Oxygen for Intermediate Risk PE – Even Without Hypoxemia?

May 7, 2024

Written by Carmen Wolfe

Spoon Feed
Utilizing oxygen, rather than room air, for patients with intermediate-risk acute PE may be helpful even if patients are not hypoxemic. We’ll need a study (but not this one), for further information.

Oxygen for all?
Acute pulmonary embolism (PE) can lead to right ventricular (RV) failure, with experimental models suggesting that increased pulmonary vascular resistance comes from vasoconstriction rather than simply obstructing clot. Given that oxygen acts as a pulmonary vasodilator, could utilization of supplemental oxygen decrease pulmonary vascular resistance and give the struggling RV a chance to recover? It certainly seems like an idea worth investigating, especially given the low cost and ubiquitous availability of oxygen in the ED.

To test this theory, investigators conducted a prospective, randomized single-blind trial across seven hospitals in Spain. From 2019-2022, 73 patients with intermediate-risk acute PE were randomized to receive either supplemental oxygen (via facemask at 7 L/min) or room air along with standard anticoagulation treatment. The primary outcome was normalization of RV size at 48 hours after randomization.

Low study enrollment and a global pandemic led to early termination of this study, and the available data did not show a difference in the primary outcome between the groups. Authors note an improvement in a secondary outcome (change in RV/LV ratio) along with lack of demonstrated harm from the intervention, and call for further trials to investigate.

How will this change my practice?
Utilizing oxygen in hypoxemic patients with acute PE is a no-brainer, and this study suggests that it may benefit intermediate-risk PE patients that are not hypoxemic. However, an under-powered study with a negative primary outcome won’t be enough for me to change my practice for now.

Editor’s Note: Interestingly, improving cardiac function may paradoxically decrease SaO2 in patient’s with pulmonary embolisms large enough to cause cardiac dysfunction. Thus it’s unclear if this intervention would be beneficial or cause hypoxemia and cancel itself out. The Curious Clinicians do a good job explaining the physiology. ~Nick Zelt

Source
Oxygen Therapy in Patients With Intermediate-Risk Acute Pulmonary Embolism: A Randomized Trial. Chest. 2024;165(3):673-681. PMID: 37717936