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Canadian Journal of Anesthesia 53:961-963 (2006)
© Canadian Anesthesiologists' Society, 2006

Correspondence

The ProSeal LMA does not cause laryngeal edema

Michael S. Stix, MD, PhD, Cornelius J. O’Connor, Jr, MD and Dennis R. Valade, CRNA

Lahey Clinic, Burlington, USA, E-mail: michael.stix{at}lahey.org

To the Editor:

We were intrigued by the case report by Chin and Chee1 but have doubts about whether the authors properly interpreted the fibreoptic image they presented. Because the entire case report is built upon the premise that this image portrays "laryngeal edema," an improper interpretation would jeopardize not only their diagnosis, but also the rationale for treatment with dexamethasone and further explanation of intraoperative events.

We suggest a more likely interpretation of the fibreoptic airway examination in patients with a ProSealTM laryngeal mask airway (PLMA; LMA North America, Inc., San Diego, CA, USA). Figures 1Go and 2Go show, in the absence of "laryngeal edema," the more common problem of mechanical obstruction of the laryngeal inlet by the cuff and drain tube of the PLMA.2,3 Mechanical obstruction of the laryngeal inlet involves medial displacement of the arytenoid cartilages and aryepiglottic folds, caused by the bulky tip of the PLMA, and can present a challenge to the clinician to accurately identify glottic and supraglottic structures in their distorted positions. To be able to interpret more complicated fibreoptic images it is helpful to appreciate the presence of the corniculate, and especially the cuneiform cartilages as in Figure 1Go. These cartilages appear quite large when viewed up close, and they provide important landmarks when trying to understand complex distortions of the laryngeal inlet with the PLMA.


Figure 1
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  		FIGURE 1 View through the PLMA in a patient where the corniculate and cuneiform cartilages are easily distinguished.

 

Figure 2
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  		FIGURE 2 Fibreoptic images A–D from four different patients, depicting increasing degrees of partial upper airway obstruction.

 
Figure 2Go shows the appearance of the larynx in four different patients with the PLMA. We used a bronchoscopic adapter to observe the larynx throughout the respiratory cycle and the fibreoptic images in the figure were all captured during inspiration. Case A has a widely patent airway whereas cases B, C, and D depict increasing degrees of compression and partial upper airway obstruction. Although cases B, C, and D resemble the image from the case report, none of these patients experienced "laryngeal edema." Instead, the fibreoptic views show narrowing of the glottis and inward displacement of the cuneiform and corniculate cartilages. Again, the bulky prominences are the corniculate and cuneiform cartilages, and do not represent "laryngeal edema" affecting the aryepiglottic folds.

Footnotes

Accepted for publication May 8, 2006.

References

1 Chin KJ, Chee VW. Laryngeal edema associated with the ProSealTM laryngeal mask airway in upper respiratory tract infection. Can J Anesth 2006; 53: 389–92.[Abstract/Free Full Text]

2 Brimacombe J, Richardson C, Keller C, Donald S. Mechanical closure of the vocal cords with the laryngeal mask airway ProSealTM. Br J Anaesth 2002; 88: 296–7.[Abstract/Free Full Text]

3 Stix MS, O’Connor CJ Jr. Maximum minute ventilation test for the ProSealTM laryngeal mask airway. Anesth Analg 2002; 95: 1782–7.[Abstract/Free Full Text]





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