The laryngeal mask airway--anatomical and physiological implications

The laryngeal mask airway (LMA) is a relatively new general purpose airway which fills a niche between the face mask and tracheal tube, both in terms of anatomical location and degree of invasiveness. It sits in the hypopharynx at the interface between the gastrointestinal and respiratory tracts, where it forms a circumferential low pressure seal around the glottis. This has advantages in terms of gas flow through the upper airway and allows direct access to the glottis without loss of airway control. LMA insertion can be considered in the context of swallowing and combines the ability to insert blindly whilst avoiding collision with highly innervated anterior pharyngeal structures. This review deals briefly with the concepts behind LMA design and insertion, and focuses on the anatomical and physiological implications of the LMA with respect to the swallowing reflex, the oesophagus, the pharyngeal mucosa, pulmonary defences, pulmonary mechanics and the cardiovascular system. The possible role of the LMA as a monitor of anaesthetic depth and areas of future research are also discussed.