Carbon monoxide poisoning

What is carbon monoxide poisoning?

Carbon monoxide poisoning is a poisoning of the brain as a result of carbon monoxide (CO) replacing oxygen in the atmosphere.

Oxygen is needed by the brain to sustain chemical processes that ultimately create energy. If the oxygen supply is interrupted by carbon monoxide buildup in the atmosphere, the functioning of the brain can be disturbed, causing a type of brain injury known as anoxic or hypoxic brain injury.

How is carbon monoxide poisoning caused?

Carbon monoxide poisoning is caused by breathing in carbon monoxide (CO). This is a gas that forms in rooms where common domestic fuels such as gas, coal, wood and charcoal are being burned. The fuels use up oxygen in the atmosphere, replacing it with carbon dioxide. When carbon dioxide starts to build up, the fuels begin releasing CO instead.

When there is a build-up of CO in the air, it is breathed in and binds tightly to molecules in the blood called haemoglobin. This takes up the space that oxygen would normally rely on. The oxygen supply that the brain so heavily relies on gets disrupted, causing a type of brain injury known as anoxic or hypoxic brain injury.

The heart, as well as the brain, is particularly vulnerable to this depleted oxygen supply. Pregnant women, children, older people and people with health conditions such as respiratory disease, cardiovascular disease and anaemia are particularly susceptible to the toxic effects of CO.

What happens in carbon monoxide poisoning?

The symptoms experienced from carbon monoxide (CO) poisoning can vary depending on how long and intensely someone has been exposed to CO.

In acute poisoning, exposure to CO has happened rapidly over a relatively short period of time. The symptoms can be as follows:

• Mild exposure: headaches, nausea, vomiting, a general feeling of unease or discomfort. These symptoms might be misdiagnosed as more common illnesses such as flu or food poisoning. As such, CO poisoning might not even be suspected at this stage.

• Moderate exposure: as exposure to CO continues, symptoms such as dizziness, weakness and unsteadiness may develop. There might be problems with concentration and thinking. Changes in behaviour, drowsiness or confusion may develop.

• Severe exposure: serious deterioration can occur quickly, resulting in seizures, coma or even death. Brain structural changes in severe exposure can include white matter, hippocampal and basal ganglia damage.

Chronic exposure means that exposure to lower levels of CO has persistently occurred over a longer period of time. Symptoms tend to be milder than those of acute poisoning and can include headaches, dizziness, nausea, light-headedness, fatigue, difficulties in concentrating, memory problems and changes in mood.

The symptoms listed above can be difficult to distinguish from common ailments. However, if the symptoms are only experienced while in the house, and disappear upon leaving the house, this can be a sign that there is an environmental cause, such as CO poisoning. Another sign is if other people in the house have also started developing symptoms.

You should also be wary of the changes in the colour of flames from a gas hob (they should be blue rather than dull yellow or orange), increased moisture building up on windows or walls, unusual smells in the house and/or flashing or blown-out pilot lights on gas stoves.

What should you do if you suspect carbon monoxide poisoning?

If you suspect carbon monoxide (CO) poisoning or if your CO alarm sounds, the first things you should do are:

1. Open any windows and doors to increase ventilation.

2. Switch off any appliances and shut off the gas supply if easily accessible.

3. Leave the building.

4. Once you are removed from the CO source (i.e. out of the building), ring the National Gas Emergency Service (available 24 hours) on 0800 111 999 or by textphone on 0800 371 787.

5. Do not re-enter the house until any faulty appliances have been properly checked and you have been told by a qualified, registered engineer that it is safe to do so.

If you are experiencing moderate or severe symptoms, or if you feel you have been exposed to high levels of carbon monoxide, visit your nearest hospital Accident and Emergency department or call 999 and ask for an ambulance immediately.

If you are experiencing mild symptoms, or you feel you have been exposed to low levels of carbon monoxide, see your GP immediately.

How is carbon monoxide poisoning treated?

It is important to get medical support for suspected carbon monoxide (CO) poisoning as early as possible, so that the necessary tests can be done to check for poisoning. This might include having a blood, breath or urine test, depending on how much time has passed since the CO exposure.

Initial treatment of exposure to CO involves immediate removal from the source of poisoning (such as leaving the house), the administration of 100% oxygen, monitoring of CO levels and general supportive care. A neurological examination may also be needed.

Severe cases of CO poisoning are sometimes treated through hyperbaric oxygen therapy. This involves giving pure oxygen at an increased pressure in an enclosed hyperbaric chamber. It has been suggested that this may improve neurological outcomes, although it does remain controversial and research into its effectiveness is limited.

Hyperbaric oxygen therapy is a specialised technique, which is only available in a few centres around the UK (mostly located around the coast, London and the Midlands). It may also be associated with complications of its own and it is not used routinely.

What happens after carbon monoxide poisoning is treated?

Exposure to chronic level carbon monoxide (CO) may not leave any long-term effects.

Acute exposure may cause a type of brain injury known as anoxic or hypoxic brain injury. There may be long-term neurological complications such as problems with cognition, emotions and behaviour, among other health complications.

The person may need to undergo a period of rehabilitation to learn to cope with these issues. For more information on this, visit Treatment and rehabilitation.