Chest. 2023 Sep 15:S0012-3692(23)05431-4. doi: 10.1016/j.chest.2023.09.007. Online ahead of print.
BACKGROUND: The effect of supplemental oxygen therapy in patients with intermediate-risk pulmonary embolism (PE) who do not have hypoxemia at baseline is uncertain.
RESEARCH QUESTION: Does supplemental oxygen improve echocardiographic parameters in non-hypoxemic patients with intermediate-risk PE?
STUDY DESIGN AND METHODS: This pilot trial randomly assigned non-hypoxemic patients with stable PE and echocardiographic right ventricle (RV) enlargement to receive anticoagulation plus supplemental oxygen for the first 48 hours versus anticoagulation alone. The primary outcome was normal echocardiographic RV size 48 hours after randomization. Secondary efficacy outcomes were the numerical change in the RV/left ventricle (LV) diameter ratio measured 48 hours and 7 days after randomization, with respect to the baseline ratio measured at inclusion.
RESULTS: The study was prematurely stopped due to the COVID-19 pandemic after recruiting 70 patients (mean [SD] age, 67.3 [16.1] years; 36 women [51.4%]) with primary outcome data. Forty-eight hours after randomization, normalization of the RV size occurred in 14 (42.4%) of the 33 patients assigned to oxygen, and in 8 (21.6%) of the 37 patients assigned to ambient air (P =0.08). In the oxygen group, the mean RV/LV ratio was reduced from 1.28 [0.28] at baseline to 1.01 [0.16] at 48 hours (P <0.001); in the ambient air group, mean RV/LV ratios were 1.21 [0.18] at baseline and 1.08 [0.19] at 48 hours (P <0.01). At 90 days, there was 1 major bleeding event and 1 death (both in the ambient air group).
INTERPRETATION: In analyses limited by small number of enrollees, compared with ambient air, supplemental oxygen did not significantly increase the proportion of patients with non-hypoxemic intermediate-risk PE who normalized their RV/LV ratio after 48 hours of treatment. This pilot trial showed improvement in some ancillary efficacy outcomes and provides support for a definitive clinical outcomes trial.