We thank Drs. Kanazawa and Suzuki for showing interest in our article1and their conclusion that the Portex Soft Seal® laryngeal mask (LM) (Smiths Medical International, Portex Ltd., Hythe, Kent, United Kingdom) offers good laryngeal seal and clinical performance. We have shown that changes in intracuff pressure in Soft Seal® LM during nitrous oxide anesthesia are minimal. The use of new materials in the design of endotracheal tube cuffs has resulted in much lower increases in cuff pressure during nitrous oxide anesthesia.2In the Soft Seal® LM cuff, the plasticizer added to soften the polyvinyl chloride makes the cuff less permeable to nitrous oxide. We have been informed by the manufacturers of the Soft Seal® LM that the material used in manufacturing the cuff of the Soft Seal® LM has changed more recently since our study. Our continuing, unpublished work on methods of insertion of the Soft Seal® LM has shown results similar to those published. We have no explanation for the pressure changes Drs. Kanazawa and Suzuki describe. The only comment we can make is that the very small numbers of patients studied, six patients, with no information about the laryngeal mask size, position during surgery, the method used to measure the cuff pressure, and the longer duration of anesthesia may have affected the results of their limited study.

* Catharina Hospital, Eindhoven, The Netherlands. zundert@iae.nl

Van Zundert AAJ, Fonck K, Al-Shaikh B, Mortier EA: Comparison of the LMA-Classic™  with the new disposable Soft Seal® Laryngeal Mask in spontaneously breathing adult patients. Anesthesiology 2003; 99:1066–71
Al-Shaikh B, Jones M, Baldwin E: Evaluation of pressure changes in a new design tracheal tube cuff, the Portex Soft Seal®, during nitrous oxide anaesthesia. Br J Anaesth 1999; 83:805–6