Fig. 2— a, c and e) Bland–Altman and b, d and f) scatter plots comparing measured arterial (a) and calculated arterial (ca)values of a and b) pH (pHa and pHca, respectively) c and d) carbon dioxide tension (Pa,CO2 and Pca,CO2, respectively) and e and f) oxygen tension (Pa,O2 and Pca,O2, respectively). a, c and e) Bias (mean difference; – – – –) and 95% limits of agreement (±2sd; ······) are shown. b, d and f) Linear regression lines between measured and calculated values (––––) and associated lines of identity (······) are shown. e and f) Data with peripheral oxygen saturation ≥97% (○) were not included in calculation of the bias or regression line for oxygen tension. Correlation coefficients (r2) and regression equations were as follows. b) r2 = 0.95, pHca = (1.00×pHa)+0.02; d) r2 = 0.98, Pca,CO2 = (1.03×Pa,CO2)-0.09; f) r2 = 0.86, Pca,O2 = (0.89×Pa,O2)+0.84.