Tissue oxygenation and capacity to deliver O2 do the two go together?

Oxidative phosphorylation is the most important source of energy in mammals. Oxygen capture, convective and diffusive oxygen transport as well as the final intracellular oxygen utilization within the mitochondria represent highly refined mechanisms, supervised by a variety of physiological control systems. Any disease process interfering with the delivery of oxygen to tissue will ultimately lead to an impairment of cellular energy production. Generally, cellular hypoxia may result from either reduced oxygen uptake (hypoxic hypoxia), reduced convective and diffusive oxygen transport (circulatory and anemic hypoxia), impaired oxygen consumption (histotoxic hypoxia), or a combination of these states. To effectively treat any of these conditions, it is mandatory to recognize the underlying specific alterations of oxidative metabolism. Identification of the various types of hypoxia as well as contemporary treatment surveillance strategies depend primarily on measuring oxygen partial pressure in inspiratory gas, blood (arterial, mixed-venous) and tissue (extracellular fluid), next to monitoring of various circulatory parameters. This review focuses (a) on the diagnostic value of different techniques used to monitor blood and tissue oxygenation and (b) on the effects of impaired capacity to deliver O2 on tissue oxygen delivery and consumption. The potential value of multiparametric monitoring in guiding specific treatment measures to improve oxygen delivery to tissue is highlighted.