REVIEW ARTICLE Evolution of the Extraglottic Airway: A Review of Its History, Applications, and Practical Tips for Success Michael R. Hernandez, MD,* P. Allan Klock, Jr., MD,* and Adranik Ovassapian, MD*† The development of the laryngeal mask airway in 1981 was an important first step toward widespread use and acceptance of the extraglottic airway (EGA). The term extraglottic is used in this review to encompass those airways that do not violate the larynx, in addition to those with a supraglottic position. Although the term extraglottic may be broad and include airways such as tracheostomy tubes, the term supraglottic does not describe a large number of devices with subglottic components and is too narrow for a discussion of modern devices. EGAs have flourished in practice, and now a wide variety of devices are available for an ever-expanding array of applications. In this review we attempt to clarify the current state of EGA devices new and old, and to illustrate their use in numerous settings. Particular attention is paid to the use of EGAs in special situations such as obstetric, pediatric, prehospital, and nontraditional “out of the operating room” settings. The role of the EGA in difficult airway management is discussed. EGA devices have saved countless lives because they facilitate ventilation when facemask ventilation and tracheal intubation were not possible. Traditionally, difficult airway management focused on successful tracheal intubation. The EGA has allowed a paradigm shift, changing the emphasis of difficult airway management from tracheal intubation to ventilation and oxygenation. EGA devices have proved to be useful adjuncts to tracheal intubation; in particular, the combination of EGA devices and fiberoptic guidance is a powerful technique for difficult airway management. Despite their utility, EGAs do have disadvantages. For example, they typically do not provide the same protection from pulmonary aspiration of regurgitated gastric material as a cuffed tracheal tube. The risk of aspiration of gastric contents persists despite advances in EGA design that have sought to address the issue. The association between excessive EGA cuff pressure and potential morbidity is becoming increasingly recognized. The widespread success and adoption of the EGA into clinical practice has revolutionized airway management and anesthetic care. Although the role of EGAs is well established, the user must know each device’s particular strengths and limitations and understand that limited data are available for guidance until a new device has been well studied. (Anesth Analg 2012;114:349–68) he laryngeal mask airway (LMA; LMA North Amer- EGAs have become much more than a simple airway device, ica, San Diego, CA) was one of the first extraglottic and now enjoy a wide range of applications and indications, Tairways (EGA) invented by Dr. Archie Brain in 1981. some of which were formerly relative contraindications. It became commercially available in the United Kingdom in The term supraglottic airway device is often used, but may 1988 and in the United States in 1991. The LMA Classic not accurately describe airways that include periglottic com- (cLMA) received wide recognition in a short time and has ponents. Use of the term extraglottic airway device is perhaps had a major impact on anesthesia practice and airway more appropriate for this review, because it encompasses management. Publication of thousands of peer-reviewed airways that do not violate the larynx. Although airway articles, book chapters, and textbooks testifies to the success devices such as a tracheostomy tube may also be considered of the LMA as an extraglottic device. Other individuals and extraglottic, this review concerns itself only with devices that manufacturers later introduced similar airway devices. are inserted via the oropharynx for temporary airway man- agement. A large number of recently introduced devices have Despite significant literature detailing the use of EGAs, the complicated efforts to establish a consistent nomenclature and constant evolution in device design encourages the clinical organizational framework for EGA devices1 (Table 1). application of the LMA outside the traditional operating room Despite a multitude of new devices introduced into the (OR) suite. This review attempts not only to describe some of market, most devices aim to allow easy placement with the history surrounding EGA devices, but also to understand predictable ventilation, minimize the chance of pulmonary how EGA use has evolved because of design modifications. aspiration, and to serve as an adjunct to tracheal intubation. This review aims to help the reader understand the simi- From the *Department of Anesthesia and Critical Care, University of Chicago Hospitals, Chicago, IL. †Deceased. larities and differences among the numerous EGAs cur- Accepted for publication October 4, 2011. rently available and will present many EGA devices. EGAs Conflicts of interest: see Disclosures at end of the article. are separated by manufacturer and then further subdivided Supplemental digital content is available for this article. Direct URL citations by the chronology of market entry and/or special features. appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site www.anesthesia-analgesia.org. LMAs Reprints will not be available from the authors. cLMA Address correspondence to Michael R. Hernandez, MD, The University of One of the first EGAs, the cLMA (LMA North America, San Chicago Medical Center, Room M252L. Department of Anesthesia and Diego, CA), was studied extensively and used in Ͼ7000 Critical Care, 5841 South Maryland Ave., MC4028, Chicago, IL 60637. Address e-mail to [email protected]. patients by Dr. Archie Brain and his associate, Dr. Chandy Copyright © 2012 International Anesthesia Research Society Verghese, before its release for routine clinical use. The details 2 DOI: 10.1213/ANE.0b013e31823b6748 of the development of LMAs are described by the inventor. February 2012 • Volume 114 • Number 2 www.anesthesia-analgesia.org 349 REVIEW ARTICLE the device at a given pressure, or the use of manometry to Table 1. Extraglottic Airway Device Classifications measure the pressure at equilibrium with the leak. All 4 techniques successfully measured the “leak” pressure in pe- EGA with an inflatable periglottic cuff 6,7 Ultra CPV family (AES) diatric and adult patients after LMA placement. Ambu Aura family (Ambu) Before inserting the LMA, the cuff is deflated so that the ILA/airQ (Cookgas) edge is smooth and wrinkle-free with the tip deflected Vital Seal (GE Healthcare) backward toward the convex side of the ventilation shaft. King LAD family (King Systems) LMA device family (LMA Company) This method encourages the LMA to slide posterior to the Soft Seal Laryngeal Mask (Portex) epiglottis without deflecting it inferiorly over the glottic Sheridan Laryngeal Mask (Teleflex) opening. The pharyngeal surface is lubricated generously; EGAs with no inflatable cuff the lingual surface is lubricated lightly for smooth advance- i-gel (Intersurgical) ment. In the technique described by Dr. Brain (Fig. 2), the SLIPA (Slipa Medical) EGAs with 2 inflatable cuffs shaft of the LMA is held between index finger and thumb Laryngeal Tube family (King Systems) with the tip of the index finger at the junction of the mask Esophageal Tracheal Combitube (Nellcor) and the tube. With the patient’s head in the “sniffing” Rusch EasyTube (Teleflex) position, the nondominant hand is placed under the oc- EGAs with single pharyngeal inflatable cuff Cobra PLA family (Pulmodyne) ciput, extending the head, while the dominant hand inserts the LMA into the mouth. With optimal technique, the LMA EGA indicates extraglottic airway. follows a path similar to a bolus of food that is about to be swallowed, traveling from the oropharynx against the hard Initial LMA prototypes were designed based on plaster casts palate to the soft palate, hypopharynx, and finally the of cadaveric airways. The use of the cLMA in anesthesia proximal esophagus. The tip of the mask is pressed against encouraged individuals and manufacturing companies to the hard palate and advanced toward the larynx until introduce other EGAs with many design modifications. resistance is felt. Manufacturer recommendations call for The cLMA is a reusable device made of silicone. Its the mask to be inflated to an intracuff pressure of no Ͼ60 disposable version, the LMA Unique (uLMA, LMA North cm H2O (44 mm Hg). Intracuff pressure should be moni- America, Inc. San Diego, CA, USA), is made of polyvinyl- tored, especially if nitrous oxide is being used, with its chloride (PVC). Both are latex-free and available in six sizes increased risk for expansion of the mask volume and to fit infants to adults (Table 2; for additional details see associated injuries.8 When no muscle relaxant is used Supplementary Table 2A, Supplementary Digital Content during insertion or throughout the anesthetic, an adequate 1, http://links.lww.com/AA/A346). Both the cLMA and depth of anesthesia is essential to prevent the contraction of the uLMA have an elliptically shaped mask attached to a pharyngeal and laryngeal muscles, which may interfere ventilation tube (Fig. 1). The mask has a cuff, a pilot tube, with proper positioning of the LMA. Occasionally, an LMA and balloon through which the cuff is inflated and main- may be used to rescue a patient during a rapid sequence tenance of intracuff pressure is monitored. The proximal induction complicated by an inability to perform tracheal end of the shaft has a standard 15-mm adapter. The cLMA intubation and failed attempts to mask ventilate the pa- can be autoclaved and the manufacturer recommendations tient. In this setting, the operator should remember that suggest that it may be reused up to 40 times. Two bars at cricoid pressure may cause compression of the hypophar- the junction of the shaft and mask prevent the epiglottis ynx that may prevent the tip of the LMA from reaching a from obstructing the ventilating lumen. In addition to its routine use in the OR during general anesthesia, the proper final position.