Supplementation of standard pre‐oxygenation with nasal prong oxygen or machine oxygen flush during a simulated leak scenario

Summary The presence of a facemask leak significantly reduces the effectiveness of pre‐oxygenation and increases the risk of post‐induction hypoxia. We randomly assigned 24 healthy volunteers to a six‐period crossover trial with and without a simulated facemask leak. Pre‐oxygenation was performed using a standard anaesthesia machine circuit supplemented either by nasal prong oxygen or by anaesthesia machine flush oxygen. Each intervention was completed with both 3‐min tidal breathing and 8 deep breath techniques: end‐tidal oxygen fraction was used as the measure of pre‐oxygenation effectiveness. The presence of a stimulated mask leak significantly reduced the effectiveness of pre‐oxygenation regardless of the breathing method used. With a simulated facemask leak introduced, the mean ( SD ) end‐tidal oxygen fraction with the 3‐min tidal breath technique was 74.7 (9.3)% compared with 57.5 (6.2%) for the 8 deep breath technique with 3‐min tidal breathing and a leak. End‐tidal oxygen fractions increased by 11.0% (95% CI 7.8–14.3%) (p < 0.0001) with the addition of nasal prong oxygenation and 16.8% (13.6–20.0%) (p < 0.0001) with machine oxygen flush compared with standard pre‐oxygenation. When a leak is present, 3‐min tidal breathing with either nasal prong or anaesthesia machine flush oxygenation is an effective pre‐oxygenation method, and preferable to the 8 deep breath method.