Hyperoxie : un réel enjeu ?

Hyperoxia applied during tissue hypoxia is debated. Some reports have demonstrated deleterious effects leading to worse outcome, but with no real clinical proof. After remembering the definitions and the key pathways involved in tissue reperfusion, dissolved oxygen seems to be a crucial factor to increase the production of reactive oxygen species (ROS). Even not proven, dissolved oxygen leads to higher level of ROS production that may overcome the physiological systems controlling the level of ROS. The ROS overproduction stimulates many pathways from transduction to enzyme expressions and functions. Even not totally known, the metabolism of ROS can be largely modified by hyperoxia changing the metabolic pathways for many cells. The classic clinical situation for which hyperoxia can be discussed concerns mainly the cardiac arrest. The toxic targets of ROS overproduction are the brain, the heart, the lung and the immune system. It seems that ROS may induce cellular DNA damage that can be repaired or not depending on duration and intensity of ROS production. After taking the main information from animal model, the review gives the main results from clinical studies. None of them provide definitive conclusion having great heterogeneity in protocol and methods used. Based on the above observation, one can propose reasonable attitude, which have to be tested and proven.