Oxygen therapy versus conservative therapy in suspected uncomplicated myocardial infarction without hypoxemia: A meta-analysis of randomized controlled studies

Background: The effect of oxygen therapy in patients with suspected uncomplicated myocardial infarction and without hypoxemia at baseline was uncertain. Objectives: We aimed to perform a rigorous and comprehensive meta-analysis to robustly quantify the efficacy of oxygen therapy in patients with suspected uncomplicated myocardial infarction and without hypoxemia at baseline. Methods: We searched EMBASE, MEDLINE, Web of Science, and the Cochrane Library from inception to August 2018. Two researchers screened studies and collected the data independently. Randomized controlled trials were included. The main outcome was mortality at the longest duration of follow-up. Results: Seven studies involving 7732 patients (median = 157 patients; range = 72–6629 patients; interquartile range = 136–441 patients; oxygen therapy group = 3856 patients; conservative group = 3876 patients) were included. Compared with conservative therapy, oxygen therapy did not significantly reduce mortality at the longest follow-up (risk ratio = 0.97; 95% confidence interval = 0.68 to 1.40; z = 0.15; p = 0.88), at discharge (risk ratio = 1.04; 95% confidence interval = 0.48 to 2.26; z = 0.11; p = 0.91), 30 days (risk ratio = 1.08; 95% confidence interval = 0.78 to 1.49; z = 0.44; p = 0.66), and 6 months (risk ratio = 0.93; 95% confidence interval = 0.73 to 1.17; z = 0.66; p = 0.51) in patients with suspected uncomplicated myocardial infarction and without hypoxemia at baseline. Furthermore, there was no significant difference between two groups with regard to infarct size (standard mean difference = 0.15, confidence interval = –0.13 to 0.44; z = 1.07, p = 0.28), cardiac troponin levels (standard mean difference = 0.30, confidence interval = –0.09 to 0.69; z = 1.51, p = 0.13), in hospital reinfarction (risk ratio = 1.49, confidence interval = 0.80 to 2.78; z = 1.25, p = 0.21), and new-onset atrial fibrillation (risk ratio = 0.91, confidence interval = 0.69 to 1.18; z = 0.72, p = 0.47). Multiple subgroup analysis, sensitivity analysis, and trial sequential analysis were consistent with overall findings. Conclusion: Compared with conservative therapy, oxygen therapy did not decrease the mortality at the longest duration of follow-up, discharge, 30 days, and 6 months in patients with suspected uncomplicated myocardial infarction and without hypoxemia at baseline. Furthermore, large-scale, multicenter studies are needed to confirm our results. Registration: PROSPERO, number CRD42017078807.