by Mervyn Singer, Paul J. Young, John G. Laffey, Pierre
Asfar, Fabio Silvio Taccone, Markus B. Skrifvars, Christian S. Meyhoff and
Peter Radermacher
Critical Care volume 25,
Article number: 440 (2021) Published: 19
December 2021
Oxygen (O2) toxicity remains a concern, particularly to the
lung. This is mainly related to excessive production of reactive oxygen species
(ROS). Supplemental O2, i.e. inspiratory O2 concentrations (FIO2) > 0.21
may cause hyperoxaemia (i.e. arterial (a) PO2 > 100 mmHg)
and, subsequently, hyperoxia (increased tissue O2 concentration),
thereby enhancing ROS formation. Here, we review the pathophysiology of O2 toxicity
and the potential harms of supplemental O2 in various ICU conditions. The
current evidence base suggests that PaO2 > 300 mmHg (40 kPa)
should be avoided, but it remains uncertain whether there is an “optimal level”
which may vary for given clinical conditions. Since even moderately
supra-physiological PaO2 may be associated with deleterious side effects,
it seems advisable at present to titrate O2 to maintain PaO2 within
the normal range, avoiding both hypoxaemia and excess hyperoxaemia.
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