Blood gas tension constant 0.0031 represents the amount of oxygen dissolved in plasma. The dissolved-oxygen term is generally small relative to the term for hemoglobin-bound oxygen, but becomes significant at very high PO (as in a hyperbaric chamber) or in severe anemia. This is an estimation and does not account for differences in temperature, pH and concentrations of 2,3 DPG. Blood gas tension Blood gas tension refers to the partial pressure of gases in blood. There are several significant purposes for measuring gas tension; the most common gas tensions measured are oxygen tension (PO), the carbon dioxide tension (PCO) and carbon monoxide tension
Fetal hemoglobin in which there may be a delay in cessation of HbF production until 3–5 years of age. In adults, fetal hemoglobin production can be reactivated pharmacologically, which is useful in the treatment of diseases such as sickle-cell disease. Oxygenated blood is delivered to the fetus via the umbilical vein from the placenta, which is anchored to the wall of the mother's uterus. The chorion acts as a barrier between the maternal and fetal circulation so that there is no admixture of maternal and fetal blood. Blood in the maternal circulation is delivered via open ended arterioles to the intervillous space