compared with ambient oxygen in a pilot study of 70 individuals.
Anticoagulation monotherapy is the standard of care for patients with intermediate-risk pulmonary embolism (PE), but persistent short-term complication rates may approach 10%, wrote Deisy Barrios, MD, of Hospital Ramón y Cajal (IRYCIS), Madrid, and colleagues. Additional strategies are needed, and the use of supplemental oxygen in non-hypoxemic patients with intermediate-risk PE has not been explored, they said.
In a study published in the journal Chest, the researchers recruited 36 women and 34 men who were non-hypoxemic with stable PE and intermediate risk, defined as echocardiographic RV enlargement. The study recruitment ended prematurely because of the COVID-19 pandemic. The mean age of the participants was 67.3 years. Patients were randomized within 24 hours of hospital admission to anticoagulation plus supplemental oxygen or anticoagulation alone. The groups were similar in echocardiographic mean RV end-diameter and RV/LV ratios at baseline.
The intervention patients received supplemental oxygen at a 35% concentration (7 L/min) continuously for 48 hours via a face mask, and through a nasal cannula during meal times.
The primary outcome was normalization of right ventricle size (defined as an RV/LV diameter ratio less than 1.0 from the subcostal or apical view) at 48 hours after randomization. Secondary outcomes included change in the right ventricle/left ventricle diameter as measured at 48 hours and 7 days after randomization compared to baseline.
The proportion of patients with an RV/LV ratio of 1.0 or less at 48 hours was not significantly different between the intervention and control groups (42.4% vs. 21.6%, P = .08). Similarly, the proportion of patients with an RV/LV ratio of 1.0 or less at 7 days was not significantly different between the groups (76% vs. 70%).
The between-group reduction in RV/LV ratio was significantly greater in the supplemental oxygen group vs. the control group from baseline to 48 hours (0.28 vs. 0.12 P = .02).
However, the within-group mean RV/LV ratio was significantly reduced in both the supplemental oxygen group and the control group compared to baseline at 48 hours and at 7 days after randomization.
None of the patients experienced hemodynamic collapse or recurrent venous thromboembolism during the follow-up period.
The findings were limited by several factors including the small sample size and open-label design, and lack of power to detect clinical outcomes, the researchers noted.
However, the results suggest that although supplemental oxygen had no significant impact of RV/LV normalization, “supplemental oxygen might increase the likelihood of reducing echocardiographic RV dilatation,” and the findings warrant a definitive clinical outcomes trial of supplemental oxygen vs. ambient air to improve outcomes in non-hypoxemic patients with intermediate-risk PE, they concluded.
The study was supported by the Instituto de Salud Carlos III. Dr. Barrios had no financial conflicts to disclose.