10.1.1 Why Were Rigid and Semirigid Fiberoptic and Video Laryngoscopes Developed?
Macewan originally performed endotracheal intubation with his fingers.1 In 1913 Janeway used a speculum very similar to the laryngoscopes introduced by Miller and Macintosh in 1941 and 1943.2 And since that time, we've remained very much dependent upon the line-of-sight technique exemplified by direct laryngoscopy (DL). It was proposed that "the sniffing position" aligns the axes of the mouth, pharynx, and trachea, yet the incisors, the tongue, the epiglottis, and occasionally the position of the larynx itself, often conspire against a clear view. Studies on conscious adults with normal airway features, in neutral, sniffing, and simple extension demonstrate that positioning alone does not align the axes3 and there was little difference between the sniffing position and simple extension in a large series of patients undergoing laryngoscopy.4 If positioning does not align these axes, how do we accomplish intubation by DL? This is achieved by the application of force to displace and compress the tongue, mandible, and frequently the larynx itself. Yet even among adults with seemingly normal airways, it is not possible to view the larynx by direct means in approximately 6% to 10%5,6 and studies suggest that when this method fails, all too often we try harder and more often7 with dire consequences.7,8
Instruments that are more or less anatomically shaped can overcome restrictions in upper airway anatomy of most patients. Unfortunately, direct laryngoscopy using these instruments is difficult or impossible in some patients. Fiberoptic and video laryngoscopes are designed specifically for this purpose.
Another significant limitation of direct laryngoscopy is that the experience is difficult to share.9,10 Only the laryngoscopist is able to view the procedure and this complicates the teaching and recording of laryngoscopy, limiting possibilities for quality improvement and the conduct of airway research. Video laryngoscopy circumvents many of these limitations but generally relies upon alternative devices. Viewing the anatomy and the procedure of intubation can be achieved using a conventional laryngoscope. The Airway Cam®, developed by Dr Richard Levitan, is a head-mounted camera which captures the laryngoscopist's view through an eye-level pentaprism and conveys the image to a video monitor and/or a recording device.11,12 This device enables a student and mentor to simultaneously view the same object, record and replay the image at a time and pace conducive to and appropriate for teaching, clinical documentation, and research. While these achievements are clearly worthwhile, this technology does not improve laryngeal exposure.
Flexible bronchoscopes have greatly expanded our ability to diagnose and manage problems in previously inaccessible body parts. These devices are versatile but complex. For tracheal intubation, flexible bronchoscopes demand a different skill set than direct laryngoscopy. Nonetheless, practitioners must master these devices, since they are the best choice for some airway challenges. Their complexity and versatility also add to ...