Optimal partial pressure of oxygen in critically ill patients receiving mechanical ventilation: A mini review

Millions of intensive care patients worldwide receive supplemental oxygen each year. Although clinicians often instinctively try to correct even mild hypoxemia, the optimal level of arterial partial pressure of oxygen (PaO 2 ) remains uncertain, as both hypoxemia and hyperoxemia can be harmful. This review provides an overview of the physiological and clinical implications of extreme PaO 2 values in critically ill, mechanically ventilated patients, and summarizes recent clinical evidence from studies comparing different oxygenation thresholds. Current findings suggest that PaO 2 should be kept close to physiological values for most intensive care unit (ICU) patients, and extreme values should be avoided to minimize harm. Future research using standardized definitions, improved tissue oxygenation monitoring techniques, and artificial intelligence or machine learning models, may help identify patient subgroups that can benefit from tailored oxygen targets, following the general move toward more personalized critical care patient management.