Hypoxemia defined in terms of reduced partial pressure of oxygen (mm Hg) in arterial blood, but also in terms of reduced content of oxygen (ml oxygen per dl blood) or percentage saturation of hemoglobin (the oxygen binding protein within red blood cells) with oxygen, which is either found singly or in combination. While there is general agreement that an arterial blood gas measurement which shows that the partial pressure of oxygen is lower than normal constitutes hypoxemia, there is less agreement concerning whether the oxygen content of blood is relevant in determining hypoxemia. This definition would include oxygen carried by hemoglobin.
Vascular remodelling in the embryo early cardiovascular flow, such as preventing the entry of red blood cells into blood plasma, thereby lowering viscosity and associated shear stresses. Starch can also be injected into the blood stream in order to increase viscosity and shear stress. Studies have shown that vascular remodelling in the embryo proceeds without the presence of erythrocytes, which are responsible for oxygen delivery. Therefore, vascular remodelling does not depend on the presence of oxygen and in fact occurs before perfused tissues require oxygen delivery. However, it is still unknown whether or not other nutrients or genetic factors may have promotional effects on vascular