Carbon Monoxide Poisoning

Carbon monoxide (chemically CO) is a poisonous gas that is generated by the incomplete combustion of organic materials containing carbon in the absence of oxygen. We must not confuse CO with the carbon dioxide (CO2). Carbon dioxide is “just” not breathable, but carbon monoxide is directly poisonous. Some concentration of carbon monoxide occurs practically every time when something burns including the traffic. Clinically important amount of carbon monoxide receive chronic cigarette smokers.


The toxicity of carbon monoxide is caused by its affinity to hemoglobin molecules. Hemoglobin is a compound in red blood cells that can carry oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. When carbon monoxide binds to the hemoglobin, it gives rise to a substance known as carboxyhemoglobin. This substance is very stable, but it is unable to bind oxygen resulting in disruption of oxygen supply to the tissues.


Symptoms of acute poisoning are sudden and unpleasant (nausea, vomiting, dizziness and fatigue). The poisoned person complains of persistent dull headache. The face tends to turn reddish due to blood congestion and sometimes it may get even cherry red color. In more severe cases, there may be muscle cramps, altered consciousness, confusion, hallucinations, heart rhythm disorders and ultimately even death. Long-term exposure to only slightly elevated concentrations of carbon monoxide may not be reflected in any way, or it has only vague symptoms. The person just does not fell well, suffers from recurring headache and fatigue.


We should think about possibility of carbon monoxide poisoning in any individual who has been in a close contact with fire. Blood tests can be done to precisely evaluate the percentage of hemoglobin with bound carbon monoxide molecules. In healthy people, carbon monoxide binds to maximally about 5% of hemoglobin molecules and the smokers may normally have even up to 10%. Higher values are clearly not normal and concentrations above 20-25% are related to serious poisoning.

First aid

The poisoned must be quickly get from the area of exposure to a place with fresh clean air. The rescuer must keep in mind that he himself is in serious danger and he must leave the environment with carbon monoxide as quick as possible.


The poisoned patients are usually admitted to hospital and treated with high doses of oxygen. The majority of cases does not need any special therapy and the condition improves very quickly. Severe cases of poisoning with unconsciousness should be hospitalized in intensive care units and in case of a respiratory failure; the artificial lung ventilation must be used. In indicated and very serious conditions, usage of hyperbaric chambers is indicated. The hyperbaric chamber is a closed space with increased oxygen pressure that improves the oxygen ability to dissolve in the blood and to bind to hemoglobin molecules.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources