New concepts for achieving accuracy and reliability in blood-gas analysis

Blood-gas analysis must be accurate because small changes in the measured variables of blood oxygen and carbon dioxide can be clinically significant. Reliability and accuracy cannot be obtained from blood-gas analyzers without a dependable quality control program that provides frequent and accurate standards for analysis. This work describes the development of two instruments which can be used for calibration, quality control and proficiency testing of blood-gas analyzers. The gas mixer as a stand-alone system provides inexpensive and accurate one and two point calibrations. The accuracy provided by the gas mixing system has been shown to be better that +/- 0.05% for CO2 in the range of 2-20% and O2 in the range of 4-50%. The basic design of a new tonometer is described and proven to be efficient in regards to temperature and gas equilibration. The accuracy and precision of this system has been shown to be as good as careful thin-film tonometry. The design has overcome the problem of air contamination by performing tonometry in the transport vessel which provides anaerobic sample transport. The combined precision gas mixer and syringe tonometer is a practical laboratory system which can be used to provide ultimate simulation of known patient blood samples with any combination of PO2 or PCO2. The implication of this work is that a reliable system now exists in which a laboratory can prepare known PO2 and PCO2 controls through whole blood tonometry to be used for internal quality control testing.