The calibration and quality control are key to obtaining accurate results from blood gas analyzers. Most modern blood gas analyzers have automatic calibration functions. A two-point calibration is performed at the beginning, multiple single-point calibrations are performed during measurements, and regular two-point calibrations are repeated to ensure reliable results. Many instruments can now automatically perform quality control, evaluate the control results, and provide warnings for unsatisfactory results. To ensure the proper operation of the instruments, a comprehensive maintenance system should be in place, including daily, weekly, monthly, and annual maintenance. Most fully automated blood gas analyzers can provide maintenance plans and guide maintenance activities.
This work must be performed when the instrument is turned on, otherwise the sample cannot be tested. The purpose of a two-point calibration is to determine the actual slope of the measuring electrode and establish the mathematical relationship between the measuring potential and the concentration of the tested substance. Single-point calibration is more frequently performed on a standard solution and aims to monitor the stability of electrode measurement performance and calculate the corresponding substance concentration in actual blood sample measurements. When the electrode drift exceeds the range specified by the instrument, the instrument will display an alarm or error code, and immediate action should be taken, otherwise it will not function properly.
The frequency of two-point calibration and single-point calibration can be manual or automatic, depending on the instrument model and its status. Many blood gas analyzers on the market today have automatic calibration designs, and under the control of microprocessors, standard gases or buffer solutions are cyclically calibrated at regular intervals.
A blood gas analyzer's calibration program can be categorized as either periodic or non-periodic. In periodic calibration, the calibration cycle is set in the settings, and the instrument automatically performs calibration at fixed time intervals according to the default cyclic calibration time. Non-periodic calibration can be performed by the operator at any other time as needed.
Previously, gas calibration was more common with blood gas analyzers, using compressed bottles as the gas supply method. Now, liquid calibration is more commonly used, which is more conducive to tracking quality standards and provides convenience for operation and transportation.
Quality control materials for blood gas analyzers are classified into different matrices, such as aqueous buffers and whole blood. The most commonly used are aqueous buffers.
In blood gas analysis laboratories, the results of daily quality control liquid measurements are manually or automatically plotted on control charts, and certain quality control rules are applied to judge the results, thereby monitoring the operational status and precision of the testing instruments. Inter-laboratory proficiency testing, organized by provincial or national clinical testing centers, is a quality control activity that evaluates the accuracy of analysis. Quality control materials are uniformly distributed by regulatory authorities and sent back for evaluation. Inter-laboratory proficiency testing can identify system errors in the internal quality control that are difficult to resolve and extend the role of internal quality assurance.