A study of laryngeal mask inflation. Pressures exerted on the pharynx.

Laryngeal mask airway cuff inflation pressures were measured when inflated with the same volume of gas firstly in free space and then in position in the pharynx. A large difference in these pressures was observed and this was related to pharyngeal mucosal perfusion pressure. This study shows that it may be easy to produce pressures on the pharyngeal mucosa in excess of the critical perfusion pressure and thus potentiate mucosal trauma. Furthermore, laryngeal mask cuff pressures were measured at intervals during anaesthesia and were found to rise by a significant amount if room air was used as the cuff inflating gas. This effect could, however, be reversed if inspired gas was used to inflate the mask cuff. We conclude that care must be taken when inflating the laryngeal mask cuff if postoperative morbidity is to be avoided and also that it may not be necessary to use as high a volume of inflating gas as has been recommended during spontaneous respiration.