The Evaluation of a Better Intubation Strategy When Only the Epiglottis Is Visible

A Randomized, Cross-over Mannequin Study

Tzu-Yao Hung; Li-Wei Lin; Yu-Hang Yeh; Yung-Cheng Su; Chieh-Hung Lin; Ten-Fang Yang


BMC Anesthesiol. 2019;19(8) 

In This Article


When the vocal cords are visible using the laryngoscope, such as in C-L grades I and IIa, successful intubation is usually anticipated. However, among C-L grades IIb–IV, blind intubations (without seeing the endotracheal tube pass through the vocal cords) are more difficult because the distances between the tip of the ET and the epiglottis or other landmarks are obscured.[1,2] Under such circumstances, if the practitioner can keep the tip of the ET moving along and just beneath the epiglottis (anterior part of the larynx), the ET would slip from the larynx into the trachea. Compared with holding the middle part of the ET and hooking an imaginary target - the tracheal inlet – that is outside of the visual field, two techniques might help. In the first method, managing and using the stylet as a Trachway intubating stylet (Biotronic Instrument Enterprise Ltd., Tai-Chung, Taiwan) could be of benefit. This involves holding the top of the ET with the right hand so that the ET can be levered immediately after the cuff passes the incisors, with the elbow bending to the chest. Such a technique may provide greater torque with which to hook and move the tip of the ET inferiorly and parallel to the epiglottis (Figure 1a & b). This technique was initially introduced by James Ducanto ( The second method involves lifting the epiglottis with the tip of the stylet-equipped ET. We always use our left hands to manipulate the laryngoscope to obtain a better glottic view. When the glottic view is insufficient to perform intubation, we adjust the tip of the laryngoscope in the vallecula and try to lift more. However, Wasa et al. reported on a patient's case that lifting the epiglottis with the stylet may also improve the glottic view directly.[3]

Figure 1.

a Holding the top of the endotracheal tube and (b) bending the elbow to the chest right after the cuff passed through the incisors to elevate the tip of the tube with greater torque. All processes were recorded with a video camera. (c) The camera was attached to the blade for recording purposes. The participants used the direct laryngoscope without watching the screen. The white arrow indicates the location of the camera

Levitan et al. proved that the shapes and bend angles of the stylet affect the success of intubation [4]. Although a hockey shape is widely used in emergency practice, the ways in which the different stylet shapes and curvatures might affect intubation remained unclear. This study was designed to optimise intubation strategies for difficult airway with higher modified C-L grades, namely, IIb or III, when the inlet of the trachea cannot be visualized.