When compared with liberal oxygen therapy, conservative oxygen therapy did not improve rates of survival with favorable functional outcomes among unresponsive patients in the intensive care unit (ICU) receiving mechanical ventilation after cardiac arrest, according to results from the investigator-initiated, open-label LOGICAL trial published June 10 in NEJM.

Carol L. Hodgson, PhD, et al., randomly assigned 1,840 patients from 53 ICUs in Australia, New Zealand and Ireland to conservative (882 patients) or liberal (958 patients) oxygen therapy from September 2021 through June 2024. The default lower limit of arterial oxygen saturation as measured by pulse oximetry (Spo2) was 90% for both groups.

The alarm for the upper limit of the Spo2 for the conservative oxygen group was set at 95%, and the fraction of inspired oxygen (Fio2) was decreased to 0.21, provided that the Spo2 was above the lower limit. In the liberal oxygen group, there were no measures limiting the upper Spo2, but the minimum Fio2 permitted during mechanical ventilation was 0.3.

The primary outcome, assessed with the Extended Glasgow Outcome Scale (GOS-E), was survival with a favorable functional outcome at 180 days. Levels on the GOS-E range from 1 (death) to 8 ("upper good recovery"). Importantly, researchers defined survival with a favorable functional outcome as a GOS-E level of 5 ("lower moderate disability") or higher.

At a median follow-up of 189 days, results showed that 38% of study participants in the conservative oxygen group and 40% of participants in the liberal oxygen group met the primary outcome (relative risk 0.97; p = 0.65). Of note, no adverse events were reported.

Hodgson et al., emphasize that "...the effect of conservative oxygen therapy on survival with a favorable functional outcome appeared to be similar regardless of whether patients were enrolled earlier or later after return of circulation or ICU admission." The available data suggests "conservative oxygen therapy does not improve patients' outcomes regardless of the timing of initiation."