Association of early supplemental oxygen therapy and long-term mortality after ICU admission in normoxic patients following myocardial infarction: A propensity matched cohort study

BACKGROUND: Supplemental oxygen therapy has been traditionally used in acute myocardial infarction (AMI) management, but recent trials have questioned its routine use in people with normal oxygen saturation. However, critically ill patients were typically excluded, leaving an evidence gap for high-risk populations. OBJECTIVES: To evaluate the association between early supplemental oxygen therapy and long-term mortality in ICU patients with AMI and normal oxygen saturation. METHODS: This retrospective cohort study analyzed data from the MIMIC-IV database (Boston, USA; 2008-2022). Adults with AMI and initial oxygen saturation of 92 % - 96 % within 6 h of ICU admission were included. The exposure was early supplemental oxygen therapy (FiO RESULTS: Among 1912 eligible patients, 838 were matched (419 per group). Early supplemental oxygen therapy was independently associated with increased 365-day mortality (29.83 % vs 21.72 %; adjusted HR 1.477, 95 % CI 1.116 - 1.954; P = 0.006). Consistent harmful associations were observed for 28-day mortality, ICU mortality, and hospital mortality. People with chronic obstructive pulmonary disease were particularly vulnerable to hyperoxia. CONCLUSIONS: Early supplemental oxygen therapy in ICU patients with AMI and normal oxygen saturation was independently associated with increased mortality. These findings support a shift from routine use toward individualized oxygen therapy reserved for patients with documented hypoxemia.