carboxyhemoglobin
noun
car·boxy·he·mo·glo·bin
variants:
or chiefly British carboxyhaemoglobin \ (ˌ)kär-ˌbäk-sē-ˈhē-mə-ˌglō-bən 
\
\
Medical Definition of carboxyhemoglobin
: a very stable combination of hemoglobin and carbon monoxide formed in the blood when carbon monoxide is inhaled with resulting loss of ability of the blood to combine with oxygen