Letters to the Editor: Letters & Announcements
To the Editor:
We read with interest the paper by Brimacombe et al. regarding the Soft Seal™ laryngeal mask airway (SSLM) (1). There have been a number of published papers showing the SSLM to provide similar clinical performance to the Classic™ LMA with significantly less frequent postoperative sore throat and lower incidence of blood on the device (2,3). The intracuff pressure in the SSLM is minimally affected by the diffusion of N2O when compared with the Classic™ LMA (4). We have also shown that the fiberoptic position for both devices to be similar (2). By inflating the cuff of the SSLM to atmospheric pressure before insertion and using size 3 for women and size 4 for men, we have achieved a 100% insertion success rate with only 3% of patients requiring second attempts; 4% had blood-stained LM with an incidence of postoperative sore throat of only 6% (5). It is not clear from the study whether the authors inserted the SSLM with a partially inflated cuff as recommended by its manufacturer, which has been shown to achieve excellent results (2,5).
Achieving a seal pressure of 20 cm H2O is thought to correlate best with the correct position of the laryngeal mask rather than the fiberoptic view of the larynx (6). According to the authors’ data regarding the oropharyngeal leak pressure, that was easily achieved in all patients using the SSLM except when it was completely deflated, which is clinically unpracticed.
The authors stated that each of the two users in the study has an experience of 50 to 300 uses with each device. It is not clear which device is associated with 50 uses and which device is associated with 300 uses. This makes their statement in the Conclusion “that the level of experience with each device was similar” unclear and vague.
We also do not agree with the authors’ conclusion that the SSLM would be less useful as an airway intubator, as the authors in this study did not test the ease of insertion of instruments into the respiratory tract. The SSLM has been shown to be a very effective device when used as an airway intubator (7).
There is evidence that the performance of extraglottic airway devices in cadavers is similar to performance in anesthetized patients (8). Interestingly, the same authors compared the ease of insertion and fiberoptic position in cadavers using the Soft Seal™ and Unique™ laryngeal mask airway and achieved 100% success rate in the first attempt in both devices and with no significant difference in the fiberoptic position (9)!
B. Al-Shaikh, FCARSI, FRCA
William Harvey Hospital
Ashford, Kent, UK
A. A.J. Van Zundert, MD, PhD, FRCA (Hon)
Department of Anesthesiology
Eindhoven, The Netherlands
1. Brimacombe J, von Goedecke A, Keller C, et al. The laryngeal mask airway unique versus the Soft Seal laryngeal mask: A randomized, crossover study in paralyzed anesthetized patients. Anesth Analg 2004;99:1560–3.
2. Van Zundert AAJ, Fonck K, Al-Shaikh B, Mortier E. Comparison of the LMA-Classic with the new disposable Soft Seal laryngeal mask in spontaneously breathing adult patients. Anesthesiology 2003;99:1066–71.
3. Cao MM, Webb T, Bjorksten AR. Comparison of disposable and reusable laryngeal mask airways in spontaneously ventilating adult patients. Anaesth Intensive Care 2004;32:530–4.
4. Van Zundert AA, Fonck K, Al-Shaikh B, Mortier EP. Comparison of cuff-pressure changes in LMA-Classic and the new Soft Seal laryngeal masks during nitrous oxide anaesthesia in spontaneous breathing patients. Eur J Anesthesiol 2004;21:547–52.
5. Al-Shaikh B, George M, Van Zundert AAJ. Using atmospheric pressure to inflate the cuff and insertion of the Portex Laryngeal Mask. Anaesthesia 2005;60:296–7.
6. Joshi S, Sciacca RR, Solanki DR, et al. A prospective evaluation of clinical tests for placement of the laryngeal mask airways. Anesthesiology 1998;89:1141–6.
7. Wennet GC, Carlisle JB. Intubation via single-use laryngeal mask airways. Anaesthesia 2004;59:1139.
8. Brimacombe J, Keller C. The laryngeal mask airway in fresh cadavers versus paralysed anesthetized patients: ease of insertion, airway sealing pressure, intracuff pressure and anatomic position. Eur J Anaesthesiol 1999;16:699–701.
9. Keller C, Brimacombe J, Moriggl B, et al. In cadavers, directly measured mucosal pressures are similar for the Unique and the Soft Seal laryngeal mask airway devices. Can J Anaesth 2004;51:834–7.