SummaryThis prospective self-controlled study was designed to evaluate the influences of head flexion on airway seal, quality of ventilation, and orogastric tube placement through the ProSeal TM laryngeal mask airway (ProSeal LMA TM ) in 80 anaesthetised, paralysed adult patients.After the ProSeal LMA was inserted and the cuff pressure was set at 5.9 kPa, ventilation quality, airway seal pressure, fibreoptic positions of the cuff and the drainage tube, orogastric tube placement and efficacy of intermittent positive pressure ventilation (IPPV) were assessed in two randomly selected positions: neutral and flexed position. When compared to the neutral head position, the head flexed significantly improved the airway seal pressure and the quality of ventilation of the ProSeal LMA (p < 0.05). Fibreoptic scores of the cuff position did not correlate with either the ability to obtain excellent or adequate ventilation through the ProSeal LMA or the ability to generate an airway seal pressure of ‡ 2 kPa. Orogastric tube placement via the drainage tube was successful on the first attempt in all patients in the neutral position compared with seven failures following three attempts in the flexed position (p < 0.05). There were no significant differences between the two head positions in the volume of air required to obtain an intracuff pressure of 5.9 kPa, fibreoptic score of the drainage tube position, and expiratory tidal volume and peak inspiratory pressure during IPPV (p > 0.05). In conclusion, head flexion improves airway seal and ventilation quality of the ProSeal LMA. However, placement of an orogastric tube via the drainage tube is impaired in the flexed position compared to the neutral position. Fibreoptic scoring of the ProSeal cuff position is not an accurate test to assess the airway seal and ventilation function. The ProSeal laryngeal mask airway (LMA TM ) is a laryngeal mask device with a modified cuff used to improve the seal around the glottis and a drainage tube to provide a channel for orogastric tube placement and to assist the diagnosis of incorrect positioning [1]. In anaesthetised patients, Brimacombe and Keller [2] demonstrated that the ProSeal and classic laryngeal mask airway are stable in different head positions, but that head flexion and rotation increase, and head extension decreases, airway seal pressure. However, this study was performed at different cuff pressures with the different head positions and did not assess ventilation quality and ease of the orogastric tube placement through the ProSeal LMA in the different head positions. It is generally recommended that inflation to an intracuff pressure of 5.9 kPa is preferred as this minimises pharyngeal mucosa pressure and prevents malposition [1].Although the fibreoptic scoring system described by Brimacombe and Berry [3] has been used to assess proper positioning and airway seal function of the classic