Mean of difference (mmHg) and 95% CI of difference (mmHg) of pH, pCO2, pO2, HCO3 - are respectively - 0.02 ((- 0.12) - 0.8); 1.9 ((- 6.9) - 10.7); 1, 2 ((- 46.3) - 48.7) and - 1.1 ((- 7.6) - 5.4), inferred from Bland-Altman analysis.