Clinical significance
Carbon monoxide is a colourless, odourless and highly toxic gas produced by the combustion of organic fuels. Direct exposure causes this substance to enter the bloodstream, where it binds to haemoglobin much more strongly than oxygen does. This leads to the formation of carboxyhaemoglobin, which prevents haemoglobin from carrying out its normal task of delivering oxygen to the tissues. Apart from serious accidental poisoning at home, all workers exposed to traffic pollution may be exposed. Acute poisoning causes severe lack of oxygen, with serious damage to the central nervous system and heart. Chronic poisoning can cause headache, dizziness, weakness, nausea and mental and sensory changes.
Carboxyhaemoglobin levels correlate well with exposure to carbon monoxide and can be used as a biological indicator of exposure.
Clinical indications
Occupational exposure to carbon monoxide.
Sample type
The patient must have a blood sample taken.
Preparation
Fasting is not required.
Notes
Carboxyhaemoglobin levels in people who are not exposed vary mainly with tobacco use: in heavy smokers levels of 8-10% can be found. This test is also used to monitor exposure to substances that produce carbon monoxide when metabolised. Methylene chloride is a specific example.