Liberal or Conservative Oxygen Therapy for Acute Respiratory
In this prospective randomized trial involving patients with a very common form of ARDS, slightly more than 40% of whom had a Pao2:Fio2 lower than 100 mm Hg, a conservative-oxygenation strategy during the first 7 days of mechanical ventilation did not reduce mortality at 28 days as expected. There was also a worrisome but not established signal of increased mortality at 90 days and mesenteric ischemia. At the time of the last meeting of the data and safety monitoring board, the trial was stopped prematurely after the enrollment of 205 patients because of this risk.

The results suggest a clinically relevant excess of mortality in the conservative-oxygen group, with mortality that was 14 percentage points higher than that in the liberal-oxygen group at 90 days.

In this trial with two groups, the oxygen exposure in the liberal-oxygen group was closer to that in the control group of the other trials, whereas the oxygen exposure in the conservative-oxygen group was close to the lower limits recommended in various ARDS trials and guidelines.

In conclusion, among patients with ARDS, early exposure to a conservative-oxygenation strategy with a Pao2 between 55 and 70 mm Hg did not increase survival at 28 days. A worrisome safety signal was observed in the group assigned to a lower oxygen exposure. The meaning of this signal to clinical practice is unclear.