Carbaminohemoglobin (carbaminohaemoglobin BrE) (COHb, also known as carbhemoglobin and carbohemoglobin) is a compound of hemoglobin and carbon dioxide, and is one of the forms in which carbon dioxide exists in the blood.  Twenty-three percent of carbon dioxide is carried in blood this way (70% is converted into  bicarbonate by carbonic anhydrase and then carried in plasma, 7% carried as free CO, dissolved in plasma).