Simulator Airway Anatomy

Dr. Doody

Anesthesiology. 2012 June; 116(5):1204-1209.

Degrees of Reality: Airway Anatomy of High-fidelity Human Patient Simulators and Airway Trainers.

Schebesta K, Hüpfl M, Rössler B, Ringl H, Müller M, Kimberger O.

In anesthesiology, airway management is a key skill and failing to manage an airway is associated with a high risk of morbidity and mortality.  Today manikins are used for education, training, and research of human airway management.  Schebesta, et al. studied how realistic these patient stimulators and airway-training manikins really are using objective, radiologic measurements.  CT scans of 20 adult trauma patients (average BMI 24) without neck collars, head or cervical trauma, inappropriate image quality, or previously placed airway devices were compared to either a low-fidelity or high-fidelity stimulator.  Low-fidelity describes simulators that facilitate the training of an isolated skill; high-fidelity simulators, in contrast, allow for full immersion into a real scenario and the ability to provide feedback.  The low-fidelity trainers in this study included the Laerdal manikin and the Ambu manikin.  The high-fidelity trainers included the SimMan, SimMan 3G, HPS, and HAL human patient stimulators.  Comparisons using 14 predetermined distances, two cross-sectional areas, and three volume parameters were made between the airways of the actual patients and the training devices.

The anatomy of the training devices does not reflect the upper airway anatomy of actual patients.  The most realistic airway trainer was the HPS Human Patient Stimulator which had 32% of its parameters with the 95% CI of human airway measurements.  As the pharyngeal airspace (retroglossal and hypopharyngeal sections) is of major importance for airway management, this measure was defined as the primary outcome parameter.  The measurements of the pharyngeal airspace were much larger in the high-fidelity trainers (smallest being 30.6 cm³) than actual patients (13.5 ± 7.7 cm³).

A wide pharyngeal airspace, as found in all manikins in this trial, could lead to an inappropriately easy airway management and thereby would bias the results of simulation based research.  These major differences question the appropriateness of simulator-based research translating into the care of actual patients.  The assumption that simulator acquired skills can transfer to a clinical setting should also be reconsidered.  These anatomical abnormalities in the training devices could be perceived as unrealistic to experienced trainees preventing adequate immersion in the training, and with inexperienced trainees, an unrealistic airway may lead to them to acquire inappropriate techniques.  Research into constructing more anatomically similar airways between human and stimulators should be strong encouraged.