The means of PvCO2 and PaCO2 were 47.94 mmHg and 43.61 mmHg repectively; the mean differences (95% CI) between venous and aterial samples were 4.32 (- 5.32 to 13.96) mmHg; regression model for prediction of PaCO2 = - 1.661 + 0, 945 x PvCO2 (R2=0.893, p < 0.0001); external validation showed good calibration, and good discrimination.