I read with interest the article by Thomas et al. on fiberoptic tracheal intubation via a laryngeal mask airway (LMA) Unique (Laryngeal Mask Company Limited, USA) in neonates. They state that, to perform this, it is necessary to use a second tracheal tube as a “pusher” (not a Food and Drug Administration–approved device), because “[a]n LMA Unique size 1 is only a few centimeters shorter than an uncuffed 2.5-mm ETT [tracheal tube], so advancing the ETT into the trachea through the LMA is impossible without assistance.” I point out that this is not accurate.

As the authors state, when a 2.5-mm or 3-mm ID tracheal tube is passed through a size-1 LMA Unique or LMA Classic (the same specification as the LMA Unique), the tracheal tube projects 2 to 3 cm beyond the grille (at the distal end of the breathing tube) of the LMA. Therefore, when the distance between the grille of the LMA and the glottis is shorter than 2 to 3 cm, it should be possible to advance a tube beyond the glottis. In adults, the mean (and the range) of this distance is 3.6 (2.5 to 4.7) cm in men and 3.1 (2.0 to 4.2) cm in women.  No studies have formally measured this distance in neonates, but this is usually less than 1 cm, and thus intubation should usually be possible. I have reported successful fiberoptic intubation through an LMA Classic in five neonates with difficult airways  and have continued to use this method since then, but I have not experienced any case in which a tracheal tube was too short to reach beyond the glottis.

The use of a second tube as a “pusher” (or more appropriately, a “stabilizer”) has already been reported and for adult patients, a “Stabilizer Rod” is commercially available. Dr. Thomas et al. described that a tracheal tube (with its connector detached) is inserted to the LMA, a fiberscope is advanced through the tube into the trachea, and the tube is “pushed” into the trachea by the second tracheal tube that has already been placed over the fiberscope. One major problem with this method is that it is impossible to ventilate the lungs, until both the fiberscope and the LMA have been removed, a connector is reattached to the intubated tube, and the breathing system is attached to the tube. In anesthetized neonates with difficult airways, apnea time taken for these procedures may not be short enough to prevent hypoxia. In addition, removal of the LMA is not an easy task, and thus doing these procedures in haste would increase the risk of inadvertent tracheal extubation, resulting in a “cannot intubate, cannot oxygen” situation. Furthermore, in an awake neonate  the removal of the LAM is stressful to the patient, and any movement of the neonate would further increase the risk of tube dislodgement. More appropriate methods would be as follows, with several merits:

  1. A tracheal tube is inserted to the breathing tube of the LMA, and the breathing system is attached to the tracheal tube (via a “swivel connector” for fiberscopy). This allows oxygenation in an awake neonate, and manual ventilation in an anesthetized neonate.
  2. A fiberscope is inserted through the swivel connector, the tracheal tube, and to the trachea, and then the tube is railed over the fiberscope to the trachea. Even during these procedures, it is possible to provide oxygen and to confirm the presence of the end-tidal carbon dioxide waveforms.
  3. The fiberscope is removed, and correct intubation can be confirmed instantly. In an awake neonate, general anesthesia is induced and a neuromuscular blocking agent is injected. In an anesthetized neonate, a neuromuscular blocking agent is added if necessary. If removal of the LMA is not required, both the tracheal tube and the LMA can be left in place during anesthesia. After operation, the tracheal tube may be removed during deep anesthesia, and the LMA is then removed after the neonate becomes fully awake.
  4. If removal of the LMA is required, adequate neuromuscular blockade and sufficient oxygenation have been confirmed, the connector of the tracheal tube is detached, and a fiberscope is reinserted to the trachea. By “stabilizing” (and not “pushing”) the intubated tube with the second tube, the laryngeal mask is removed over these two tracheal tubes. The connector is reattached and ventilation is restarted. The appropriate position of the tracheal tube is adjusted with the aid of the fiberscope.