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Airway management is often undertaken by a variety of practitioners, with a wide array of skills and experience. Individual practitioners develop habits and preferences for the class and types of devices used in airway management based on those devices that are available, supported by protocol as applicable, used with some degree of frequency, and with which proficiency has been achieved.
The challenge is when new airway management devices are brought in for evaluation. Terminology alone can be very confusing—direct, indirect, video, optical, fiber optic, lighted, flexible, rigid, intubating, etc.—making it difficult to choose which class of device, much less a specific device, may work for an individual practice. With this article we hope to help practitioners wade through the sea of names, and understand each class of device and how they work. The airway practitioner can then assess differences between devices within the same class to make knowledgeable decisions about the type to evaluate and use. To guide us through this journey into the nomenclature of airway devices, let’s first take a look at the history of laryngoscopy.
The most common class of laryngoscopy devices, and one that has been in use for over 100 years—since 1895, is the direct laryngoscope (DL) class. First developed and used by the German Alfred Kirstein (1863–1922), this class of laryngoscope used a modified esophagoscope to directly visualize the glottic structures. This class of scopes went through a rapid growth phase and by 1913 Chevalier Jackson proved placement of an endotracheal tube could be obtained with a high rate of success using this technique. In 1919, Sir Ivan Magill in the U.K. introduced the straight blade, modified by Robert A. Miller in 1941, which is still in use today. Sir Robert Macintosh introduced the “curved” blade DL in 1943, which remains in common practice 60-plus years later.
Each device in the DL class utilizes a light source at the distal tip of a (generally) removable locking blade with a handle. The airway practitioner creates a view of the glottic structures by lifting the tongue and other oropharyngeal structures out of the way. Consequently this class of laryngoscopes is extremely dependable and applicable to patients of all sizes and most clinical conditions.
Over the past several decades a newer class of devices known as indirect laryngoscopes (IL) has emerged. An indirect laryngoscope utilizes different methods to look “around” the corner, so the airway practitioner is not required to obtain a direct line of site with the glottis. This is advantageous for those patients in whom manipulating their anatomy into position for the view is impractical or not possible. We begin by discussing the video-assisted indirect laryngoscope, or video laryngoscope.
The video laryngoscope utilizes a small camera, often located midway down the device’s shaft, to view the glottic structures distal to the camera. The camera then sends a video image up the device shaft to a video screen. Examples of this class of device include the GlideScope® series, the C-MAC, the McGRATH®, the Pentax-AWS and the King Vision laryngoscopes. Each device in this group is similar in that there is not the need to move the tongue and oropharyngeal structures out of the way in order to “see” the glottic opening.
Another group of indirect laryngoscopes are the indirect optical devices, or optical laryngoscopes. Optical devices existed even before the DL method, beginning in 1854 with Manual Garcia, a Spanish voice teacher who was the first person in recorded history to view the functioning glottis of a living person. These devices employ an integrated light source and a series of mirrors to transmit the view from the distal lens to a proximal lens that the airway practitioner looks into, and thus provide indirect visualization of the glottis rather than a direct line of site. Two optical laryngoscopes currently available commercially include the Airtraq and the Truview PCD video laryngoscope devices. The Truview is included in this category because it uses an optical blade that incorporates a video feed at its proximal end in order to enlarge the view for the clinician on a separate screen.