Removal Methods of Rigid Stylets to Minimize Adverse Force and Tracheal Tube Movement：A Mathematical and In-vitro Analysis in Manikins

Abstract

The intubating stylet is a powerful tool for facilitating tracheal intubation. Although stylets improve the maneuverability of the tube, the rigidity of styletted tubes can cause laryngeal complications. This study investigated the potential risk for laryngeal injury when using a stylet and assessed the optimal method of stylet extraction through in vitro experiments and mathematical analysis. When the stylet was extracted along a straight path towards the stylet end, the distance travelled by the tube tip significantly increased as the bending angle increased. Mathematical analysis revealed that the stylet should be diagonally extracted at an appropriate angle rather than along a straight path towards the direction of the stylet end. In simulated tracheal intubation, the extraction force and force applied to the vocal cords both significantly increased as the bending angle increased. Compared to the hockey-stick-shaped stylet, the arcuate-shaped stylet resulted in smaller force. The present results indicate the potential risk for vocal cord injury when using hockey-stick-shaped stylets with large bending angles. The intubater or assistant should therefore use great caution during stylet extraction and tube insertion.