Impact of Restrictive Versus Liberal Oxygenation on Pulmonary Decline After Cardiac Surgery: A Substudy of the GLORIOUS Randomized Clinical Trial.
Astrid Duus Mikkelsen, Sebastian Wiberg, Hans Henrik Lawaetz Schultz et al.
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In 30 seconds
This predefined, exploratory substudy of the GLORIOUS randomized clinical trial compared restrictive (FiO₂ 50%) with liberal (FiO₂ 100%) oxygenation during cardiopulmonary bypass and the first hour after weaning in adults undergoing nonemergent CABG and/or surgical aortic valve replacement at a single tertiary centre. Among 878 patients, pulmonary function declined across all measured parameters at 3 months, but the decline did not differ significantly between oxygenation groups (all p > 0.3). The findings suggest that restrictive oxygenation did not attenuate postoperative pulmonary-function decline.
Key findings
- At 3 months, median FEV₁ (% predicted) declined by 8.3 percentage points (95% CI 6.6 to 8.3) in the overall population.
- Median FVC (% predicted) declined by 6.1 percentage points (95% CI 5.2 to 7.0), and FEV₁/FVC by 1.6 percentage points (95% CI 1.0 to 2.1).
- Diffusion capacity of carbon monoxide (% predicted corrected) declined by 7.7 percentage points (95% CI 6.2 to 9.1).
- Decline in pulmonary function did not differ significantly between restrictive and liberal oxygenation groups (all p > 0.3), including in subgroup analyses.
Why it matters
Pulmonary-function decline was evident 3 months after cardiac surgery, but this study did not find that lowering inspired oxygen during bypass weaning and the immediate postoperative period reduced that decline. The results help clarify the limits of this proposed strategy for preventing postoperative pulmonary dysfunction, while leaving the causes of the observed decline unresolved.
What to keep in mind
This was a predefined exploratory substudy at a single tertiary centre; the authors describe the findings as hypothesis-generating.