• William Poncin, Lia Baudet, Frederic Braem, Gregory Reychler, Frédéric Duprez, Giuseppe Liistro, Leila Belkhir, Jean Cyr Yombi, and Julien De Greef.
• Institut de recherche expérimentale et clinique (IREC), pôle de Pneumologie, ORL et Dermatologie, Université Catholique de Louvain, Avenue Hippocrate 55, 1200, Brussels, Belgium. william.poncin@uclouvain.be.
• J Gen Intern Med. 2022 Apr 1; 37 (5): 122612321226-1232.

BackgroundTreating hypoxemia while meeting the soaring demands of oxygen can be a challenge during the COVID-19 pandemic.ObjectiveTo determine the efficacy of the surgical facemask and the double-trunk mask on top of the low-flow oxygen nasal cannula on arterial partial pressure of oxygen (PaO2) in hypoxemic COVID-19 patients.DesignRandomized controlled trial.ParticipantsHospitalized adults with COVID-19 and hypoxemia treated with the low-flow nasal cannula were enrolled between November 13, 2020, and March 05, 2021.InterventionsPatients were randomized in a 1:1:1 ratio to receive either the nasal cannula alone (control) or the nasal cannula covered by the surgical facemask or the double-trunk mask. Arterial blood gases were collected at baseline and 30 min after the use of each system. The oxygen output was adapted afterwards to retrieve the baseline pulse oxygen saturation. The final oxygen output value was recorded after another 30-min period.Main MeasuresThe primary outcome was the absolute change in PaO2. Secondary outcomes included changes in oxygen output, arterial partial pressure of carbon dioxide (PaCO2), vital parameters, and breathlessness.Key ResultsArterial blood samples were successfully collected in 24/27 (8 per group) randomized patients. Compared to the nasal cannula alone, PaO2 increased with the surgical facemask (mean change: 20 mmHg, 95% CI: 0.7-38.8; P = .04) and with the double-trunk mask (mean change: 40 mmHg; 95% CI: 21-59; P < .001). Oxygen output was reduced when adding the surgical facemask (median reduction: 1.5 L/min [95% CI: 0.5-4.5], P < .001) or the double-trunk mask (median reduction: 3.3 L/min [95% CI: 2-5], P < .001). The double-trunk mask was associated with a PaCO2 increase of 2.4 mmHg ([95% CI: 0-4.7], P = .049). Neither mask influenced vital parameters or breathlessness.ConclusionsThe addition of the surgical facemask or the double-trunk mask above the nasal cannula improves arterial oxygenation and reduces oxygen consumption.© 2022. The Author(s) under exclusive licence to Society of General Internal Medicine.

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