O2Unterschied

O2Unterschied is a term used in physiology to denote the arteriovenous oxygen difference, the amount of oxygen extracted by tissues during circulation. It is defined as the difference between arterial oxygen content (CaO2) and venous oxygen content (CvO2), typically expressed in milliliters of O2 per 100 milliliters of blood (mL O2/100 mL). The calculation is CaO2 − CvO2, with CaO2 ≈ (Hb × 1.34 × SaO2) + (0.003 × PaO2) and CvO2 computed similarly from venous blood.

Physiologically, the O2Unterschied reflects tissue oxygen extraction and, together with cardiac output (Q), determines oxygen delivery via the Fick principle: VO2 = Q × (CaO2 − CvO2). A larger O2Unterschied indicates greater extraction, as in exercising muscle or reduced oxygen delivery, while a smaller difference implies lower extraction.

Normal resting values are around 4–5 mL O2/100 mL blood; during intense exercise, the difference can rise substantially, reflecting higher metabolic demand and increased extraction.

Measurement requires arterial and venous blood sampling, often from the radial artery and a central venous line or pulmonary artery catheter. It is used in critical care and exercise physiology to assess oxygen delivery, extraction, and overall cardiopulmonary function. Limitations include the invasiveness of sampling, variability with hemoglobin levels, and the influence of mixed venous blood composition.

O2Unterschied is synonymous with arteriovenous oxygen difference; related concepts include oxygen delivery, oxygen extraction fraction, and the Fick equation.