Association between arterial oxygen and mortality across critically ill patients with hematologic malignancies: results from an international collaborative network

Purpose Patients with hematological malignancies are at high risk for life-threatening complications. To date, little attention has been paid to the impact of hyperoxemia and excess oxygen use on mortality. The aim of this study was to investigate the association between partial pressure of arterial oxygen (PaO 2 ) and 28-day mortality in critically ill patients with hematologic malignancies. Methods Data from three international cohorts (Europe, Canada, Oceania) of patients who received respiratory support (noninvasive ventilation, high-flow nasal cannula, invasive mechanical ventilation) were obtained. We used mixed-effect Cox models to investigate the association between day one PaO 2 or excess oxygen use (inspired fraction of oxygen ≥ 0.6 with PaO 2 > 100 mmHg) on day-28 mortality. Results 11,249 patients were included. On day one, 5716 patients (50.8%) had normoxemia (60 ≤ PaO 2 ≤ 100 mmHg), 1454 (12.9%) hypoxemia (PaO 2 100 mmHg). Excess oxygen was used in 2201 patients (20%). Crude day-28 mortality rate was 40.6%. There was a significant association between PaO 2 and day-28 mortality with a U-shaped relationship ( p 100 mmHg) were associated with day-28 mortality with a dose–effect relationship. Subgroup analyses showed an association between hyperoxemia and mortality in patients admitted with neurological disorders; however, the opposite relationship was seen across those admitted with sepsis and neutropenia. Excess oxygen use was also associated with subsequent day-28 mortality (adjusted hazard ratio (aHR) [95% confidence interval (CI)]: 1.11[1.04–1.19]). This result persisted after propensity score analysis (matched HR associated with excess oxygen:1.31 [1.20–1.1.44]). Conclusion In critically-ill patients with hematological malignancies, exposure to hyperoxemia and excess oxygen use were associated with increased mortality, with variable magnitude across subgroups. This might be a modifiable factor to improve mortality.