<unk>  (also known as "Total ") is a blood test that usually appears on a "Chem 19" or an electrolyte panel. The value measures the total dissolved Carbon dioxide () in blood. It is determined by combining the Bicarbonate () and the partial pressure of multiplied by a factor which estimates the amount of pure that is dissolved in its natural form (usually 0.03). One given reference range is 24–32 mEq/L.
CO2 content
Oxygen equivalent
Gas exchange
Respiratory quotient
PCO2
Oxygen saturation
Oxygen saturation 
Blood gas tension