To the Editor:
We read the article by Schebesta et al. 1with great interest because it is the first study to compare airway simulators with normal human anatomy using objective anatomical measurements.
Previous studies have compared the effectiveness of four airway simulators, including Airway Management Trainer (Ambu, St Ives, United Kingdom), Airway Trainer (Laerdal, Stavanger, Norway), AirSim (Trucorp, Belfast, Northern Ireland), and Bill 1 (VBM, GmbH, Sulz, Germany) for demonstrating the LMA-Classic™ (LMA North America Inc., San Diego, CA), other supraglottic airway devices, difficult airway management procedures, and other advanced airway skills.2–5The results of these studies have rated AirSim as one of the better devices. Given the previous favorable ratings for the AirSim simulator, we were surprised that AirSim was not included in the study by Schebesta et al .1
At our institution, we are currently using the AirSim Bronchi simulator for training residents to place supraglottic airway devices, single lumen endotracheal tubes, double lumen endobronchial tubes, and bronchial blockers.6
We have performed a computed tomography scan of the AirSim Bronchi simulator and made the same measurements as reported by Schebesta et al. 1(table 1). Most of the AirSim simulator measurements (with the exception of the tongue dimensions) were similar to human subjects, with 11 of 19 measurements within the 95% CI for human subjects as reported by Schebesta et al . The best simulator tested by Schebesta et al. was similar in only 6 of 19 measurements.
Our tongue measurements may have been smaller and oral space volume larger than human subjects in part because we did not add any additional air to the AirSim tongue volume, which can be adjusted by syringe inflation or deflation.
Schebesta et al. 1used the pharyngeal space volume as their primary outcome with none of the airway simulator pharyngeal volumes within the 95% CI of human subjects. The AirSim pharyngeal volume (26 cm3) was also outside the 95% CI of human subjects (17 cm3), but was closer to the upper limit than the next best simulator tested by Schebesta et al. (31 cm3).
We agree with the conclusions of Schebesta et al. 1that airway simulators do not reflect normal human airway anatomy. However, the AirSim simulator seems to be of much higher fidelity based on the objective anatomical measurements than the other airway simulators that were tested. Obviously, there are other important properties than dimensions that determine the realism of airway simulators, especially the appearance and physical properties of the simulated tissues.