Does efficacy of seal and fibreoptic view change during anaesthesia with the laryngeal mask airway: A comparison of oxygen and oxygen-nitrous oxide gas mixtures

Background: We test the hypothesis that oropharyngeal leak pressure (OLP) and fibreoptic position (FP) are stable for the laryngeal mask airway (LMA) during anaesthesia with and without nitrous oxide. Methods: Forty paralysed anaesthetised patients (ASA 1-2, aged 18-80) were randomly allocated to receive 100% oxygen (O group) or 33% oxygen in nitrous oxide (O-NO group) for maintenance. In vivo intracuff pressure (CP) using a size 5 LMA was adjusted to 60 cm HO. OLP, FP and CP were measured every 5 min for 30 min. Results: CP was higher in the O-NO group than the O group, other than at time zero (all: