The venous and arterial PCO2
were not comparable because the 95% prediction
interval of the bias for venous PCO2 was unacceptably
wide, extending from −10.7 mm Hg to +2.4 mm Hg.
The PO2 values compared poorly, the arterial PO2 typically
36.9 mm Hg greater than the venous with significant
variability (95% confidence interval from 27.2 to
46.6 mm Hg).