Emergency clinicians commonly encounter difficult airways. Estimates run as high as 20 percent for difficult airways  and approximately 1 percent for failed airways . Difficulty in airway management is variably defined, and includes the need for excess lifting force, poor view of the vocal cords, multiple or prolonged attempts, multiple operators, and the use of multiple intubating devices.
A wide range of devices have been developed to aid in the management of the difficult airway. They incorporate a variety of fiberoptic, video, optical, and mechanical technologies to enable the operator to obtain a better view of the larynx and facilitate passage of an endotracheal tube (ETT) into the trachea. These devices are useful for management of the difficult or failed airway and for routine intubation.
This topic review will discuss the types of devices designed to facilitate management of difficult and failed airways. The overall approach to the management of such airways is reviewed elsewhere. (See "The difficult airway in adults" and "The failed airway in adults" and "The difficult pediatric airway".)
We define a stylet as a device loaded within the lumen of an endotracheal tube (ETT) in order to assist tracheal placement. A standard malleable metal stylet is inserted into an ETT to lend greater stiffness and thereby improve control. In contrast, specialized stylets facilitate intubation in situations of poor glottic exposure and if adapted with advanced optics, can provide a better view of the glottis than is obtained with direct laryngoscopy.
Endotracheal tube introducers (gum elastic bougie) — The endotracheal tube introducer (ETI) is an effective and inexpensive adjunct to difficult airway management that is easy to use. We recommend that an ETI be readily available in every emergency department. The technique for using these devices and evidence of their effectiveness are reviewed separately. (See "Endotracheal tube introducers (gum elastic bougie) for emergency intubation".)