Use of the Laryngeal Mask for Exchange of Orotracheal Tubes 

A 45-yr-old man, (height, 172 cm; weight, 68 kg) who attempted suicide by taking diazepam and by stabbing himself in the abdomen, was scheduled for emergency laparotomy. Preoperatively, he was drowsy and responsive to simple verbal command only. Chest radiography showed opacity in the right lower lobe. Analysis of arterial blood gases showed arterial oxygen tension (Pa^O2) of 70 mmHg, arterial carbon dioxide tension (Pa^CO2) of 30 mmHg, and p  H of 7.45 (fractional inspired oxygen tension [FI^O2]= 0.21). A gastric tube was inserted and gastric lavage was performed; the tube was left in place.

There was no difficulty in opening the mouth or in extending or flexing the neck; the jaw was not small, nor was the neck short or “bull-necked”; the thyromental distance was greater than three-fingers width. It was not possible to assess other features of his airway after factors caused by insufficient patient cooperation.

In the operating room, routine monitors were attached while the patient was breathing oxygen. Cricoid pressure was applied and anesthesia was induced using thiopental and succinylcholine. Tracheal intubation using a size 4 Macintosh-type laryngoscope was attempted; however, only the tip of the epiglottis was seen, and it was impossible to insert an 8.0-mm ID endotracheal tube into the trachea. Ventilation via  a face mask was attempted, but it was inadequate. Another two attempts at tracheal intubation, using the same laryngoscope but optimizing the patient's head and neck position and using a gum elastic bougie, failed and oxygen saturation by pulse oximeter (Sp^O2) decreased to 88%. While a laryngeal mask and a percutaneous transtracheal airway were being prepared, the fourth attempt at tracheal intubation was made, and Sp^O2further decreased to 65%. This time, a 7-mm ID tube was successfully inserted into the trachea and Sp^O2rapidly increased to 99%. A suction catheter was passed through the endotracheal tube and a considerable amount of viscous fluid was aspirated. Anesthesia was maintained with fentanyl, nitrous oxide, and sevoflurane in oxygen, and muscle relaxation was produced with vecuronium. Excision of a perforated segment of the small intestine proceeded uneventfully.

After surgery, it was decided to transfer the patient to the intensive care unit before tracheal extubation. Nitrous oxide was discontinued, and 4 mg midazolam, 200 μg fentanyl, and 3 mg vecuronium were injected. Because the pilot balloon of the endotracheal tube was overexpanded, it was planned to adjust the cuff volume. An assistant attempted to remove air from the cuff, but it was difficult. An attempt at adding a small amount of air also was difficult, but suddenly obstruction was relieved and approximately 5 ml air was inadvertently infused. This caused a marked gas leak around the endotracheal tube. It was apparent that the cuff had ruptured, and therefore it became necessary to replace the tube.

Sevoflurane in oxygen was given. The existing endotracheal tube was affixed to the jaw using tape, and a size 5 laryngeal mask was placed without difficulty while the endotracheal tube was still in place. The cuff of the laryngeal mask was inflated with 20 ml air. A fiberoptic bronchoscope (4 mm in diameter) was passed through a 7.0-mm ID endotracheal tube, and the combination was passed through the laryngeal mask so that the tip was just beyond the grill at the aperture of the laryngeal mask. The old endotracheal tube could be seen passing through the vocal cords. The fiberscope was then passed through the vocal cords into the trachea, alongside the old tube. After the carina was identified, the old tube was removed while the laryngeal mask was held in position. The lungs were ventilated through the new tube, which was in the laryngeal mask. The new tube was then advanced over the fiberscope into the trachea without difficulty, and correct reintubation was confirmed by fiberscopy, capnography, and auscultation. The length of the new endotracheal tube was extended by using a second endotracheal tube, and the laryngeal mask was removed over these tubes. The entire exchange procedure took only a few minutes, and time from removal of the old tube to reintubation took less than 10 s. Sp^O2remained 100% throughout the exchange procedure.

The presence of an orotracheal tube does not prevent the placement of the laryngeal mask because the tube passes through the larynx, whereas the distal part of the laryngeal mask is inserted into the hypopharynx. When the endotracheal tube is affixed to the jaw and the laryngeal mask is inserted, using the index finger to slide the mask against the hard palate, it is possible to place the mask while barely touching the endotracheal tube and the tongue. The endotracheal tube can also be removed without dislodging the laryngeal mask. In our previous descriptions of 30 patients, it was always possible to place the laryngeal mask while the endotracheal tube was still in place, to remove the tracheal tube, and to ventilate through the laryngeal mask. 6,11 

The laryngeal mask often can be placed successfully in patients in whom tracheal intubation, ventilation through a face mask, or both, has been difficult, 9,10although there are circumstances in which placement of the laryngeal mask is also difficult. 12Even if correct placement of the laryngeal mask has failed, a patent airway will not be lost, because an endotracheal tube is still in place. Attempt at placement of the mask may be repeated (possibly using a different size), or the technique of the use of the laryngeal mask may be abandoned.

There are three possibly useful features of the use of the laryngeal mask for tube exchange. First, by connecting the breathing system to a new endotracheal tube that is inserted in the laryngeal mask, it is possible to ventilate the lungs after removal of the old endotracheal tube during insertion of the fiberscope and during reintubation. Even if ventilation through the new endotracheal tube is inadequate during exchange procedure, jet ventilation through the suction port of the fiberscope can be applied. 13Although not used in this case, by inserting a tube exchanger through the existing tracheal tube before extubation, it is also possible to apply jet ventilation through the exchanger. 14Second, the laryngeal mask may facilitate location of the vocal cords using a fiberscope. 15Third, advancement of a new endotracheal tube over the fiberscope into the trachea is less likely to be difficult when the tube is passed through the laryngeal mask than when it is not passed through the laryngeal mask. 6 

The limitation of the use of the laryngeal mask for tube exchange is that this method can be used only for the exchange of oral endotracheal tubes: it is not possible to place the laryngeal mask while a nasotracheal tube is in place; nor is it possible to insert a nasotracheal tube while the laryngeal mask is in place. Another limitation is that a 6.0-mm ID endotracheal tube is the largest that can be passed through the size 3 or size 4 laryngeal mask, although a 7.0-mm ID tube can be passed through the size 5, as used in this patient.

Possible pitfalls of this technique include dislodgment of the fiberscope, laryngeal mask, or both, during removal of the old endotracheal tube and failure in advancing a new tube into the trachea. To reduce such problems, the old endotracheal tube should be removed gently while the laryngeal mask is stabilized and while confirming that the fiberscope is in the trachea. In addition, the old tube should be removed only after the position of the laryngeal mask is confirmed to be optimal.