A Silent Death

Carbon monoxide poisoning poses risks to both patients and providers

This CE activity is approved by EMS World Magazine, an organization accredited by the Continuing Education Coordinating Board for Emergency Medical Services (CECBEMS) for 1 CEU. To take the CE test that accompanies this article, go to www.rapidce.com to take the test and immediately receive your CE credit. Questions? E-mail editor@EMSWorld.com.


  • Review the incidence and sources of carbon monoxide poisoning, including increased risk following natural disasters
  • Review the pathophysiology, symptoms and assessment of CO poisoning, including the use of newer monitors to measure carboxyhemoglobin in the field.
  • Highlight steps to be taken to ensure rescuer safety.
  • Discuss management strategies for victims of CO poisoning, including the use of hyperbaric oxygen.


The death earlier this year of a Texas EMT student sleeping in an EMS station is a tragic reminder that carbon monoxide's nickname, "silent killer," is all too accurate. Carbon monoxide (CO) knows no racial, ethnic, gender or geographic boundaries, and rescuers and citizens alike are at risk.

   According to investigators, Casey Steenland and two coworkers became victims when a small generator onboard their ambulance was left running after the vehicle was parked inside the building.1 Since the facility's heating, hot water and stove were all electric, a carbon monoxide detector had not been installed. Steenland's exposure was fatal; her two coworkers were later released from the hospital after hyperbaric oxygen treatments. A third EMT was also treated at the hospital for CO exposure during the rescue of the initial victims.

Incidence and Sources

   Carbon monoxide poisoning is one of the leading causes of accidental poisoning death in the United States. It contributes to a minimum of 40,000 emergency department visits and 500 unintentional deaths annually. There are an additional 4,500-5,000 intentional (suicide) carbon monoxide poisoning deaths each year.2 As the symptoms are often vague and attributed to other ailments such as the flu, many experts believe that an additional 11,000 cases per year are undetected or misdiagnosed.

   Smoke inhalation in structure fires is the leading source of unintentional carbon monoxide exposures.2 Likewise, CO poisoning is the leading cause of death of fire victims, not the thermal injuries many would suspect. Dangerous carbon monoxide sources include portable generators, automobiles, boats, furnaces, water heaters, household stoves, camping lanterns and stoves, snow blowers, floor buffers, pumps, power sprayers, lawn mowers and garden tractors. It is important for EMS professionals to consider these or look for potential CO sources as part of their scene assessment. The Centers for Disease Control and Prevention (CDC) and the Consumer Product Safety Commission (CPSC) both have in-depth information about spotting potential CO sources. (See http://www.cdc.gov/co and www.cpsc.gov/cpscpub/pubs/464.pdf.)

   Not unlike the mechanism of injury in trauma calls, EMTs and paramedics may be the only members of the healthcare team who have the opportunity to recognize these clues. The literature contains a number of case studies of patients who were seen in the ED for vague, flu-like symptoms, then discharged and unwittingly sent back to the source of the carbon monoxide. Sadly, these stories typically end with near-fatal or fatal exposures. An observant prehospital professional can help prevent that scenario.


   One particular setting where EMS professionals have an opportunity to educate the public and prevent CO poisoning is in severe weather or natural disaster emergencies. There is a significant increase in CO cases when electrical service is disrupted after events like hurricanes, wind storms, blizzards and ice storms. One study of nine different storms over a 15-year period documented 930 CO poisonings with a total of 23 fatalities.3 An interesting variety of causes were noted. During a 1996 winter storm in the northeastern part of the U.S., 25 motorists suffered CO poisoning when their vehicles were stranded in deep snow. They kept their cars running, not realizing that the snow was obstructing the exhaust systems and returning dangerous fumes to the passenger compartment.

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