Carbon monoxide poisoning
A common, often fatal poisoning from colorless, odorless carbon monoxide gas.
Carbon monoxide poisoning is a common and often fatal condition resulting from inhaling excessive levels of carbon monoxide (CO), a colorless, odorless, and initially non-irritating gas produced during incomplete burning of organic matter. It is the most common type of fatal poisoning in many countries, with non-fire related cases causing more than 400 deaths annually in the United States and over 20,000 emergency room visits each year.
- Common cause
- Incomplete burning of organic matter (cooking equipment, motor vehicles, heaters)
- Primary mechanism
- Binds with hemoglobin to form carboxyhemoglobin, preventing oxygen transport
- Diagnostic threshold (nonsmokers)
- HbCO > 3%
- Diagnostic threshold (smokers)
- HbCO > 10%
- Severe poisoning threshold
- 30% COHb
- Highest reported non-fatal level
- 73% COHb
- Annual US emergency visits
- More than 20,000
Lore & Background
The toxic effects of CO have been known since ancient history. The discovery that hemoglobin is affected by CO emerged from an investigation by James Watt and Thomas Beddoes into the therapeutic potential of hydrocarbonate in 1793, and was later confirmed by Claude Bernard between 1846 and 1857. As pioneered by Esther Killick, different species and people have varying CO tolerance levels, influenced by genetics, activity level, ventilation rate, pre-existing disease, and other factors.
Reader's Guide
Carbon monoxide poisoning is a significant public health issue, responsible for more than 20,000 emergency room visits and over 400 non-fire related deaths each year in the United States. Poisonings occur more often in winter, particularly from portable generators during power outages. The condition is diagnosed based on carboxyhemoglobin levels exceeding 3% in nonsmokers or 10% in smokers, with severe poisoning generally considered at 30% COHb. Treatment consists of administering 100% oxygen until symptoms resolve and HbCO falls below the diagnostic thresholds. Prevention relies on carbon monoxide detectors, proper venting of gas appliances, and maintaining vehicle exhaust systems. Long-term complications can include chronic fatigue, memory problems, and movement disorders, while delayed neurological sequelae may occur in up to 50% of poisoned individuals after 2 to 40 days.
Did You Know?
- The classically described 'cherry red skin' rarely occurs in carbon monoxide poisoning.
- The highest reported non-fatal carboxyhemoglobin level was 73% COHb.
- Carbon monoxide is produced naturally by the enzyme heme oxygenase, which converts heme into biliverdin.
- Small amounts of CO are beneficial and act as a neurotransmitter (gasotransmitter); enzymes produce it during oxidative stress.
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