Investigation of the optimal method of oxygen administration with simultaneous use of a surgical mask in postoperative patients: a randomized cross-over study

Background: From the standpoint of infection prevention, anesthesiologists need to simultaneously use a surgical mask and an oxygen mask when administering oxygen to patients. However, there is a lack of scientific evidence to justify this method. We aimed to investigate a suitable method of oxygen administration when using a surgical mask in postoperative patients. Methods: This was a randomized, single-blind, cross-over study involving 42 patients admitted to the ICU. We compared three methods of oxygen administration: nasal cannula under the surgical mask, oxygen mask under the surgical mask, and oxygen mask above the surgical mask, using a cross-over design. The primary endpoint was partial pressure of arterial oxygen (PaO₂). The secondary endpoint was partial pressure of arterial carbon dioxide (PaCO₂). Results: PaO₂ was higher when the oxygen mask was placed under the surgical mask (median values 197.7 mmHg), the nasal cannula was under the surgical mask (180.6 mmHg), and the oxygen mask was above the surgical mask (143.0 mmHg), in descending order, with significant differences between all groups (P < 0.001). PaCO₂ did not differ between groups. Conclusions: The current standard method of administering oxygen to postoperative patients using an oxygen mask over a surgical mask results in poor oxygenation. Adopting the method of oxygen administration under the surgical mask via an oxygen mask or nasal cannula should be considered instead.