OXYGEN PARAMETERS OF ARTERIAL AND MIXED VENOUS-BLOOD, - NEW AND OLD

A complete pH and blood gas analysis of arterial and mixed venous bloo d may comprise more than forty different quantities. We have selected sixteen, including patient temperature. The arterial oxygen tension gr oup includes the oxygen tension, fraction of oxygen in inspired air, a nd fraction of mixed venous blood in the arterial (total physiological veno-arterial shunting). The haemoglobin oxygen capacity group includ es effective haemoglobin concentration and fractions of carboxy- and m ethaemoglobin. The haemoglobin oxygen affinity group includes half-sat uration tension and estimated 2,3-diphosphoglycerate concentration of erythrocytes. In a neonatal care unit fraction of fetal haemoglobin ne ed to be included. The arterial oxygen extractivity is measured as the oxygen extraction tension, which indicates the degree of compensation among the oxygen tension, capacity, and affinity. The mixed venous gr oup includes mixed venous oxygen tension, and, when measured, cardiac output, and oxygen consumption rate. The acid-base status includes blo od pH, arterial carbon dioxide tension, and extracellular base excess. Other quantities such as haemoglobin oxygen saturation, respiratory i ndex, total oxygen concentration (oxygen content), oxygen extraction f raction, oxygen delivery, and several others, seem robe redundant.