It???s a Disposable LMA, Just Cut It Shorter???for Fiberoptic Intubation

To the Editor: For a difficult airway, the laryngeal mask is a conduit for fiberoptic endotracheal intubation (1). Users of this technique have recognized that the LMA is too long, or the ETT too short to ensure that the inflated ETT cuff will lie below the vocal cords (2). Substituting a longer nasal RAE tube (NRT) for the standard ETT gains depth (3) but then the fiberoptic bronchoscope (FOB) may be held too far back to reach the vocal cords, then, 2 cm cut from the proximal end of the NRT allows the FOB to reach the trachea (4). We suggest that the disposable LMA can be improved for fiberoptic intubation by shortening the shaft, we found the optimum distance to be equal in centimeters to the model size number of the LMA (i.e., 5 cm for size 5 LMA, etc.). Since it is stiffer than the reusable LMA, the disposable LMA retains greater maneuverability. This is relevant in cases where there is restricted access and the handle of an intubating LMA may be an obstruction. During an emergent pediatric intubation I.O. cut the shaft of a classic LMA to suit the child and found that it eased bronchoscope movement and passage of an endotracheal tube. She removed the LMA before proceeding with the case. Similar modifications in other difficult airway cases have confirmed this initial impression, and one case is briefly described here. A 63-year-old man with lung cancer was undergoing stereotactic brain biopsy. A head frame placed under local anesthesia included a transverse bar at the level of the nasal tip. This restricted airway access and mobility and intubation was expected to be difficult. Before induction a disposable size #5 LMA was prepared by cutting 5 cm off the circuit end of the shaft and transferring the adapter to the new end (Fig. 1). The LMA was inserted and the patient was easily ventilated four breaths preoxygenation before the fiberoptic bronchoscope with ET tube was entered. It was possible to visualize the position of the LMA in the larynx and the path of the endotracheal tube as it exited the LMA shaft through the vocal cords into the trachea. When in place, the ETT cuff was inflated and was seen to be clearly below the vocal cords. The bronchoscope was removed and the LMA was deflated and left in place throughout the neurosurgical procedure and was later used to assist in maintaining an airway during extubation.Figure 1: Fiberoptic examination and endotracheal tube placement through the laryngeal mask airway (LMA) is assisted by shortening the LMA tube.This letter draws attention to what is an occasionally useful modification of the instrument in these particular and limited circumstances; it is not a modification recommended by the manufacturer. However, in North America this year, the disposable LMA has gained acceptance and has been added to emergency anesthesia carts, thus the procedure-related modification of the disposable LMA that is described here may have wide applicability, but will be limited to the single use of this disposable instrument. Dr Irene Osborn has been a consultant to the Laryngeal Mask Airway Company. Irene P. Osborn, MD Robert Soper, MD