[Evaluation of 13 cases of upper airway obstruction caused by laryngeal mask ProSeal, improved by other types of laryngeal mask airway].

BACKGROUND: Although the cases of upper airway obstruction with ProSeal laryngeal mask airway (PLMA) during spontaneous respiration were reported, the structural comparison with other types of laryngeal mask are not known. We thus examined the relationship between upper airway obstruction and the structure of laryngeal mask.

METHODS: With approval of the human research committee at Kawanishi City Hospital, and written informed consent, we enrolled 27 patients scheduled for elective surgery. Anesthesia was induced with fentanyl 25-50 microg and propofol (2-4 mg x kg(-1)), and PLMA was inserted without neuromuscular blockade. There was no failure in insertion of each supraglottic airway under spontaneous breathing. In the case of airway obstruction, the position of PLMA was determined by passing a flexible fiberoptic laryngoscope, and we attempted to adjust the cuff volume or change the size of PLMA. However, the airway obstruction was not improved. We exchanged PLMA for the other types of LMA (Supreme: SLMA or Classic: CLMA) and assessed the movement of arytenoids and respiratory condition.

RESULTS: In 13 cases (48.1%), upper airway obstruction occurred. In all cases, changing the cuff volume or the size of PLMA was not effective, but, the airway obstruction was immediately improved after the changing the PLMA for another type of LMA.

CONCLUSIONS: The upper airway obstruction is caused by PLMA due to the deep bowl cup form which is distinctive design of PLMA. Bulky side cuff limits the movement of arytenoids. The bowl cup pushes up the oral cavity forward, and the supraglottic soft tissues are displaced inward because those tissues are not fixed by the thyroid cartilage. Other types of LMA listed above do not have these features. This suggests that Supreme or Classic LMA is suitable for spontaneous respiration than PLMA, and it is risky to choose PLMA for emergency airway management without knowing these features.