To the Editor:—
I read with interest Wrobel and Ziegeler’s article1that airway obstruction occurred during the use of a reusable laryngeal mask airway classic (LMA-Classic; The Laryngeal Mask Company, Henley-on-Thames, United Kingdom). In their report, a clear airway was obtained after insertion of a size 4 LMA-Classic and after inflation of the cuff with 20 ml air. During anesthesia, 10 ml air was added to the cuff to prevent airleak around the device, but the airway was obstructed. Close examination of the device after its removal showed that there was a cuff herniation that had not been detected at preuse checking.
In a previous study,2which Wrobel and Ziegeler did not mention in their report, I showed that cuff herniation of the LMA-Classic may not be apparent if the cuff is inflated with the volume less than the recommended maximal volume (e.g. , 30 ml for size 4) but may only become apparent when inflated with a volume of air 50% greater (45 ml). I also reported that if the cuff is inflated with smaller volume of air (e.g. , 20 ml), there may be a dimple in the herniated part of the cuff, suggesting that there is a weakness of the cuff. 2Wrobel and Ziegeler1stated that there was no problem at preuse checking, but the cuff was checked by inflating it with 20 ml air (Marc Wrobel, M.D., Department for Anesthesiology and Intensive Care Medicine, University of Saarland, Homberg/Saar, Germany; personal written commnunication, 2007). In figure 1 of their report,1cuff herniation was apparent when the cuff was inflated with 40 ml air (Marc Wrobel, M.D., Department for Anesthesiology and Intensive Care Medicine, University of Saarland, Homberg/Saar, Germany, personal written communication, 2007), and when the cuff was inflated with smaller volume of air (fig. 2 of their report), there was a dimple in the herniated part of the cuff.1These features are strikingly similar to results obtained in my previous article.2Therefore, if the integrity of the cuff had been checked by inflating the cuff with 45 ml air in their case, airway obstruction resulting from the damaged LMA-Classic might have been avoided.
Wrobel and Ziegeler suggested that the use of a silicone lubricant may damage the cuff. 1I pointed out that sterilization of the device in an autoclave with the cuff not tightly deflated or before any fluid has been infused into the cuff may also damage the cuff.2Any reusable device, particularly a well-used one, should undergo a proper preuse checking, and I suggest the following.
Before each use, the absence of cuff herniation (and any other deformities) should be confirmed by inflating the cuff with a volume of air 50% greater than the recommended maximal volume. This practice is now recommended by the manufacturer.
Before use, the absence of dimple in the cuff should be confirmed by inflating the cuff with 15-20 ml air.
After insertion of the LMA-Classic, the cuff should be inflated with approximately 15 ml air,3and if airleak occurs around the cuff, air may be added until the cuff volume reaches the recommended maximal value.
If there is still airleak, the device should be removed, and a larger one should be used. The integrity of the removed device should be rechecked.
Kansai Medical University, Osaka, Japan. email@example.com