Standard Wire-reinforced and Silicone-tipped Endotracheal Tube Designs Compared for Ease of Intubation. Greer et al. (page 729)
The passage of standard-design endotracheal tubes over fiberoptic endoscopes is often difficult because of the bevel impinging on laryngeal structures. Greer et al. compared the ease with which tubes with different tip designs could be passed into the trachea. They compared two types of endotracheal tubes: a polyethylene wire-reinforced tube with standard bevel and a wire-reinforced tube with a flexible silicone tip and hemispherical bevel. (This is the same tube provided with the Intubating Laryngeal Mask Airway; Intavent, Maidenhead, Berkshire, United Kingdom). The team recruited 30 adult patients scheduled to undergo elective surgery. After anesthetizing patients with propofol and fentanyl followed by atracurium, investigators passed the selected endotracheal tube over the fiberscope, advanced fiberscopes through the patient’s glottis, and left the tip of the tube above the vocal cords. Then, the fiberscope, tube, and patient’s face were covered with a green towel. A blinded investigator entered the room and passed the tube into the patient’s trachea. After the investigator left the room, the tube and fiberscope were removed. Patients underwent manual ventilation for a brief period to ensure maintenance of adequate oxygen, and then, the maneuver was repeated with the second type of tube. Tubes were oriented on the fiberscopes so that the bevel of the tube faced left. An observer graded the difficulty of intubation using a three-point scale.
The silicone-tipped tubes were passed without difficulty in 27 cases; minimal manipulation was required in 3 cases. With the wire-reinforced tubes, a 90° counterclockwise rotation was required in 8 cases, and in another 8 cases, the difficulty of intubation required more than one maneuver, including external laryngeal manipulation or movement of the head. The investigators conclude that the silicone-tipped tube with a hemispherical bevel confers a clinical advantage over the more rigid-tipped, standard bevel tubes during fiberoptic intubation.