No clear benefit of intensive oxygen therapy in ICU patients: NEJM

Australia: The use of conservative oxygen therapy versus usual oxygen therapy made no significant impact on the number of ventilator-free days in patients undergoing mechanical ventilation in the ICU (intensive care unit), according to a recent study presented at the World Congress of Intensive Care in Melbourne, Australia. The study was also subsequently published in the New England Journal of Medicine.

Patients undergoing mechanical ventilation in the ICU often receive a high fraction of inspired oxygen (Fio₂) and have a high arterial oxygen tension. The conservative oxygen therapy reduces oxygen exposure, diminishes lung and systemic oxidative injury, and thereby decreasing the number of days patients needed mechanical ventilation.

Paul Young, Medical Research Institute of New Zealand, and colleagues randomly assigned 1000 adult patients who were anticipated to require mechanical ventilation beyond the day after recruitment in the ICU to receive conservative or usual oxygen therapy.

In the two groups, the default lower limit for oxygen saturation as measured by pulse oximetry (Spo₂) was 90%. In the conservative-oxygen group, the upper limit of the Spo₂ alarm was set to sound when the level reached 97%, and the Fio₂ was decreased to 0.21 if the Spo₂ was above the acceptable lower limit. In the usual-oxygen group, there were no specific measures limiting the Fio₂ or the Spo₂.

The primary outcome was the number of ventilator-free days from randomization until day 28.

Key findings include:

• The number of ventilator-free days did not differ significantly between the conservative-oxygen group and the usual-oxygen group, with a median duration of 21.3 days and 22.1 days, respectively, for an absolute difference of −0.3 days.


• The conservative-oxygen group spent more time in the ICU with an Fio₂ of 0.21 than the usual-oxygen group, with a median duration of 29 hours and 1 hour, respectively (absolute difference, 28 hours); the conservative-oxygen group spent less time with a Spo₂ exceeding 96%, with a duration of 27 hours and 49 hours, respectively (absolute difference, 22 hours).


• At 180 days, mortality was 35.7% in the conservative-oxygen group and 34.5% in the usual-oxygen group, for an unadjusted odds ratio of 1.05.