No Benefit to Targeting a Lower Partial Pressure of Oxygen

Patricia Kritek, MD

A lower oxygenation target didn’t prevent mortality or adverse events in patients with hypoxemic respiratory failure.

Oxygen is a life-saving intervention for patients with hypoxemic respiratory failure. However, might too much oxygen be harmful? Although small studies have suggested a benefit for lower oxygenation targets, a conservative oxygen strategy did not result in earlier extubation or lower mortality in a previous trial of nearly 1000 patients (NEJM JW Gen Med Dec 15 2019 and N Engl J Med 2020; 382:989).

Now, European investigators randomized 2888 patients with hypoxemic respiratory failure to a partial pressure of arterial oxygen (PaO2) target of either 60 mm Hg or 90 mm Hg. More than half of patients had pneumonia; 13% had acute respiratory distress syndrome. Hypoxemia was moderately severe, with median ratio of PaO2 to fraction of inspired oxygen of approximately 120. Nearly 60% of patients were intubated, 30% were on supplemental oxygen alone, and the remainder were supported by noninvasive ventilation.

Median PaO2 differed significantly between the high- and low-target groups (93 mm Hg vs. 71 mm Hg), with a corresponding difference in oxygen saturation values (96% vs. 93%). Overall mortality was virtually identical in the two groups, and rates of adverse events also were similar.


Like the previous trial, this trial showed no benefit or harm to targeting a lower PaO2 for critically ill patients with hypoxemic respiratory failure. Notably, median PaO2 in the lower-target group was 10 mm Hg higher than the goal. This likely reflects the challenge of titrating to an exact PaO2, as well as potential provider discomfort with lower saturation values. For now, I feel comfortable continuing to target oxygen saturation in the low to mid 90s.

Schjørring OL et al. Lower or higher oxygenation targets for acute hypoxemic respiratory failure. N Engl J Med 2021 Jan 20; [e-pub]. (

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