Capnography for Safe Use of the Laryngeal Mask During Emergence from Anesthesia

It has been suggested that the use of the laryngeal mask, while the patient is still deeply anaesthetized, may minimize the stress response while providing a patent airway during emergence from anesthesia (1–5). An uninterrupted patent airway can be obtained by placing the laryngeal mask before tracheal extubation (1–3). With this method, even if placement of the mask has failed, a patent airway will not be lost; attempt at placement of the mask is either repeated or abandoned (1–3). However, even with this method, airway obstruction could occur after tracheal extubation if the position of the laryngeal mask is not optimal. Correct position of the laryngeal mask can be confirmed using a fiberoptic bronchoscope (6), but its routine use may not be practical. We suggest a simple method using a capnograph for confirming a patent airway via the laryngeal mask before tracheal extubation. After return of spontaneous breathing and reversal of neuromuscular block, the laryngeal mask is placed while a tracheal tube is still in place (1–3). A sampling port of a capnograph is attached to the laryngeal mask. The cuff of the tracheal tube is then deflated, and the tracheal tube is occluded by a finger. When the laryngeal mask is positioned correctly, exhaled breaths will pass around the tracheal tube and pass through the tube of the laryngeal mask, producing a normal capnographic pattern. In contrast, if the laryngeal mask is malpositioned, exhaled breaths will either be hampered by or leak around the laryngeal mask, producing no or an obstructed capnographic pattern. This simple procedure would further decrease the possibility of the loss of a patent airway in the use of the laryngeal mask after tracheal extubation. Takashi Asai MD, PhD Koh Shingu MD