The authors discuss parameters characterizing the oxygen metabolism and their clinical impact: Partial oxygen pressure in arterial and mixed venous blood, lactate and new parameters derived from direct assessment of haemoglobin saturation with oxygen in arterial blood. Oxygen extraction tension (px): partial oxygen pressure in mixed venous blood at which 2.3 mmol oxygen are released from one litre of blood. Extractable oxygen (cx): the amount of oxygen released from on litre of blood when the partial oxygen pressure drops to 5.0 kPa. Oxygen compensation factor (Qx): it is the factor that cardiac output should increase to maintain a normal mixed venous p O2 of 5.0 kPa. Effective haemoglobin: haemoglobin participating in oxygen transmission which determines the oxygen capacity of blood for oxygen. Half the haemoglobin saturation (p50): characterizing the haemoglobin affinity for oxygen and corresponding to the shape and position of the haemoglobin saturation curve. Pulmonary shunts. Advantages, pitfalls and limitations of the mentioned parameters are given.

Keywords: Hemoglobins /analysis/; Humans; Oxygen /blood/; Partial Pressure