The laryngeal mask airway (LMA) has been in widespread use by anesthesiologists in Europe since the 1980s, when it was developed by Dr. A.I.J. Brain.¹ It is used worldwide in the operating room (OR) to ensure airway patency during general anesthesia. The device is available in both reusable and disposable forms (Fig. 26-1), and comprises a tube attached to an ovoid mask that is placed in the hypopharynx and advanced to cover the glottic opening. When inflated, the cuff of this mask provides a seal around the glottic aperture.² However, this seal is inadequate at high peak inspiratory pressures, and leakage of inspiratory gases is manifest, especially when pressures begin to exceed 30 cm H₂O. In elective settings, spontaneous breathing (as opposed to positive pressure ventilation) is preferred with the use of this device, but it can be used safely and effectively for positive pressure ventilation if tidal volumes and peak inspiratory pressures are kept low (tidal volume should not exceed 8 mL/kg and peak inspiratory pressures should be limited to 20 cm H₂O). Reusable LMA masks are typically made from silicone, whereas single-use devices are often constructed with polyvinylchloride; however, some single-use devices such as the AES Ultra are made with silicone. The LMA is manufactured in many sizes, ranging from those for neonates to those for large adults. In adults, the usual range of sizes is 3, 4, and 5 (Fig. 26-2). Multiple manufacturers have now begun to offer similar devices, often with functional modifications. The Ambu AuraOnce (Ambu, Ballerup, Denmark) (Fig. 26-3) is a disposable LMA with an angled tube designed to follow the natural curve of the supraglottic airway, with recent evidence suggesting increased ease of insertion compared with the original LMA design.³,⁴ Several other manufacturers offer LMAs with flexible, wire-reinforced tubes for use in intraoral and other procedures that require positioning of the airway tube away from the surgical field, with less risk of LMA dislodgement or malposition.

Because the LMA does not provide an intratracheal seal, regurgitation and aspiration are potential risks of its use. This prompted the development of a version of the device that incorporates a gastric port to allow decompression of the stomach after insertion. The Proseal LMA (LMA of North America, San Diego, CA, USA) (Fig. 26-4) was designed to separate the respiratory and gastrointestinal tracts and provide higher airway sealing pressures, thus allowing dependable positive pressure ventilation. The Proseal LMA can be somewhat more challenging to insert than the standard LMA device, due to its larger size and different conformation. This device can be placed freehand, or with an optional insertion tool. A newer alternative, the LMA Supreme (LMA of North America) (Fig. 26-5) is a disposable, single-use device that incorporates a gastric port similar to the Proseal LMA, with an integral bite block and a premolded curved tube similar to the Ambu AuraOnce. Both the standard LMA and the Proseal LMA devices can be overinflated, with resultant mucosal injury.⁵ Ideally, a manometer should be used to gauge the correct pressure of inflation, as recent evidence suggests that limiting cuff pressures to less than 60 cm H₂O (44 mm Hg) results in significantly less postoperative sore throat, dysphagia, and dysphonia.⁶

One relatively new supraglottic airway, the i-gel (Intersurgical Ltd, Wokingham, UK), resembles the LMA in shape and insertion technique but is made from a thermoplastic elastomer to conform to the perilaryngeal anatomy and does not have an inflatable cuff. This simplifies use and may reduce the risk of compression injury. Like the Proseal LMA and the LMA Supreme, this airway also incorporates a gastric channel. It is available in three adult sizes.

The LMA is effective for ventilation in the OR during many types of elective surgical cases.¹,² Originally used mainly for cases in the supine position, recent evidence suggests that the LMA may be a useful airway tool for elective cases in the prone position as well.⁷,⁸,⁹ The LMA has also been used as an emergency ventilation adjunct in various circumstances.²,¹⁰,¹¹ It can be used effectively as a “bridge” to fiberoptic intubation, because a size 6.0 endotracheal tube (ETT) (or 7.0 in the size 5 LMA) may be passed through the LMA and into the glottis, while the lumen of the device effectively guides the fiberscope to the laryngeal opening.¹¹,¹² The LMA has proven useful as a both an alternative to bag-valve-mask (BVM) ventilation
in cardiopulmonary arrest and as a rescue device in difficult airway management. Among intensive care nurses, Martin¹³ found that the LMA proved easier to use and provided superior tidal volumes with less likelihood of airway obstruction than BVM ventilation with or without an oral airway. When untrained volunteers were assessed for the ability to ventilate patients under general anesthesia, Alexander¹⁴ described marked improvement in the success of ventilation and oxygenation when the LMA was used, compared with BVM ventilation. He reported a 43% rate of failure to ventilate effectively with the latter device, whereas the LMA was successful in all but 13% of cases. Likewise, Smith¹⁵ found that anesthetists were better able to maintain oxygen saturation and a patent airway in 64 patients under general anesthesia randomly assigned to ventilation using the LMA as opposed to a face mask.

In an evaluation of the utility of LMA for prehospital care, Pennant¹⁶ described placement of LMA by paramedics in 100% of cases in less than 40 seconds, whereas ETT placement took more than twice that long and resulted in 31% misplacement. Davies¹⁷ described placement of an ETT or LMA in a mannequin model by paramedics with little training: 94% of LMA insertions were successful, compared with only 51% of ETT insertions.

The LMA has been well established for effectiveness during difficult airway management in the OR.¹⁰,¹¹