The determinants for oxygen delivery: is increased fraction of inspired oxygen always crucial?

Oxygen (O2) therapy consists in the administration of a gas mixture with a percentage of O2 increased and it is one of the most common aids used in hypoxia. In this paper we presented the data analyzed by Huang, as a pretext to try to provide an explanation of the physiopathological effects of oxygen administration on tissue oxygenation. The rationale of O2 therapy is to increase the inspired partial pressure of O2, increasing the fraction of inspiratory O2. Oxygen induces a vasoconstriction on sistemic circulation and this effect reduces the cardiac output, increasing the afterload. The mechanisms by which hyperoxia induces vasoconstriction are different. Oxygen also has effects on lung function, redox balance, and it is involved in the production of reactive O2 species (ROS) and other systemic effects, which in turn are involved in the changes of reduced oxygen delivery (DO2). This last would possibly help to consider carefully the risk of DO2 in each patient.