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Department of Anaesthesiology and Intensive Care Medicine, University Hospital Mannheim, Mannheim, Germany
To the Editor:
We have some comments on the recent article by Brimacombe (1) comparing LMA-ProSealTM and Laryngeal Tube (LT).
The LT used was not the device currently distributed (Fig. 1). Improvements are two distal airway apertures and a reshaped proximal cuff, reducing the chance of epiglottic downfolding suggested as a possible reason for more difficulties to form an effective airway with the LT. Improvement with chin lift is consistent with our own experiences but would not be considered a major airway intervention as classified in the article. Our experiences with the LT show higher success rates than described (2). Tidal volumes over the LT were comparable with those reached with a tracheal tube (3).
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The esophageal drain tube mentioned as advantage of the PLMA is a feature of a new Laryngeal Tube, the LTS (Fig. 2) available in Europe since June 2002. Comparison of this device with the LMA-ProSealTM should offer new valuable insights.
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James Cook University, Department of Anaesthesia and Intensive Care, Cairns Base Hospital, Cairns, Australia Department of Anaesthesia and Intensive Care Medicine, Leopold-Franzens University, Innsbruck, Austria
In Response:
We thank Genzwuerker et al. for their comments. Our study was conducted in mid-2001, and we were unaware that plans were afoot for a "next generation" Laryngeal Tube airway (LTA). Given the poor performance of the original LTA against the ProSealTM (1) and ClassicTM laryngeal mask airways (2), these new features may breathe new life into an otherwise doomed device.
The drain tube, probably the best new feature, should provide protection against regurgitation, prevent gastric insufflation during positive pressure ventilation, facilitate passage of a gastric tube, help diagnose malposition, and allow bougie-guided insertion, as it does with the ProSealTM laryngeal mask airway (3). The reshaped proximal cuff will probably have little impact on epiglottic downfolding, as this occurs during insertion when the cuff is deflated and therefore the same shape as the original LTA. Another tactic to alleviate epiglottic downfolding might be to insert the LTA using a laryngoscope, as has been suggested for the ClassicTM laryngeal mask airway (4). One problem that the redesign does not address is the potential for mucosal ischemic injury secondary to the high pressures required to form an effective seal (5).
The authors suggest that that O’Connor et al. (6) and Brain (7) do not recommend the use of the ProSealTM for spontaneous ventilation. However, the former authors merely noted a complication associated with spontaneous ventilation, and the latter author only proposed that positive pressure was preferable. The one study where data has been collected for spontaneous and positive pressure ventilation suggests that both modes of ventilation are effective and probably safe (8).
Sherlock Holmes, in Arthur Conan Doyle’s A Scandal in Bohemia, published in 1891, considered that, "It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." We wholeheartedly agree with Genzwuerker et al. that the most valuable insights will come from future studies.
References
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