Evaluation of blood gas quality control and proficiency testing materials by tonometry

Because of consistent differences found by other investigators and by us, we systematically tonometered, sampled, and measured PO2 and PCO2 concentrations of fresh blood, plasma, and several commercial quality control materials in three models of semiautomated blood gas machines. We found no significant differences between materials or machines for PCO2 between 25 to 72 mm Hg. For tonometered PO2 of approximately 25 to 100 mm Hg, the measured PO2 concentrations were accurate for blood, high for materials with hemoglobin or fluorocarbon (high O2 capacity), and very high for other materials (low O2 capacity). A low O2 capacity material tonometered to a PO2 of 0 mm Hg gave very high values in semiautomated machines and gave correct values only when injected repeatedly without interrupting rinse cycles into a manual machine. These findings indicate significant contamination of blood gas machines with fluids other than the sample so that low O2 capacity quality control materials are inadequate for proficiency testing at degrees of PO2 below 100 mm Hg.