Accuracy and reproducibility of arterial blood-gas and pH measurements

In 30 patients blood samples were taken from both radial arteries and analysed for PCO2, PO2 and pH. The influence of sampling technique on the accuracy of blood-gas analysis was determined. The 95% confidence limits for PCO2 measurements were +/-0.32 kPa (2.4 mmHg), and for PO2 measurements were +/-1.16 kPa (8.8 mmHg) in the range below 20 kPa, and +/-2.94 kPa (22.0 mmHg) above 20 kPa. For pH, the 95% confidence limits were +/-0.014. Only the PO2 measurements were significantly influenced by the sampling procedure.