[Measurement of differences in oxygen between arteries and veins. Application to the study of cerebral metabolism].

The cerebral metabolic exploration requires a precises measurement of the arterio-venous differences and this, for each metabolite. As far as oxygen is concerned, there are many techniques to measure the blood contents (CaO2 - CvO2). Direct methods give accurate results but their high technicality makes it difficult to adapt them to the increasing medical demand. The authors report the principle and the technique of the indirect method based upon the measurement of the total hemoglobin concentration and the saturation in oxygen. They recall the possible causes of errors, the main of which - induced by an insufficient homogenization of the sample - is (by the way) to be found in both groups of methods although to a lesser degree in the indirect method. Therefore, the latter, that all normally equipped laboratories can carry into practice, seems quite adapted to the "hospital demand" and its validity confirmed by an experience that now belongs to the past.