Unsuccessful attempts to recruit participants

This study will look at key performance indicators of 2 supraglottic airway devices in anaesthetised adults in a crossover manner.

A supraglottic airway device (SAD), also referred to as laryngeal mask airway (LMA), is a medical device that maintains a patients airway, allowing unobstructed ventilation during anaesthesia. They are designed to sit in the patient's hypopharynx (throat), with their elliptical head forming a seal around the supraglottic structures (the patients "voice box"). They have been in common use since 1989, transforming anaesthetic practice and are now the predominant airway device within anaesthesia, being used in approximately 56% of all general anaesthetic cases in the UK(1). Their popularity for routine use stems from its perceived benefits over traditional forms of airway management coupled with their high overall success rate and low complication rate.

SADs, in anaesthetic practice, are inserted after induction of general anaesthesia, by or under supervision of, a trained medical professional. All patients are fully monitored as set out by the Association of Anaesthetist of Great Britain and Ireland; Recommendations for standards of monitoring during anaesthesia and recovery (2). Devices are used in concordance with manufacturer instruction. Successful first time placement is achieved in a large majority of patients and allows provision of oxygen and ventilation. In some patients, one device or size of device may present sub-optimal performance resulting in the removal of the device. Further actions in this scenario would include attempting a second insertion of the same device, attempting an insertion with an alternative size of the same device or a further attempt with an alterative design of device in order to achieve a patent airway. Further attempts may be taken but should be limited to avoid unnecessary trauma. In some cases the use of the SAD is abandoned and the patient is intubated with an endotracheal tube in order to provide a safe secure airway.

Alternatives to use of a SAD for airway management include use of a simple facemask or tracheal intubation with an endotracheal tube. Advantages of using a SAD for anaesthetic airway management compared to a facemask are improved oxygen saturation and less operator/anaesthetist fatigue. Compared to an endotracheal tube the advantages of using a SAD are improved haemodynamic stability at induction and emergence from anaesthesia, reduced anaesthetic requirements, improved quality of emergence, lower incidence of sore throat, increased ease of placement and reduced risk of dental damage. Risks of using an LMA compared to an endotracheal tube are increased gastric insufflation and aspiration with these being more common in patients who are poorly selected for anaesthesia with a SAD. Sore throat is the most common complication with a study

There have been significant developments in design in the SAD market in recent years with development of a "second generation" range of devices involving new materials and designs that integrate protective bite blocks, gastric drainage channels and improved supraglottic seal enhancing patient safety when using these devices. There are now some new "third generation" SADs on the market with designs that may enhance anaesthetic practice and improve patient safety further.

This study will follow similar ethically approved protocols used in published studies comparing airway equipment (3,4). These are only 2 examples but there are hundreds of LMA studies throughout the literature. The Ambu AuraGain is a new device and has not been studied fully. Comparative studies frequently assess oropharyngeal leak pressure (OLP), a fibre optic assessment of glottic alignment, ease of insertion, ability to insert a nasogastric tube down the gastric port and frequency of manipulations.

We propose a crossover design to better detect differences between the two devices as this eliminates confounding differences in patient characteristics and demographics.

There have been significant developments in design in the SAD market in recent years with

Our proposal would be to carry out a randomised crossover comparison between a new "third generation" SAD; the AuraGainTM (Ambu, Copenhagen, Denmark) and our current "second generation" SAD; the i-gel (Intersurgical Ltd, Wokingham, UK) to examine and compare key performance indicators with their use.

The AuraGain is a new device on the market and has not been compared to other devices yet.

Inclusion Criteria:

• patients who have read and understood patient information leaflets about the study and undergo informed consent.
• patients whose anaesthesia management is being carried out by one of the named investigators
• adult (age >18 years) patients undergoing general anaesthesia
• American Society of Anaesthesiology Grading (ASA) 1-3
• suitability for general anaesthesia using a laryngeal mask airway device

Exclusion Criteria;

• the presence of significant acute or chronic lung disease
• pathology of neck or upper respiratory tract
• an identified or anticipated difficult intubation
• an increased risk of aspiration (hiatus hernia, gastro-oesophageal reflux or full stomach etc.) pregnant women
• a body mass index greater than 35kg.m-2
• patients unable to communicate fully in English.