Intraoperative FiO₂ and risk of impaired postoperative oxygenation in lung resection: A propensity score-weighted analysis

Study objective: To assess whether, in a lung resection cohort with a low probability of confounding by indication, higher FiO₂ is associated with an increased risk of impaired postoperative oxygenation – a clinical manifestation of lung injury/dysfunction. Design: Pre-specified registry-based retrospective cohort study. Setting: Two large academic hospitals in the United States. Patients: 2936 lung resection patients with an overall good intraoperative oxygenation (median intraoperative SpO₂ ≥ 95 %). Measurements: We compared patients with a higher (≥0.8) and lower (<0.8) median intraoperative FiO₂ after propensity score-weighting for 75 perioperative variables based on a causal inference framework. The primary outcome of impaired oxygenation was defined as at least one of the following within seven postoperative days: (1) SpO₂ < 92 %; (2) imputed PaO₂/FiO₂ < 300 mmHg [(1) or (2) at least twice within 24 h]; (3) intensive oxygen therapy (mechanical ventilation or > 50 % oxygen or high-flow oxygen). Main results: Among the 2936 included patients, 2171 (73.8 %) received median intraoperative FiO₂ ≥ 0.8. Impaired postoperative oxygenation occurred in 1627 (74.9 %) and 422 (55.2 %) patients in the higher and lower FiO₂ groups, respectively. In a propensity score-weighted analysis, higher intraoperative FiO₂ was associated with an 84 % increase in the likelihood of impaired postoperative oxygenation (OR 1.84; 95 % CI 1.60 to 2.12; P < 0.001). Conclusions: Despite plausible harm from hyperoxia, high intraoperative FiO₂ is extremely common during lung resection. Nearly three-quarters of lung resection patients with acceptable oxygenation received median intraoperative FiO₂ ≥ 0.8. Such higher FiO₂ was associated with an increased risk of impaired postoperative oxygenation – a clinically relevant manifestation of lung injury or dysfunction. This observation supports the administration of a lower (< 0.8) intraoperative FiO₂ and its further assessment in clinical trials.