Mixed Venous and Arterial Pco2

The rebreathing method of measuring oxygenated mixed venous Pco(2) (Pvco(2)) was originally introduced as a bloodless way to estimate arterial Pco(2) (Paco(2)). It has become common practice to subtract 6 mm Hg from the Pvco(2) to obtain the Paco(2) but there are many circumstances in which this leads to an overestimate of the Paco(2). Measurements of Pvco(2) and Paco(2) in 19 patients have shown that a better approximation to Paco(2) under …