True intratracheal oxygen concentration delivered by SentriO Oxy™ masks under various respiratory conditions: a bench study

SentriO Oxy™ is a newly available, Food and Drug Administration-approved oxygenation mask system that provides high oxygenation, even on low-flow (5–10 L/min) oxygen. This study aimed to accurately measure the intratracheal fraction of inspired oxygen (FiO₂) using SentriO Oxy™ masks under relatively low oxygen flow rates. A manikin-ventilator-test lung simulation system was used. We measured FiO₂ at the level of the carina, 5 minutes after applying 45 different respiratory parameter combinations using SentriO Oxy™ masks. Tidal volume (TV) was set to 300, 500, and 700 mL; respiratory rate (RR) was set to 8, 12, 16, 20, and 24 breaths per minute; and oxygen flow rate was set to 6, 8, and 10 L/min. Our hypothesis was that FiO₂ would be proportional to the difference between oxygen flow rate and minute ventilation. FiO₂ measured by smaller TV, lower RR, or higher oxygen flows revealed a significantly higher value, confirming our hypothesis. In addition, using linear regression analysis, we found that TV, RR, and oxygen flow were all significant factors influencing the measured FiO₂. Our experiment proposed two prediction equations considering the oxygen flow rate, TV, and RR. The results of our study may provide information and prediction of FiO₂ for clinicians to use SentriO Oxy™ masks during sedative anesthetic procedures under low oxygen flow rates.