Depth of insertion of the ProSeal™ laryngeal mask airway

Background. The depth of insertion of the ProSeal(TM) laryngeal mask airway (PLMAdagger) is unknown. We measured depth of insertion in satisfactorily positioned PLMAs. Methods. All women received size 4 masks and men size 5 masks. We measured the position of the integral bite block in relation to the upper incisors documented in patients over a 6-month period. Depth of insertion was scored by dividing the integral bite block into quarters. Satisfactory positioning of the ProSeal(TM) itself was determined by (i) positive 'suprasternal notch test', (ii) no venting via the drain tube during maximal lung inflation, and (iii) an unobstructed airway. Results. We studied 274 patients (147 women and 127 men). The midway point of the bite block was proximal to the incisors (e.g. within the oropharynx) in 78% of women (95% Cl 71-85%) and 92% of men (95% Cl 87-97). The standard deviation for the depth distribution in women was 0.8 cm and for men was 1.0 cm. Conclusions. Usually most of the integral bite block lies within the oropharynx. It was never normal for the entire bite block to stick out of the mouth (4 SD from the mean for both men and women). The position of the integral bite block relative to the upper incisors gives valuable information during assessment of PLMA position.