A simple quality control protocol for haemoximetry using standard p50.
We have designed a quality control tool for haemoximetry using the principle that standard p50, calculated from blood gas and haemoximetry measurements using the Siggaard-Andersen algorithm, remains unchanged when a specimen of venous blood is oxygenated progressively to 97% saturation of haemoglobin. If the haemoximeter is inaccurate, progressively larger deviations of standard p50 from the constant value occur above 80% saturation. Deviations too small to be detected by analysis of quality control materials comprised of non-haemoglobin dyes and yet sufficient to cause significant errors in derived extractivity parameters can be detected by this method. The suggested protocol is easy to perform, and is recommended as a quality control tool for blood gas analyser/haemoximeters used to determine arterial extractivity parameters.