British Journal of Anaesthesia, 2003, Vol. 91, No. 2 299
© 2003 The Board of Management and Trustees of the British Journal of Anaesthesia
Correspondence |
Mechanical closure of the vocal cords with the Airway Management Device
1 Cardiff, UK 2 Cairns, Australia 3 Innsbruck, Austria
Editor—We were interested to read O’Neil’s correspondence1 in reference to the case report by Brimacombe and colleagues.2 Brimacombe and colleagues claim that the Airway Management Device (AMDTM) cannot cause cord closure and still form an effective seal in the hypopharynx. We would like to share our experience in using the recently introduced AMDTM that has design modifications claimed to prevent glottic compression.
Insertion of the AMDTM is easy and relatively atraumatic,3–5 but airway obstruction was quite common using the original device.4 5 The failures reported were 114 and 29%.5 Our experience with the newly modified AMDTM is not very different from that with the original AMDTM, as we encountered a 20% incidence of airway obstruction. We cannot comment on the reason for the airway obstruction, as fibreoptic examination was not performed. We hypothesize that it may be due to epiglottic down folding or mechanical cord closure as suggested by Brimacombe and colleagues.2 An interesting observation from our recently concluded study is the difference in the incidence of obstruction between the sexes. We had a 6% incidence of airway obstruction in females where a size 3 AMDTM was used, compared with 33% in males where sizes 4 and 5 were used.
Even though the AMDTM was redesigned to reduce the incidence of airway obstruction, our recent study suggests that this is still a common problem with the AMDTM, particularly in the male population.
M. R. Stacey
R. Sivasankar
U. B. Bahlmann
R. C. Hughes
J. E. Hall
Cardiff, UK
Editor—Stacey and colleagues’ findings support our previously stated view that any extraglottic airway device with a large and/or inflatable hypopharyngeal component can cause mechanical airway obstruction by vocal cord closure secondary to glottic compression.2 Another cause of mechanical obstruction, which we failed to mention in our earlier communication, is infolding of the aryepiglottic folds.6 7 It is not surprising that the new Airway Management Device (AMDTM) still causes airway obstruction since the hypopharyngeal component is essentially unchanged. We suspect that Stacey and colleagues’ low (6%) incidence of obstruction using the size 3 AMDTM in females is partly due to the smaller hypopharyngeal component causing less glottic compression. The high (33%) incidence of obstruction in males using the size 4 and 5 AMDTM suggests that these sizes have little clinical utility, but further research is required to verify these negative findings. It is a pity that Stacey and colleagues were unable to perform a fiberoptic assessment since this would have provided important clues about the aetiology of the obstruction. We recommend the use of a fiberoptic scope in the assessment of airway obstruction with extraglottic devices whenever clinical circumstances allow.
J. Brimacombe1
C. Keller2
1Cairns, Australia
2Innsbruck, Austria
References
1 O’Neil MJ. Mechanical closure of the vocal cords with ProsealTM. Br J Anaesth 2002; 89: 936–7
2 Brimacombe J, Richardson C, Keller C, Donald S. Mechanical closure of the vocal cords with ProsealTM laryngeal mask airway. Br J Anaesth 2002; 88: 296–7
3 O’Neil MJ. Development and evaluation of the AMDTM including comparison with LMA in spontaneously breathing anaesthetised patients. Today’s Anaesthesist 2001; 16: 98–103
4 Cook TM, Gupta K, Gabbott DA, Nolan JP. An evaluation of the airway management device. Anaesthesia 2001; 56: 1–6[CrossRef][Web of Science][Medline]
5 McGill F, Shoba R, Stacey M, Turley A, Hall JE. Clinical assessment of the use of the Airway Management Device. Eur J Anaesth 2003; (in press)
6 Dubreuil M, Janvier G, Dugrais G, Berthoud MC. Uncommon laryngeal mask obstruction. Can J Anaesth 1992; 39: 517–8[Web of Science][Medline]
7 Seto A, Aoyama K, Takenaka I, Kadoya T. Ventilation difficulties through the intubating laryngeal mask. Anesth Analg 1999; 88: 1181–2
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