Lay summary
More than 20,000 New Zealanders (and 20M people globally) are admitted to an intensive care unit (ICU) annually. ICU patients are the sickest patients in the hospital, most require life support (invasive mechanical ventilation), and many die from their critical illness. Supplemental oxygen is universally administered to patients who require life-support but the correct dose of oxygen to provide is currently not known. We are undertaking a 1000-participant randomised controlled trial to establish whether careful titration of oxygen to avoid exposure to either abnormally high or low levels of oxygen (conservative oxygen therapy) improves outcomes compared to standard oxygen therapy in ICU patients who require life support.