7.0 carbon monoxide poisoning

A life-threatening condition caused by exposure to carbon monoxide, characterised by tissue hypoxia, impaired cellular respiration, and direct cellular toxicity.

Carbon monoxide poisoning can arise from exposure to various sources. Its increased affinity for haemoglobin leads to tissue hypoxia, disruption of cellular respiration, and direct cellular toxicity. Symptoms may be acute or chronic, depending on the dose and duration of exposure, and are often non-specific.

These range from headaches, nausea, and dizziness to severe cardiovascular and neurological effects. Individuals at greatest risk of adverse outcomes include those with coronary heart disease, vascular disorders, asthma, or anaemia, as well as pregnant women and their foetuses, children, and older adults. Approximately one-third of severe cases result in death. 

Carbon monoxide (CO) poisoning is a serious and potentially fatal condition caused by the inhalation of carbon monoxide gas. Often referred to as a "silent killer," carbon monoxide is colourless, odourless, and tasteless, making it difficult to detect without specialised equipment. This gas is produced during the incomplete combustion of fuels such as natural gas, gasoline, wood, coal, and propane. Common sources of CO exposure include malfunctioning household appliances, vehicle exhaust, and improper use of generators in enclosed spaces.

The primary mechanism through which CO exerts its toxic effects is by binding to haemoglobin in the blood to form carboxyhaemoglobin. Carbon monoxide has an affinity for haemoglobin over 200 times greater than that of oxygen, effectively displacing oxygen and preventing its transport to vital tissues. This results in tissue hypoxia, impairing cellular respiration and energy production. Furthermore, CO interferes directly with mitochondrial function and other cellular processes, amplifying its toxic effects.

Symptoms of CO poisoning can vary depending on the level and duration of exposure. Initial symptoms are often nonspecific and may include headache, nausea, dizziness, and fatigue. Prolonged or high-level exposure can lead to confusion, chest pain, shortness of breath, and loss of consciousness. Severe cases may result in permanent neurological damage, cardiovascular complications, or death. Children, pregnant women, the elderly, and individuals with pre-existing health conditions such as coronary artery disease or respiratory disorders are particularly vulnerable.

The diagnosis of CO poisoning is based on a combination of clinical history, symptoms, and measurement of carboxyhaemoglobin levels in the blood. Pulse oximetry, which measures oxygen saturation, may be misleading, as it cannot distinguish between oxyhaemoglobin and carboxyhaemoglobin. Therefore, blood gas analysis or CO-oximetry is essential for accurate diagnosis.

Treatment focuses on removing the individual from the source of exposure and administering 100% oxygen via a mask or endotracheal tube. This accelerates the dissociation of CO from haemoglobin and enhances oxygen delivery to tissues. In severe cases, hyperbaric oxygen therapy may be employed to further hasten the elimination of CO and mitigate neurological damage.

Preventing CO poisoning is crucial and involves the proper maintenance of fuel-burning appliances, such as heaters, stoves, and water heaters. Carbon monoxide detectors should be installed in homes, workplaces, and other enclosed environments, as they provide an early warning of elevated CO levels. Additional preventive measures include ensuring adequate ventilation when using fuel-powered devices and never running vehicles or generators in enclosed spaces like garages.

Carbon monoxide poisoning is a significant public health concern, with thousands of cases reported annually worldwide. Many incidents occur during the winter months when heating systems are in frequent use, and windows are often kept closed. Public awareness campaigns and stricter safety regulations for CO-emitting devices are essential to reduce the incidence of this preventable condition.

In England, the risk of CO poisoning is higher in rural areas, deprived areas, and ethnically diverse areas. Therefore, these groups should be kept in mind when planning and implementing targeted preventive measures, such as designing information/awareness campaigns, distributing free CO alarms, and implementing improvements in the housing sector to alleviate fuel poverty. More on public health measure to combat respiratory conditions will be discussed in the public health workshop.

Carbon monoxide poisoning remains a silent but preventable threat. By understanding the sources and symptoms of CO exposure and implementing effective preventive measures, the risk of poisoning can be greatly reduced. Awareness, early detection, and prompt treatment are key to saving lives and minimising long-term health impacts.