CO

By Peter Galvin, MD

CO (carbon monoxide) is a colorless, odorless, and tasteless gas that is produced by burning organic materials such as charcoal, gas (household gases like methane and propane), gasoline, oil, and wood. While the combustion of oil, for example diesel oil, produces some CO, the combustion of gasoline produces vastly greater amounts of CO. In marine use, gasoline powered vessels are strongly recommended to have CO detectors while diesel-powered vessels do not usually need a detector. CO is produced naturally in the environment and is not toxic to all life, however it is toxic to mammals because when CO is inhaled, it is absorbed into the bloodstream where it competitively binds to hemoglobin, producing carboxyhemoglobin (HbCO). CO has a stronger affinity for hemoglobin than oxygen, so CO displaces oxygen making that hemoglobin molecule unable to transport oxygen. Also, once HbCO is formed, the CO-hemoglobin bond is permanent and cannot be undone.

More than 400 people in the U.S. die every year from unintentional CO poisoning not associated with fires. In addition, CO poisoning causes more than 100,000 emergency department visits and 14,000 hospitalizations per year in the U.S. CO poisoning most commonly results from breathing fumes in enclosed spaces from gas appliances (stoves, ovens, water heaters, gas dryers, and furnaces), portable generators, fireplaces, charcoal grills, lawn mowers, and vehicle exhaust. Symptoms of CO poisoning are non-specific, making it difficult to identify. It is most commonly described as having “the flu.” Often, multiple people in the same household have similar symptoms, such as headache, nausea, fatigue, dizziness, chest pain, stomach pain, impaired coordination, and confusion. At high levels of exposure, CO poisoning can cause heart attacks, brain injury, and death. This is because the central nervous system, which includes the brain, and the heart require more oxygen than the body’s other organs. Those at the highest risk from CO exposure are infants, young people, pregnant women, those with pre-existing medical problems, and older adults.

CO poisoning is diagnosed by measuring HbCO using a device called a co-oximeter. A HbCO level of more than 5% in nonsmokers and 10% in smokers strongly suggests a diagnosis of CO poisoning. Treatment usually involves the administration of 100% oxygen using a face mask until symptoms resolve, which typically takes about 4 to 5 hours. Some patients with high HbCO levels or severe symptoms, children, elderly people, and pregnant women may require breathing oxygen in a pressurized chamber (hyperbaric oxygen).

Every home should have functioning CO detectors in every sleeping area. Batteries should be checked twice a year, although many detectors today are sealed and have a 10-year battery life. These detectors should have a visible date of installation. If the alarm sounds, get everyone out of the house first, then call 911. All gas appliance systems should be professionally installed and checked at least once a year. Never burn charcoal or use portable generators inside. Appliances should not be used for purposes other than those intended (i.e., heating a home with a gas oven). Chimneys and fireplaces should be inspected once a year, and if the car is in a garage, it should never be started before the garage doors are open.

For more information go to the website of the Centers for Disease Control and Prevention at www.cdc.gov

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