Potential Damage to the Larynx Associated with Light-guided Intubation: A Case and Series of Fiberoptic Examinations

A 78-yr-old, 150-cm, 64-kg woman with sternal osteomyelitis was scheduled for curettage of a lesion. Preanesthetic examination showed Mallampati class 2 airway. After induction of anesthesia and muscle relaxation, an experienced anesthesiologist performed orotracheal intubation with use of a 7.5-mm ID endotracheal tube using a lighted stylet (Trachlight, Laerdal Medical, Armonk, NY). This was performed using the standard method, 4with the patient’s head and neck extended and the jaw thrust. During tube advancement, the operator felt the tube tip touch something slightly, and then proper transillumination of the soft tissues of the neck immediately was seen below the thyroid prominence. The Trachlight was removed, and placement of the endotracheal tube was confirmed by use of capnography and auscultation. After the tube was secured, a fiberscope–video camera system was passed into the nasopharyx 5to examine the supraglottic airway. Fiberscopy showed that the epiglottis was partially pushed into the laryngeal inlet, along with the endotracheal tube (fig. 1). We unsuccessfully attempted to restore the epiglottis to the correct position using a laryngoscope and Magill forceps for 10 min. We then extubated the trachea and replaced the endotracheal tube during video visual control. 5The epiglottis was seen to be in the normal position. The patient reported a slight sore throat the next day.

After institutional approval and written informed consent was obtained, we fiberoptically observed the advancement of the endotracheal tube during light-guided intubation 6in 20 patients. After anesthetic induction and paralysis, an assistant inserted a fiberoptic bronchoscope attached to a video camera monitoring system into the nasopharyx 5before intubation. An experienced anesthesiologist performed routine orotracheal intubation using a Trachlight. Endotracheal tubes with 7.5 mm ID were used for female patients and those with 8.0 mm ID were used for male patients. The operator advanced the tube gently, and when a resistance was felt or a glow was seen at an improper location, the tube tip was withdrawn backward and redirected. The assistant recorded the location where the tube advanced and whether the tube came in contact with the laryngeal structures. If the operator felt a resistance, the assistant recorded this information. The time to intubation also was measured.

Nine men and 11 women were studied (mean age, 65 ± 12 yr; mean weight, 56 ± 9 kg [mean ± SD]). Rapid tracheal intubation was successful in all patients. Fiberscopy showed that the epiglottis was lifted from the posterior pharyngeal wall by use of a jaw thrust maneuver before intubation. In nine patients (45%), the endotracheal tube tip was advanced into the trachea without making contact with the laryngeal structures. In 11 patients (55%), the tube tip came in contact 13 times with the laryngeal structures at some point during intubation (table 1). In four occurrences of contact, the operator either felt resistance or saw the glow in an improper location; however, in nine occurrences of contact, the operator could not notice the contact or could not detect the incorrect tube position. In two cases in which the tube tip made contact with the epiglottis, the tube pushed the epiglottis into the laryngeal inlet during tube advancement; however, the epiglottis returned to the correct position. No resistance was felt in these instances. In two cases, during probing in the pharynx with use of a light wand, the tube tip markedly displaced the arytenoids, and the operator did not feel resistance (fig. 2). In two cases, although the glow was seen in the correct location, the forward advancement of the tube was halted after the stiff inner stylet was retracted. Fiberscopy showed that the tube collided with the anterior commissure. In one of the cases, the tube slipped and entered the glottis after the tube was rotated. In another case, the tube and Trachlight were withdrawn, and intubation was successful on the second attempt.

The current case report shows that incorrect positioning of the epiglottis can occur during light-guided intubation, and is difficult to restore. In this case, the tube probably pushed the epiglottis into the laryngeal inlet during tube advancement; however, we thought the intubation was successful because proper transillumination was immediately observed. We did not advance the tube forcefully. A similar event was encountered in our formal study. Our study confirmed that, without the operator feeling resistance, the tube could push the epiglottis into the laryngeal inlet; however, in both cases observed during our prospective study, the epiglottis spontaneously returned to the correct position. A displaced epiglottis might not return to its original position depending on the size and elasticity of the epiglottis, on the size of the endotracheal tube, and on the degree of the folding of the epiglottis. Fortunately, we detected this complication early and restored the displaced epiglottis to the proper position. However, further complications would have developed, such as edema, circulatory disturbance, or mechanical damage to the epiglottis, if the malposition of the epiglottis had remained unnoticed. We reported a case of a similar malposition of the epiglottis during blind intubation through the intubating laryngeal mask, which resulted in edema of the epiglottis. 7 

Our study suggests that there are potential risks of laryngeal damage in addition to the down-folding of the epiglottis. If the operator detects resistance or sees a glow in an improper location when the tube makes contact with the laryngeal structures, the tube is redirected and damage can be avoided. However, the tube tip could displace the arytenoid cartilages markedly even though resistance could not be felt because the tissues are soft, floppy, and relaxed. If the operator continues to advance the tube forcefully, injury to the arytenoid cartilages may occur. 8,9When the tube makes contact with the anterior commissure, tube position may be judged as adequate because the glow was seen in the correct location. The tube may slip when the tube is rotated 4; however, forceful advancement and multiple attempts should be avoided to avert damage to the vocal cords.