ICU-ROX: conservative oxygen therapy adds no ventilator-free days

  • Mackle D & al.
  • N Engl J Med
  • 12 mar. 2020

  • de Jenny Blair, MD
  • Clinical Essentials
El acceso al contenido completo es sólo para profesionales sanitarios registrados. El acceso al contenido completo es sólo para profesionales sanitarios registrados.


  • For ICU patients undergoing mechanical ventilation, minimizing exposure to high oxygen saturation (SpO2) does not lead to more ventilator-free days. 
  • Editorial discusses challenges to measuring oxygen saturation, heterogeneity of organ perfusion; concludes “avoiding excess oxygen seems sensible,” suggests setting lower SpO2 target bound at 90%.

Why this matters

  • Hyperoxemia has been tied to mortality in observational studies, suggesting potential benefit to a more conservative approach. 

Key results

  • Conservative vs liberal group:
    • Median ventilator-free days: 21.3 vs 22.1 (P=.80).
    • Time in ICU with fraction of inspired oxygen (FIO2) of 0.21: 29 vs 1 hour.
    • Time with SpO2 ≥97%: 27 vs 49 hours.
    • 180-day mortality: 35.7% vs 34.5%;
      • aOR, 1.05 (95% CI, 0.81-1.37).
    • No differences in later employment status, cognitive function.
  • Possible benefit to conservative oxygen in subgroup with acute hypoxic encephalopathy.

Study design

  • Multicenter parallel-group randomized clinical ICU-ROX trial (n=965).
  • Participants intubated, mechanically ventilated in ICU were randomly assigned to:
    • Conservative oxygenation, in which FIO2 was decreased to 0.21 if SpO2 hit 97%.
    • Usual oxygenation, with no FIO2 limit or SpO2 upper limit.
  • Outcome: ventilator-free days through day 28.
  • Funding: Health Research Council of New Zealand.


  • Nonblinded.
  • Clinicians allowed to increase oxygen under some circumstances, potentially reducing outcome differences.

Additional study

  • Appearing in same issue: LOCO2 trial of conservative oxygen in acute respiratory distress syndrome.
  • Editorial discussed both.