The Macintosh Laryngoscope: the Mechanism of Laryngeal Exposure and the Optimal Maneuver

Hiroyuki Nakao

Abstract


Background: The Macintosh laryngoscope enables safer and easy intubation. However, the mechanism of laryngeal exposure remains unclear. I hypothesized that extension of the hyoepiglottic ligament contributes to elevation of the epiglottis, and laryngoscope maneuvers that pull the hyoid bone rostrally will effectively elevate the epiglottis and expose the glottides.

Methods: To test this hypothesis, I developed a model in which the epiglottis and hyoid bone were connected with a Velcro tape to allow flexible movement and applied different maneuvers to investigate their effects on epiglottis and hyoid bone movement.

Results: A comparison of the original Macintosh maneuver, a modified Macintosh maneuver and the McCoy maneuver found that the McCoy maneuver elevated the epiglottis most, and was associated with rostral and anterior displacement of the hyoid bone. When the model was adjusted so that the hyoid bone was positioned caudal to the epiglottic vallecula, the hyoepiglottic ligament was shortened and the original Macintosh maneuver failed to elevate the epiglottis. Based on these results, a modified Macintosh maneuver was applied that elevated the hyoid bone rostrally and anteriorly and enhanced epiglottis elevation.

Conclusions: The position of the hyoid bone should be considered to achieve epiglottic elevation and a good view of the glottides when performing laryngeal exposure. The position of the hyoid bone relative to the epiglottic vallecula could determine the response of the hyoepiglottic ligament and epiglottis elevation. Increased understanding of the mechanism of laryngeal exposure enables development of improved intubation devices and training models.




J Curr Surg. 2018;8(1-2):1-6
doi: https://doi.org/10.14740/jcs348w


Keywords


Hyoepiglottic ligament; Hyoid bone; Epiglottis

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