Surgical mask on top of high-flow nasal cannula improves oxygenation in critically ill COVID-19 patients with hypoxemic respiratory failure

Objective Critically ill patients admitted in ICU because of COVID-19 infection display severe hypoxemic respiratory failure. The Surviving Sepsis Campaign recommends oxygenation through high-flow nasal cannula over non-invasive ventilation. The primary outcome of our study was to evaluate the effect of the addition of a surgical mask on a high-flow nasal cannula system on oxygenation parameters in hypoxemic COVID-19 patients admitted in ICU who do not require urgent intubation. The secondary outcomes were relevant changes in PaCO_2 associated with clinical modifications and patient’s feelings. Design We prospectively assessed 21 patients admitted in our mixed Intensive Care Unit of the Cliniques Universitaires Saint Luc. Main results While FiO2 was unchanged, we demonstrate a significant increase of PaO_2 (from 59 (± 6), to 79 mmHg (± 16), p  < 0.001), PaO_2/FiO_2 from 83 (± 22), to 111 (± 38), p  < 0.001) and SaO_2 (from 91% (± 1.5), to 94% (± 1.6), p  < 0.001), while the patients were under the surgical mask. The SpO_2 returned to pre-treatment values when the surgical mask was removed confirming the effect of the device rather than a spontaneous positive evolution. Conclusion A surgical mask placed on patient’s face already treated by a High-flow nasal cannula device improves COVID-19 patient’s oxygenation admitted in Intensive Care Unit for severe hypoxemic respiratory failure without any clinically relevant side.