To the Editor:—
The NIM® electromyographic endotracheal tube (Medtronic Xomed, Jacksonville, FL) is a wire-reinforced endotracheal tube equipped with surface electrodes often used to monitor recurrent laryngeal nerve function during thyroid surgery. Recently, while preparing a new NIM® tube we noticed a kink midway along its shaft. The mechanism of this tube kink was not known but at least one other anesthesiologist in our department has experienced a similar problem with this tube. Closer examination of our tube revealed that the reinforcing metal coil had separated from the internal surface of the tube (fig. 1). To see how the coil had become dislodged we hooked part of the separated metal coil with a flexible stylette and intentionally pulled it out with minimum effort. It is possible to pull out the entire length of the reinforcing wire once a portion of it has been dislodged (fig. 2). The coil in these tubes is normally held in place by a thin plastic layer that keeps it adhered to the internal surface of the tube. This is in contrast with other reinforced tubes in which the reinforcing wire is embedded within the wall of the tube.
Such a foreign body within the lumen of an endotracheal tube can potentially cause airway management problems, including difficulty suctioning the trachea and advancing a fiberoptic instrument or airway obstruction. From our experience, it is possible for the reinforcing wire to become dislodged during normal use of this tube. For instance, a patient could bite on the tube separating the wire. Anesthesiologists should be aware of this possibility. Clinicians are cautioned not to excessively bend the NIM® tube and to carefully inspect its lumen before each use.
* Boston University Medical Center, Boston, Massachusetts. email@example.com