Oxygen insufflation via the C-MAC® video stylet increased the fraction of inspired oxygen during intubation in general anesthesia: a bench study

Abstract

Purpose The C-MAC® video stylet provides optimal visualization and controlled intubation, and oxygen insufflation via the endotracheal tube (ETT) holder oxygen port shortens the apnea period. However, oral saliva and mucus can block the visual field, hindering intubation and prolonging the apnea period. We assessed the fraction of inspired oxygen (FiO2) under different oxygen flows via the ETT holder port, visibility through the bevel, and factors influencing the FiO2, including the ETT internal diameter (ID), breathing pattern, and nasal cannula use. Methods Artificial oral mucus was spread on the bevel to mimic a visual field barrier during intubation. Different oxygen flows (1-15 L/min) were provided via ETTs with two different IDs (6.5 and 8.0 mm) to break the mucus barrier, and the ratio of visible area was calculated. The FiO2 was measured at the carina level in 3-min intubating periods, with and without simultaneous nasal cannula use at 3 L/min. Two different breathing patterns were simulated, apnea and shallow breathing. Results Oxygen flow (>6 L/min with 6.5-mm or >9 L/min with 8-mm ETT) could break the mucus barrier and provide a visible area of 66-82% within 1 s. Higher oxygen flow, longer oxygen insufflation, larger-ID ETT during apnea, lower-ID ETT during shallow breathing, and simultaneous nasal cannula use provided a significantly higher FiO2. Conclusion Oxygenation via the C-MAC® video stylet improved the visual field and increased the FiO2 during intubation, and can be used with or without a nasal cannula for safer intubation.