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Carbon monoxide, also called CO, is a poisonous gas. It has no odor, no taste, and no color. It is not to be confused with carbon dioxide, CO2, the body's normal gas byproduct when nutrients are consumed. Carbon monoxide poisoning is a life-threatening condition caused by inhaling too much CO.

What is going on in the body?

• leaking exhaust systems from internal-combustion engines or motor-powered vehicles
• sewers
• cellars
• mines
• faulty gas stoves or heating systems without good ventilation
• fires
• industrial plants
• cigarette smoking, or breathing in secondhand smoke

If fresh air is limited and CO is released in the air, it can reach a dangerously high level.

When CO is inhaled, it enters the bloodstream and attaches to a blood cell protein called hemoglobin. Hemoglobin helps blood cells carry oxygen from the lungs to the rest of the body.

Unfortunately, CO attaches very tightly to hemoglobin, preventing it from carrying oxygen to the tissues or CO2 away from them. This prevents the body's cells from functioning. If too much of the body's hemoglobin is bound to CO, death will result.

What are the signs and symptoms of the condition?

• a cherry-red skin color due to the mixture of hemoglobin and CO in the blood
• confusion
• dilated pupils and visual impairments
• dizziness
• headache
• a heartbeat that is either too fast or too slow
• muscle spasms, paralysis, twitching, or convulsions
• muscle weakness
• nausea and vomiting
• palpitations, which is when a person can feel the heart beating in the chest
• ringing in the ears
• trouble breathing, called shortness of breath
• loss of consciousness, known as coma

What are the causes and risks of the condition?

CO poisoning can occur when small amounts of CO are inhaled over a long time. It can also occur when large amounts of CO are absorbed over a short time, especially in a closed setting such as a garage or car.

What can be done to prevent the condition?

Since CO is odorless and colorless, a person may not realize he or she is around harmful levels of CO. The following actions can help prevent CO poisoning:

• keep appliances in proper working order and use them as directed
• make sure the house has a working smoke detector (preferably one that detects smoke and CO) and accessible fire exits
• make sure there is lots of fresh air before using gas-powered engines or chemicals such as paint remover
• have chimneys checked to be sure the flue is open and connected in the correct manner before using a fireplace
• never leave a car in idle when it is inside a garage
• do not sleep in a room with a gas or kerosene space heater if it is not properly vented
• install CO detectors in the house as a backup
• move into a well-ventilated area if any CO poisoning symptoms develop
• call the local gas company if there is a suspected gas leak in the home

How is the condition diagnosed?

A history of activity or illness as well as a complete physical exam help the doctor to diagnose this condition. A series of blood tests called an arterial blood gas test can measure the oxygen and CO levels in the blood. Other blood or X-ray tests can check the extent of the CO poisoning and rule out other conditions.

What are the long-term effects of the condition?

Long-term effects of CO exposure depend on the extent of the poisoning and how quickly it is treated. Long-term effects may include damage to the brain, heart, or lungs. There may also be short-term memory loss. These effects usually improve over time but may be lasting.

What are the risks to others?

Any persons near the person who has CO poisoning may also have been exposed to the CO, and should be checked by their healthcare professionals.

What are the treatments for the condition?

• Oxygen through a tight-fitting mask
• intravenous fluids
• medicines such as steroids
• a ventilator, which is an artificial breathing machine
• sedatives to decrease any excitability caused by the CO buildup in the body

What are the side effects of the treatments?

Side effects will depend on the treatments used. For instance, steroids may cause irritability, weight gain, or stomach upset. A ventilator can cause lasting lung problems.

What happens after treatment for the condition?

Often a person will get better with no need for further treatment. Physical therapy or other treatments may be needed for problems such as paralysis and memory loss.

How is the condition monitored?

• confusion
• fatigue
• memory loss
• weakness

Any new or worsening symptoms should be reported to the healthcare professional.