Oxygen tension at 50% haemoglobin saturation (P50), which reflects the degree of peripheral oxygen offloading and tissue oxygenation, plays an important role in the diagnosis and treatment of disease, as well as in transfusion research. Blood gas analysers are commonly used in clinical and obtain P50 values through complex calculations and analysis. Oxygenation-dissociation analysers are specially designed to record the oxygen dissociation curves and obtain P50 values of whole blood, red blood cells (RBCs), and stroma-free haemoglobin. However, whether the two equipment obtain comparable data is still uncertain. Herein, we used both equipment to detect P50 values of blood and stroma-free haemoglobin from human and bovine sources, venous and arterial blood of beagle and rat, and stored rat blood. For human blood, both analysers yielded similar data. P50 of the stroma-free haemoglobin and bovine blood could only be properly detected by oxygenation-dissociation analysers. Blood gas analysers showed different P50 values, while oxygenation-dissociation analysers got similar P50 values for arterial and venous samples. Oxygenation-dissociation analysers distinguished changes in P50 values during RBCs storage. Compared with the blood gas analysers, oxygenation-dissociation analysers had a stronger detection capability in P50 measurement with regard to both sample types and species.
Keywords: P50; Red blood cells; blood-gas analyser; haemoglobin; oxygenation-dissociation analyser.