Carbon Monoxide Poisoning

Carbon monoxide (CO) is an odorless, colorless, poisonous gas. It can cause sudden illness and death if present in high enough concentration in the surrounding air. When power outages occur during emergencies such as hurricanes or winter storms, the use of alternative sources of fuel or electricity for heating, cooling, or cooking can cause CO to build up in a home, garage, or camper and poison the people and animals inside.

Generators, grills, camp stoves, or other gasoline, propane, natural gas, or charcoal-burning devices should never be used inside a home, basement, garage, or camper – or even outside near an open window or window air conditioner.

Carbon Monoxide Poisoning Symptoms

The symptoms and signs of carbon monoxide poisoning are variable and nonspecific. The most common symptoms of CO poisoning are headache, dizziness, weakness, nausea, vomiting, chest pain, and altered mental status.

The clinical presentation of CO poisoning is the result of its underlying systemic toxicity. Its effects are caused not only by impaired oxygen delivery but also by disrupting oxygen utilization and respiration at the cellular level, particularly in high-oxygen demand organs (i.e., heart and brain).

Symptoms of severe CO poisoning include:

        shortness of breath




        chest pain






        altered mental status


        other neurologic symptoms


        loss of consciousness





Other signs include tachycardia, tachypnea, hypotension, various neurologic findings including impaired memory, cognitive and sensory disturbances; metabolic acidosis, arrhythmias, myocardial ischemia or infarction, and noncardiogenic pulmonary edema, although any organ system might be involved.

With a focused history, exposure to a CO source may become apparent. Appropriate and prompt diagnostic testing and treatment is very important.


The key to confirming the diagnosis is measuring the patient’s carboxyhemoglobin (COHb) level. Carbon Monoxide levels can be tested either in whole blood or exhaled air. It is important to know how much time has elapsed since the patient has left the toxic environment, because that will impact the COHb level. If the patient has been breathing normal room air for several hours, COHb testing may be less useful.

The most common technology available in hospital laboratories for analyzing the blood is the multiple wavelength spectrophotometer, also known as a CO-oximeter. Venous or arterial blood may be used for testing. A fingertip pulse CO-oximeter can be used to measure heart rate and oxygen saturation, and COHb levels. The conventional two-wavelength pulse oximeter is not accurate when COHb is present.

An elevated COHb level of 2% for non-smokers and >9% COHb level for smokers strongly supports a diagnosis of CO poisoning.

COHb levels do not correlate well with severity of illness, outcomes or response to therapy so it is important to assess clinical symptoms and history of exposure when determining type and intensity of treatment.

Other testing, such as a fingerstick blood sugar, alcohol and toxicology screen, head CT scan or lumbar puncture may be needed to exclude other causes of altered mental status when the diagnosis of carbon monoxide poisoning is inconclusive.