- Headache (most common early sign)
- Dizziness
- Nausea and vomiting
- Fatigue
Progressive Symptoms
- Dyspnea (shortness of breath)
- Confusion or altered mental status
- Loss of consciousness
- Seizures
NCLEX Tip:
Pulse oximeter readings can be falsely normal in CO poisoning because the device cannot differentiate between oxyhemoglobin and carboxyhemoglobin. A patient can have SpO₂ of 100% but still be severely hypoxic.
Diagnosis
Carboxyhemoglobin Level (via blood gas analysis):
- Normal: < 2% in non-smokers, < 10% in smokers
- Toxic: > 15% (symptoms appear), > 50% (life-threatening)
Arterial Blood Gas (ABG): May show metabolic acidosis
Clinical History: Exposure to a potential CO source
Priority Emergency Action
Immediate treatment is critical to prevent brain and organ damage.
Oxygen Therapy
100% Oxygen via Non-Rebreather Mask
- Flow rate: 15 L/min
- Oxygen displaces CO from hemoglobin, restoring oxygen delivery to tissues
Hyperbaric Oxygen Therapy (HBOT)
Considered for:
- Carboxyhemoglobin > 25%
- Pregnant women with > 15% levels
- Neurological symptoms
HBOT delivers oxygen under high pressure to rapidly clear CO from the blood
NCLEX Tip:
High-flow oxygen is given even if pulse oximeter readings are normal because readings are unreliable in CO poisoning.
Nursing Priorities in CO Poisoning
1. Airway and Oxygenation
- Administer high-flow oxygen immediately
- Monitor respiratory effort and mental status
2. Cardiac Monitoring
- Hypoxia can cause arrhythmias
3. Neurological Assessment
- Monitor for confusion, restlessness, or decreased LOC
4. Education
- Advise on installing CO detectors at home
- Stress importance of proper ventilation
Prevention Strategies
- Install carbon monoxide detectors in homes and workplaces
- Ensure regular maintenance of heating systems and fuel-burning appliances
- Never run cars or generators in enclosed spaces
- Ventilate rooms when using stoves or fireplaces
Summary Table – CO Poisoning Nursing Guide
| Category | Details |
|---|---|
| Cause | Inhalation of CO from incomplete combustion |
| Pathophysiology | CO binds to hemoglobin → displaces oxygen → tissue hypoxia |
| Key Symptom | Headache, dizziness, confusion |
| Pulse Oximetry | Falsely normal |
| Priority Treatment | 100% O₂ via non-rebreather at 15 L/min |
| Definitive Therapy | Hyperbaric oxygen in severe cases |
| NCLEX Alert | SpO₂ can be normal despite hypoxia |
Frequently Asked Questions (FAQs)
Q1. Why is CO poisoning dangerous if oxygen levels look normal on a pulse oximeter?
Because pulse oximeters cannot differentiate between oxygen and CO bound to hemoglobin.
Q2. How long does it take for CO to leave the body?
With 100% oxygen therapy, the half-life of carboxyhemoglobin decreases from about 4–5 hours to 60–90 minutes.
Q3. Can CO poisoning cause long-term effects?
Yes, severe cases may lead to neurological damage, memory loss, or heart problems.
Q4. Why is hyperbaric oxygen recommended in some cases?
It accelerates CO removal and improves oxygen delivery, reducing the risk of long-term brain injury.
