Conservative oxygen therapy fails to increase ventilator-free days in mechanically ventilated patients
The conservative use of oxygen, as compared with usual care, had no significant effect on the number of ventilator-free days in patients undergoing mechanical ventilation in the ICU, according to data published in The New England Journal of Medicine.
For the ICU-ROX trial, the researchers randomly assigned 1,000 adults expected to require mechanical ventilation after recruitment from 21 ICUs in Australia and New Zealand to conservative or usual oxygen therapy.
The default lower limit for oxygen saturation as measured by pulse oximetry (SpO2) was 90% in both groups. For those assigned conservative oxygen therapy, the upper limit of the SpO2 alarm was set to sound when the level reached 97% and the fraction of inspired oxygen (FiO2) was decreased to 0.21 if the SpO2 was above the acceptable lower limit. For those assigned usual oxygen therapy, FiO2 and SpO2 were not limited by any specific measures.
At 28 days, results revealed no significant differences in the number of ventilator-free days — the study’s primary outcome — between the conservative-oxygen and usual-oxygen groups (median, 21.3 vs. 22.1 days; absolute difference, –0.3 days; P = .8).
Notably, when compared with patients assigned usual oxygen, those assigned conservative oxygen spent more time receiving an FiO2 of 0.21 (median duration, 1 hour vs. 29 hours; absolute difference, 28 hours; 95% CI, 22-34) and less time with an SpO2 exceeding 96% (median duration, 49 vs. 27 hours; absolute difference, 22 hours; 95% CI, 14-30).
At day 180, mortality did not differ significantly between the conservative-oxygen group and usual-oxygen group (35.7% vs. 34.5%; OR = 1.05; 95% CI, 0.81-1.37). Additionally, among those who survived, employment status among those who were being paid for work at baseline and cognitive function were similar between treatment groups. However, patients assigned conservative oxygen did have a greater frequency of moderate problems and a lower frequency of severe problems than those assigned usual oxygen with respect to the mobility and personal-care components of the five-level EuroQoL-5D questionnaire.
Adverse events included one patient with an ischemic stroke in the usual-oxygen group and one patient with hypoxemia with a partial pressure of arterial oxygen of 33.5 mm Hg and one patient with a low SpO2 in the conservative-oxygen group. The actual value for the latter patient, however, was not recorded, according to the researchers.
Because of these results, the researchers concluded that conservative oxygen therapy yielded no advantage over usual oxygen therapy in this study.
“In this binational, multicenter, randomized clinical trial involving adults undergoing mechanical ventilation in the ICU, there was no significant difference in the number of ventilator-free days between those who received conservative oxygen (as implemented in our trial) and those who received usual oxygen therapy,” they wrote. – by Melissa Foster
Disclosures: This study was funded by the New Zealand Health Research Council. One author reports receiving grant support from Fisher and Paykel Healthcare. Another author reports receiving travel support from Hamilton Medical and IMT (Bellavista).