Carboxyhemoglobin
Carboxyhemoglobin (carboxyhaemoglobin BrE) (symbol COHb or HbCO) is a stable complex of carbon monoxide and hemoglobin (Hb) that forms in red blood cells upon contact with carbon monoxide. Carboxyhemoglobin is often mistaken for the compound formed by the combination of carbon dioxide (carboxyl) and hemoglobin, which is actually carbaminohemoglobin. Carboxyhemoglobin terminology emerged when carbon monoxide was known by its historic name, "carbonic oxide", and evolved through Germanic and British English etymological influences; the preferred IUPAC nomenclature is carbonylhemoglobin.
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| Names | |||
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| Preferred IUPAC name
Carbonylhemoglobin | |||
| Other names
Carboxyhemoglobin Carboxyhaemoglobin Kohlenoxyhaemoglobin Kohlenoxyhämoglobin Kohlenoxydhämoglobin Kohlenmonoxyhämoglobin Carbonmonoxyhemoglobin Carbon-monoxide-hemoglobin Carbon-monoxide-Methemoglobin Carbonic oxide hæmoglobin | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The average non-smoker maintains a systemic carboxyhemoglobin level under 3% COHb whereas smokers approach 10% COHb. The biological threshold for carboxyhemoglobin tolerance is 15% COHb, meaning toxicity is consistently observed at levels in excess of this concentration. The FDA has previously set a threshold of 14% COHb in certain clinical trials evaluating the therapeutic potential of carbon monoxide.